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Giardia lamblia and Giardiasis With Particular Attention to the Sierra Nevada
... Hence, deep wells are considered safe. By implication, springs in the wilderness should be safe too (Rockwell, 2002). ...
... WHO, 2008 ). Boiling water kills Giardia (Rockwell, 2002). ...
... The use of filters is the best, but they are costly, heavy, bulk, and some are awkward to use. Giardia cysts are highly susceptible to heat instead (Rockwell, 2002). Chlorine is the most widely used disinfectant for water (WHO, 2008). ...
Wells are the most affordable means of water supply in developing countries. The search for potable water supply in these countries is yet to be achieved. Wells are largely prone to surface and underground contaminations by parasites. This situation remains a great public health concern because it poses threats to wellbeing of man and safety of water. Well water contamination can be described as a multiparasitic condition, where a single well may be contaminated by more than one type of parasite. The users of both public and private wells should be conscious of possible contamination and observe adequate treatment of water obtained from wells. Contamination of a single well can affect surrounding wells using the same aquifer. There is a need for awareness about the danger of well contamination by pathogenic (protozoan) parasites. This will limit carelessness rendered to the wells and subsequently result into full well protection by man. 'Water is life'. Hence, there is need to keep it safe always to prevent waterborne diseases.
... The symptoms of lambliosis are very diverse. Most characteristic and frequent are mild to moderate abdominal symptoms, abdominal bloating due to intestinal gasses, pain, belching, and rarely colics [1][2][3][4]. Lambliosis should be suspected if the above symptoms last approximately ten days. Diarrhea that lasts less than a week without any therapy is most likely not lambliosis [3]. ...
... Lambliosis should be suspected if the above symptoms last approximately ten days. Diarrhea that lasts less than a week without any therapy is most likely not lambliosis [3]. ...
... G. lamblia is a cosmopolitan parasite, affecting people of all ages and of different socioeconomic backgrounds [4][5][6][7][8]. High risk groups for infection are: children, personnel in the centers for infant care, persons in closed communities (psychiatric institutions, centers for developmentally compromised children and adults, prisons), then international travellers, promiscuous individuals (especially homosexuals), immunodeficient patients and family members of those from the high risk groups [2][3][4][5][6][7][8][9]. ...
The aim of this study is to determine the difference in efficiency of direct immunoenzyme-linked assay (EIA) and conventional
microscopy (CM) plus conventional concentration technique (CCT) using comparative analysis in the diagnosis of symptomatic
and asymptomatic lambliosis when only one stool sample is to be tested. The study enrolled 577 examinees: 208 patients and
369 asymptomatic examinees. Lambliosis was diagnosed using CM plus CCT (three stool samples) and direct EIA (the first sample).
All statistical parameters of the EIA method were 100% in the patients with symptoms of infection. In addition to that, in
the group of asymptomatic carriers of Giardia lamblia (G. lamblia) some very high values of these parameters were recorded too, with sensitivity and negative predictive value being both at
100%. In contrast to the EIA method, CM plus CCT of the first stool sample demonstrated significantly lower sensitivity (66.67%)
compared to the reference standard. The study did not demonstrate any statistically significant differences in diagnostic
efficiancy between the EIA testing of one stool sample and CM plus CCT (p<0.05). However, the observed difference in diagnostic
efficiency between the methods was very close to the cut-off value for statistical significance (p=0.06).
KeywordsConventional microscopy-Immunoenzyme-linked assay-Lambliosis
... Giardia can spread between persons and animals through fecal-oral transmission. There are about 2,500,000 cases, or one for every 100 persons per year, in the United States (Rockwell, 2003). In some countries, including China, giardiasis is listed in the drinking water standards. ...
... while that for advanced treatment is 4log-4.5log (Rockwell, 2003;WHO, 2009). As shown in Table 1, under the conventional treatment, the total DALYs were 0.625 per 10 5 persons (95% CI: 0.137-2.05 ...
... The DALY for Giardia from water and food in the Netherlands was 364 in a population of about 16.4 million (Vijgen et al., 2007), which was equivalent to 2.2 DALYs per 10 5 person-years, and much higher than our result (0.625 per 10 5 person-years) from the water exposure route. This was likely related to the habits of drinking boiled water and eating cooked food, because Giardia cysts are highly susceptible to heat (Rockwell, 2003). ...
The occurrence and risks of Giardia in China have been unclear to date, which has made it difficult to properly manage source water as well as to create reasonable drinking water standards. The levels of Giardia in river networks of several cities in Zhejiang Province, China were found to be in the range of 0-5 oocysts/10 L in the rainy season in 2008. The mortality due to Giardia infection for people in this region was calculated to be from 0 to 1.95 x 10(-8) persons using a conditional probability equation. Based on multiple unboiled water intake routes, the disability-adjusted life years (DALYs) due to Giardia infection for people who consumed conventionally treated water was 0.625 (95% CI: 0.137-2.05) per 10(5) persons, with the symptom of hospitalization making the highest contribution to total DALYs (0.56 per 10(5) persons; 95% CI: 0.122-1.84). The DALYs decreased to 0.425 (95% CI: 0.137-2.05) per 10(5) persons per year for those consuming water treated with advanced technology. These values were lower than the acceptable risk (1.97 x 10(-5) DALYs per year). This study revealed the risk of Giardia infection to the people in river networks of Zhejiang Province for the first time, and provides a method to evaluate the risk of Giardia infection. The results are useful for the modification of drinking water quality standards based on cost-benefit analysis.
... Its oval with a length (8 -12 mm) and width (6 -9 mm) contain four nuclei and often found in one side of the cyst, flagella and the sucking discs lose from the mature cyst, but axonemes and median bodies are present (Rockwell, 2002). The cyst wall appears under an electron microscope composed of a layer of fibers and chitin-like materials, these materials help cyst to resist inappropriate environmental conditions, and it's able to spread and cause infection (Arcueilo et al., 2002). ...
... This parasite causes Giardiasis (also named traveler's diarrhea or beaver fever), infection occurs by ingesting food and drink water contaminated with cysts of parasite or directly by hands contaminated with feces (Adam, 2001), parasite released from cyst due to stomach acid and gastric enzymes and formation of Trophozoite stage by a process called excystation (Dawson, 2010),After a short time the Trophozoite stage leaves the host's stomach in response to low PH (Faubert, 2000) and adheres to the surfaces of the intestinal epithelial cells by using their ventral sucking disks,when it begins to multiply by binary fission (Hagen et al., 2011), binary fission occurs approximately every 12 hours so that one parasite can be more than one million parasites within 10 days, and one billion parasites within 15 days (Rockwell, 2002), then Trophozoite encystation in the distal part of the small intestine, whenreleasing with host's stool and ingested by another host the life cycle is repeated again (Brown et al., 2016) ( Figure -1). ...
Giardia lamblia is one of the most prevalent parasites in the world and affects a large number of people, especially children, causing Giardiasis. It is easily transmitted through ingesting food and drink water contaminated with cysts of parasite or directly by hands contaminated with feces, especially in areas with high population density. Some infections with this parasite are asymptomatic but acute cases are characterized by fatty diarrhea, nausea, abdominal pain, vomiting, fever, poor absorption of carbohydrates and fats and a deficiency of vitamin B12, infection diagnosed by examining the Stool microscopically to detect parasite cysts. Prevention of this parasite depends on caring for personal hygiene and washing hands well before preparing food, and treatment is carried out using the drug Metronidazole according to the doctor's prescription.
... Although the first reports on G. lamblia protozoan are 325 years old (1), this parasitosis is still diagnosed in many people worldwide as asymptomatic infection of the digestive tract. The fact that asymptomatic lambliosis is more prevalent than symptomatic infection certainly deserves attention (2). In humans, G. lamblia most commonly causes diarrhoeal syndrome, associated with reduced resorption of fats, proteins, and liposoluble vitamins. ...
... In some of them, the disease occurs sporadically; however, the sporadic patterns of occurrence can be transformed into epidemics within the environment where large population groups are exposed to the causative agent (travels, migrations, international interpersonal contacts). The existance of a large number of asymptomatic cyst carriers causes the risk of spread of this infection to rise substantially (2). ...
Preventive, legally prescribed medical examinations of the population under sanitary supervision, with the aim of diagnosing asymptomatic lambliasis, include the application of conventional microscopic examination (CVM) with concentration technique (CT)of one stool sample. The aim of the paper was to compare the results obtained by the enzyme imnunoassay (EIA) for detection of Giardia lamblia (G. lamblia) antigen in stool, with the results of the investigation of asymptomatic lambliasis by CVM with CT in routine laboratory procedure. The investigation included 279 healthy subjects under sanitary control. One stool samples of investigated subjects were analyzed by using CVM with CT and by EIA for detection of Giardia lamblia (G. lamblia) antigen in stool. Positive result was found in one sample by CVM with CT (1/279; 0,36%). Using EIA method, two positive subjects with asymptomatic lambliasis were detected (2/279; 0,72%). Having applied EIA, a higher prevalence of this parasitosis within the investigate group was proved. EIA method for detection of the presence/absence of antigen for G. lamblia in stool is a method of choice in the laboratory procedures where one stool sample is used to investigate this parasitosis.
... Giardiasis can be treated with drugs, including metronidazola, furazolidone, trinidazole, and paromomycin, therefore, it is not regarded as a fatal disease. Many individuals are asymptomatic carriers of Giardia (Rockwell 2002). ...
Since the first identified Cryptosporidium outbreaks occurred in the 1980s and the massive 1993 Milwaukee, WI outbreak affected more than 400,000 people, the concern over the public health risks linked to protozoan pathogens Cryptosporidium and Giardia has grown. Cryptosporidium and Giardia, found in streams, rivers, groundwater, and soil, form hardy, disinfection-resistant oocysts and cysts. Both organisms are recognized causative agents of gastrointestinal illnesses linked to the consumption of contaminated surface or groundwater. This study, the first in a planned series to estimate the urban contribution to the total Cryptosporidium and Giardia receiving-water loads, focused on combined sewer overflow (CSO). CSOs are discharges of mixed untreated sewage and stormwater released directly into receiving waters during rainfall. This engineered relief is necessary to accommodate hydraulic strain when the combined rain and sanitary flows exceed the system capacity. Limited comprehensive data are available assessing the CSO discharge contribution as a source of these two pathogens. Works by States et al. and Gibson et al. each found Cryptosporidium and much greater Giardia concentrations in CSOs draining parts of Pittsburgh, PA. This project estimated the relative detection frequency and concentration of Cryptosporidium and Giardia in CSO. Analytical results were obtained using a modification of Method 1623, originally developed for much cleaner environmental samples. These data are useful for drinking water treatment plants located downstream of CSOs. It is also significant in determining the potential concentrations of parasites at treatment plant intakes and for assessing health risks for water contact and fishing activities. Commonly monitored indicator organisms (total coliform, fecal coliform, E. coli, Enterococcus, and fecal streptococcus), endospores, and selected physical and chemical parameters were analyzed to further describe the samples. CSO from urban areas was not found to be a significant contributor of Cryptosporidium, however, it was found to be a Giardia source.
... An episode of diarrhea lasting less than a week, untreated, is probably not giardiasis. The disease can persist for several months if left untreated, and can be described as a continual worsening of diarrheal symptoms (3,4). In chronically affected individuals, malabsorption of fats, lactose, and vitamin A and B has been reported, and in children a slower weight gain and growth retardation have been observed (2). ...
... iardia sp. are single-celled, intestinal parasitic flagellates found in the intestines of a wide range of domestic and mammalian hosts including dogs, cats, deer mouse, ground squirrel, chinchilla, swine, pocket mouse, ox and guinea pig (1)(2)(3). The organism consists of six species, distinguished based on the morphology and the ultrastructure of its trophozoites (2). ...
Background
This study was conducted to determine the prevalence of Giardia duodenalis in captive animals in a wildlife facility. This is the first study conducted in these animals from the facility.
Methods
Eight captive tigers (Panthera tigris), two Palawan bearcats (Arctictis binturong whitei) and one Asian Palm Civet (Paradoxurus hermaphroditus) currently housed at a wildlife facility in Manila, Philippines were considered in 2012. These animals were apparently healthy with no signs of disease during the study. Sample collection was done twice at two months interval where freshly voided fecal samples were grossly examined, characterized and preserved in Sodium Acetate Formalin (SAF). The samples were used to determine the presence of G. duodenalis using modified flotation-sedimentation and commercially available immuno-chromatographic assay test kit.
Results
All fecal samples tested were negative for the presence of G. duodenalis trophozoites, and cysts using the former. Furthermore, none of the samples tested positive for and G. duodenalis antigen using immune-chromatographic assay.
Conclusion
There is no existing infection of G. duodenalis among captive tigers, Palawan Bearcats and Asian palm civet housed at the wildlife facility.
... Estima-se que 20% da população mundial esteja parasitada por Giardia spp. (Rockwell, 2003). No Brasil, a criptosporidiose e a giardiose representam importante causa de morbidade em crianças de 0 a 5 anos (Carvalho-Almeida et al., 2006, Gonçalves et al., 2006. ...
Giardia spp. e Cryptosporidium spp. são protozoários patogênicos de transmissão fecal oral de veiculação hídrica, que causam vários problemas de saúde, como doenças gastrointestinais associados com consumo de água contaminada. Devido à escassez de dados sobre a ocorrência destes protozoários em águas superficiais no Sul do Brasil, este estudo teve como objetivo analisar a presença de cistos e oocistos na água bruta das estações de tratamento de água no município de Blumenau, SC, Brasil. Para a pesquisa dos protozoários foi utilizada a metodologia de filtração em membranas de ésteres mistos de celulose, seguida por reação de imunofluorescência utilizando o kit Merifluor®. Para as análises microbiológicas, empregou-se a metodologia do “Standard Methods for the Examination of Water and Wastewater”; para as análises físico-químicas foi utilizada sonda multiparâmetros. Cistos de Giardia spp. foram encontrados em 23,19% das amostras e oocistos de Cryptosporidium spp. em 7,24% do total de amostras analisadas (n=67). Todas as amostras analisadas apresentaram contaminação por Escherichia coli e 11,76% apresentaram valores de turbidez da água bruta acima do recomendado. Nas análises da turbidez da água tratada 23,52% apresentaram valores acima do preconizado pela Portaria 2914/2011. A detecção de protozoários patogênicos na água bruta das estações de tratamento de água aponta para a importância de adoção de medidas preventivas, como a proteção de áreas de mananciais e tratamento adequado do esgoto doméstico objetivando reduzir os riscos de transmissão de protozoários por meio da água de consumo humano na região de Blumenau, SC, Brasil.
... Estima-se que 20% da população mundial esteja parasitada com Giardia spp. (ROCKWELL, 2007). O Cryptosporidium spp. ...
In this study, the efficiency of centrifuge-concentration and membrane filtrated methods was evaluated in the detection of Cryptosporidium spp. oocysts and Giardia spp. cysts in raw or treated wastewater samples, from activated sludge systems (ETE - Samambaia, Campinas, in São Paulo). The samples were collected once a fortnight for two years: 53 samples of influent (AFL), 53 samples of treated effluent without ultraviolet disinfection (EFL), and 38 samples of treated effluent with ultraviolet disinfection (EFL+UV). Giardia spp. cysts were found in 90.5% of the AFL samples; in 96.2% of the samples, EFL; and in 94.7%, EFL+UV. Cryptosporidium spp. oocysts were detected in 6.4% of AFL samples and 2.6% of EFL+UV. Both methods showed efficiency when detecting protozoa in all types of samples, besides having low costs by analysis.
... Many individuals are asymptomatically affected by Giardia, as demonstrated by a CDC study of a population who consumed water heavily contaminated with Giardia due to malfunction in the 1-15 water disinfection system. Only 11 percent of the exposed population developed symptoms even though 46 percent had the organism in their stools (Rockwell, 2002). ...
Abstract This document,is written as a resource for state and local watershed managers,who have the responsibility of managing pathogen contamination in urban watersheds. In addition it can be an information source for members,of the public interested in watershed mitigation efforts aimed at reducing microbial contamination. It is written to support specific steps of the total maximum,daily load (TMDL) process for meeting water quality standards in urban watersheds. The information provided can also support watershed evaluations conducted when disease outbreaks occur in the absence of standards violations. The document,discusses the regulation of waterborne pathogens (Chapter 1), detection methods (Chapter 2), and combined sewer overflow control technologies and stormwater best management,practices (Chapter 3). The table below identifies the steps of the TMDL process supported by each of the chapters. The intent is to supplement,the information included in the EPA document,Protocol for
... The prevalence of Giardia duodenalis (G. duodenalis) symptomatic and asymptomatic infection is high in the population groups in schools [1][2][3], institutions for children daily care [4,5], the institutions for mentally retarded persons [6], psychiatric institutions, prisons, and among international travelers [7]. A high prevalence of giardiasis has also been recorded among immigrant refugees [8,9] and in population groups with low economic status [10][11][12]. ...
Giardiasis is a parasitic infection of the digestive tract, most commonly occurring in closed communities such as schools,
kindergartens, prisons, and campuses. The civil war in the former Yugoslav republics and in Kosovo caused a large number of
refugees to take shelter in the territory of Serbia. Such large numbers of refugees could be accommodated only in the collective
centers. Our aim was to examine the differences in the prevalence of asymptomatic giardiasis among 122 refugees from the former
Yugoslav republics who lived in the collective centers in Nis, Serbia, and 241 native Nis inhabitants. Conventional microscopic
examination (CME) of three stool samples with or without concentration technique and the enzyme immunoassay (EIA) methods
were used. The CME method of three stool samples is considered the gold standard in our statistical survey. Asymptomatic giardiasis
is found in 7 refugees (5.7%) using the EIA method, while using the CME (3 samples) Giardia duodenalis (G. duodenalis) was detected in 6 persons (4.9%). Using the EIA method and the CME (3 samples) G. duodenalis was detected in only 1 person in the population group of native inhabitants (0.4%). Asymptomatic giardiasis was more prevalent
in the population group of refugees accommodated in collective centers than in native inhabitants in the Nis municipality,
Serbia.
Introduction
This study aimed to estimate the contamination of water sources along the Tahoe Rim Trail (TRT) through evaluation of the presence and concentration of Escherichia coli , Giardia, and Cryptosporidium spp.
Methods
Sample sites were selected from 6 of the 8 sections of the TRT. Each stream was sampled 3 or 4 times during the summer and early fall of 2023. Samples were collected and analyzed for E. coli using Standard Methods 9223B and Giardia and Cryptosporidium spp. using EPA Method 1623.
Results
E. coli counts ranged from <1 to 29.2 most probable number (MPN)/100 mL. There was no difference in contamination with E. coli between streams ( P =0.287) or sampling rounds ( P =0.413). Giardia counts ranged from 0 to 7 count/10 L. There was a difference in contamination with Giardia between the highest and lowest concentration streams ( P =0.028) but no difference in contamination between other streams or between sampling rounds ( P =0.924). Cryptosporidium counts ranged from 0 to 1 count/10 L. There was no difference in contamination with Cryptosporidium between streams ( P =0.589) or between sampling rounds ( P =0.888).
Conclusions
E. coli , Giardia, and Cryptosporidium are present in the streams along the TRT. Results from this study show that the risk of illness from occasional direct consumption of water from the streams sampled is low; however, it is always advisable to filter or treat water from any backcountry source prior to consumption. More extensive studies are recommended to evaluate backcountry water sources in the Tahoe Basin to further evaluate the risk to human health from direct consumption .
NOISE ANNOYANCE IN RESIDENTIAL AREAS IN NOVI SAD, 2012-2016
Institute of Public Health of Vojvodina, Novi Sad, Serbia
Objectives: The aim of paper is to quantify the annoyance of the population in the residential areas in the City of Novi Sad (RA-NS) using environmental noise data, in the first place by road traffic noise. It is important for perceiving the noise impact on the human health.
Methods:Public Health Institute of Vojvodina taken 26 24-hour noise measurements on one measuring spot in RA-NS, during 2012 – 2016.
Results: Daily noise indicator (Lday) ranged from 54,6 dB to 70,1 dB, evening noise indicator (Levening) from 51,2 dB to 60,0 dB, night noise indicator (Lnight) from 47,2 dB / 50,7 dB, while total noise indicator (Lden)ranged from 58,0 dB to 67,6 dB. Relative to limit values, there were increased 92% of Lday, 38% of Levening and 100% of Lnight. Relative to results, the percentage of highly annoyed population (%HA) amounts 11%during the day and 6% during the night, while prevalence of population highly annoyed (PHA) is 11% - more specifically in the range 9,2-33,9%.
Conclusion: The results confirm that urban noise annoying population in the residential
areas. and, in conclusion, that fact is the challenge, the problem and the topic for the public health system.
Keywords: noise, annoyance, population
There are many things outdoor educators agree on. For example, a warm meal feels great at the end of the day. Cotton fabrics take forever to dry in the field and should thus be avoided. Most small groups generate less impact than large groups do. Mosquitoes and black flies come straight from hell. And, all backcountry water must be treated due to the presence of Giardia, a protozoan that has infested water sources throughout the United States, causing the debilitating gastrointestinal illness giardiasis. Now, there is no denying hot meals are soothing, cotton kills, good things come in small packages, and camping during bug season is cruel and unusual punishment. But, has Giardia really infested our water sources? Ask this question to nearly any outdoor educator and you will receive a harried, "Oh, yes it has!" However, to the above question I calmly answer, "No, it has not." I teach an evidence-based curriculum that embraces drinking straight from the source. Why do I veer from the educators that teach an "industry standard" of treating literally every drop of water? Because I've done my homework. The supporting evidence for not treating backcountry water is presented in five logical, myth-busting arguments that will encourage educators to rewrite unproven curriculum. Safety in (lack of) numbers Despite popular belief in professional circles, water sources are not crawling with Giardia, as proven by a 1984 examination of nearly seventy Sierra Nevada water sources. Department of Public Health drew two interesting conclusions. First, data showed that more than 55 percent of high-use sources and nearly 85 percent of low-use sources had zero Giardia cysts.
Worldwide literature on serological methods and sero-surveys on waterborne pathogens has been reviewed. Outbreak investigation and research reports have also been examined to aid understanding of the serological response and transmission dynamics. The aim was to seek an estimate of seroprevalence and to determine if this could inform the US national estimate of risk for endemic waterborne infection associated with public water supplies. Antibody responses indicate infection, both symptomatic and asymptomatic, so probably give a truer indication of prevalence. Outbreak data can probably be regarded as the upper bound for seroprevalence estimations. Antibody is not necessarily protective per se but is a good indicator for at least partial resistance to symptomatic infection; absence of antibody will normally imply susceptibility. Pathogens transmitted by water are commonly transmitted by other routes. However, the fact that other transmission routes are more common does not detract from the potential protective effect of immunity when waterborne transmission occurs. Data indicate that seroprevalence varies widely, reflecting geographic, social and hygiene factors, but is generally greater where surface water sources are used rather than groundwater. Areas of low seroprevalence may expect a high attack rate in the event of contamination of their water supply.
To evaluate newer techniques such as coproantigen detection and serology in the diagnosis of symptomatic Giardia lamblia infection.
Blinded comparison of copro-antigen detection (by ELISA), serology (immunoglobulin IgG and IgM anti-G lamblia by ELISA, and IgG, IgM and IgA by immunoblot) and microscopy in clinical samples. Microscopic findings for three preserved stools were considered the gold standard.
Travel medicine clinic.
Adults, post-travel, with gastrointestinal symptomatology.
For 152 previously collected stools, copro-antigen detection had a sensitivity of 73 of 74 (98.6%) and a specificity of 78 of 78 (100%). In clinical samples of 62 patients, eight of the 62 patients (13%) were diagnosed with G lamblia infection on microscopy. Copro-antigen diagnosis was accurate in symptomatic patients, with sensitivity of seven of eight (87.5%) and specificity of 52 of 54 (96.8%). Serology was less accurate. IgG response to G lamblia had sensitivity of four of seven and specificity of 24 of 50 (48%), and IgM response had sensitivity of three of six and specificity 27 of 48 (56%). Western blot had a sensitivity of five of seven and a specificity of 38 of 49 (78%).
Copro-antigen diagnosis of G lamblia is highly accurate in patients with chronic gastrointestinal complaints, while serology is less accurate and appears to be less useful diagnostically.
In the present study, neonatal ZU.ICR mice and their mothers were infected with trophozoites of Giardia lamblia clone GS/M-83-H7 expressing the variant surface protein (VSP) H7. The infection experiments included a detailed analysis of the specificities of anti-Giardia immunoglobulin A (IgA) antibodies in mother's milk and a determination of the effects of the milk antibodies on both the growth of the parasite during in vitro cultivation and colonization of the parasite within the intestine of suckling offspring. These investigations revealed that transiently emerging milk IgA antibodies against a variant-specific 314-amino-acid N-terminal region of VSP H7 exhibit a strong parasiticidal effect on VSP H7-type trophozoites both in vitro and in vivo. These findings indicated that parasiticidal effects of local IgA antibodies against the N-terminal part of VSP H7 select for new variant types within the intestinal parasite population of suckling mice. The selective influence of such antibodies promotes in vivo antigenic variation of G. lamblia clone GS/M-83-H7 and modulates the early course of parasite infection in these animals.
The natural history of Giardia muris has been studied in inbred mouse strains and hypothymic (nude) mice derived from a specific pathogen-free facility. Although giardiasis was readily established in several mouse strains, marked variation was observed in the time course of spontaneous elimination of the parasite. During a 10-week study, fecal excretion of Giardia cysts remained relatively constant in C3H/He mice, but decreased at a variable rate in other mouse strains. Resistance to reinfection was greater in strains in which the duration of primary infection was relatively short. Hypothymic (nude) mice derived from a strain showing a relatively rapid elimination of Giardia (BALB/c) maintained a stable infection with high cyst counts. Nude mice reconstituted with lymphoid cells from syngeneic thymus-intact mice showed a progressive reduction in cyst excretion and reconstitution with limited numbers of lymphoid cells from thymus-intact mice previously exposed to Giardia accelerated resolution of infection. In nude mice, giardiasis was associated with a reduction in the villus-crypt ratio of jejunal mucosa, but the degree of change was greater in nude mice reconstituted with lymphoid cells. This Giardia model involving inbred strains and nude mice permits further dissection of the function of thymus-derived cells in intestinal immune responses and induction of changes in small bowel morphology.
The Weibel graticule was used to assess quantitatively histological changes in proximal jejunal mucosal biopsies from patients with Giardia lamblia infections. Most had malabsorption. A group of patients who had mild abdominal symptoms but no intestinal infection and normal absorption were the controls. There were significant differences in mean surface area (SA) measurements between patients with giardiasis and severe malabsorption and controls (P less than 0.001) and infected patients with normal absorption (P less than 0.05). SA measurements correlated significantly with D-xylose excretion results (r = 0.55; P less than 0.01) and daily facal fat output (r = -0.61; P less than 0.001). Significant correlations between duration of symptoms and SA measurements (r = 0.43; P less than 0.05) and D-xylose excretion (r = 0.43; P less than 0.05) in giardiasis suggest that histological and functional impairment are maximal soon after infection and resolve in time. Treatment with metronidazole or mepacrine was associated with a significant increase in SA (P less than 0.05) in patients with severe malabsorption but there was little change in SA in a similar group of patients who received tetracycline. The Weibel graticule was found to be useful in assessing the severity of histological changes and in following changes after treatment.
Malabsorption was present in 29 of 40 symptomatic patients with giardiasis. Twenty-three had impaired D-xylose absorption; in 20 vitamin B12 absorption was low, and 15 patients had steatorrhoea. More severe malabsorption was associated with more marked histological abnormalities. Metronidazole, 2-0 g as a single daily dose on three successive days, produced a parasitological cure rate of 91%. In contrast, the standard course of mepacrine, 100 mg thrice daily for 10 days, eradicated the parasite in only 63% of patients. Improvements in absorption and jejunal morphology followed anti-giardial treatment. Tetracycline in eight patients failed to eradicate the parasite, intestinal absorption was unaltered, and histological appearances of the jejunal mucosa often deteriorated.
During in vitro encystation, Giardia lamblia expresses several stage-specific proteins which are recognized in immunoblots by antisera raised against antigens from three different pathogens. The antigens belong to two different families of conserved stress proteins: (i) HSP60 purified from Legionella pneumophila and recombinant HSP60 from Mycobacterium bovis BCG and (ii) recombinant HSP70 from Plasmodium falciparum.
Giardia lamblia trophozoites demonstrate variable expression of a repertoire of cysteine-rich surface antigens in vitro and in vivo. The size of the repertoire has been estimated at 20 to 184, and specific variants can be detected after approximately 12 generations of in vitro growth for the WB isolate. In earlier studies, we cloned a portion of the gene for a 170-kDa surface antigen (CRP170) and demonstrated by DNA sequencing that it was cysteine rich (12%) and contained 2.6 copies of a tandemly repeated 195-bp pair sequence. The clone hybridized to multiple bands on a Southern blot of G. lamblia DNA in a pattern that was variable among the cloned lines but did not correlate with expression of CRP170. We have now cloned a nearly full length cDNA as well as genomic clones for CRP170 from the WBA6 cloned isolate. In addition, we have isolated a cDNA clone from the WB1269 line (expressing CRP72), an antigenic variant which was derived from WBA6. Sequence analysis of the CRP170 and CRP72 genes revealed marked C-terminal amino acid homology, suggesting a conserved functional role such as membrane anchoring. The CRP170 repeat oligonucleotide hybridized to a stairstep of bands approximately 6 kb in size on HindIII-digested WBA6 DNA representing the expressed copy(ies) of CRP170. In contrast, there was no hybridization to a fragment of similar size in WB1269, suggesting that WB1269 trophozoites have lost the expressed copy of the CRP170 gene.
Gastrointestinal immune events in giardiasis are important in controlling infection. In this study, Peyer's patch lymphocytes from mice infected with Giardia muris developed specific, proliferative responses to G. muris antigen. This proliferation correlated with clearance of infection. Further understanding of the gut immune response will be helpful in developing immunoprophylactic strategies in the control of giardiasis.
In a recent study, we identified Giardia lamblia 65- and 70-kDa antigens in the feces of infected Mongolian gerbils. The 65-kDa antigen was from a strain isolated from a human with symptoms of giardiasis, and the 70-kDa antigen was from a strain isolated from a human with no symptoms of giardiasis. In this study, we used preparative electrophoresis and electroelution techniques to purify these antigens to a degree which showed a single discrete protein band on silver-stained polyacrylamide gels. By enzyme-linked immunoelectrotransfer blot, common epitopes on the 65- and 70-kDa antigens were indicated by their cross-reactivity with rabbit anti-65-kDa and anti-70-kDa sera. By indirect immunofluorescence assay, the cysts and trophozoites of the two strains cross-reacted with these sera. Of seven lectins tested, only concanavalin A bound to the 70-kDa antigen, suggesting a glycoprotein, and it possessed a low isoelectric point as assessed by preparative isoelectric focusing. Molecular mass estimations of these antigens by sodium dodecyl sulfate-polyacrylamide gradient gel electrophoresis were similar to the 65- and 70-kDa estimations obtained by native polyacrylamide gradient gel electrophoresis. Although the 65- and 70-kDa antigens proved to be resistant to 100 degrees C heat and stable in storage for up to 25 months at -20 degrees C, neither appeared to be the same as a fecal G. lamblia antigen with similar molecular mass found by other investigators. This suggests that variable G. lamblia antigens may be found in the feces of infected humans.
The variability in duration and severity of infection with Giardia lamblia is likely to be due to trophozoite interactions with immune and nonimmune components of the small intestinal milieu. Despite its potential importance, nothing is known of the isotype or the specificity of the secretory antibody response to G. lamblia. In the present study, we show that serum and secretory antibodies recognize many Giardia antigens whose expression is induced by exposure to selected intestinal conditions. Isotype-specific immunoblots of antigens from trophozoites grown at pH 7.0 without bile or at the intestinal pH of 7.8 with bile were reacted with milk or serum antibodies from subjects with or without histories of giardiasis. While the results were complex, several key observations emerged. Serum and secretory immunoglobulin A (IgA), IgM, and IgG antibodies reacted with many regulated antigens. Antigen recognition patterns varied with isotype and between milk and serum antibodies of the same isotype. Antigen recognition also differed among subjects. Antibodies from virtually every patient recognized some G. lamblia antigens. Furthermore, milk and/or serum samples from putative controls without histories of giardiasis were positive more frequently than would be predicted from published prevalence studies, suggesting either that these antibodies may be cross-reactive or that undiagnosed infections with G. lamblia may be more common than previously thought. Thus, recognition of neoantigens induced by host conditions may be due to conserved or cross-reactive epitopes which could constitute a form of immune evasion by G. lamblia.
1.Mucosal suction biopsies from the duodenum and proximal jejunum were studied in 10 patients with documented Giardia infection. Invasion of the intestinal mucosa was demonstrated in 6 of the patients having diarrhea and trophozoites in the stool. We feel that we have established Giardia as an invasive organism in man.
2.The difficulties in identifying the organism in extraluminal sites are briefly discussed.
3.While the significance of this invasion is not as yet known, we suggest that the organism is potentially an important pathogen.
Clones of the WB isolate of Giardia lamblia were exposed to cytotoxic mAb 6E7 which reacts with a 170-kDa surface Ag. Surviving progeny occurred at a frequency of about 1 in 1000 and were resistant to the effects of mAb 6E7. Analysis of progeny and clones of these progeny by surface radiolabeling, surface immunofluorescence, and Western blotting failed to detect the 170-kDa Ag. Loss of this Ag was associated with the appearance of a series of new surface Ag. A cytotoxic mAb (5C1) was produced to one of the newly appearing antigens (approximately equal to 64 kDa) and Giardia resistant to the cytotoxic effects of 5C1 isolated. Neither the approximately equal to 64 kDa nor the 170 kDa Ag were present and were replaced by a second series of new Ag. These studies clearly establish the loss and subsequent replacement of two antigenically distinct epitopes on Giardia derived from a single organism.
Sludge produced by a model wastewater treatment plant and anaerobically digested at 37°C in a laboratory digester was seeded with G. muris cysts. Samples from the digester were collected at 0:15, 4:00, 8:00, 11:30 and 26:00 hrs. Cyst inactivation was measured by excystation and direct counts of G. muris cysts using a hemacytometer and a phase contrast microscope, The results showed that 99.9% of the cysts were inactivated within approximately 18:00 hrs of exposure. This demonstrates that the standard sludge digestion (37° C for 24 hrs) will eliminate most of the cysts (greater than 99.9%).
Athymic nude mice of the outbred Zur:ICR-nu and inbred BALB/c strain and scid mice were infected with a cloned human isolate of Giardia lamblia (GS M-83-H7). Changes in the expression of the major surface epilope of the intestinal trophozoites (characterized by the binding capacity of monoclonal antibody MoAbG 10/4) as well as cellular and humoral immune parameters of the hosts were followed during the course of infection. Self-cure was observed in hetcrozygous (nu/+) BALB/c mice by day 22 post-infection (p.i.) and in heterozygous (nu/+) Zur:ICR-nu strain by day 65 p.i. Homozygous (nu/nu) mice of both strains remained chronically infected until end of the experiments (day 45 p.i. for BALB/c mice and day 122 p.i. for Zur:ICR-nu mice, respectively). Only heterozygous (nu/+) mice were able to mount a gut-associated (Peyer's patch) lymphoproliferative response to G. lamblia antigen. Therefore, T-cell dependent mechanisms were necessary for a self-cure. Antigenic variation occurred in all nu/+ and nu/nu animals of both strains. Trophozoiles expressing the major surface epitope (assessed by direct immunofluorescence with FITC-labelled MoAb G10/ 4) decreased to zero by day 22 p.i. In contrast, the proportion of trophozoites expressing the major surface epitope in infected scid mice remained at the initial level (>99%) until termination of the experiment (day 25 p.i.); therefore, antigenie variation did not occur. All nu/nu and nu/+ mice but not scid mice demonstrated a humoral immune response to G. lamblia antigen. These experiments suggest functional B-cell dependent mechanisms are most likely responsible for the surface antigen switch. Transfer of infection occurred naturally from experimentally infected scid-mice to their mother, proving the initial antigenic surface variant remains unchanged after encystment and subsequent excystmenl followed by infection in a new host.
A portable apparatus was used to filter large quantities of water from streams in California's Sierra Nevada. Samples were processed and examined for Giardia spp. Cysts of Giardia were detected in 22 of 49 (44.9 percent) samples collected at sites downstream from areas of high recreational use and in 5 of 29 (17.2 percent) samples collected at sites downstream from areas of low recreational use. These data indicate that intensity of human use may play a significant role or be a useful indicator in Giardia contamination of surface water.
The aim of this study was to assess and correlate changes in weight gain, food intake, small intestinal disaccharidase activities and microvillous border surface area over the course of a primaryGiardia duodenalis infection in weanling Mongolian gerbils (Meriones unguiculatus). Weight gain in infected animals was significantly impaired between days 8 and 20 postinoculation when compared to age-and weight-matched controls. No difference in food intake was observed between groups. Trophozoite population in the small intestine was maximal on day 4 and 6 of infection, and colonization persisted in the duodenum throughout the experiment (30 days). In infected gerbils, mucosal sucrase and maltase activities were significantly depressed in the duodenum and jejunum on day 4 and in all areas of the small intestine by day 6. Eight and 25 days postinoculation, disaccharidase activities had recovered in the jejunum and distal small intestine but remained depressed in the duodenum, the area where trophozoite colonization persisted. Diffuse loss of microvillous border surface area was observed in the duodenum and jejunum after 6 days of infection. Eight days postinoculation, microvillus surface area had returned to normal in the jejunum, but not in the duodenum. Our findings demonstrate that acute giardiasis in weanling gerbils impairs weight gain, depresses disaccharidase activities, and diffusely reduces mucosal microvillous border surface area. The brush border injury occurred at times and sites of maximal trophozoite colonization and correlated with disaccharidase impairment. This is the first report of a diffuse mucosal injury associated with giardiasis. We postulate thatGiardia infection impairs small intestinal function by markedly decreasing microvillous border surface area and that this mechanism explains in part retarded growth and appearance of symptoms associated with the disease.
The objective of this study was to determine the incidence of Giardia lamblia acquisition in back-country travelers to a wilderness area, provide longitudinal follow-up on the incidence of symptomatic gastrointestinal illness and relate such information to concentrations of Giardia cysts in water samples from a high-use area. A prospective cohort non-interventional study of 41 healthy adult backcountry travelers from age 19 to 71 years in Desolation Wilderness, Lake Tahoe Basin was carried out.
The incidence of Giardia cyst acquisition in backcountry travelers was only 5.7% (95% CI 0.17–20.2%). Mild, self-limiting gastrointestinal illness occurred in 16.7% of subjects (95% CI 4.9%–34.50%), none of whom demonstrated G. lamblia infection. Water sampling from three popular stream sites revealed cyst contamination to be generally at low levels with cyst concentrations in the single digit range for every 100 gallons filtered. G. lamblia contamination of water occurs, but at low levels. Acquisition of this parasite may be infrequent in backcountry recreationalists. Symptomatic gastrointestinal illness following wilderness travel can be due to other etiologies. Our findings may not be representative of all wilderness areas, but suggest that in the absence of documented G. lamblia infection, persons symptomatic following travel may suffer a self-limiting gastrointestinal illness. In such circumstances, empiric therapy for giardiasis is tempting but difficult to justify.
Attachment of Entamoeba histolytica and of Giardia lamblia trophozoites to glass was monitored during the culture cycle. Attachment of each parasite was greatest during the exponential phase of axenic growth. The effects of l-cysteine upon the kinetics of attachment of trophozoites to glass were determined quantitatively. Attachment in complex growth media required cysteine, even under N2, atmosphere. With cysteine, the rates of attachment were greatest for the first 2 hr, then continued more slowly. The numbers of attached trophozoites decreased immediately upon exposure to medium without cysteine. The role of cysteine in protecting trophozoites of both species from the lethal effects of oxygen was assessed using clonal growth in agar or agarose medium to determine viability following exposure to varying oxygen tensions in liquid medium. Cysteine was required for viability of trophozoites. Without cysteine, decreasing the oxygen tension prolonged survival. Under increased oxygen tension, cysteine delayed the onset of exponential killing. Although it has no thiol reducing group, l-cystine similarly protected E. histolytica.
To understand murine host responses to extracellular protozoa, the capacity of peritoneal macrophages to exhibit Cytotoxicity for [3H]thymidine-labeled Giardia lamblia trophozoites was investigated. Resident peritoneal macrophages from C3H/HeN mice expressed spontaneous cytotoxicity for G. lamblia in a manner that was dependent on both time and effector cell number; this cytotoxic activity was increased with cells elicited by an intraperitoneal injection of thioglycollate. In contrast, spontaneous Cytotoxicity for G. lamblia by resident and thioglycollate-elicited peritoneal macrophages from C3H/HeJ mice was markedly reduced. In the presence of anti-G. lamblia serum (ADCC), however, peritoneal macrophages from both C3H/HeN and C3H/HeJ mice exhibited striking augmentation of their cytotoxic activity for G. lamblia to equivalent levels. We conclude that macrophages from C3H/HeJ mice express defective spontaneous Cytotoxicity but normal ADCC for the extracellular protozoan parasite, G. lamblia. The dissociation between the expression of these two effector cell functions suggests that macrophage spontaneous Cytotoxicity and ADCC for extracellular protozoa are mediated by separate macrophage functions.
The circulating anti-parasite antibody response against Giardia lamblia in symptomatic and asymptomatic Egyptian children with confirmed giardiasis was examined. Symptomatic patients were identified using the following criteria: presence of only G. lamblia cysts in the feces, and one or more of the following symptoms, diarrhea, abdominal pain, loss of weight, vomiting and/or nausea, and abdominal distention. The anti-parasite humoral response was measured using indirect immunofluorescence (IFA), ELISA, and immunoblotting. There was a significant difference in the anti-parasite antibody response measured by IFA of asymptomatic and symptomatic patients, in which more than 34% of the asymptomatic patients had a titer equal to or less than 1:500, and more that 29% of the symptomatic patients had a titer of 1:8,000 or higher. The circulating anti-parasite total IgM and IgA but not IgG, measured by ELISA, was significantly higher in symptomatic than in asymptomatic patients, and were related to higher cyst output observed in symptomatic individuals. Although total anti-parasite IgG response was similar in symptomatic and asymptomatic patients, the analysis of the IgG isotype responses revealed that both IgG1 and IgG3 were significantly higher in symptomatic patients. The antigen recognition by anti-parasite IgM, IgA, IgG1, and IgG3 of symptomatic and asymptomatic individuals, determined by immunoblotting, was heterogeneous and revealed only minor differences in the response of the two groups.
The common protozoan Giardia lamblia has a fecal-oral mode of transmission, usually from contaminated water or food or person-to-person contact. Infection may be asymptomatic or result in a broad spectrum of symptoms-most commonly, subacute illness that is mistaken for other gastrointestinal problems. Although most infections are self-limited, treatment is indicated due to the long duration and the risk of transmission. Several therapeutic agents are available, but none is 100% effective. Prevention for people involved in outdoor sports or recreation and for international travelers includes treatment of all surface water and rigorous personal hygiene.
CBA/N mice have an X-linked immune defect that is associated with the absence of a subpopulation of mature or late developing B lymphocytes. The effect of this B cell defect on susceptibility of mice to Salmonella typhimurium was investigated. The 50% lethal dose (LD50) of S. typhimurium for CBA/N mice was 1000-fold less than for the immunologically normal, histocompatible CBA/CaHN strain. Genetic analysis revealed that the susceptibility of the CBA/N strain to S. typhimurium, like the immune defect, was X-linked since immune-defective F1 male mice derived from crosses between CBA/N and immunologically normal strains were susceptible to S. typhimurium (LD50 ≤ 20), whereas immunologically normal F1 males and females derived from these matings were resistant (LD50 ≥ 5 × 103). By contrast, both immune-defective and normal F1 mice were resistant to another facultative intracellular parasite, Listeria monocytogenes. Deaths among the immune-defective mice occurred primarily late in the course of infection (>10 days) whereas deaths of immunologically normal, S. typhimurium-susceptible strains (e.g., C57BL/6 and BALB/c) occurred early in the infectious process. To determine if the increased susceptibility of B cell-defective mice to S. typhimurium and the expression of the X-linked immune-deficiency gene (xid) were actually linked, F2 and backcross mice were phenotyped for the immune defect by measuring serum IgM levels and then challenged with the organism. Although no formal linkage was established, there was a close correlation between low serum IgM levels and susceptibility, since 93% of such mice succumbed to infection. These studies suggest that B cells play an important role in those events that govern the development of resistance to S. typhimurium late in the course of infection.
The purpose of this article is to demonstrate that mice subjected to continuous injections with anti-IgM antibodies, initiated within one day of birth, or in adulthood, lose all their B lymphocyte functions, but retain T lymphocyte reactivity. The B lymphocyte status of these mice was analyzed by histology, radioautography, serum immunoglobulin levels, the antibody response and reactivity to LPS in vitro. T lymphocyte functions were evaluated in vivo by tumor allograft rejection, contact sensitization, and in vitro by reactivity to mitogens and allogeneic cells. On the basis of the results described, it is suggested that the anti-IgM-treated mouse may be considered as a balid and useful experimental model of the "T mouse".
Organisms in the genus Giardia are widely distributed, flagellated protozoan parasites of all classes of vertebrates. Giardia is an intestinal protozoan parasite of humans.. Under appropriate conditions, they can cause disease. This chapter summarizes the progress in the study of Giardia and its relation with its host. Studies in this regard have resulted in a number of developments, most occurring within the past decade. These include (1) information regarding the nature of Giardia infection and disease, the host–parasite interaction, and the development of a mouse model of disease; (2) their axenic cultivation and the determination of conditions for excystment; (3) information regarding their spread via water, via sexual contact, and from one animal species to another; (4) data regarding the role of the immune system in affecting host susceptibility to these organisms and the possibility of severe disease in immunodeficient individuals; (5) recognition of the frequent difficulty in detecting this parasite, the introduction of a new method of obtaining trophozoites from the patient, and efforts to diagnose the infection immunologically; and (6) the demonstration that some Giardia infections are not eradicated with presently recommended drugs.
Infected immunocompetent mice were studied prospectively in a well-described murine model system with the use of ultrastructural techniques to establish normal distribution of Giardia muris trophozoites, their relationships to intestinal mucosa, particularly Peyer's patches, and structural indications of the normal reaction of intestine and intestinal immune organs. Trophozoites colonized the proximal 25% of the intestine, adhered to microvilli of columnar cells near the bases of villi, wedged into furrows in the epithelial surface, or lodged in mucus within the unstirred layer. Density of trophozoite colonization of the jejunal epithelium correlated with stool cyst excretion. Over Peyer's patches, Giardia adhered to columnar cells and not to M-cells, which transport soluble antigens and particulate material from the lumen into the lymphoid system. Giardia entered intestinal lymphoid structures by incursions through defects in the lymphoid follicle epithelial barrier. During clearance of parasites, lymphocytes crossed the epithelium and attached to Giardia in the lumen. Giardia produced no apparent ultrastructural damage in normal mice but elicited a previously undescribed intraluminal cellular immune response during clearance by the host.
The effects of chronic protozoal infection on small intestinal architecture have been examined in mice, infected with Giardia muris and Hexamita muris. Techniques used were conventional histology, quantitation of intraepithelial lymphocytes, microdissection and measurement of individual villi and crypts, and epithelial cell kinetic studies. The histology of small intestine from infected mice appeared normal apart from the intraepithelial lymphocyte numbers. Mean intraepithelial lymphocyte counts in two groups of uninfected mice were 11.6 and 13.6 per 100 epithelial cells, and in two groups of infected mice were 17.6 and 21.8. Dynamic studies showed that protozoal infection doubled the cell production per crypt per hour from mean values of 6.2, 7.3, and 8.2 in three groups of uninfected animals, to 11.8, 13.4, and 17.1 in groups of chronically infected mice. Cell production per villus was also influenced by protozoal infection, with values of 93, 99, and 101 cells per hr in groups of uninfected animals whereas in infected mice the values were 155, 162, and 180 cells per hr. Although there was no reduction in villus height in the infected animals, radioautography using [3H]thymidine confirmed that the enterocytes moved rapidly up the sides of the villi than was the case for uninfected mice.
Infection of normal mice by the intestinal protozoan Giardia muris is self-limited and is followed by resistance to subsequent reinfection (1, 2). Similar observations have been made in G. lamblia infection in limited studies in human volunteers (3). The nature and mechanism of this parasite elimination are, however, unclear. Immune mechanisms may be suspected in human infection with G. lamblia because of the high prevalence of chronic giardiasis in persons with variable immune deficiency syndrome (4). Congenitally hypothymic (nude, nu/nu) mice provide a useful model to test the contribution of thymus-dependent immune mechanisms in resolution of this protozoan infection. We have previously described the natural history of G. muris infection in mice (1). The infection can be measured by counting trophozoites in small intestine and cysts in feces; peak fecal cyst excretion occurs 1 to 2 weeks after oral inoculation of cysts in CF-1 outbred mice and in A/J and BALB/c inbred strains followed consistently by resolution of infection in 4 to 7 weeks (1, 2).
In an outbreak of giardiasis at two day-care nurseries in metropolitan Toranto Giardia lamblia appeared to be transmitted person to person. No common source of infection could be found. The proportions of children infected in the two nurseries were 39% and 17%; infection was spread to 7% and 23% of their household contacts. Of the infected children and household contacts 26% and 30% respectively of those for whom detailed information could be obtained were symptomatic. Canadian children were more likely to be infected and symptomatic than were immigrant children attending the nurseries. The most susceptible ages for infection were 1 to 3 years. The results of this study suggest that all children in day-care nurseries who are infected with G. lamblia should be treated, regardless of whether they are symptomatic.
The number of plaque-forming cells (PFC) per spleen is reduced in mice experimentally infected with 200 Trichinella larvae at 14 and 28 days after infection, whereas no difference is shown at days 7 and 56. The worms of the three different phases of the life cycle of Trichinella have been isolated and kept alive in vitro at 37 degrees in the inner compartment of a Marbrook chamber. The outer compartment of the chamber contained normal spleen cells and sheep erythrocytes. After 4 days, the spleen cells were removed and assayed for PFC. The results indicate that the new-born larvae are capable of producing substances which can diffuse through a Millipore filter and affect the spleen cells forming antibody to sheep erythrocytes. The suppression of antibody to sheep red blood cells in mice infected with Trichinella is a transitory phenomenon and can be related to the migrating phase of the life cycle of the parasite.
Epidemic Giardia lamblia infection has usually been associated with contaminated water. In this paper, five proved and one presumed case of G. lamblia infection among homosexual men are reported. The sequential onset of their clinical illnesses and their sexual interrelationships suggest that this outbreak could have been caused by the direct faecal-oral transmission of G. lamblia. Other parasitic diseases with possible venereal transmission have been described, and parasitic diseases should be considered in homosexual men with diarrhoea or other gastrointestinal symptomatology.
Thirty-four of 54 campers on a 2 week trip in mountains of Utah had diarrhea during and after their trip. Twenty-two (79%) of 28 symptomatic campers' stools examined contained Giardia lamblia cysts, whereas 4 (29%) of 14 asymptomatic campers' stools had cysts. The temporal distribution of cases and the absence of clustering among food preparation subgroups suggested a common source exposure. Although the epidemiologic data and fecal coliform counts implicated the remote mountain stream used as water source by the group as the vehicle of transmission, Giardia lamblia cysts were not recovered from stream water nor were they found in intestines or feces of sampled mammals living in the drainage area. Twenty-five other campers had stools examined before and after a subsequent hiking trip in another area of Utah; none had Giardia cysts before, but 6 (24%) had them after return. Questionnaires returned by 133 of the campers showed that 5% had an illness compatible with giardiasis within 2 weeks after their trip. These surveys show that campers exposed to mountain stream water are at risk of acquiring giardiasis.
Infection of the gastrointestinal tract with the protozoan Giardia lamblia is increasingly recognized as a cause of gastrointestinal symptoms, including diarrhea and malabsorption (1–3). Indeed it was the most frequently identifiable cause of water-borne diarrhea in the United States in 1974 (4). Studies of jejunal morphology and function have shown a spectrum of change from normal mucosa with unaltered small bowel absorption to severe mucosal lesions with steatorrhea (1, 5).
The mechanisms that protect man from infection with G. lamblia are largely unknown. Although some persons show spontaneous resolution of infection (6) others may show persistent symptoms for months or years (7). Reports of giardiasis in children with protein-calorie malnutrition (8, 9) and in adults after gastrectomy (5) suggest that susceptibility to infection might be influenced by nutritional factors and changes in gastrointestinal physiology. On the other hand, the importance of normal host immunity is suggested by the high frequency of giardiasis in persons with hypogamma-globulinemia (10, 11).
An immunofluorescent test, using Giardia lamblia cysts as antigen, gave positive results in 32/36 cases of giardiasis with malabsorption, 0/2 cases of giardiasis without malabsorption, and 0/17 control patients without giardiasis or malabsorption. The test was positive in 10/34 patients with malabsorption in whom G. lamblia could not be detected by stool examination or biopsy; some of these cases were presumed to be cryptic giardiasis. There was a crude correlation between antibody titre and the severity of the histological lesion in the jejunum. The finding of a reliable source of antigen remains a problem.
An animal model for giardiasis was developed using Giardia muris in Swiss albino mice. Intraesophageal inoculation of G. muris cysts caused a reproducible pattern of infection, with trophozoite and cyst counts reaching a maximum on days 5 to 14 after cyst inoculation and thereafter showing a progressive decline. Spontaneous resolution of infection occurred in most mice after 21 to 28 days. When compared to uninfected controls, Giardia-infected mice had significant impairment of weight gain and a significant reduction in the villus to crypt ratio of jejunal mucosa. Although maximal trophozoite and cyst counts were independent of the size of the cyst inoculum, those mice receiving inoculations of larger numbers of cysts showed earlier attainment of maximal counts, greater impariment of weight gain, and earlier and more severe small bowel changes than mice receiving inoculations of smaller numbers of cysts. This model offers unique opportunities for study of this poorly understood gastrointestinal parasite.
Prior systemic-oral immunization of inbred mice with Giardia lamblia surface-associated antigen of molecular mass 56 kDa not only significantly blocked colonization but also resulted in elimination of G. lamblia trophozoites by 9-11 days following challenge. The colonization and multiplication of the trophozoites in unprotected animals were accompanied by a pronounced influx of suppressor T cells in intraepithelial or lamina propria of the small intestine and a significant decline in IgA-bearing plasma cells in the lamina propria. An induction of helper/inducer T cells in the intraepithelial and lamina propria and significant enhancement of IgA and IgG-bearing cells in the lamina propria of the small gut resulted in a decline, and eventual elimination, of the trophozoites from the gut. The completion of the immunization of animals with 56 kDa G. lamblia antigen resulted in: significant enhancement of helper/inducer T lymphocytes with no effect on suppressor T cells in the intraepithelial and lamina propria of the small gut; significant enhancement of IgA- and IgG-bearing plasma cells in lamina propria; and significant elevation of antibodies to 56 kDa G. lamblia antigen in the systemic circulation. The stimulation of such effector mechanisms in 56 kDa-immunized animals appears to result in failure of the trophozoites to get established, prevention of multiplication and earlier elimination from the gut. The data suggest that the 56 kDa molecule of G. lamblia immunoregulates the giardial infection.
In one of the largest outbreaks of waterborne giardiasis reported from Europe, more than 3000 persons were exposed to contaminated water and over 1400 cases of giardiasis were diagnosed by microscopy. The outbreak resulted from an overflow of sewage water into the drinking water system of a Swedish ski resort. The period of contamination was about 1 week. Sweden is a non-endemic area for Giardia lamblia infection and, for most individuals affected, this was their first contact with the parasite. Few other enteropathogens were isolated from the patients involved. Therefore, an immune response to Giardia was unlikely to be biased by other concomitant infections. Serum samples from 352 exposed persons were collected and analysed for specific IgG and IgA antibodies to G. lamblia by indirect immunofluorescence and the results were related to the microscopic examination of faeces and the occurrence of diarrhoea. As controls, sera from 428 healthy persons were analysed at the same time by identical methods. IgG or IgA antibodies, or both, were found in 68% of patients whose diagnosis was made by microscopy, and in 22% of exposed by microscopically Giardia-negative persons, but in only 10% of healthy controls. The findings show that patients reported as negative for parasites might be infected. The time between infection and blood sampling influenced the result of the antibody test. The results suggest that stool examination should be the primary means of diagnosis of G. lamblia infection and that serological analysis performed at least 3 weeks after infection could contribute to diagnosis in a non-endemic region, when giardiasis is suspected but the parasite has not been detected.
Giardia lamblia undergoes surface antigenic variation. The capability of different isolates to express certain epitopes on the surfaces of trophozoites from different isolates and clones was determined using 4 surface-reacting monoclonal antibodies (mAbs) to variants derived from WB or WB-like Giardia (mAbs 6E7, 5C1, and 3F6) and GS/M (mAb G10/4). Of 28 isolates, 11 possessed trophozoites reactive with mAbs 6E7, 5C1 and 3F6, 6 with mAb 3F6, 2 with Mab G10/4, 1 with mAb 6E7, and 8 showed no reactivity as determined by direct or indirect immunofluorescence. Newly established clones from different isolates generated small numbers of reactive trophozoites similar to their parents. Only one epitope was found on any single trophozoite. Southern blots hybridized to a probe encoding for the epitope recognized by mAb 6E7 revealed that the inability to express the antigen in most isolates was due to lack of the gene. Analysis of the surface antigens of mAb 6E7 reactive clones from 3 isolates revealed that mAb 6E7 reacted with surface antigens of different molecular masses.
Giardia lamblia undergoes antigenic variation. The rate of antigenic variation and the size of the variant antigen repertoire were estimated in clones of Giardia lamblia which reexpresses surface variant antigens that are characteristics of its parent. Calculations were based on determinations of the number of trophozoites expressing defined or nondefined epitopes as well as the total number of trophozoites in newly established clones. The rate of appearance of variant antigens containing defined epitopes was expressed as the number of generations until the first trophozoite expressing a defined epitope appeared. In clones of isolate WB, tested because their major surface variant antigens were largely nondefined, variants expressing epitopes recognized by Mabs 6E7 or 3F6 appeared after approximately 12 generations. Variants expressing epitopes recognized by Mab 5C1 appeared at about 13 generations, significantly greater than for the other epitopes. The rate of antigenic variation was studied in another isolate, GS/M, whose surface epitope repertoire differs from that of isolate WB. A single epitope recognized by Mab G10/4 was tested. Trophozoites reexpressing this epitope first appeared after about 6.5 generations, significantly less than in WB. Therefore, the single epitope studied in isolate GS/M is reexpressed much more frequently than those of WB. In isolate WB, the epitopes recognized by Mab 6E7 and 3F6 tended to appear at the same time. The median number of variant antigens in WB was estimated to lie between 20.5 and 184.
Neonatal mice (CR:NIH:S) were infected with a cloned human isolate of Giardia lamblia (GS/M-83-H7) and the surface antigens of the intestinal trophozoites, as well as the cellular and humoral immune responses, were analysed during the course of infection. Infections in mice peaked 2-3 weeks after inoculation and were self-cured by day 42 post-infection (p.i.). The proportion of trophozoites expressing the Mr 72,000 surface antigen of the initial inoculum had decreased by day 12 and approached zero by day 22 p.i., similar to infections in humans. The predominant parasite-specific humoral response was an IgM- and IgG-isotype directed to the original Mr 72,000 surface antigen as well as other antigens. T-lymphocytes (predominantly LY4(CD4)+) isolated from Peyer's patches 12 days p.i. and later showed a significant proliferative response to Giardia lamblia antigens. Spleen and lymph node cells showed no lymphoproliferative response. T-cell blot analysis revealed the presence of dominant T-cell epitopes in the areas of Mr 200,000-75,000 and less than 50,000 polypeptides. No response was demonstrated in the Mr 72,000 region (migration site of the major surface antigen), suggesting T-cell dependent mechanisms are most likely not responsible for the surface antigen switch which occurred during the course of infection. This model infection can be used to study the role of immunological mechanisms in Giardia lamblia variant antigen switching and in the control of infections.
Athymic nude mice of the outbred Zur:ICR-nu and inbred BALB/c strain and scid mice were infected with a cloned human isolate of Giardia lamblia (GS/M-83-H7). Changes in the expression of the major surface epitope of the intestinal trophozoites (characterized by the binding capacity of monoclonal antibody MoAbG10/4) as well as cellular and humoral immune parameters of the hosts were followed during the course of infection. Self-cure was observed in heterozygous (nu/+) BALB/c mice by day 22 post-infection (p.i.) and in heterozygous (nu/+) Zur:ICR-nu strain by day 65 p.i. Homozygous (nu/nu) mice of both strains remained chronically infected until end of the experiments (day 45 p.i. for BALB/c mice and day 122 p.i. for Zur:ICR-nu mice, respectively). Only heterozygous (nu/+) mice were able to mount a gut-associated (Peyer's patch) lymphoproliferative response to G. lamblia antigen. Therefore, T-cell dependent mechanisms were necessary for a self-cure. Antigenic variation occurred in all nu/+ and nu/nu animals of both strains. Trophozoites expressing the major surface epitope (assessed by direct immunofluorescence with FITC-labelled MoAb G10/4) decreased to zero by day 22 p.i. In contrast, the proportion of trophozoites expressing the major surface epitope in infected scid mice remained at the initial level (greater than 99%) until termination of the experiment (day 25 p.i.); therefore, antigenic variation did not occur. All nu/nu and nu/+ mice but not scid mice demonstrated a humoral immune response to G. lamblia antigen. These experiments suggest functional B-cell dependent mechanisms are most likely responsible for the surface antigen switch. Transfer of infection occurred naturally from experimentally infected scid-mice to their mother, proving the initial antigenic surface variant remains unchanged after encystment and subsequent excystment followed by infection in a new host.
Phagocytosis of Giardia lamblia trophozoites by cytokine-activated and non-activated bone marrow-derived macrophages was examined in vitro. Macrophages treated with recombinant interferon-gamma (IFN-gamma) and bacterial lipopolysaccharide (LPS) ingested a significantly higher number of in vitro-grown trophozoites than untreated macrophages. Maximal uptake of parasites occurred after 4 h and 6 h of incubation where 81.4% and 79.1% of macrophages were positive for trophozoites. Other cytokines tested, IL-2, IL-3, IL-4, IL-5, GM-CSF, CSF-1 and tumour necrosis factor-alpha (TNF-alpha) either alone or in combination with LPS, failed to activate macrophages to phagocytose G. lamblia. The induction of this activated macrophage anti-microbial function was achieved pharmacologically using phorbol myristate acetate (PMA) and ionophore A23187. The giardicidal activity of macrophages activated with IFN-gamma and LPS or that induced by PMA and A23187 was inhibited by H-7, indicating the role for protein kinase C in the intracellular events following activation.