The American journal of tropical medicine and hygiene

Published by American Society of Tropical Medicine and Hygiene
Online ISSN: 1476-1645
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Article
Cholera outbreak following the earthquake of 2010 in Haiti has reaffirmed that the disease is a major public health threat. Vibrio cholerae is autochthonous to aquatic environment, hence, it cannot be eradicated but hydroclimatology-based prediction and prevention is an achievable goal. Using data from the 1800s, we describe uniqueness in seasonality and mechanism of occurrence of cholera in the epidemic regions of Asia and Latin America. Epidemic regions are located near regional rivers and are characterized by sporadic outbreaks, which are likely to be initiated during episodes of prevailing warm air temperature with low river flows, creating favorable environmental conditions for growth of cholera bacteria. Heavy rainfall, through inundation or breakdown of sanitary infrastructure, accelerates interaction between contaminated water and human activities, resulting in an epidemic. This causal mechanism is markedly different from endemic cholera where tidal intrusion of seawater carrying bacteria from estuary to inland regions, results in outbreaks.
 
Article
Calling population the most important health problem in the world (with nutrition 2nd tuberculosis 3rd and malaria 4th) the role of infant and child mortality in fertility is examined. Excess of births over deaths is greatest in poor countries which are expected to increase 66% by the year 2000. Even if birthrates decline by 15 or 20/1000/year by the year 2000 world population would still reach 10 billion by the end of the 21st century. One of the strongest factors in this increase is the desire for surviving sons coupled with high infant and child mortality. In a study in the Punjab area of India it was found nearly 40% of live-born children die before their mothers reach age 45 53% of families have lost 2 or more children while 36% of high cast and 67% of low cast families have lost 3 or more and women age 45 or more averaged 7.5 live births with 4.7 surviving children. He recommends revising priorities to attack problems affecting large numbers of people in developing countries devoting more resources to common illnesses which hold people to low levels of productivity such as trachoma and make fertility control services an integral part of basic health care for all families regardless of socioeconomic status.(GR BBB: Dept. of Population Sciences)
 
Pharmacokinetic regression modeling comparison of intravenous bolus with non-compartmental analysis (dashed line), short-term intravenous infusion with non-compartmental analysis (dotted line), and short-term intravenous infusion with compartmental analysis (solid line) (raw data from volunteer ART5-018 after single intravenous AS at 8 mg/kg). 
Mean plasma concentration-time profiles of AS (top) and DHA (bottom), an active metabolite of AS measured by LC-MS/MS after a single intravenous dosage with a 2-minute short-term infusion of AS at 0.5, 1, 2, 4, and 8 mg/kg in healthy volunteers ( N = 6 for each dose cohort). 
Correlations ( r 2 = 0.969-0.997) are shown between single intravenous doses and C max or AUC with AS or DHA, an active metabolite from AS. A , Mean samples (markers) were taken from C max of AS. B , Mean values were taken from AUC of AS. C , Mean samples were taken from C max of DHA. D , Mean values were taken from AUC of DHA in all dose groups after AS single treatments at 0.5, 1, 2, 4, and 8 mg/kg. The line represents linear repression whose statistical parameters are shown in the inset ( A-D ). 
Article
The pharmacokinetics of good manufacturing process injection of artesunate (AS) were evaluated after single doses at 0.5, 1, 2, 4, and 8 mg/kg with a 2-minute infusion in 40 healthy subjects. Drug concentrations were analyzed by validated liquid chromatography and mass spectrometry system (LC-MS/MS) procedures. The drug was immediately converted to dihydroartemisinin (DHA), with elimination half-lives ranging 0.12-0.24 and 1.15-2.37 hours for AS and DHA, respectively. Pharmacokinetic model-dependent analysis is suitable for AS, whereas DHA fits both model-dependent and -independent methods. Although DHA concentration was superior to that of AS with a 1.12-1.87 ratio of area under the curve (AUC)(DHA/AS), peak concentration of AS was much higher than that of DHA, with a 2.80- to 4.51-fold ratio of peak concentration (C(max AS/DHA)). Therefore, AS effectiveness has been attributed not only to its rapid hydrolysis to DHA, but also to itself high initial C(max).
 
Article
To determine the role of Vibrio cholerae as a cause of diarrheal illness in Cancun, Mexico, an investigation was conducted in July and August 1983. Although toxigenic V. cholerae 01 were not found, non-01 V. cholerae were isolated from 22 (16%) of 134 stools from persons with diarrheal illness and none of 22 stools from well persons; 58 (92%) of 63 sewage samples; 12 (86%) of 14 untreated well water samples; a home storage tank for treated water; and 5 (21%) of 24 samples of raw seafood. None of the V. cholerae isolates from patients were toxigenic. The illness occurred mainly in small children, and were characterized principally by diarrhea and abdominal pain. No patient was seriously ill, and all recovered without sequelae. Seven different serotypes of non-01 V. cholerae were isolated from the stool specimens, and Smith serotype 12 accounted for 10 (46%) of the 22 isolates. A matched-pair case-control study found that cases were more likely than controls to have eaten home prepared gelatin (P = 0.03, OR = 5/0) and seafood (P = 0.06, OR = 4/0).
 
Article
Of 115 patients with symptomatic intestinal amebiasis, 56 were treated with Ro 7-0207 and 59 with metronidazole in a double blind study. Results of treatment were similar in the two groups and side effects were of low intensity except in one patient who received Ro 7-0207 and developed numbness of hands and tongue, difficulty in speaking, and headache. These symptoms disappeared after termination of treatment.
 
Demographic characteristics of subjects 
HLA antigen frequencies in study subjects 
Odds ratios for severe malaria and HLA-DRB1*04 
Distribution of HLA-DRB1*04 in human populations* 
Article
Several associations between specific HLA alleles and susceptibility or resistance to Plasmodium falciparum malaria have been previously reported, but no associations have been confirmed in multiple populations. We studied associations between HLA-A, -B, and DRB1 alleles and severe malaria in northern Ghana. We analyzed HLA-DRB1*04 in 4,032 subjects from a severe malaria case-control study, 790 severe malaria cases, 1,611 mild malaria controls, and 1631 asymptomatic controls. The presence of HLA-DRB1*04 was associated with severe malaria (OR = 2.42, 95% CI = 1.64, 3.58). The allele frequency of DRB1*04 was similar in the two major ethnic groups in the study population, Kassem (4.4%) and Nankam (4.7%), and the OR for the association between DRB1*04 and severe malaria was similar in both ethnic groups. These findings are consistent with results from Gabon suggesting that DRB1*04 is a risk factor for severe malaria.
 
Article
The pharmacokinetics of the filaricidal benzimidazole compounds UMF-078 and UMF-289 were evaluated in beagle dogs experimentally infected with Brugia pahangi. Twenty-four infected microfilaremic beagles were selected and randomly allocated into 4 treatment groups of 6 dogs each: oral (PO) UMF-078, PO UMF-289 (the HCl salt form of UMF-078), intramuscular (IM) UMF-078, and untreated controls. Equivalent doses of 50 mg/kg of the free base were given twice a day for 3 days to the 3 groups of treated dogs. Oral absorption is rapid compared with IM dosing; the absorption half-life (K01-HL) for the IM treatment is approximately 14 hr compared with 1 and 2 hr for the PO regimen of salt and free base forms, respectively. The elimination half-lives (K10-HL) for the PO regimens are 13 and 15 hr for the salt and free base forms, respectively. Because of sustained absorption following IM dosing, the K10-HL is prolonged. In contrast to oral administration, IM dosing of UMF-078 provides sustained, relatively low plasma drug levels, with good tolerance and efficacy.
 
Article
Strongyloidiasis, a human intestinal infection with Strongyloides stercoralis, is difficult to treat with drugs. The factors influencing this phenomenon remain unclear. To determine the host factors involved in response to treatment, 46 patients with strongyloidiasis were treated with albendazole, followed-up for 1 year, and separated into two groups: cured and non-cured. Serum levels of specific IgA, IgE, IgG, IgG1, and IgG4 antibodies were estimated using S. stercoralis antigen. Significantly higher titers of IgG4 antibody were observed in the non-cured group than in the cured group (P = 0.016). A total of 88 patients were typed for HLA-DRB1 alleles and analyzed for serum levels of antibody. The S. stercoralis-specific IgG4 antibody titers were significantly higher in the HLA-DRB1*0901-positive group than in the negative group (corrected P = 0.044). These results suggest that HLA-DRB1*0901 is a possible genetic marker for resistance to treatment of S. stercoralis that is associated with elevation of S. stercoralis-specific IgG4 antibody titer.
 
Article
Paracoccidioidomycosis has been known for over 100 years, and until now, there were only few estimates of the disease's incidence. We aim to analyze 1,000 cases treated between 1960 and 1999 at Ribeirão Preto city, São Paulo, Brazil, where the disease's incidence range detected was 1.6 to 3.7 cases per 100,000 habitants per year (mean = 2.7 cases/year). We observed a male to female ratio of 6:1 and an age distribution from 3 to 85 years. The acute/subacute form of the disease accounted for 25.4% of cases. Most of the patients (93.5%) had lived or worked in rural areas before the disease development. Smoking and alcoholism were reported by 64.7% and 37.2% of patients, respectively. Comorbidities identified included tuberculosis (8.3%), Chagas' disease (8.6%), and human immunodeficiency virus/acquired immunodeficiency syndrome (4.2%). The present study revealed an area in Brazil where paracoccidioidomycosis is hyperendemic (has the highest reported incidence of this disease); this endemic area is probably caused by geological and climatic conditions as well as intensive agriculture.
 
Article
A serologic survey was carried out to demonstrate the present distribution of antibodies to certain arboviruses in Egypt. An examination of serum specimens from 1,113 male university students from different localities of Egypt showed that West Nile, phlebotomus fever, and Sindbis viruses are endemic, having overall prevalence rates of 50%, 23%, and 6%. The geographic distribution of West Nile and Sindbis viruses was identical, and dissimilar to that of the ecologically different phlebotomus fever virus. The prevalence of West Nile and Sindbis viruses has decreased from that reported 10 to 15 years ago, whereas that of phlebotomus fever remained unchanged. No antibodies were detected to eastern equine encephalomyelitis, western equine encephalomyelitis, or Bunyamwera virus. Only four serum samples (0.3%) were positive for dengue 1 virus.
 
Article
The aim of this study was to assess the utility of ultrasonography in a rural African hospital in Cameroon with scarce resources. A prospective questionnaire was administered and completed for each of the 1,119 consecutive cases included in the study. Among these 1,119 cases, the diagnosis made by clinicians and by echography could be verified by another means for 323 patients. Ultrasonography showed abnormal findings in 78% of the cases. In the group of 323 patients in which the diagnosis made by echography could be verified, it was correct in 95.4% of the cases, erroneous in 4.6% of the cases, judged useful for diagnosis in 67.8% of the cases, and not contributive in 27.6% of the cases. Ultrasonography was judged useful when treatment was decided upon in 62% of the cases. This study demonstrated the value of ultrasonography in the context of a developing country and the conditions by which its use could be delineated.
 
Article
The synthesis of CI-501 is described. The drug was examined in mice and monkeys for potential value as a repository antimalarial substance. The dihydrotriazine moiety of CI-501 as the hydrochloride was tested in mice for background purposes. Activity was assessed on the basis of the period of protection against patent infections afforded by a parenteral dose prior to challenge with blood stages of Plasmodium berghei or P. cynomolgi. The duration of protection was directly related to the amount of CI-501 injected. Protection of mice ranged from 1 to 9 weeks with a subcutaneous dose of 50 to 660 mg/kg. In monkeys, protection ranged from 5 weeks to more than 94 weeks with an intramuscular or subcutaneous dose of 38 to 400 mg/kg. A gradual but strong therapeutic response in monkeys with patent infections was induced by 50 mg/kg intramuscularly. The doses used in mice and monkeys were well-tolerated, locally and systemically. Corroborative evidence of a slow and sustained release of the active moiety from the injection site is cited from chemical tests, microbiological assays, and dialysis studies in rats. The results of this first report on CI-501 encourage further study of it as a repository antimalarial drug.
 
Article
This report deals with the activities of a pamoate salt of the triazine metabolite of chlorguanide (CGT·P) against experimental infections with Plasmodium cynomolgi, with special emphasis on sporozoite-induced disease. The major objectives of the study were: (1) to determine the duration of protection afforded by a single dose of CGT·P against repeated challenge with massive doses of sporozoites; (2) to ascertain whether resistance of the plasmodia to chlorguanide triazine (CGT) develops during the protective period, especially in its terminal phases; (3) to determine whether CGT·P acts in effect as a “prophylactic” or merely as a long-term suppressive; and (4) to compare the rapidity of clearance of established parasitemias in recipients of CGT·P with the rates of parasite clearance achieved by the water-soluble hydrochloride salts of CGT and chlorguanide (CG). The results of these explorations have led to the following conclusions: (1) A single 50 mg per kg dose of CGT·P confers protection against repeated sporozoite challenges for at least 6 months and in isolated cases for 11 to 15. (2) When breakthroughs do occur, the parasites which appear exhibit no evidence of resistance to CGT. (3) CGT·P administered in an appropriate doseacts as an effective “prophylactic” against challenge with a massive dose of sporozoites. (4) Parasite clearance in established infections is as rapid in recipients of a single 50 mg per kg dose of CGT·P as it is when conventional daily doses of the hydrochlorides of CGT and CG are administered. The significance of the above findings for control of human malarias is discussed as are some of the problems which must be dealt with before the full potential of CGT·P can be realized.
 
Article
We have concluded initial preclinical studies with synthetic trioxanes numbered 3-9 and have compared them with artemisinin (numbered 1) using CD-1 mice infected with Plasmodium berghei. Based on their antimalarial effectiveness in mice, two of these synthetic trioxanes were selected for evaluation in Aotus monkeys infected with multidrug-resistant (MDR) P. falciparum. Trioxane numbered 8 (12 and 48 mg/kg), trioxane numbered 9 (12 and 48 mg/kg) and arteether (numbered 2, 48 mg/kg) were administered intramuscularly in three 12-hr doses to A. lemurinus lemurinus (Panamanian owl monkeys) infected with the Vietnam Smith/RE strain of P. falciparum and monitored for parasitemia. Trioxane numbered 8 at 12 mg/kg cleared parasitemia in two monkeys, but recrudescence occurred in one animal. Treatment of the recrudescent infection with 48 mg/kg was curative. Infections in two monkeys treated initially with 48 mg/kg were cured (six-month follow-up). Trioxane numbered 9 produced a similar outcome: 12 mg/kg suppressed parasitemia in two monkeys but was not curative; however, 48 mg/kg cured infections in all four monkeys treated. These preliminary observations show synthetic trioxanes numbered 8 and 9 to be as effective as arteether (numbered 2) against MDR in P. falciparum in the Aotus monkey.
 
Effect of chalcone derivatives on motility of worms 
A , Structure of diethylcarbamazine (DEC). B , The proposed Michael-type addition of glutathione to chalcones mediated by glutathione-S-transferase. 
In vivo and in vitro effect of chalcone derivatives on S. cervi GST activity Compound Activity (U/mL)* In vivo percent activation † Activity (U/mL)* In vitro percent inhibition ‡ 
GSH level in S. cervi treated with chalcone derivatives 
Article
Chalcone derivatives were evaluated for their antifilarial activity on Setaria cervi using glutathione-S-transferase (GST) as a drug target. The compounds 1-(4-benzotriazol-1-yl-phenyl)-3-(4-methoxyphenyl)prop-2-en-1-one (5), and 3-(4-methoxyphenyl)-1-(4-pyrrolidin-1-yl-phenyl) prop-2-en-1-one (7) showed a significant suppression (P < 0.01) in GST activity of adult female parasite extract at 3 microM concentration in vitro. However, GST activity was detected along with depletion in GSH level. Except Compounds 1 and 2, all exhibited a significant effect on the motility and viability of adult parasites. Compounds 3-(4-chlorophenyl)-1-(4-piperidin-1-yl-phenyl)prop-2-en-1-one (3), 1-(4-benzotriazol-1-yl-phenyl)-3-(4-methoxyphenyl)prop-2-en-1-one (5), and 3-(4-methoxyphenyl)-1-(4-pyrrolidin-1-yl-phenyl) prop-2-en-1-one (7) exhibited major irreversible effects on viability and resulted in parasite death and also inhibited the GST activity by 84-100% in vitro. We report for the first time the antifilarial activity of chalcones on GST of adult parasites. This study also strengthens our previous findings where GST is reported as a potential drug target for antifilarials.
 
Article
The efficacy of oxantel pamoate (1, 4, 5, 6-tetrahydro-2-[trans-3-hydroxystyryl]-1-methyl pyrimidine pamoate) was evaluated in 25 children with severe Trichuris infection. The presence of chronic dysentery and sigmoidoscopic demonstration of whipworms in the intestinal mucosa were the criteria for inclusion in the trial. Most of these patients had severe anemia, rectal prolapse, digital clubbing, hypoproteinemia, and growth retardation. There were a high incidence of concomitant parasitism with other intestinal helminths and with Entamoeba histolytica and Giardia lamblia. Sigmoidoscopic grading of Trichuris load and egg count in the feces were carried out prior to treatment and 2 days after each course of oxantel therapy. Oxantel was administered at a dose of 10 mg/kg body weight twice daily for a 3-day course. Satisfactory response, as judged by relief of dysentery and absence of whipworms from the mucosa at sigmoidoscopy, was achieved in 17 patients after the first course and in the remaining 8 patients after a second course of oxantel. The drug was well tolerated and no side effects were noted during or after treatment. It is concluded that oxantel is a safe and effective anthelmintic for severe clinical trichuriasis.
 
Article
We studied 1,629 febrile patients from a rural area of Malaysia, and made a laboratory diagnosis in 1,025 (62.9%) cases. Scrub typhus was the most frequent diagnosis (19.3% of all illnesses) followed by typhoid and paratyphoid (7.4%); flavivirus infection (7.0%); leptospirosis (6.8%); and malaria (6.2%). The hospital mortality was very low (0.5% of all febrile patients). The high prevalence of scrub typhus in oil palm laborers (46.8% of all febrile illnesses in that group) was confirmed. In rural Malaysia, therapy with chloramphenicol or a tetracycline would be appropriate for undiagnosed patients in whom malaria has been excluded. Failure to respond to tetracycline within 48 hours would usually suggest a diagnosis of typhoid, and indicate the need for a change in therapy.
 
Article
An outbreak of classical dengue fever occurred from March to August 1988 in the city of Taxco, Guerrero State, Mexico. Taxco is at an elevation of 1,700 meters above sea level, and this study represents the highest altitude at which an outbreak of dengue has been documented. An investigation was conducted to obtain serologic confirmation of dengue infection, determine the extent of the outbreak, and identify risk factors for dengue illness. Toxorhynchites cell lines were used for viral isolation, and hemagglutination inhibition was used to measure anti-dengue antibody titers. The case definition used in the investigation was any person with fever, headache, myalgias, and arthralgias, or rash or retroocular pain. Dengue virus type 1 was isolated from five acute cases. Of 1,686 persons living in the affected area, 42% (715) met the case definition. Large (200-liter) water containers were significantly associated with infection (relative risk = 1.7, 95% confidence interval 1.5-1.9). The effect of altitude on epidemic transmission is most likely modulated by seasonal temperatures. The epidemiologic and serologic confirmation of a dengue outbreak at 1,700 meters above sea level represents the capability of Aedes aegypti to adapt to new environments, and the potential for epidemic spread in cities at comparable altitudes or higher.
 
Findings with the Sysmex XE-2100 analyzer for 1,801 patients with or without malaria infection 
Comparison of differential count between results with the Sysmex XE-2100 analyzer and results with microscopic examination in 161 patients with pseudoeosinophilia 
Comparison of parasite counts and platelet counts between samples with and without atypical features on the Sysmex XE-2100 analyzer in 413 malaria-infected patients Parasite count mean ± SD (copies/μL) P value Platelet count mean ± SD (10 3 /μL) P value 
Article
Recently, the XE-2100 hematology analyzer was investigated in a rather small patient group; pseudoeosinophilia or abnormal white blood cell (WBC) scattergrams reported by this instrument were considered as significantly valuable diagnostic parameters in detecting vivax malaria. This study was conducted not only to assess the usefulness of pseudoeosinophilia or abnormal WBC scattergram in vivax malaria-endemic areas with large patient groups (N = 1,801) but also to investigate the correlation of parasitemia and platelet count with pseudoeosinophilia and abnormal WBC scattergrams. Of the 1,801 analyzed patients, 413 (22.9%) were found to have malaria by Wright-Giemsa stained blood smears. Overall, either pseudoeosinophilia or abnormal WBC scattergram was detected in 191 of 413 malaria patients and 4 of 1,388 patients without malaria (sensitivity = 46.2%, specificity = 99.7%). We suggest that clinical hematology laboratories using the XE-2100 analyzer should be aware of such specific parameters, even with the absence of a clinical request.
 
Cerebral malaria according to platelet count at presentation, Kampala. Uganda.
Clinical and laboratory features among 855 children with severe Plasmodium falciparum malaria, Kampala, Uganda*
Associations between clinical syndromes among children with severe Plasmodium falciparum malaria, Kampala, Uganda*
Increase in case-fatality rate (CFR) with increasing number of severe malaria features, Kampala, Uganda. CFRs are shown for 855 children with one or more combinations of the following features: cerebral malaria, lactic acidosis, severe anemia, severe thrombocytopenia, or hyper-parasitemia. The x-axis separates children into five groups based on an increasing number of co-existing severe malaria features present in combination. The groups show an increasing median CFR. The size of each bubble indicates the number of persons ranging from n = 558 for the single feature of severe anemia (lower left) to n = 4 for all five features simultaneously present (upper right).
Article
Malaria remains a challenging diagnosis with variable clinical presentation and a wide spectrum of disease severity. Using a structured case report form, we prospectively assessed 1,933 children at Mulago Hospital in Kampala, Uganda with acute Plasmodium falciparum malaria. Children with uncomplicated malaria significantly differed from those with severe disease for 17 features. Among 855 children with severe disease, the case-fatality rate increased as the number of severity features increased. Logistic regression identified five factors independently associated with death: cerebral malaria, hypoxia, severe thrombocytopenia, leukocytosis, and lactic acidosis. Cluster analysis identified two groups: one combining anemia, splenomegaly, and leukocytosis; and a second group centered on death, severe thrombocytopenia, and lactic acidosis, which included cerebral malaria, hypoxia, hypoglycemia, and hyper-parasitemia. Our report updates previous clinical descriptions of severe malaria, quantifies significant clinical and laboratory inter-relationships, and will assist clinicians treating malaria and those planning or assessing future research (NCT00707200) (www.clinicaltrials.gov).
 
Article
In the present work, we analyze the recognition of synthetic polypeptides encompassing the aminoterminal (amino acids 22-125) and the carboxy terminal (289-390) regions of the circumsporozoite (CS) protein of Plasmodium falciparum by sera from donors living in endemic area of South America and Africa. Two populations were studied: one on the Colombian Pacific coast, with low endemicity for malaria; and a western African village exposed to a very intense transmission of P. falciparum. Antibodies directed to the two polypeptides were found at high titers in both populations. Furthermore, this response was observed in individuals lacking antibodies to the highly repetitive central sequence of the CS protein (NANP). The epitopes responsible for this recognition were mapped to the region 81-125 and 316-346 of the N- and C-termini, respectively. When the two populations were compared, both showed high titers of antibodies to the two flanking peptides. However, while 95% of the sera from African adults showed antibodies against the repeat region of the CS protein, only 37% of the Colombian adults studied had these antibodies. Furthermore, African donors of various ages exhibited different patterns of recognition of the two polypeptides. In African children less than five years of age, antibodies were found in comparable levels to Colombian adults; however, in older African donors, the response to NANP became dominant. These findings may reflect the skewing effect of the humoral response towards the central repetitive epitope under conditions of frequent exposure to malaria infections. The production of such polypeptides encompassing regions that contain multiple epitopes for antibodies, T helper, and cytotoxic T lymphocyte epitopes would be advantageous in the generation of new and more efficient malaria vaccines.
 
Article
Clinical findings were analyzed in a group of 57 Orientals and 48 Caucasians infected with Clonorchis sinensis and compared with those in a control group of uninfected individuals. Abdominal symptoms were rare in the Orientals and common in Caucasians whether infection was or was not present. Laennec's cirrhosis was more common in the Orientals, infected or not. Hepatomegaly, splenomegaly, peptic ulcer or eosinophilia was not found in either infected group in excess over its control group. These facts are presented in favor of the benignity of clonorchiasis.
 
Article
Confirmation of the existence of a persistent, uninucleate, dormant pre-erythrocytic stage, the hypnozoite, of the relapsing simian malaria parasite, Plasmodium cynomolgi bastianellii, has been obtained by means of experiments involving the intravenous injection into susceptible monkeys of 48 to 85 x 10(6) sporozoites derived from mosquitoes of a different species and source than employed previously. The development of these hypnozoites was traced from 3 days until 105 days after sporozoite inoculation, employing a sensitive immunofluorescence technique followed by restaining with Giemsa. From an average mean diameter of 4 micrometers at 3 and 5 days, uninucleate hypnozoites grow to 5 micrometers at 7 days, then persist with little change until at least 105 days after infection. Strong evidence for the viability of these persistent forms was obtained by treatment of a host monkey with primaquine, which eliminated all trace of hypnozoites present 2 weeks before. Examination of hepatic tissue from a monkey injected with sporozoites 36 and 40 hours earlier revealed rare uninucleate pre-erythrocytic forms of 2.5-micrometers diameter. These early forms were present in hepatocytes in a density only approximately 1/30th of that expected on the basis of numbers of pre-erythrocytic stages found in the same animal's liver 7 days after infection. Nevertheless, subinoculation experiments appeared to rule out the circulation as a vehicle for dissemination of any putative early intermediate hepatotropic forms from another site.
 
Article
Strain IP-106 of Entamoeba histolytica was isolated 12 yr ago from a case of amebic dysentery and has been maintained in axenic culture for the past 11 yr. Hamsters were inoculated intrahepatically, intraperitoneally, and intracecally with 6.5, 5.0, and 8.0 X 10(4) axenic trophozoites, respectively. With the first two routes of inoculation all the animals developed liver abscesses, and most developed amebic metastases to other sites. After intracecal inoculation only 3 out of 6 animals developed abscesses at the primary site and metastases to other sites. Most numerous metastases were obtained following intrahepatic inoculation. Intrahepatic inoculation with 1 and 2 X 10(4) axenic amebae resulted in an increase in the size of the liver abscess for a period of 2 wk and its apparent total resorption by day 17 post-inoculation, accompanied by a corresponding gain of body weight. With 4 and 6 X 10(4) amebae there was a steady increase of the size of the liver abscess and corresponding loss of body weight. High antiamebic indirect hemagglutination titers were observed only on day 17 post infection in animals inoculated with 2, 4, and 6 X 10(4) amebae. The extent of amebic metastases was roughly proportional to the size of the inoculum.
 
Article
Pyrimethamine resistance in cultivated laboratory isolates of Plasmodium falciparum is linked to the dihydrofolate reductase mutation Asn-108, a mutation that acts by interrupting drug binding within the active site of the enzyme. To determine the prevalence of this mutation in endemic regions harboring pyrimethamine-resistant malaria, we used a mutation-specific polymerase chain reaction assay to survey P. falciparum strains from a wide section of the Brazilian Amazon. Mutations were identified directly from blood samples without intervening steps of in vitro cultivation. Of 42 samples collected from four states in Brazil, 38 (90%) contained the Asn-108 codon AAC that confers pyrimethamine resistance, four samples contained only the wild-type Ser-108 codon AGC, and none contained the Thr-108 codon ACC found in cycloguanil-resistant pyrimethamine-sensitive strains. These findings indicate that a very high incidence of the Asn-108 DHFR mutation is responsible for pyrimethamine resistance in the Amazon, and they are consistent with recent failure rates reported for Fansidar (pyrimethamine-sulfadoxine). We suggest that limited use of proguanil be evaluated as an alternative to pyrimethamine.
 
Article
Several point mutations in the dihydrofolate reductase (DHFR) gene of Plasmodium falciparum have been correlated with in vitro anti-folate drug resistance of laboratory and field isolates. Furthermore, two different point mutations that generate amino acid substitutions at the same position of the enzyme have been observed in all the isolates studied to date. These point mutations change a serine (Ser-108) in the wild type to an asparagine (Asn-108 mutation) or to a threonine (Thr-108 mutation). Using the polymerase chain reaction (PCR), it is possible to identify isolates that present these mutations. We used a mutation-specific PCR to screen 71 samples from several geographic locations of Colombia for the Asn-108 mutation (pyrimethamine resistance). In this initial screening 53 of 71 yielded amplification product with the DHFR mutation-specific primers. We further analyzed the 18 samples that did not amplify using a mutation-specific nested PCR. Of those 18 samples, seven amplified with primers specific for the Thr-108 mutation (proguanil resistance), one with the wild type (Ser-108), and 10 did not amplify. Of these 10 samples, three were identified as P. falciparum using a species-specific diagnostic nested PCR base on sequences from the small ribosomal RNA subunit gene. Overall, 51.6% of the samples amplified for the Asn-108 mutation, 10.9% for the Thr-108 mutation, 35.9% with the wild type specific primer, and 4.8% did not amplify with any of the DHFR primers. We observed variability in the frequency of the mutation between the different geographic location. The frequency of the Asn-108 and Thr-108 mutations in the state of Narifio was 25% each, while in Valle del Cauca the frequencies were 59% and 11%, respectively. These results contrast with observations in Brazil in which the Asn-108 mutation was found in 90% of the blood samples screened.
 
Prevalence of allelic polymorphisms at 4 sites of the dihydrofolate reductase gene of Plasmodium falciparum before and after treatment with co-trimoxazole in isolates from west Uganda (n 41, multiclonal infections present). 
Prevalence of allelic polymorphisms at 5 sites of the dihydropteroate synthetase gene of Plasmodium falciparum before and after treatment with co-trimoxazole in isolates from west Uganda (n 41, multiclonal infections present). 
Article
In vivo testing for resistance of Plasmodium falciparum to co-trimoxazole (trimethoprim/sulfamethoxazole) was performed in Uganda in 41 children with uncomplicated malaria, and blood samples were screened before and after treatment for polymorphisms in the antifolate target genes for dihydrofolate reductase (DHFR) and dihydropteroate synthetase (DHPS). Selection towards a specific genotype at some codons of the DHFR and DHPS genes was observed in samples collected after exposure to co-trimoxazole drug pressure. The alleles 51-isoleucine, 59-arginine, and 108-serine of DHFR were significantly associated with clinical resistance, as was allele 581-alanine of DHPS. Resistance against antifolate combinations probably requires resistance-related polymorphisms in both the DHFR and the DHPS genes. In addition, it appears that the trimethoprim-resistant DHFR genotype differs from that for pyrimethamine at residue 108.
 
Geographic location of the in vivo study site (square) and origin of the clinical samples used in the polymerase chain reaction study. 
Comparison between in vivo and mutation-specific nested polymer- ase chain reaction (PCR) results 
Article
Sulfadoxine/pyrimethamine (SP) is considered an alternative treatment for acute uncomplicated malaria caused by Plasmodium falciparum resistant to chloroquine. However, the appearance of resistance to this drug has been reported since its initial use in Colombia. Molecular analysis of the dihydrofolate reductase gene indicates a correlation between in vitro resistance to SP and the Asn-108 point mutation. Little is known about the association of this point mutation and in vivo resistance to SP. We used a mutation-specific polymerase chain reaction strategy to analyze the presence of the Asn-108 point mutation in 48 clinical samples with adequate clinical response (ACR), 2 early treatment failures (ETF), and 1 late treatment failure (LTF). The Asn-108 mutation was detected in 36 of the ACR samples and in all of the ETF and LTF samples. Eleven ACR samples amplified with the wild-type-specific primer and one amplified with the primer for the Thr-108 mutation described for resistance to cycloguanil. These results suggest that the Asn-108 marker may not be useful in predicting SP treatment failure.
 
Article
Erythema nodosum leprosum (ENL) or type 2 lepra reactions complicate lepromatous leprosy and borderline lepromatous leprosy. We report an 11-year retrospective case record analysis of 481 outpatients with borderline lepromatous and lepromatous leprosy at the Dhoolpet Leprosy Research Center in Hyderabad, India.. The overall prevalence of ENL was 24%, 49.4% among cases of lepromatous leprosy (LL) and 9% among cases of borderline lepromatous (BL) leprosy. Logistic regression analysis identified LL (odds ratio [OR] = 8.4, 95% confidence interval [CI] = 4.6-15.4, P < 0.001) and BL with a bacterial index > or = 4+ (OR = 5.2, 95% CI = 2.1-12.9, P = 0.001) as major risk factors. The average patient with ENL was male, 34.7 years of age, and had multiple episodes of ENL (mean = 3.1) over an 18.5-month period. Three types of ENL were identified: single acute ENL, multiple acute ENL (repeated discrete episodes), and chronic ENL (continuous episodes). Acute single ENL is rare, accounting for only 8% of cases. Chronic ENL accounted for 62.5% of the cohort. Chronic ENL was of longer duration and more severe. An age > or = 35 years was a risk factor for developing chronic ENL. Patients with chronic ENL were more compliant with multi-drug therapy, especially during the first six doses of multi-drug therapy. Distinguishing these different types of ENL would be useful for patient management and developing improved treatment of these debilitating reactions. Improved strategies for treatment and management of these reactions need to be developed.
 
Article
Malaria and dengue fever are the most prevalent vector-borne diseases worldwide. This study aims to describe the clinical profile of patients with molecular diagnosis of concurrent malaria and dengue fever in a tropical-endemic area. Eleven patients with concurrent dengue virus (DENV) and Plasmodium vivax infection are reported. Similar frequencies of DENV-2, DENV-3, and DENV-4 were found, including DENV-3/DENV-4 co-infection. In eight patients, the World Health Organization (WHO) criteria for severe malaria could be fulfilled (jaundice being the most common). Only one patient met severe dengue criteria, but warning signs were present in 10. Syndromic surveillance systems must be ready to identify this condition to avoid misinterpretation of severity attributed to a single disease.
 
Top-cited authors
Robert F Breiman
  • Emory University
Nicholas Philip John Day
  • University of Oxford
Gustavo H Dayan
Donald S Shepard
  • Brandeis University
Betzana Zambrano
  • Sanofi - Sanofi Pasteur