-
[show abstract]
[hide abstract]
ABSTRACT: The combination of a rapidly growing stray animal population and the lack of animal control in Bangkok has resulted in a unique opportunity to evaluate the potential role of companion animals as sentinels and reservoirs of infectious diseases, including several of those caused by vector-borne parasites. The purpose of this study was to determine the prevalence and factors associated with the distribution of Babesia species infections among stray cats in Bangkok. Blood samples were collected from 1490 stray cats residing in 140 monasteries of 50 metropolitan districts of Bangkok, and assayed with light microscopy and PCR for evidence of Babesia spp. Pear-shaped merozoites were observed microscopically from two (0.13%) of these cats, while a nested 18S rDNA-based PCR assay detected babesial infections in 21 (1.4%) of the cats tested. The prevalence of infection was significantly different between sexes (p<0.05), and PCR-positive cats were found in 30% (15/50) of the districts surveyed. All 21 amplicon sequences were identical, and were determined to be closest to that reported for B. vogeli (98% identity). These results represent the first molecular confirmation that a Babesia sp. is enzootic among stray cat populations in Thailand, and suggest that the presence of pet companion animals could be a risk factor for exposure of stray cats to vector-borne parasites.
Veterinary Parasitology 10/2010; 173(1-2):70-5. · 2.58 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Doxycycline is the treatment of choice for canine monocytic ehrlichiosis (CME), a well-characterized disease and valuable model for tick-borne zoonoses. Conflicting reports of clearance of Ehrlichia canis after treatment with doxycycline suggested that the disease phase during which treatment is initiated influences outcomes of these treatments. The purpose of this study was to evaluate the efficacy of a 28-day doxycycline regimen for clearance of experimental E. canis infections from dogs treated during three phases of the disease. Ten dogs were inoculated with blood from E. canis carriers and treated with doxycycline during acute, subclinical, or chronic phases of CME. Daily rectal temperatures and semiweekly blood samples were monitored from each dog, and Rhipicephalus sanguineus ticks were acquisition fed on each dog for xenodiagnosis. Blood collected from dogs treated during acute or subclinical CME became PCR negative for E. canis as clinical parameters improved, but blood samples collected from dogs treated during chronic CME remained intermittently PCR positive. R. sanguineus ticks fed on dogs after doxycycline treatments became PCR positive for E. canis, regardless of when treatment was initiated. However, fewer ticks became PCR positive after feeding on two persistently infected dogs treated with doxycycline followed by rifampin, suggesting that antibiotic therapy can reduce tick acquisition of E. canis.
Antimicrobial Agents and Chemotherapy 10/2010; 54(12):5012-20. · 4.84 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The efficacy of existing vaccines against Thai strains of Rhipicephalus (Boophilus) microplus remains to be determined, and these vaccine antigens should be compared to homologues derived from local strains. The purpose of this study was to compare Bm95 from Thai R. microplus to the previously reported sequence from Argentinean ticks. mRNA was isolated from R. microplus midgut samples, and cDNA was amplified with Bm95-specific primers. The cDNA and protein sequences of Thai Bm95 were 94 and 92% identical, respectively, to Argentinean Bm95. Although the sequence was similar to Argentinean Bm95, there were 45-amino acid differences among the homologues. Amplicons encoding Bm95 were cloned into pPICZalphaA and expressed in Pichia pastoris strain KM71H. The recombinant plasmid Bm95 (rBm95) was reactive to bovine hyperimmune serum to Thai R. microplus midgut, indicating that the Thai rBm95 was immunogenic. Further work is needed to compare the efficacies of Thai and Argentinean rBm95 for protection of cattle against infestation with Thai R. microplus.
Annals of the New York Academy of Sciences 01/2009; 1149:45-8. · 3.15 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Tick burdens cause direct damage to hosts and transmit several disease agents, the majority of which are secreted into feeding lesions through tick salivary glands. Reduced incidence of naturally transmitted tick-borne diseases was recently observed among cattle immunized with tick salivary gland extracts (TSGE). The aim of this work was to compare the ultrastructure of salivary glands from Rhipicephalus (Boophilus) microplus removed from cattle that were immunized with TSGE to those from control cattle injected with saline. Partially fed female ticks that infested these cattle were collected, and their salivary glands were removed and compared with light microscopy. More extensive salivary gland damage was observed in ticks collected from cattle immunized with TSGE than those from saline controls. Salivary glands from immunized cattle had extensive necrosis in agranular c and f cells; partial necrosis in granular b, c, and e cells; and slight necrosis in a and d cells. These results indicated that host immunization with TSGE causes detrimental effects to female tick salivary glands and correlated with the reduced incidence of naturally transmitted tick-borne diseases observed among these cattle.
Annals of the New York Academy of Sciences 01/2009; 1149:200-4. · 3.15 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The tropical cattle tick, Rhipicephalus (Boophilus) microplus, is an important ectoparasite of livestock in Thailand that causes economic losses due to the direct effects of tick feeding and by the pathogens they transmit. Intensive acaricide use has several drawbacks, which spurred efforts to develop anti-tick vaccines. Vaccines targeting concealed antigens localized in the tick midgut result in reduced tick fecundity, but molecules localized in the tick salivary glands, which could play a role in pathogen transmission, remain largely unexplored for R. microplus. Calreticulin (CRT) is a protein found in tick salivary glands and saliva, and CRT might facilitate tick feeding and pathogen transmission through anti-thrombotic and complement-inhibition activities. This then suggests that CRT should be evaluated as a vaccine candidate antigen to control cattle ticks in Thailand. The objective of this work was to clone, sequence, and analyze cDNA encoding CRT from salivary glands of R. microplus indigenous to Thailand. Nucleotide sequence analysis showed an open reading frame of 1233 bp. Comparison of the amino acid sequence showed 65-99% identities to other known CRTs from Oryctolagus cuniculus, Rattus norvegicus, Homo sapiens, Bos taurus, R. sanguineus, and R. microplus. The N- and P-domains of CRT were the most conserved, whereas the C-domain was high acid and more variable. CRT primary sequences were most conserved among mammals. Further investigations are warranted to determine whether immunization with Thai B. microplus CRT can affect tick performances and experimental pathogen transmission.
Annals of the New York Academy of Sciences 01/2009; 1149:53-7. · 3.15 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Canine monocytic ehrlichiosis caused by Ehrlichia canis is of veterinary importance worldwide. In Thailand, there has been little information available on E. canis and its phylogeny. The objective of this study was to characterize and establish molecular structure and phylogeny of Thai Ehrlichia and Anaplasma strains. Genus-specific primers for Ehrlichia and Anaplasma were used to amplify the 16S rRNA gene from naturally infected canine blood samples, and these amplicon sequences were compared with other sequences from GenBank. Both homology and secondary structure analysis of 16S rRNA sequences indicated that they were novel E. canis and A. platys strains. Phylogenetic analysis revealed that the Thai E. canis strain was closely related and formed a single cluster with E. canis from different countries. A. platys found in this study showed close relationship with earlier report of A. platys from Thailand. To our knowledge this report represents the first molecular characterization of the nearly complete 16S rRNA gene from E. canis in dogs from Thailand.
Infection Genetics and Evolution 08/2008; 8(4):433-8. · 3.13 Impact Factor
-
Jose R C delos Santos,
Kirsten Boughan,
William G Bremer,
Brian Rizzo,
John J Schaefer,
Yasuko Rikihisa,
Glen R Needham,
L A Capitini,
David E Anderson,
Michael Oglesbee,
S A Ewing, Roger W Stich
[show abstract]
[hide abstract]
ABSTRACT: Human monocytic ehrlichiosis (HME) is a zoonotic emerging tick-borne disease with clinical signs that range from mild symptoms to multiple organ failure and death. Ehrlichia chaffeensis, the aetiologic agent of HME, is reported to infect a divergent range of mammals. Although cattle are common hosts of the primary vector of this pathogen, the susceptibility of this host to E. chaffeensis has not been reported to date. This study was undertaken to determine if cattle could provide a useful infection model of E. chaffeensis. Dairy calves were injected with DH82 cells infected with the Arkansas, St Vincent or 91HE17 strain of E. chaffeensis, and monitored for signs of clinical ehrlichiosis and for infection of peripheral blood and ticks by PCR assay. Splenectomized and spleen-intact calves were injected with cryopreserved stabilates of E. chaffeensis-infected DH82 cells for the first experiment. Mild clinical signs were occasionally observed among these calves, and only two blood samples were PCR-positive, while several ticks fed on each calf tested PCR-positive. The second experiment involved injection of normal calves with active cultures of the same E. chaffeensis strains. Interestingly, three of six calves inoculated with active cultures became recumbent and died or had to be euthanized. All of the surviving calves in this experiment tested PCR-positive on multiple dates, but fewer ticks fed on these calves were PCR-positive. These results suggest that a bovine disease model could facilitate the understanding of factors that affect the severity of HME.
Journal of Medical Microbiology 01/2008; 56(Pt 12):1660-8. · 2.50 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Trypanosomes were observed in a peripheral blood smear from a 45-day-old Thai infant displaying fever, anaemia, cough and anorexia. Human trypanosomiasis is not endemic to Thailand, so parasite identification was undertaken to determine likely sources of the infection. Several morphological parameters of the trypanosomes were similar to those of Trypanosoma evansi and statistically different from those of Trypanosoma lewisi-like parasites from a naturally infected indigenous rat. However, duplicate PCR assays with primers flanking trypanosome rRNA internal transcribed spacer 1 (ITS1) resulted in amplicons of approximately 623 bp that corresponded to the expected size for T. lewisi-like parasites. The ITS1 sequence from the infant's blood was 98 and 49 % identical to T. lewisi and T. evansi sequences, respectively. Based on molecular results, it was concluded that the infant was infected with a T. lewisi-like (Herpetosoma) species.
Journal of Medical Microbiology 09/2007; 56(Pt 8):1118-21. · 2.50 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Swine have been identified as the primary reservoir of pathogenic Yersinia enterocolitica (YE), but little research has focused on the epidemiology of YE at the farm level. The objective of this study was to describe the prevalence of YE in different production phases on swine farms. In this cross-sectional study, individual pigs on eight swine operations were sampled for the presence of YE. On each farm, both feces and oral-pharyngeal swabs were collected from pigs in five different production phases: gestating, farrowing, suckling, nursery, and finishing. A pig was considered positive if either sample tested positive. Samples were cultured with cold enrichment followed by isolation on selective media plates. Presumptive isolates were confirmed as YE and assayed for the presence of ail with a multiplex PCR. Of the 2,349 pigs sampled, 120 (5.1%) tested positive, and of those, 51 were ail positive (42.5% of YE isolates). On all farms, there was a trend of increasing prevalence as pigs mature. Less than 1% of suckling piglets tested positive for YE. Only 1.4% (44.4% of which were ail positive) of nursery pigs tested positive, but 10.7% (48.1% of which were ail positive) of finishing pigs harbored YE. Interestingly, gestating sows had the second highest prevalence of YE at 9.1% (26.7% of which were ail positive), yet YE was never detected from the farrowing sows. These results represent the first on-farm description of YE in U.S. herds and provide the initial step for designing future studies of YE.
Journal of food protection 02/2007; 70(1):11-6. · 1.94 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A rapidly increasing stray animal population in Bangkok has caused concern regarding transmission of vector-borne and zoonotic diseases. The purpose of this study was to determine if stray animals in Bangkok are a potential reservoir of Hepatozoon, a genus of tick-borne parasites that has received little attention in Thailand. Blood samples were collected from stray companion animals near monasteries in 42 Bangkok metropolitan districts. Both dogs and cats were sampled from 26 districts, dogs alone from 4 districts and cats alone from 12 districts. Samples were collected from a total of 308 dogs and 300 cats. Light microscopy and an 18 S rRNA gene-based PCR assay were used to test these samples for evidence of Hepatozoon infection. Gamonts were observed in blood smears for 2.6% of dogs and 0.7% of cats by microscopy. The PCR assay detected Hepatozoon in buffy coats from 11.4% of dogs and 32.3% of cats tested. The prevalence of infection was the same between male and female dogs or cats, and PCR-positive dogs and cats were found in 36.6% and 36.8% of the districts surveyed, respectively. There was an association between the percentages of PCR-positive dogs and cats in districts where both host species were sampled. Sequences of representative amplicons were closest to those reported for H. canis. These results represent the first molecular confirmation that H. canis is indigenous to Thailand. The unexpectedly high prevalence of Hepatozoon among stray cats indicates that their role in the epizootiology of hepatozoonosis should be investigated.
Annals of the New York Academy of Sciences 11/2006; 1081:479-88. · 3.15 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Cryptosporidium species are frequently associated with diarrhea among AIDS patients in Thailand, and dairy herds are a possible source of some of these infections. A cross-sectional study was performed to determine if Cryptosporidium is present among dairy cows in Thailand. Fecal samples were randomly collected from 363 Holstein-Friesian dairy cows from 108 of 860 farms in the Nong Pho region of central Thailand. The average prevalence of Cryptosporidium among dairy cows was 9.4%, according to an assay for Cryptosporidium-specific antigen (CSA) and 0.6% by microscopic examination of acid-fast stained feces. CSA was detected in all host age categories tested, but was most prevalent among calves (15.1%). Overall, 31.5% of farms were contaminated with Cryptosporidium infections. Fifty percent of poorly managed farms had CSA-positive cows, which were more likely to contaminate water and raw milk, while 12.9% of farms with acceptable management practices had CSA-positive cows. There was no association between the detection of Cryptosporidium and other gastrointestinal parasites. These results indicate that Cryptosporidium is enzootic among Thai dairy cattle, and suggest that cattle could have a role in zoonotic cryptosporidiosis in Thailand.
Annals of the New York Academy of Sciences 11/2006; 1081:328-35. · 3.15 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The acquisition and transmission of rickettsial pathogens by different tick developmental stages has important epidemiological implications. The purpose of this study was to determine if male Rhipicephalus sanguineus can experimentally acquire and transmit Ehrlichia canis in the absence of female ticks. Two trials were performed where nymphal and male R. sanguineus were simultaneously acquisition fed on the same infected donor hosts, and transstadially or intrastadially exposed male ticks were fed on separate pathogen-free dogs as a test for transmission. A single-step p30-based PCR assay was used to test canine and tick hosts for E. canis infections before and after tick feeding. E. canis was detected after either intrastadial or transstadial passage in male ticks, the organism remained detectable in both tick groups after transmission feeding, and both tick groups transmitted the rickettsia to susceptible dogs. Infection of dogs via tick feeding resulted in milder clinical signs and lower antibody titers than intravenous inoculation of carrier blood, but further investigation is needed to understand the mechanisms responsible for this observation. These results demonstrate that male R. sanguineus can take multiple feedings, and that they can both acquire and transmit E. canis in the absence of female ticks. This tick development stage could be important in transmission of E. canis, and perhaps related pathogens, between vertebrate hosts under natural and experimental conditions.
Veterinary Parasitology 08/2005; 131(1-2):95-105. · 2.58 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A liquid culture followed by molecular confirmation was evaluated for potential to improve sensitivity and reduce time to diagnosis of Mycobacterium avium subsp. paratuberculosis infection. Fecal samples from 240 animals from Ohio farms were assessed for presence of M. avium subsp. paratuberculosis using four different protocols: (i) sedimentation processing followed by inoculation on Herrold's Egg Yolk media (HEYM) slants (monitored biweekly up to 16 weeks), (ii) double centrifugation processing followed by inoculation on HEYM slants (monitored biweekly up to 16 weeks), (iii) liquid-solid double culture method using modified 7H9 broth (8 weeks) followed by subculture on HEYM slants (monitored up to 8 weeks), and (iv) liquid culture using modified 7H9 broth (8 weeks) followed by molecular assays for the presence of two M. avium subsp. paratuberculosis-specific targets. The number of positive samples detected by each protocol was 37, 53, 65, and 76, respectively. Twenty-seven samples were positive by all four methods. Based on samples positive by at least one method (n = 81), the sensitivities for sedimentation processing, double centrifugation processing, liquid-solid double culture, and liquid culture followed by molecular confirmation were 46%, 65%, 80%, and 94%, respectively. Fingerprinting of the positive samples using two polymorphic (G and GGT) short sequence repeat regions identified varying levels of within-farm and between-farm diversity. Our data indicate that liquid culture followed by molecular confirmation can significantly improve sensitivity and reduce time-to-diagnosis (from 16 to 8 weeks) of M. avium subsp. paratuberculosis infection and can also be efficiently employed for the systematic differentiation of M. avium subsp. paratuberculosis strains to understand the epidemiology of Johne's disease.
Journal of Clinical Microbiology 06/2005; 43(5):2111-7. · 4.15 Impact Factor
-
Roger W Stich,
Glenn A Olah,
Kelly A Brayton,
Wendy C Brown,
Marcus Fechheimer,
Kari Green-Church,
Sathaporn Jittapalapong,
Katherine M Kocan,
Travis C McGuire,
Fred R Rurangirwa,
Guy H Palmer
[show abstract]
[hide abstract]
ABSTRACT: The rickettsial pathogen Anaplasma marginale assembles an actin filament bundle during intracellular infection. Unlike other bacterial pathogens that generate actin filament tails, A. marginale infects mature erythrocytes, and the F-actin appendages are assembled on the cytoplasmic surface of a vacuole containing several organisms. To identify A. marginale molecules associated with these filaments, two complementary approaches were used: matrix-assisted laser desorption ionization-time-of-flight mass spectrometry and tandem mass spectrometry of A. marginale proteins identified with an appendage-specific monoclonal antibody and expression screening of an A. marginale phage library. Amino acid and nucleotide sequences were mapped to a full-length gene in the genome of the St. Maries strain of A. marginale; the correct identification was confirmed by expression of full-length recombinant protein and its reactivity with appendage-specific antibodies. Interestingly, there is marked variation in the abilities of diverse A. marginale strains to assemble the F-actin appendages. Comparison of four strains, the Florida, Illinois, St. Maries, and Virginia strains, revealed substantial polymorphism in the gene encoding the appendage-associated protein, with amino acid sequence identity of as low as 34% among strains. However, this variation does not underlie the differences in expression, as there is no specific polymorphism associated with loss of ability to assemble actin appendages. In contrast, the ability to assemble an actin filament bundle reflected dramatic strain-specific differences in the expression level of the appendage-associated protein. Understanding how this protein influences the cycle of invasion, replication, and egress in the host cell may provide new insights into pathogen-host interactions.
Infection and Immunity 01/2005; 72(12):7257-64. · 4.16 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Boophilus microplus is an important vector of bovine disease agents having a major economic impact on cattle production in many tropical and subtropical countries. Components of tick saliva that enable ticks to feed may also facilitate establishment of tick-borne pathogens in the vertebrate host. It has been suggested that acquired resistance against molecules in tick saliva could inhibit parasite transmission, and there is increasing evidence to support this hypothesis. The effect of immune resistance to B. microplus on the incidence of tick-transmitted pathogens was the focus of this experiment. Groups of four dairy cows were injected with antigen extracts of tick salivary glands, midgut, adjuvant only, or PBS, prior to a grazing period in a pasture in Thailand where ticks are abundant and babesiosis is enzootic. These animals were then observed for evidence of babesiosis throughout the rainy season. A reduction in the incidence of clinical babesiosis was observed among cattle immunized with salivary gland preparations compared to nonimmunized controls (P < 0.05). Immunization with midgut or adjuvant only both resulted in a slight reduction in observed disease compared to the same negative control group. B. bigemina was detected in fewer ticks (24.43%) collected from salivary gland-immunized cattle than those collected from the remaining groups (> or =44.57%). These results indicated that immunization with salivary gland antigens could affect pathogen transmission and appears promising for control of tick-borne diseases of cattle.
Annals of the New York Academy of Sciences 11/2004; 1026:312-8. · 3.15 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Boophilus microplus has a major impact on cattle production, and an antitick vaccine would be a valuable tool for control of this important ectoparasite in Thailand. Previous work has shown that immunization of hosts with different tick tissues has different implications regarding tick feeding and fecundity under experimental conditions. The purpose of this study was to assess the effects of immunization of dairy cattle with B. microplus salivary gland or midgut extracts on natural infestations by this tick species. The different antigen extracts (1 mg total protein) or equivalent amounts of adjuvant alone were injected intradermally every two weeks for a total of three times before allowing cattle to graze in a tick-contaminated pasture. Animals were checked daily, and engorged female ticks collected, counted, weighed, and maintained in tick incubators to observe tick performance parameters, including engorged weight, egg mass weight, nonviable eggs, mortality, oviposition period, egg incubation period, and F1 larval weight. After six months, each group was reimmunized with the same antigen and/or adjuvant, and ticks were again collected and evaluated. Immunization of cattle with salivary gland preparations resulted in reductions in mean tick counts and in engorged female weights. Immunization with midgut antigens reduced tick oviposition and reduced egg mass weights. In addition, more ticks recovered from midgut-immunized cows produce nonviable eggs. This investigation indicates that a vaccine based on these antigen preparations could induce a lasting, protective immune response against B. microplus that would be expected to provide a safe nontoxic means of tick control.
Annals of the New York Academy of Sciences 11/2004; 1026:289-97. · 3.15 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Detection of Ehrlichia chaffeensis is necessary to study interactions between the parasite and its vertebrate and invertebrate hosts. The purpose of this study was to develop a sensitive, specific PCR assay for E. chaffeensis based on the outer membrane protein gene, p28. Candidate primer sets were identified and ranked based on annealing scores, similarities to three major p28 sequence clusters, dissimilarity to E. canis p30, an ortholog of p28, and the proximities of flanking primer sequences for nested PCR. The relative sensitivities of five optimized single-step and two nested PCR assays were determined, and the most sensitive assay was found to be a single-step PCR that was as much as 1000-fold more sensitive than a standard 16S rDNA-based nested PCR assay. This p28-based PCR assay amplified the target amplicon from isolates representative of all three major clusters of known p28 sequences, and this assay did not amplify template prepared from either of the two species most closely related to E. chaffeensis, E. canis and E. muris. These results indicate that this sensitive, specific and isolate-universal single-step PCR assay will be a useful tool in characterizing the transmission of this important zoonotic pathogen.
Molecular and Cellular Probes 05/2004; · 2.08 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Cultivation of Mycobacterium avium subsp. paratuberculosis (M. paratuberculosis) from feces remains the most reliable method to detect infected animals. The purpose of this study was to evaluate a broth-based automated system used for cultivation of mycobacteria such as M. tuberculosis from human hosts, for the detection of M. paratuberculosis in bovine feces. Bovine feces was spiked with tenfold serial dilutions of M. paratuberculosis (5x10(5) to 5x10(-1) organisms), then processed with a double-centrifugation technique that included disinfection prior to inoculation into broth tubes. The same pathogen dilution series was also inoculated directly into broth and broth with uninfected processed feces. All of the system signal-positive bottles were identified within 30 days, with the highest concentration of M. paratuberculosis detected by the system in as few as 8 days. The presence of the pathogen was confirmed with acid-fast staining and an IS900-based PCR assay when growth of M. paratuberculosis was indicated by the system. However, some of the signal-negative cultures inoculated with the equivalent of 0.5 organisms tested PCR-positive 56 days post-inoculation, indicating that longer culture periods may lead to detection of small quantities of the organisms. Additionally, it was indicated that the processing step had a detrimental effect on detection of the organism. Comparison of the broth- and Herrold's egg yolk medium (HEYM) solid media-based culture methods with defined check test specimens corroborated the experimental evaluation of this system, indicating that broth-based detection could provide a more rapid assay for M. paratuberculosis. These results suggest that this automated system could be used to detect this organism in bovine feces, but that new approaches to processing the feces for culture should be explored.
Journal of Microbiological Methods 03/2004; 56(2):267-75. · 2.09 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Sixteen of 22 omp-1 paralogs encoding 28-kDa-range immunodominant outer membrane proteins of Ehrlichia chaffeensis were transcribed in blood monocytes of dogs throughout a 56-day infection period. Only one paralog was transcribed by E. chaffeensis in three developmental stages of Amblyomma americanum ticks before or after E. chaffeensis transmission to naïve dogs.
Infection and Immunity 09/2002; 70(8):4701-4. · 4.16 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Equine protozoal myeloencephalitis (EPM) is a disease of horses that is primarily associated with infection with the apicomplexan Sarcocystis neurona. Infection with this parasite alone is not sufficient to induce the disease, and the mechanism of neuropathogenesis associated with EPM has not been reported. Nitric oxide (NO) functions as a neurotransmitter, a vasodilator, and an immune effector and is produced in response to several parasitic protozoa. The purpose of this work was to determine if the concentration of NO metabolites (NO(x)(-)) in the cerebrospinal fluid (CSF) is correlated with the development of EPM. CSF NO(x)(-) levels were measured before and after transport-stressed, acclimated, or dexamethasone-treated horses (n = 3 per group) were experimentally infected with S. neurona sporocysts. CSF NO(x)(-) levels were also compared between horses that were diagnosed with EPM after natural infection with S. neurona and horses that did not have clinical signs of disease or that showed no evidence of infection with the parasite (n = 105). Among the experimentally infected animals, the mean CSF NO(x)(-) levels of the transport-stressed group, which had the most severe clinical signs, was reduced after infection, while these values were found to increase after infection in the remaining groups that had less severe signs of EPM. Under natural conditions, horses with EPM (n = 65) had a lower mean CSF NO(x)(-) concentration than clinically normal horses with antibodies (Abs) against S. neurona (n = 15) in CSF, and horses that developed ataxia (n = 81) had a significantly lower mean CSF NO(x)(-) concentration than horses that did not have neurologic signs (n = 24). In conclusion, lower CSF NO(x)(-) levels were associated with clinical EPM, suggesting that measurement of CSF NO(x)(-) levels could improve the accuracy of diagnostic tests that are based upon detection of S. neurona-specific Abs in CSF alone and that reduced NO levels could be causally related to the development of EPM.
Clinical and Diagnostic Laboratory Immunology 06/2002; 9(3):605-10. · 2.51 Impact Factor
