Progress 01/01/08 to 09/30/09
Outputs
OUTPUTS: Increasing evidence suggests that Giardia is zoonotic and can be transmitted from animals to humans (Ryan UM, et al. Appl Environ Microbiol, 71, 2005; Thompson RC. Int J Parasitol, 30, 2000; van Keulen H, et al. Vet Parasitol. 108, 2002). Prevalence rates have been found to be as high as 38% in adult sheep and 68% in lambs (Olsen ME, et al. Vet Parasitol, 68, 1997; Ryan UM, et al. Appl Environ Microbiol, 71, 2005). Risk of Giardia exposure to humans in the research environment is high due to the following factors: dynamic turnover in animal populations, close contact with humans and resiliency of cyst forms to cleaning products. The gold standard for diagnosis is microscopic identification (i.e. visual exam of Giardia cyst or trophozoite from fecal float). However, high false negative results due to intermittent shedding of organisms. The need for rapid and cost-effective methods of diagnosis of Giardia in domestic animal species has led to the development of enzyme-linked immunosorbent assays (ELISA) that can be run in-house, are user-friendly, and require minimal personnel training to achieve proficiency. We hypothesized that in-house rapid ELISA tests would be sensitive and specific for ovine giardiasis; in addition, we compared this ELISA with classical testing methods to determine the most effective and reliable means of Giardia detection in sheep used in biomedical research. Fecal samples (~16 grams) collected directly from animals and divided for Giardia testing using six different methods: 1) Fecal floatation performed on site on two consecutive days (n=93); 2) Fecal floatation at a reference laboratory (n=93); 3) Giardia ELISA developed for a reference laboratory (n=93) ; 4) Commercially available enzyme immunoassay (EIA) (ProSpecT Giardia Microplate Assay) (n=82); 5) Direct Immunoflourescence Assay (Merifluor Cryptosporidium/ Giardia DFA) (n=71); 6) In-house rapid ELISA Giardia test (SNAP Giardia) (n=62). Samples were considered true positive if at least one in-house fecal floatation yielded the presence of Giardia cysts or trophozoites. PARTICIPANTS: Jolaine Wilson, DVM, is a third-year resident in Laboratory Animal Medicine at the University of Pennsylvania. She was involved with the initial project creation and directly responsible for collecting fecal samples and running tests inhouse, as well as coordinating shipments for off-site testing. F. Claire Hankenson, DVM, MS, DACLAM is an Assistant Professor in the Department of Pathobiology and was the Principal Investigator on the grant. She was involved with conceiving the project, data analysis and interpretation of the findings. We received SNAP tests gratis from IDEXX for this project. TARGET AUDIENCES: Target audiences include veterinary staff, husbandry personnel and researchers that work with sheep models in biomedical research. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Prevalence of Giardia infection in sheep entering our facility was 11.8% (11 of 93 animals tested). In-house rapid ELISA had 0% sensitivity for sheep giardiasis. 3 of 11 sheep were confirmed positive by multiple (5 of 6) testing methods. 5 of 11 sheep were positive only by microscopy. In-house fecal floatation with centrifugation found 8 samples positive on only one of the two consecutive testing days. Overall, comparing testing methodologies, microscopic examination appeared to be the most accurate method to detect Giardia infection in sheep. Examined diagnostic methods had low sensitivities and low positive predictive values when evaluating sheep fecal samples for Giardia. Of the 11 sheep that tested positive for Giardia by microscopic examination, only one was observed to have diarrhea. Two other sheep out of the 93 tested were observed to have diarrhea and tested negative for all intestinal parasites. We deduced that the in-house rapid ELISA likely detects antigen specific to the canine and feline Assemblage of Giardia and does not detect the assemblage that is most common in sheep; this could explain the 0% sensitivity of the rapid ELISA test when used for Giardia detection in sheep feces. Despite the low prevalence of Giardia infection in sheep at our facility, the close contact between sheep and humans in the research environment warrants that Giardia continue to be viewed as a zoonotic risk to personnel.
Publications
- JM Wilson, FC Hankenson. ABSTRACT. Comparison of Diagnostic Testing Methods for Giardia duodenalis in Domestic Sheep (Ovis aries). Journal of the American Association for Laboratory Animal Science. 48(5), 623; 2009.
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