Prevalence of Enteropathogens in Dogs Attending 3 Regional Dog Parks in Northern California

Hascall, K.L.; Kass, P.H.; Saksen, J.; Ahlmann, A.; Scorza, A.V.; Lappin, M.R.; Marks, S.L.

The reasons for the low amplification rates of DNA for Giardia genotyping were multifactorial and might have been associated with the lack of freshly extracted DNA, the method of DNA extraction, or the presence of Giardia species from birds and rodents that were not Giardia duodenalis. It is also plausible that the amount of Giardia DNA and the gene abundance (single and multicopy genes) was below the assay's detection limit. The results of Giardia genotyping testing of the isolates in this study were in agreement with most previous studies showing assemblage C or D represents the most common assemblages in the dog. 15, 29 Different amplification rates of the loci tested in the study have also been reported in similar multilocus genotyping studies in dogs. 15, 30, 31 Humans are primarily infected with assemblages A and B, and these have also been infrequently isolated from dogs, thus posing a potential zoonotic risk. 5 Although fecal consistency correlated with both the presence and number of enteropathogens detected, 62/ 114 dogs (54%) were nondiarrheic. Thus, positive results obtained for any of the enteropathogens do not prove disease causation. In addition, the discordant findings between the university and the commercial reference laboratories in detection of Giardia cysts and Cystoisospora oocysts via fecal flotation warrant further scrutiny of the methods employed at both laboratories so the diagnostic yield can be increased. The discrepancy in the detection of Cryptosporidium via PCR versus DFA is also concerning because the DFA-positive specimens should have also been PCR positive. These results could be explained by the presence of fecal PCR inhibitors or the incomplete extraction of DNA from oocysts. In addition, all PCRpositive Cryptosporidium cases were DFA negative, which raises questions about the utility of DFA and PCR for diagnosing Cryptosporidium in dogs. The detection reagent in the commercial Cryptosporidium DFA kit utilizes a fluorescein isothiocyanate-labeled monoclonal antibody directed against cell wall antigen of C. parvum, and it is plausible that false-negative results could have been obtained if dogs were infected with C. canis. Lastly, although companion animals may pose a potential risk for zoonotic infections, the frequency of attending dog parks in this study did not significantly increase the risks of infection with an enteropathogen(s).