Callitrichid Preventive Medicine Protocols at the Bronx Zoo: A Case Example of the Reevaluation Process
Preventive medicine protocols (PMP) are important tools for keeping zoological animals healthy, but to be effective they need to be regularly reviewed and updated. Bronx Zoo callitrichid PMP included yearly fecal ova and parasite (O&P) evaluation and scheduled anthelmintic treatments. Protocols were last adjusted in 2009 to include monthly anthelmintics in response to increased cases of Gongylonema. O&P (n=1360), enteric culture (n=417), and necropsy (n=141) results from January 2000 to July 2016 were reviewed for all captive callitrichids (16 species) at the Bronx Zoo. O&P tests were infrequently positive (4–9%), revealing incidental parasites in nearly all cases. Necropsy results identified 10 cases of pancreatic nematodiasis—presumptive Trichospirura leptosoma—seven of which (5%) were significant, and 12 cases of Gongylonema spp. infection. All of these nematodiasis cases occurred prior to 2013. Fecal O&P examinations failed to detect the presence of either of these parasites. Antemortem diagnostic enteric cultures were frequently positive (28%) for clinically relevant organisms. The same pathogens were occasionally cultured at necropsy, but only Klebsiella sp. was consistently found both ante- and postmortem in the same animals (n=9).
Analysis of these results indicated that 1) O&P screening was insufficient to detect significant parasitic disease, but necropsy results were very useful; 2) enteric cultures were often helpful in identifying pathogens; and 3) necropsy results were by far the most useful tool to help adjust PMP. As a result of this analysis, annual O&P screening for healthy individuals has been discontinued; the annual screening was clearly not sensitive enough to be helpful in making treatment decisions. An alternative approach considered was to increase the frequency of fecal monitoring of healthy individuals, but it was decided that necropsy surveillance and continued screening of sick and shipping individuals would be sufficient to identify parasitic infections that require a change in the preventive medicine treatments. In addition, the aggressive deworming protocol of monthly anthelminthic treatments is believed to have disrupted the life cycle of these parasites in callitrichids at the Bronx Zoo and thus routine treatments have been decreased to once yearly ivermectin and once yearly fenbendazole. The authors also have adjusted the approach to diarrhea cases to perform a culture earlier in the clinical course. This presentation serves as an example of how PMPs should be periodically reevaluated in order to tailor PMP to both the individual institution and to changes in disease prevalence over time.