Wild lagomorphs as potential sources of Francisella tularensis in an urban zoo: a case study

Abstract

A 9-y-old captive male Pallas' cat (Otocolobus manul) had a 1-mo history of worsening lameness and was euthanized. The animal was submitted to the North Dakota State University-Veterinary Diagnostic Laboratory for autopsy with differential diagnoses of suspected degenerative joint disease or neoplasia. Autopsy revealed icteric tissues and pinpoint foci in the liver, spleen, and all lung lobes. PCR testing was positive for Francisella tularensis, the causative agent of tularemia. Additional cases of tularemia were later identified in wild eastern cottontail rabbits found dead at the same urban zoo. Tularemia has been reported in captive non-human primates and rodent populations with one case linked to wild lagomorph exposure, which was likely the route of exposure in our Pallas' cat case. Tularemia is an occupational risk for zoo staff and laboratorians. Pest management and disease surveillance of wild lagomorph populations in zoos are important preventive measures.

Keywords: Francisella tularensis; Pallas’ cat; lagomorphs; occupational health; tularemia.

Figure 1.

A. Spleen from a deceased domestic cat infected with tularemia. (Photograph taken by previous NDSU-VDL pathologist Dr. Laura Rice.) B, C. Spleen of a Pallas’ cat (Otocolobus manul) with tularemia, with multifocal-to-coalescing, necrohemorrhagic foci. H&E.