Disease Surveillance of California Ground Squirrels (Spermophilus beecheyi) in a Drive-through Zoo in Oregon, USA

Abstract

Rodents and other small wild mammals are often considered to be pests and vectors for disease in zoos that house small populations of valuable threatened and endangered animals. In 2005, three nonhuman primates at a drive-through zoo in Oregon, US, acquired tularemia from an unknown source. Due to an abundance of California ground squirrels ( Spermophilus beecheyi ) on zoo grounds, we instituted serosurveillance of this species from July through September 2008 to determine the prevalence of antibodies against pathogens considered to be potentially transmissible to collection animals. Serologic testing was performed for Francisella tularensis ; Leptospira interrogans serovars Canicola, Grippotyphosa, Hardjo, Icterohemorrhagiae, and Pomona; Toxoplasma gondii ; and Yersinia pestis . All squirrels were seronegative for Yersinia pestis (0%; 0/45) and Toxoplasma gondii (0%; 0/20); there was a prevalence of 2% (1/45) for Francisella tularensis antibodies and 57% (24/42) were positive for various Leptospira serovars. Although it remains unclear whether ground squirrels present a significant risk for transmission of disease to zoo animals, vaccination of high-risk zoo animals against leptospirosis warrants consideration. Beyond this, continued vigilance and persistence with various forms of pest control may reduce the likelihood of disease transmission from wildlife hosts to animals in human care.

Wild Small Mammals and Ticks in Zoos—Reservoir of Agents with Zoonotic Potential?

“…), which are the most important sources of Leptospira infection, varies widely from 0% to 73.7% [ 33 ]. On the other hand, another small mammal, ground squirrel ( Spermophilus beecheyi ), also considered to be a reservoir of diseases in zoos, exhibited 57% ( n = 42) seropositivity for various L. interrogans serovars when tested in Wildlife Safari, a wild animal park in Winston, Oregon, USA [ 34 ]. The prevalence was much higher compared with our study, even though the monitoring of seroprevalence in the squirrel population was done during a hot and dry summer in contrast to the summer in Brno, which is not so hot and dry.…”

Francisella and Antibodies

“…Seroprevalence to tularemia of wild animals has also been demonstrated in various parts of Russia [43][44][45], Armenia [46], and North America. Antibodies to Francisella have been detected in hares in Ontario, Alberta, and Nova Scotia [47][48][49][50], snowshoe hares, muskrats, and coyotes (Canis latrans) in Québec [51], domestic dogs in New Mexico [52], prairie dogs in Texas [53], wildlife and humans in Alaska [54], and ground squirrels (Spermophilus beecheyi) in Oregon [55]. Generally known are studies on tularemia at Martha's Vineyard in Massachusetts.…”