Annual Seroprevalence ofYersinia pestisin Coyotes as Predictors of Interannual Variation in Reports of Human Plague Cases in Arizona, United States

Abstract

Although several health departments collect coyote blood samples for plague surveillance, the association between reported human cases and coyote seroprevalence rates remains anecdotal. Using data from an endemic region of the United States, we sought to quantify this association. From 1974 to 1998, about 2,276 coyote blood samples from four Arizona counties were tested for serological evidence of exposure to Yersinia pestis, the causative agent of plague. Using a titer threshold presumed to be indicative of recent infection (serum titers of q1:256), we found a statistically significant relationship between years with > 17% sero-positive coyotes and years with two or more human cases reported. Moreover, when the annual coyote seroprevalence rates were dichotomized at 17%, 84% of the years were correctly classified using four biologically relevant meteorological variables in a linear regression. This is the first time a statistically significant temporal association between human plague cases and coyote seroprevalence rates has been shown. However, issues with data resolution and surveillance effort that potentially limit the public health utility of using coyote seroprevalence rates are discussed.

Endemic Foci of the Tick-Borne Relapsing Fever Spirochete Borrelia crocidurae in Mali, West Africa, and the Potential for Human Infection

“…Serological approaches for the surveillance of other vector-borne pathogens have been used for many years, such as wild carnivore serology for plague [54] and the use of sentinel chickens to monitor seroconversion for seasonal activity of numerous mosquito-borne viruses [55]. Serological surveys for relapsing fever have rarely been used for field studies [56], [57] and have never been utilized for the studies of enzootic foci of relapsing fever in Senegal or other regions of Africa.…”

Plague Exposure in Mammalian Wildlife Across the Western United States

“…Collection was opportunistic, in conjunction with permitted wildlife damage management activities, other wildlife management activities (e.g., re-introductions), or wildlife mortality investigations. Samples from various carnivores, especially canids, were prioritized for collection and testing because of previously published research showing high levels of Y. pestis exposure in generalist carnivores (Gage et al 1994, Brown et al 2011. For sample collection, Nobuto filter paper strips were saturated with whole blood and then allowed to air dry before being shipped in a sealed plastic bag with desiccant packs.…”

Plague risk in the western United States over seven decades of environmental change

“…This is especially true for predators, which can be exposed through consumption of plague-positive rodents or through bites from plague-positive fleas. These predator species do not necessarily play a direct role in plague transmission and dynamics, but instead act as sentinels of plague activity on the land-scape 94,95 . Correspondingly, the USDA National Wildlife Disease Program tests wildlife for evidence of plague exposure throughout much of the western U.S.…”