Geographic Variation in the Prevalence of Candidatus Neoehrlichia procyonis in Raccoons (Procyon lotor) in the United States and Canada

TL;DR

This study finds that a tick-borne pathogen in raccoons is widespread in the U.S. but varies by region, with higher rates in the Southeast and California.

Contribution

The study provides the first comprehensive geographic prevalence data for Candidatus Neoehrlichia procyonis in raccoons across the U.S. and Canada.

Findings

42.4% of raccoons tested positive for Candidatus Neoehrlichia procyonis.

Higher prevalence was observed in the Southeast U.S. (68%) and California (55.1%).

No positive cases were found in Canadian raccoons.

Abstract

Raccoons (Procyon lotor) are reservoirs for pathogens of other wildlife species, domestic animals, and humans, including several tick‐borne pathogens. A relatively understudied organism in raccoons is Candidatus Neoehrlichia procyonis which has been detected in raccoons from the southeastern United States. A related species in Europe and Asia, Neoehrlichia mikurensis, uses rodents as reservoirs and Ixodes spp. as vectors; however, studies on rodents suggest they are not susceptible to Ca. N. procyonis. N. mikurensis has been associated with cases of neoehrlichiosis in people and dogs, which emphasizes the need to better understand the natural history of Ca. N. procyonis. We conducted a molecular survey of raccoons from selected regions of the United States and Canada. Of 394 raccoons tested, 167 (42.4%) were confirmed to be positive for Ca. N. procyonis based on sequence analysis. There was spatial variation in prevalence with significantly higher prevalence (68%, 268/394) being detected in the Southeast region of the United States compared with all other regions, although a high prevalence (55.1%, 217/394) was detected in California. Lower prevalence was detected in the Midwest (3.8%, 15/394) and none of the raccoons from Canada were positive. These data suggest that Ca. N. procyonis is widespread in raccoon populations in the United States but there is spatial variation which may be related to vector distribution or some other factor. Although not known to infect hosts other than raccoons, neoehrlichiosis should be considered in cases of suspected ehrlichiosis in immunocompromised dogs or people that have no known etiologic agent.

A total of 167/394 (42.4%) raccoons were positive for Candidatus Neoehrlichia procyonis. Spatial variation was noted with higher prevalences in the Southeast region of the United States and in California. Ca. N. procyonis is widespread in raccoon populations, but the spatial variation in prevalence may be related to vector distribution or another factor.

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