Abstract
BackgroundIn the USA, there are several Ehrlichia spp. of concern including Ehrlichia canis, Ehrlichia ewingii, Ehrlichia chaffeensis, Ehrlichia muris eauclarensis, and “Panola Mountain Ehrlichia”. Of these, E. canis is considered the most clinically relevant for domestic dogs, with infection capable of causing acute, subclinical, and chronic stages of disease. Changes in climate, land use, habitats, and wildlife reservoir populations, and increasing contact between both human and dog populations with natural areas have resulted in the increased risk of vector-borne disease throughout the world.MethodsA Bayesian spatio-temporal binomial regression model was applied to serological test results collected from veterinarians throughout the contiguous USA between January 2013 and November 2019. The model was used to quantify both regional and local temporal trends of canine Ehrlichia spp. seroprevalence and identify areas that experienced significant increases in seroprevalence.ResultsRegionally, increasing seroprevalence occurred within several states throughout the central and southeastern states, including Missouri, Arkansas, Mississippi, Alabama, Virginia, North Carolina, Georgia and Texas. The underlying local trends revealed increasing seroprevalence at a finer scale. Clusters of locally increasing seroprevalence were seen from the western Appalachian region into the southern Midwest, along the Atlantic coast in New England, parts of Florida, Illinois, Wisconsin and Minnesota, and in a couple areas of the Mountain region. Clusters of locally decreasing seroprevalence were seen throughout the USA including New York and the mid-Atlantic states, Texas, the Midwest, and California.ConclusionsCanine Ehrlichia spp. seroprevalence is increasing in both endemic and non-endemic areas of the USA. The findings from this study indicate that dogs across a wide area of the USA are at risk of exposure and these results should provide veterinarians and pet owners with the information they need to make informed decisions about prevention of tick exposure.
Highlights
In the USA, there are several Ehrlichia spp. of concern including Ehrlichia canis, Ehrlichia ewingii, Ehrlichia chaffeensis, Ehrlichia muris eauclarensis, and “Panola Mountain Ehrlichia”
The predominately recognized agents for canine ehrlichiosis in the USA include Ehrlichia canis, Ehrlichia ewingii and Ehrlichia chaffeensis [1]. They are transmitted by different vectors: Amblyomma americanum is the primary vector of E. ewingii [2] and E. chaffeensis [3], and Rhipicephalus sanguineus is the primary vector of E. canis [4]
The distribution of infected dogs follows that of the associated tick vectors, and the seroprevalence of antibodies against E. ewingii or E. chaffeensis generally exceeds that of E. canis [5, 6]
Summary
In the USA, there are several Ehrlichia spp. of concern including Ehrlichia canis, Ehrlichia ewingii, Ehrlichia chaffeensis, Ehrlichia muris eauclarensis, and “Panola Mountain Ehrlichia”. The predominately recognized agents for canine ehrlichiosis in the USA include Ehrlichia canis, Ehrlichia ewingii and Ehrlichia chaffeensis [1]. Despite their shared genus, they are transmitted by different vectors: Amblyomma americanum is the primary vector of E. ewingii [2] and E. chaffeensis [3], and Rhipicephalus sanguineus is the primary vector of E. canis [4]. Recent evidence suggests that dogs are susceptible to infection by Ehrlichia muris, believed to be transmitted by Ixodes scapularis [7] and “Panola Mountain Ehrlichia”, which is transmitted by A. americanum [8]. In Canada, over 1000 dogs tested positive out of 168,216 tested, but this is likely an underestimate as these data have just recently started being collected [9]
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