A serosurvey of granulocytic Ehrlicha spp. and Borrelia burgdorferi sensu lato in 2018 Swedish horses

Egenvall A, Franzén P, Gunnarsson A, Olsson Engvall E, Vågsholm I, Wikström U-B, Artursson K.

To study the seroprevalence to Borrelia burgdorferi sensu lato and granulocytic Ehrlichia spp. in Swedish horses a cross-sectional study was conducted. The aim was to evaluate associations between positive serotiters to these agents and demographic, clinical and tick-exposure factors. Blood samples from 2,018 horses were collected during September 1997 to September 1998. Horses were sampled from the animals presented to veterinary clinics affiliated with the Swedish Horserace Totalizator Board (regardless of the primary cause for consultation). Standardized questionnaires with information both from owners and attending veterinarians accompanied each blood sample. The seroprevalence to B. burgdorferi s. l. was 16.8% and the seroprevalence to granulocytic Ehrlichia spp. was 16.7%. The northern region had the lowest seroprevalences. Substantial differences in the seroprevalences at different locations within the southern part of Sweden was noted. Logistic regression was used to associate demographic variables and other possible risk factors with positive serostatus to the agents under investigation. In one model of seropositivity to B. burgdorferi s. l., age, breed, geographic region, the serologic titre to granulocytic Ehrlichia spp., season and the diagnosis coffin-joint arthritis were significant. For Ehrlichia spp. age, , geographic region, season and the serologic titre to B. burgdorferi s. l. were associated with seropositivity. The risk of positive serologic reactions to Ehrlichia spp. was increased in the horse population in the south and middle of Sweden but only among horses not used for racing. In the multivariable models there were no significant associations between clinical signs (specific or non specific) or disease and seropositivity to either of these agents apart from for the positive association between coffin-joint arthritis and serologic reactions to B. burgdorferi s. l.

References:

Egenvall A, Franzen P, Gunnarsson A, Olsson Engvall E, Vågsholm I, Wikström U-B, Artursson K. Cross-sectional study of the seroprevalence to Borrelia burgdorferi sensu lato and granulocytic Ehrlichia spp. and demographic, clinical and tick-exposure factors in Swedish horses. Preventive Veterinary Medicine (accepted februari 2001)

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