Serological and molecular analysis of feline vector-borne anaplasmosis and ehrlichiosis using species-specific peptides and PCR

With the exception of Bartonella spp. or Cytauxzoon felis, feline vector-borne pathogens (FVBP) have been less frequently studied in North America and are generally under-appreciated as a clinical entity in cats, as compared to dogs or people. This study investigated selected FVBP seroreactivity and PCR prevalence in cats using archived samples.

Cats are exposed to and can be infected with vector-borne pathogens that commonly infect dogs and humans. To our knowledge, this study provides the first evidence for E. chaffeensis and E. ewingii infection in naturally-exposed cats in North America. Results from this study support the need for regional, serological and molecular FVBP prevalence studies, the need to further optimize serodiagnostic and PCR testing for cats, and the need for prospective studies to better characterize clinicopathological disease manifestations in cats infected with FVBP.

Feline blood samples submitted to the Vector Borne Diseases Diagnostic Laboratory (VBDDL) at North Carolina State University College of Veterinary Medicine (NCSU-CVM) between 2008 and 2013 were tested using serological assays and PCR. An experimental SNAP® Multi-Analyte Assay (SNAP® M-A) (IDEXX Laboratories, Inc. Westbrook, Maine, USA) was used to screen all sera for antibodies to Anaplasma and Ehrlichia genus peptides and A. phagocytophilum, A. platys, B. burgdorferi, E. canis, E. chaffeensis, and E. ewingii species-specific peptides. PCR assays were used to amplify Anaplasma or Ehrlichia DNA from extracted ethylenediaminetetraacetic acid (EDTA)-anti-coagulated blood samples. Amplicons were sequenced to identify species.

Overall, 7.8% (56/715) of cats were FVBP seroreactive and 3.2% (13/406) contained Anaplasma or Ehrlichia DNA. Serologically, B. burgdorferi (5.5%) was the most prevalent FVBP followed by A. phagocytophilum (1.8%). Ehrlichia spp. antibodies were found in 0.14% (12/715) of cats with species-specific seroreactivity to E. canis (n = 5), E. ewingii (n = 2) and E. chaffeensis (n = 1). Of seropositive cats, 16% (9/56) were exposed to more than one FVBP, all of which were exposed to B. burgdorferi and either A. phagocytophilum (n = 7) or E. ewingii (n = 2). Based upon PCR and DNA sequencing, 4, 3, 3, 2, and 1 cat were infected with A. phagocytophilum, A. platys, E. ewingii, E. chaffeensis and E. canis, respectively. Conclusions: Cats are exposed to and can be infected with vector-borne pathogens that commonly infect dogs and humans. To our knowledge, this study provides the first evidence for E. chaffeensis and E. ewingii infection in naturally-exposed cats in North America. Results from this study support the need for regional, serological and molecular FVBP prevalence studies, the need to further optimize serodiagnostic and PCR testing for cats, and the need for prospective studies to better characterize clinicopathological disease manifestations in cats infected with FVBP.