Retrospective Serological Survey of Equine Influenza Virus and Piroplasm Parasites in Free-Ranging Wild Equids from Kenya and Tanzania

Wild equids may act as reservoirs for infectious pathogens affecting domestic equine populations, yet data on exposure to equine infectious anemia virus (EIAV), equine influenza virus (EIV), and equine piroplasmosis agents in African wildlife remain scarce. Our objectives were to retrospectively determine serological evidence of exposure to EIAV, EIV, Theileria equi, and Babesia caballi among Grevy’s zebras and rhinoceroses from Kenya and Tanzania. A total of 284 archived serum samples from 215 Grevy’s zebras and 69 rhinoceroses were analyzed using commercial ELISAs. Positive EIAV screening tests were retested using a second confirmatory assay. No confirmed EIAV antibodies were detected in zebras or rhinoceroses. Antibodies against EIV were identified in 20/215 zebras (9.3%), all originating from Serengeti National Park. Theileria equi antibodies were detected in 194/206 zebras (94.2%), while Babesia caballi antibodies were detected in 8/206 zebras (3.9%). Rhinoceroses were negative for all pathogens tested. This study provides evidence of widespread exposure of Grevy’s zebras to T. equi and limited exposure to EIV in East Africa while failing to identify serologic evidence of EIAV infection in zebras or rhinoceroses. These findings improve understanding of infectious disease ecology at the wildlife–livestock interface and support continued wildlife surveillance programs.