Prevalence of Anaplasma phagocytophilum infection in feral cats in Massachusetts

OBJECTIVES: The primary objective of this study was to determine the prevalence of Anaplasma phagocytophilum infection and exposure in adult feral cats in Massachusetts, an endemic area for A phagocytophilum and its tick vector Ixodes scapularis. The secondary objective was to determine if there were correlations between A phagocytophilum infection and the presence of anemia and thrombocytopenia. METHODS: Blood samples were collected between June and December 2015 from 175 apparently healthy adult feral cats that were presented to trap and release spay/neuter centers in Massachusetts. Complete blood count, blood smear evaluation, SNAP 4Dx Plus test (IDEXX) and A phagocytophilum PCR were performed on all samples to document acute infection (PCR-positive and/or inclusions observed on blood smear) and exposure to A phagocytophilum (SNAP 4Dx Plus-positive for A phagocytophilum antibodies). RESULTS: The prevalence of exposure to A phagocytophilum in feral cats in Massachusetts was 9.7%, whereas the prevalence of acute infection was 6.9%. All blood smears were negative for Anaplasma species inclusions; therefore, acute infection was defined as testing positive on PCR analysis. No statistically significant correlations were identified for cats that were positive for A phagocytophilum on PCR analysis or SNAP 4Dx Plus test and the presence of anemia or thrombocytopenia. CONCLUSIONS AND RELEVANCE: The prevalence of A phagocytophilum exposure in feral cats approaches 10% and is higher than the previously reported national average prevalence of 4.3% in the USA. A phagocytophilum infection may be an emerging infectious disease in cats. Further research is needed to determine the prevalence of clinical illness associated with A phagocytophilum infection in cats living in endemic areas.