ABSTRACT
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.
ABSTRACT
Feline immunodeficiency virus (FIV) infection in cats follows a disease course similar to HIV-1, including a short acute phase characterized by high viremia, and a prolonged asymptomatic phase characterized by low viremia and generalized immune dysfunction. CD4(+)CD25(hi)FoxP3(+) immunosuppressive regulatory T (Treg) cells have been implicated as a possible cause of immune dysfunction during FIV and HIV-1 infection, as they are capable of modulating virus-specific and inflammatory immune responses. Additionally, the immunosuppressive capacity of feline Treg cells has been shown to be increased during FIV infection. We have previously shown that transient in vivo Treg cell depletion during asymptomatic FIV infection reveals FIV-specific immune responses suppressed by Treg cells. In this study, we sought to determine the immunological influence of Treg cells during acute FIV infection. We asked whether Treg cell depletion prior to infection with the highly pathogenic molecular clone FIV-C36 in cats could alter FIV pathogenesis. We report here that partial Treg cell depletion prior to FIV infection does not significantly change provirus, viremia, or CD4(+) T cell levels in blood and lymphoid tissues during the acute phase of disease. The effects of anti-CD25 mAb treatment are truncated in cats acutely infected with FIV-C36 as compared to chronically infected cats or FIV-naïve cats, as Treg cell levels were heightened in all treatment groups included in the study within two weeks post-FIV infection. Our findings suggest that the influence of Treg cell suppression during FIV pathogenesis is most prominent after Treg cells are activated in the environment of established FIV infection.
