Histoplasma capsulatum seroprevalence in free-roaming cats from 2 endemic regions.

Abstract

OBJECTIVE: The aim of this study was to investigate Histoplasma seroprevalence and associated risk factors in free-roaming cats from 2 endemic regions: north central Oklahoma and eastern Tennessee. METHODS: Seroprevalence was determined using frozen serum samples from trap, neuter, release programs in Tennessee (n = 426) and Oklahoma (200) from 2013 to 2024. For Tennessee samples, those with complete signalment information were included. For Oklahoma samples, no demographic information was available. An anti-Histoplasma immunoglobulin G antibody enzyme immunoassay was used to evaluate for the presence of anti-Histoplasma immunoglobulin G, and results were categorized as positive, intermediate, or negative. The Fisher exact test was used to assess risk factor associations. RESULTS: In total, 51 of 626 (8.1%) tested positive or intermediate, and 575 of 626 (91.9%) were negative. Of the samples from Tennessee, 24 of 403 (6.0%) were seropositive. From Oklahoma, 4 of 200 (2.0%) were seropositive. Of 47 Tennessee samples with positive or intermediate results, the median was 10.3 ELISA units/mL (EU; range, 8 to 31.1; positive, ≥ 10.0 EU), and of 4 Oklahoma samples with positive or intermediate results, the median was 20.3 EU (range, 18.8 to 22.6). There was no association between retrovirus infection, sex, pregnancy status, or presence of injury/disease and Histoplasma seropositivity. CONCLUSIONS: Our study is the first to document seropositivity of this regionally endemic fungus in free-roaming cats. Additional studies are encouraged to evaluate if similar seroprevalence is seen in indoor cats and if seropositivity is associated with clinical infection. CLINICAL RELEVANCE: Given the reported seroprevalence of histoplasmosis in felines, continued monitoring for Histoplasma infection by veterinary practitioners is warranted.