Serologic investigation of exposure to influenza A virus H3N2 infection in dogs and cats in the United States.

We investigated, in a cross-sectional study, the prevalence of antibodies against canine influenza A virus (CIV) H3N2 in serum samples collected from dogs and cats using a commercial ELISA and a hemagglutination inhibition (HI) test. Samples were obtained from 519 cats and dogs from 13 states within the United States. Data were analyzed for potential risk factors with positive sera (vs. negative sera) by logistic regression. Odds ratios and their 95% confidence intervals (CIs) were calculated by exponentiation of the regression coefficients. Ten dogs (2.21%; 95% CI: 1.05-3.98%) and 6 cats (8.96%; 95% CI: 3.36-18.48%) tested seropositive for CIV H3N2 by HI. One feline sample (1.49%; 95% CI: 0.04-8.04%) and 16 canine samples (3.53%; 95% CI: 2.01-5.61%) tested seropositive by ELISA for influenza A virus. There were no apparent associations between seropositivity and putative risk factors. All positive animals were from Indiana or Illinois; however, CIV H3N2 seroprevalence was not common in Illinois and Indiana.