Outcomes of and risk factors for presumed canine H3N2 influenza virus infection in a metropolitan outbreak

Abstract

OBJECTIVE To determine clinical signs, case fatality rate, and factors associated with positive results of PCR testing for canine influenza virus (CIV) in dogs during an H3N2 CIV outbreak in the Atlanta area. DESIGN Cross-sectional study. ANIMALS 220 dogs with a nasal swab specimen submitted to an Atlanta-area diagnostic laboratory between May 1 and July 2, 2015, for PCR assay detection of CIV specifically or CIV and 5 other respiratory pathogens. PROCEDURES Veterinarians of tested dogs were surveyed by various means to collect information regarding clinical signs, survival status at the time of survey completion, vaccination history (≤ 12 months prior to testing), and travel history (≤ 2 months prior to testing). Data were compared between CIV-positive and CIV-negative dogs. RESULTS Surveys for 120 (55%) dogs were completed. Forty (33%) of these dogs had positive results of CIV testing. No significant differences were identified between CIV-positive and CIV-negative dogs regarding breed, sex, reproductive status, duration of clinical signs prior to testing, other dogs in the household, or travel history. When other factors were controlled for, CIV-positive dogs were more likely to be adult (> 1 year of age) than juvenile (≤ 1 year of age) and to be inappetent. Only 1 (3%) CIV-positive dog died during the study period (shortly after it was evaluated because of respiratory signs). CONCLUSIONS AND CLINICAL RELEVANCE From May 1 to July 2, 2015, the reported clinical signs of dogs tested during the Georgia H3N2 CIV outbreak were similar to those reported for dogs with H3N8 CIV infection, and the case fatality rate was low.

Emergence and Containment of Canine Influenza Virus A(H3N2), Ontario, Canada, 2017–2018

“…Information about CIV H3N2 mortality rates is limited. The 2% mortality rate reported here is consistent with the 2.5% (1/40) rate reported in a metropolitan US outbreak ( 8 ). Mortality rates for CIV can be overestimated if animals with serious illness are more likely to be tested; however, testing bias is less of a concern in this study, given the scope of the investigation.…”

“…International, including transcontinental, movement of dogs is common, and CIV is one of many pathogens that can accompany transported dogs. In 2015, CIV H3N2 was introduced into the United States through the importation of dogs from Asia; the virus continues to circulate in the canine population within the country from that or subsequent importations ( 5 , 6 , 8 ). Despite its presence in the United States, CIV H3N2 had not been identified in Canada until the end of 2017.…”