Influenza virus infections in dogs and cats

During the last decade reports of influenza A virus infections in dogs and cats draw considerable attention to veterinary practitioners and scientists in the fields of virology and epidemiology. Earlier experimental studies showed that dogs and cats are susceptible to influenza A virus infection, but animals did not develop clinical signs. In recent years transmission of influenza virus of subtype H3N8 from horses to dogs, however, was accompanied by severe clinical signs and the infection was shown to be transmitted to other pet dog populations in the US. In Asia respiratory disease caused by influenza virus H3N2 was documented in dogs and also a fatal infection with the highly pathogenic avian influenza virus (HPAIV) H5N1 was reported. Transmission of HPAIV H5N1 from infected poultry or wild birds to large felids and domestic cats has been reported from eight countries in Asia and Europe which caused considerable problems and concerns for both veterinary and public health in recent years. Experimentally the infection could also be transmitted from diseased to naive cats. Due to the heterogeneity of influenza viruses in their natural reservoirs of water fowl and the recent clinical natural infections in carnivores with influenza viruses of the subtypes H3 and H5, influenza virus infections should also be considered in dogs and cats with lower respiratory disease. The transmission of influenza A virus to carnivores from different mammalian and avian species may allow viral adaptation and therefore the epidemiological role of infected dogs and cats needs close attention.