Transmission and control of influenza virus in pig populations

Abstract

Influenza A virus (IAV) is a common cause of respiratory disease in pigs and has been detected in pigs in most pig producing regions of the world. Influenza A viruses are able to infect many different animal species, including pigs, humans, and birds. In addition, influenza A viruses may be transmitted between pigs and other species, including humans. Following the first clinical description of influenza virus infection in pigs in the United States in 1918, research targeting influenza A viruses in pigs and other animal species has intensified quite rapidly. At the same time, control of influenza in swine farms has become increasingly challenging as there are many diverse influenza virus lineages present in the United States. Influenza control is further hindered by the relatively small amount of information assessing influenza virus transmission and within herd infection dynamics as compared to other research disciplines. This thesis aimed to 1) describe within herd influenza virus infection dynamics and temporal patterns of infection in breeding and grow-finish herds, 2) assess the prevalence and temporal patterns of influenza virus infection in weaning-age pigs on commercial swine breeding herds, 3) evaluate influenza virus transmission via indirect routes, and 4) determine the impact of vaccination and maternally derived immunity on influenza virus transmission in weaning-age pigs. The findings of this thesis have advanced the understanding of influenza virus transmission and epidemiology in swine. Researchers, veterinarians and swine producers may utilize this information to investigate influenza virus infections within herds and to help mitigate influenza virus infections.