Disease ecology of low pathogenic avian influenza in the Australian environment

Abstract

Australia has been fortunate with its history of influenza in animals. The stringent biosecurity restrictions that govern the import and export of animals, and their products, has almost certainly contributed to maintaining the relative isolation from highly pathogenic (HPAIV) viral incursion. However, there are endemic and occasional exotic low pathogenic avian influenza viruses (LPAIV) circulating throughout Australian birdlife, particularly the waterbirds (Anseriformes) and shorebirds (Charadriiformes). HPAIV H7 viruses, which evolved from LPAIV H7 viruses, have been identified in a handful of poultry outbreaks since the 1970’s and attributed to the contamination of water sources with low pathogenic influenza viruses by infected wild birds defaecating into the water. My projects have identified new potential surveillance species, feral pigs, for LPAIV and other influenza A viruses in Australia. The close association of the native waterbird and shorebird species with feral pigs in the harsh environments of arid Australia gives rise to infection opportunities, both from bird to pig and pig to bird. The virus shed by natural hosts is able to persist in the environment, and the abiotic factors affecting viral persistence have been quantified for effect and size and strength in this thesis. Many gaps exist in our understanding of influenza viral ecology in the environment. Understanding more about the ecology of LPAIV in the environment, and the risk host species present can be used to reduce the likelihood of important captive populations becoming infected, and acting as a source of infection for in contact humans. The human public health and veterinary public health domains are inextricably linked when it comes to zoonotic diseases with pandemic potential, such as influenza. I conclude with a discussion of the direction I believe we should move into, and suggestions of steps to take to improve our knowledge base. In particular, increasing the degree of realism in experimental studies will yield more translatable results to assist the prediction of areas of increased viral persistence, and thereby identify areas for targeted surveillance.