The role of rodents in Avian Influenza outbreaks in poultry farms: a review.

Avian influenza outbreaks continue to strike poultry worldwide, affecting human and animal health and welfare and representing a substantial economic burden. Wild migratory birds, especially waterfowl and shore birds, are associated with global spread of avian influenza virus (AIV). Although direct contact with wild birds and virus-contaminated fomites is unlikely in modern non-free range poultry farms applying standard biosecurity measures, AIV outbreaks still occur. This suggests involvement of other intermediate factors for virus transmission between wild birds and poultry. This review describes current evidence of the potential role of rodents in AIV transmission from wild birds to poultry and between poultry houses. Rodents can be abundant around poultry houses, share their habitat with wild waterfowl and can readily enter poultry houses. Survival of AIV from waterfowl in surroundings of poultry houses and on bodies of rodents suggests that rodents are likely to act as mechanical vector. Although most rodent populations do not act as a natural reservoir, AIVs have been shown to successfully replicate in rodents without adaptation. AIV infections in rodents can result in high viral titres in lungs and nasal turbinates, presence of virus in nasal washes and saliva, and transmission to naïve contact animals. Therefore, active AIV shedding by infected rodents may play a role in transmission to poultry. Further field and experimental studies are needed to provide solid evidence for a role of rodents in AIV epidemiology. Making poultry houses rodent-proof and immediate surroundings unattractive for rodents are recommended as preventive measures against possible AIV introduction.