Review of Biological Factors Relevant to Import Risk Assessments for Epizootic Ulcerative Syndrome (Aphanomyces invadans)

Epizootic ulcerative syndrome (EUS) is a disease affecting both wild and farmed fish in freshwater and estuarine environments. After it was first described in Japan in 1971, the disease has spread widely across Asia and to some regions of Australia, North America and Africa. In Asia and Africa, the spread of the disease has substantially affected livelihoods of fish farmers and fishermen. No reports are yet published showing the presence of the disease in Europe or South America. Given its epizootic nature and its broad susceptible fish species range, it would appear that the disease has the potential for further spread. This study provides a review of the scientific literature on several biological factors of the pathogen, Aphanomyces invadans, associated with the disease EUS and aspects of the disease that are relevant to undertaking import risk assessments (IRA) covering (i) Life cycle and routes of transmission; (ii) Minimum infectious dose; (iii) Tissue localization and pathogen load; (iv) Predisposing factors for infection and factors influencing expression of disease; (v) Carrier state in fish; (vi) Diagnostic methods; (vii) Survival in the environment; (viii) Permissive temperature range; (ix) Stability of the agent in aquatic animal products; (x) Prevalence of infection; and (xi) Affected life stages. Much of the biological information presented is relevant to a broad range of risk questions. Areas where data are lacking were identified, and the information provided is put into context with other aspects that need to be addressed in an IRA.