Epidemiology of epizootic ulcerative syndrome (EUS) in fish in the main water bodies of the Kavango–Zambezi and Great Limpopo transfrontier conservation areas of Zimbabwe

Abstract

A three-year study investigated the epidemiology of epizootic ulcerative syndrome (EUS) in fish from Kavango–Zambezi (KAZA) and Great Limpopo (GL) transfrontier conservation areas of Zimbabwe. A total of 38 sites comprising 27 wild fisheries and 11 aquacultures, from Mashonaland West, Matabeleland North and South, and Midlands were selected. Of the 27 wild fisheries, EUS-positive fish were detected from 9 (33.3%) and none from the 11 aquacultures. No positive cases were detected from Nile tilapia (Oreochromis niloticus) from both aquacultures and wild fisheries. A total of 9.9% (239/2423) fish from the nine positive fisheries had typical EUS lesions, and infection was confirmed in 15 species. Prevalence was significantly higher (p < 0.05) in KAZA (11.5%; 95% CI: 9.6–13.4) compared with GL (8.6%; 95% CI: 7.1–10.1). The most affected were Clarias, followed by Barbus and Oreochromis species. Most cases (>80%) were reported in winter when ambient temperature was low. Further studies are required to determine water parameters associated with EUS outbreaks. These results suggested that the African sharptooth catfish (Clarias gariepinus) could be used potentially as an indicator species for EUS surveillance programmes. Thus, implementation of surveillance and biosecurity programmes that take into consideration the epidemiology of EUS will be beneficial.