Management of avian cholera Pasteurella multocida outbreaks on Dyer Island, South Africa, 2002–2005

Abstract

In 2002 there was a widespread epizootic involving seabirds on five of the offshore islands of the Western Cape, South Africa. Since then, avian cholera Pasteurella multocida outbreaks have been occurring annually on one of these islands, Dyer Island. This paper reports on the three subsequent summers, 2003/04, 2004/05 and 2005/06, during which further avian cholera outbreaks were recorded. It focuses on the outbreak in 2004/05, which was the largest in extent and the most closely monitored. The mortalities during 2005/06 were not as extensive as expected. The management measures used to bring these outbreaks under control are described. Removal of all the carcasses from the entire island in one day is important in reducing mortality. Management intervention is required to reduce the negative impacts of disturbance due to kelp gull Lasus dominicanus predation on other breeding seabirds, primarily the African penguin Spheniscus demersus, during the carcass collection process.

Keywords: avian cholera; Cape cormorant; disturbance; Dyer Island; epizootic; Pasteurella multocida; Phalacrocorax capensis; wildlife disease

African Journal of Marine Science 2007, 29(1): 105–111