Zambezi Fish Disease Mystery Cracked

Researchers have identified the disease as Epizootic Ulcerative Syndrome (EUS), caused by a fungal pathogen. Infected fish develop large sores and die from secondary infections.

The researchers say this is the first known outbreak of the disease in Africa.

But they still don't know how the pathogen got into the Zambezi, which flows through eight southern African countries.

EUS also affects fish in Australia, the United States, and many countries in Asia. When EUS broke out in Asia in the 1970s, approximately 80 per cent of the fish population perished.

In December last year fishermen in Namibia reported finding sores on fish caught in the Zambezi (see Deadly infection hits Zambezi fish). The government imposed a two-month ban on fishing to safeguard the public. A similar ban was imposed in Botswana, and was only lifted at the end of March this year.

Shaft Nengu, a member of the research team and Botswana's assistant director of fisheries, said the spread of the disease downstream is inevitable. The research team has warned that the disease could become pandemic, damaging aquaculture, fisheries and aquatic biodiversity.

"We do not have the capacity to establish the extent of the outbreak. We are trying to come up with a regional effort to respond to this outbreak and have written to all countries that share the Zambezi River to support this initiative," Nengu said.