An incurable fungal disease is killing large numbers
of fish in the Zambezi River Valley. The
UN Food and Agriculture organization says food security and the livelihoods of
people in seven African countries could be seriously affected.
The disease is called Epizootic Ulcerative Syndrome,
or EUS for short. It causes ugly lesions
on fish and is spreading both upstream and downstream in the Zambezi.
FAO Senior Fishery Resources Officer Rohana
Subasinghe says EUS is fairly new to Africa, first seen there in 2007. But other regions of the world have felt its
effects for a long time.
"This is an old story in a new form because this
disease has been devastating Asia for a long time… killing all sorts of fish, many
species, devastating people who are living on fish," he says.
The disease has also been found in Australia and the
United States but over the years may have been called by a number of different
Subasinghe says it appears the disease may first
take hold in fish that are bruised or have skin damage.
"Then, this particular spore of this particular
pathogen can go inside…to grow within the musculature and also can go into the
internal organs," he says.
EUS, with its "ulcerative lesions" can "decimate"
"We have experienced in Asia mass mortalities of fish
-- hundreds and thousands of them dying over a period of months," says
As many as 20 varieties of fish may be susceptible,
including tilapia, a staple food in the Zambezi basin. Tilapia is very popular
in other parts of the world as well and is often grown in fish farms.
FAO officials don't know for sure, but they think
the disease may be triggered by environmental factors -- things like water
temperature or the rainy season.
"In Africa, the rainy season begins around October,
November. So we suspect to see another
round of disease outbreak around October, November this year," he says.
As fish die off, the catch in subsequent years will
be smaller. That increases food
insecurity and raises the prospect of food aid.
"This has managed to almost completely eradicate
certain species in the systems. I am a
Sri Lankan. I have seen [it] in Sri
Lanka. But it took four or five years to
see these fish coming back in the rivers," he says.
EUS is very difficult to control in the wild, but it
can be controlled in fish farms. The FAO says many fishers in the Zambezi River
Valley may need to diversify into fish farming to maintain their livelihoods.