Fish farmers in Vietnam are being warned about the risks of spreading the deadly bird flu virus through feeding chicken excrement to fish.
According to news agency Reuters, the Ho Chi Minh City Law newspaper says that residents of Vietnam's Dong Nai province throw up to 100 tonnes of chicken manure into Tri An lake to feed fish.
The waters from Tri An lake flow into the Dong Nai River, which flows through Ho Chi Minh City, the most heavily populated area of the country.
The virus can remain alive in wet conditions, including in water, and earler this year a boy died after contracting the disease through swimming in water into which infected poultry had been thrown.
Le Hoang Sang, Deputy Director of the Pasteur Institute in Ho Chi Minh City, told the paper that chicken manure was one of the main carriers of the lethal H5N1 strain of the bird flu virus: "Dropping chicken excrement into Tri An lake during the period when bird flu is evolving into a pandemic is extremely dangerous."Throwing chicken excrement into the lake must be stopped immediately."Reuters says that 91 people have caught bird flu since it first arrived in Vietnam in late 2003, and of those 41 have died.
Chicken manure is often fed to fish in developing countries, often in a pelleted form, both to provide a cheap source of nutrition and to recycle the wastes of the commercial production of chickens.
At around six times the length of the bird, the digestive system of a chicken is rather short, so some of the food eaten passes through relatively undigested.
According to the FAO, 20% of the food that has passed through the gut of the chicken hasn't been digested, and this, combined with the chicken food thrown around the enclosure by the pecking chickens creates stinking manure that can contain up to 30% protein.