Ivory Coast said on Friday that H5N1 bird flu had spread to a third location in the country, in the latest in a series of outbreaks in West Africa.
The case was discovered on a farm in the village of Modeste, about 15 km (nine miles) east of the commercial capital Abidjan.
Farm owner Moussa Dicko said he had lost 27,000 chickens in the outbreak, including about 7,000 slaughtered by veterinary agents.
The H5N1 strain of the virus can be transmitted to humans, though such cases are rare.
Jonas Oulai, vice-director of animal health at the Ministry of Animals and Fisheries, told journalists that there was cause for concern about the spread of the virus, which struck in Ivory Coast in April.
"We had thought we were able to contain the virus in Bouake (a central town) but we are being overwhelmed," he said.
Nigeria, Burkina Faso, Niger and Ghana have been hit with the same virus over the last six months.