The spread of bird flu in Nigeria could spell disaster for the region, the United Nations agriculture agency has warned, as it changes its advice.
Many Nigerians earn their living from the poultry trade
The FAO is now recommending vaccination because the current strategy of containment and slaughter of at-risk birds is not working, it says.
The H5N1 bird flu strain has been found in five states and the capital, Abuja.
Large scale bird deaths are being investigated in another three states. No human cases have been recorded.
Many of the chickens are being suffocated using plastic bags, to avoid the risk of contamination, reporters say.
FAO chief veterinary officer Joseph Domenech said he was particularly concerned about the disease spreading across the border to Niger, where an estimated two million people are vulnerable to acute hunger.
"The deadly H5N1 avian influenza virus continues to spread in poultry in Nigeria and could cause a regional disaster despite strong control efforts taken by the Nigerian authorities," Mr Domenech said in a statement.
"Considering the possible widespread entrenchment of the disease in poultry, FAO is advising the government to prepare for a targeted vaccination campaign.".
Several thousand vets would be needed to carry out a mass vaccination programme for chickens in Nigeria, and international support would be vital, he admitted.
The FAO has allocated a million dollars to step up surveillance across west Africa.
There are also calls for clarification on the issue of compensation for farmers.
Almost 60% of poultry producers raise chickens in their backyards and health officials are worried that they would not tell the authorities if their birds fell ill.
"Compensation is key to the process, people must know how much they will be paid and the first of the payments must be widely publicised," Unicef official Christine Jaulmes told AFP news agency.
Nigeria's Health Minister Eyitayo Lambo has admitted that planned compensation of 250 naira ($2) per chicken is inadequate as the market price is more than double that.
More than 90 people have died of H5N1 bird flu since the disease's resurgence in December 2003 - most of them in South-East Asia.
Experts say that cross-infection to humans is still relatively rare and usually occurs where people have been in close contact with infected birds.
But they say if the H5N1 strain mutates so it can be passed between humans, it could become a global pandemic, killing millions.