By Tan Ee Lyn GUANGZHOU, China, Jan 17 (Reuters) - Nigeria is taking the threat of bird flu seriously and will take action to prevent its spread, acknowledging that failure to do so will hurt its economy, a leading official said. The country last week culled more than 20,000 chickens at a northwestern farm where bird flu had been detected. Workers fumigated the area. Nigeria first discovered the disease in poultry early last year in a northern state. But despite culling and quarantine, it quickly spread to many parts of the country. Hitting back at some experts who regard the country as a weak link in the global fight against the H5N1 virus, Ahmed Abdulkadir, special adviser to the Nigerian president, told Reuters in an interview that Nigeria took the threat of the disease extremely seriously. "We are very, very serious because if we are not, it will affect the economy. When we had the first case in 2006, some foreign airlines said no more meals from Nigeria (were allowed) on board their aircrafts so they (brought) in their meals. That affected our economy and the airline industry," he said in an interview on the sidelines of an anti-malaria conference in China's southern city of Guangzhou. His comments come as concern about the disease rippled across Asia this week, with an Indonesian hospital overwhelmed by human H5N1 cases and the virus spreading among flocks in Vietnam and flaring again in Thailand. Although the World Health Organisation (WHO) said there were no signs of the virus spreading between humans and that most countries' reaction to the disease had improved, experts maintain that the world could suffer a pandemic and millions of people could die if the virus learns to spread among humans. TAKING ACTION Abdulkadir said Nigeria would play its part. "Everything is under control, culling has taken place. Once there is a bird flu infection, they take care of it straightaway, they don't have to wait for (confirmation of) H5N1. If it's flu they'll take care of it," he said, referring to Nigeria's agriculture authorities. He said changes had taken place in Nigeria since it first discovered the disease last year. A new laboratory to test for H5N1 had been built and a project to remove backyard poultry had been launched. "When we had the first case in February 2006, we didn't have a lab. But instantly, we had all the necessary donations and support from various countries and (they) gave us the equipment and our experts went on training and they are doing all the testing now," he said. "In fact, all the African countries come for testing in Nigeria. But we get it tested outside if a second opinion is required," he said. He added that attempts were being made to get rid of backyard poultry -- which experts see as a weak link as the birds run a higher risk of picking up the disease from wild birds. "Public education has been going on in the capital. Nobody is allowed to have poultry in their household, nobody. It's banned," he said. "Before, it was part of our culture. Everybody had some chickens, ducks around the house. But, as a precaution, we decided to say no one will be allowed to have poultry in their household after February (2006)." "So in the capital, we don't have that. I would expect that other state governors would take similar controls in the near future," he said, referring to Nigeria's 36 states.