The virus has probably been killing poultry for weeks, but migratory birds are likely not to blame
By Stephen Pincock | February 14, 2006
The outbreak of avian influenza in Nigeria that emerged last Wednesday (February 8) has probably been simmering for weeks without being detected, increasing the risk the disease has spread to neighboring countries, according to a senior scientist at the Food and Agriculture Organization (FAO). However, experts say they don't believe that migratory birds brought the virus to Africa.
Nigerian authorities notified the World Organization for Animal Health about the outbreak last Monday after tens of thousands of chickens in battery cages died in the northern state of Kaduna. It was confirmed as H5N1 on Wednesday, and in following days, officials reported worrying outbreaks in two neighboring states. This week (February 13), the country's health minister Eyitayo Lambo reportedly said that officials were examining suspected H5N1 cases in a further 5 states. If confirmed this would mean that 8 of Nigeria's 36 states were affected.
The expanding crisis comes amidst concerns that the virus had been circulating in the country for a long time before it was first reported. Juan Lubroth, head of FAO's Emergency Prevention System livestock component, told The Scientist that the disease had likely been killing domestic poultry before it hit commercial farmers. "We have suspicions that it had been going on for several weeks," he said. "We were all a little bit amazed that it took several weeks to get samples sent outside the country to confirm it."
Furthermore, "the longer the diagnosis takes, the higher the likelihood that the disease spreads," Lubroth said. "The delays are a disaster."
In response to last week's announcement, neighboring countries including Benin, Cameroon, Chad, Ghana, Niger, and Togo were urged to tighten restrictions on poultry imports. "I do think that they are at this moment scrambling," Lubroth said. Nigeria has also begun culling birds and screening possible human cases.
FAO has sent $45,000 to each of the high-risk countries for emergency purchases such as protective equipment, water purifiers, gasoline, and lab reagents, Lubroth said. Technical collaborative programs have also been established in an effort to improve laboratory facilities and epidemiology.
Meanwhile, wildfowl experts at Wetlands International said it was unlikely that migratory birds had brought the disease to Nigeria. The organization is working with the United Nations and the European Union to identify the risks from migratory birds. Spokesman Alex Kaat told The Scientist that two duck species considered to pose the greatest risk of spreading H5N1 are Garganey and Northern Pintail ducks, currently present in large numbers in Nigeria.
"But we don't think they brought it to Nigeria," he said, explaining that the site of the initial outbreak was in a dry region, distant from the wetlands where the migratory species breed, and there is no evidence that infected birds can fly long distances.
"There might have been a chain of infections from wild birds across Africa, but again we don't think so," he said. If this had been the case, it would have been more likely to see outbreaks in regions such as the Senegal coast, Lake Chad, or the Inner Niger Delta in Mali, he said.
"So, we don't think there is any connection between migratory birds and the outbreak in Nigeria," Kaat said. "We think that it is more likely that some poultry trade brought the virus."
The migrating duck species arrived in Nigeria from August last year, and will begin their migration north again before the end of February, Kaat said. Although they will most likely not bring the disease to Europe, he said, there is a risk that the ducks could spread the virus within Africa if the population becomes infected after contact with diseased poultry.
The current outbreaks among swans in Italy, Greece, and Bulgaria were unlikely to be related to the African outbreak, he added. The mute swan population -- in which the cases have been seen -- was already known to be affected in Eastern Europe, he said.
Cold weather in the Caspian and Black Sea region had probably forced the birds to fly to warmer regions, Kaat said, adding that a major risk now was that infected swans would pass the virus to other migratory birds.
Links within this article
S. Pincock, "And if bird flu hits Africa..." The Scientist, January 23, 2006.
"Fears over Nigeria bird flu spread," Press Association, February 14, 2006.
FAO/OIE, "Step up surveillance and border controls in Africa," February 10, 2006.
D. Mbachu, "Nigeria screens farm workers for deadly H5N1 strain of avian flu virus," Associated Press, February 14, 2006.
http://www.wetlands.org/news.aspx?ID=bb47207c-3109-4d86-826a-d438ada02b83Editor's note: Please see a letter about this story