Aug 11, 2008 (CIDRAP News) – The global H5N1 avian influenza situation in birds improved in the first half of this year, but an H5N1 strain not previously seen in Africa recently cropped up in Nigeria, according to the United Nations Food and Agriculture Organization (FAO).
"Considering the number of outbreaks reported worldwide, the global HPAI [highly pathogenic avian influenza] situation can be said to have improved markedly in the first half of 2008," the FAO said in the latest issue of its avian flu bulletin, AIDEnews.
However, four countries where H5N1 is endemic—Egypt, China, Indonesia, and Vietnam—continued to report outbreaks during the 6-month period, and the virus re-emerged in Pakistan and in Hong Kong's live bird markets, the agency noted.
In June, 11 H5N1 outbreaks were reported in five countries (China, Egypt, Indonesia, Pakistan, and Vietnam), compared with 65 outbreaks in June 2006 and 55 in June 2007, the FAO said. Europe reported no outbreaks, unlike in June of previous years, and no cases were reported in wild birds.
However, Indonesia has not submitted reports on H5N1 events since May, because the new database for the country's Participatory Disease Surveillance system is being modified, according to the report.
"Although there has been an improvement in disease awareness, outbreaks/cases of HPAI are still underestimated and underreported in many countries because of limitations in country disease surveillance systems, which may affect considerably the shape of the distribution of outbreaks by region," the FAO said.
Novel strain in Nigeria
In a statement today about Nigeria, the FAO said recent avian flu outbreaks in the states of Katsina and Kano involved a strain that has never been reported in Africa before but is similar to strains identified in Italy, Afghanistan, and Iran in 2007. The agency did not identify the strain by clade or subclade.
Scott Newman, international wildlife coordinator for the FAO's Animal Health Service, said the discovery is a concern because it is not known how the virus was brought into Africa.
"It seems to be unlikely that wild birds have carried the strain to Africa, since the last migration of wild birds from Europe and Central Asia to Africa occurred in September 2007 and this year's southerly migration into Africa has not really started yet," Newman said.
He said the new strain could have been introduced through international trade or illegal and unreported movement of poultry, adding, "This increases the risk of avian influenza spread to other countries in western Africa."
A team of FAO animal health experts and veterinary epidemiologists is working with the Nigerian government on disease surveillance, outbreak investigations, and the establishment of veterinary drug stockpiles, the agency said.
Increased pathogenicity in Vietnam
In other developments, the pathogenicity of H5N1 strains circulating in Vietnam seems to be rising, according to another article in the FAO's AIDEnews.
Investigators from the US Department of Agriculture and colleagues from Vietnam's National Centre for Veterinary Diagnosis said the increase in pathogenicity is manifested by more severe respiratory tract infections in ducks and an increase in cloacal virus levels, according to the article.
The higher pathogenicity has been seen in H5N1 viruses circulating in the Red River Basin (clades 2.3.2 and 2.3.4) and the Mekong delta (clade 1), the report says.
Jan Slingenbergh of the FAO's Animal Health Service said that despite the increased pathogenicity, avian flu in Vietnam is generally "fairly well in check," according to the report. Slingenbergh participated in an avian flu conference in mid June in Hanoi.
He reported that avian flu in southern Vietnam is well in check, but that efforts in northern Vietnam need "strengthening with measures other than vaccination, and the cost of vaccination cannot continue to be entirely supported by public funds only," the article states.
Aug 11 FAO statement on H5N1 strain in Nigeria
Jul 25 issue of FAO's AIDEnews
Jul 25 CIDRAP News story "Nigeria finds H5N1 in bird markets"