Apr 27, 2011 (CIDRAP News) – Indonesia and Vietnam reported fresh H5N1 avian influenza outbreaks yesterday, as researchers who sampled birds in Bangladesh's live bird markets reported finding little of the virus, but a fair amount of H9N2 and other subtypes.
In a report to the World Organization for Animal Health (OIE), Indonesia's agriculture ministry detailed 18 outbreaks that were detected in villages in four districts of Gorontalo province from late March through early April.
OIE reports on Indonesian H5N1 outbreaks are rare, as they are for other countries where the H5N1 virus is endemic. However, Indonesian officials said in the report that the Gorontalo outbreaks signify a recurrence of the disease, the first in the area since June 2007. The province is located on the northern part of Sulawesi island.
The virus killed 817 birds in the villages, and 4,119 more were destroyed to curb the spread of the disease. Officials said the source of the virus was illegal movements of animals.
Meanwhile, Vietnam's agriculture ministry said the virus struck a village in Vinh Long province, killing 1,050 birds and leading to the culling of 950 more to control the outbreak, according to a report to the OIE. The province is located in the southern part of the country in the Mekong Delta. The source of the virus is unknown.
In other developments, researchers who spent parts of 2008, 2009, and 2010 in Bangladesh taking samples from poultry and birds, especially at live-bird markets, found very little of the H5N1 virus, with nearly all of the isolates identified as a low-pathogenic H9N2 subtype. The group, from St Jude Children's Research Hospital in Memphis and Bangladesh, published its findings yesterday in an early online edition of PLoS One.
Bangladesh has reported several H5N1 outbreaks at poultry farms over the past few years, including 157 this year, according to reports from the OIE. However, little is known about the circulation of the virus at other locations, because the country relies on passive surveillance.
The researchers collected cloacal or oropharyngeal samples from birds, along with fecal and environmental samples. Locations included bird markets in Dhaka and a few villages in an outbreak region, a pet bird market, a layer farm, a lake, and domestic flocks.
Samples were screened for influenza by injecting them into chicken eggs or using real time RT-PCR. The authors used sequence analysis or hemagglutination-inhibition assays to determine the subtypes of 252 influenza isolates collected from eggs.
In total, they tested 5,717 samples for avian influenza viruses. About 84% of the samples were collected from chickens. Most of the viruses (94%) were H9 subtypes, which were identified at most of the retail markets. All of the H9 samples that were further subtyped were H9N2. Other subtypes included H1N2, H1N3, H3N6, H4N2, H5N1, and H10N7. The H5N1 virus was found at an extremely low prevalence, 0.08%, leading the authors to suggest that the risk to humans in the markets is negligible.
The group said the prevalence of avian influenza (23%) in samples in Bangladesh bird markets is similar to that in poultry markets in other countries. The investigators also said H9 subtypes have the potential to reassort with the more lethal H5N1 virus, which underscores the importance of active surveillance at the markets.
Apr 26 OIE report on Indonesian outbreaks
Apr 26 OIE report on Vietnamese outbreak
Apr 26 PLoS One study