Web exclusive by Dr. Terry Mabbett — Asia has been relatively quiet on the H5N1 front, but new suspected outbreaks in South Korea and Thailand in the last seven days will, if confirmed, have deeper, wider, and more worrying implications. Not least of which is that the two countries concerned are among the most diligent, ruthless, and successful in stamping out the disease.
Domestic ducks suspected in South KoreaAccording to Reuters, the South Korean news agencies reported a suspected bird flu outbreak at a duck farm in Yesan city in the central region of the county south of Seoul on Oct. 4, 2008. This would be the first instance of H5N1 since the outbreak earlier this year (April 1, 2008, infecting 31 farms in the following six weeks) and the worst to date. The announcement comes just several weeks after South Korea was officially pronounced free of H5N1 HPAI (highly pathogenic avian influenza) on Aug. 15, 2008.
Samples taken from the ducks are undergoing confirmatory tests by the National Veterinary Research Quarantine Service with final results due soon, said Yonhap News, citing Seoul's agriculture ministry. Initial tests at the farm, which is home to 5,000 ducks, had given positive readings for the virus. The government plans to slaughter all birds on the farm as a pre-emptive measure. During May 2008, the South Korean authorities culled all domestic fowl in Seoul in a bid to contain the virus within the city and its surrounds.
Duck farm worker dies from bird-flu like symptoms At the end of Sept. 2008, the Bangkok Post reported how a worker on a free-range duck farm in Pho Prathap, Chang district of Phichit province in Thailand, had died from bird-flu like symptoms the previous day (Sept. 29, 2008). Forty-eight-year-old Manee Mankhetkit had been taken to the provincial hospital after he developed a high fever with cough, sore throat, chest pains, and breathing difficulties. Doctors treated the patient in an isolated intensive care ward after being told he had been in contact with poultry.
Manee was a hired hand at a duck farm with over 1,600 birds. He died, said the hospital, due to kidney and heart failure. His 12-year-old son, Sakda, who worked alongside his father, was taken to Phichit hospital and placed in an isolation ward for observation with no visitors. Public health permanent-secretary Prat Boonyawongwirot told Bangkok Post that lab tests were being performed on samples collected from the dead man's body to see whether he was infected with the deadly H5N1 virus as believed. However, Dr. Prat said leptospirosis could not be ruled out because the area was affected by floods.
Meanwhile, livestock officials had collected samples from the free-range ducks to test for H5N1 HPAI. There had been reports of poultry, and especially free-range ducks, dying en masse in the district during the previous 7 days. H5N1 HPAI had never occurred in this particular district of Phichit, although the province itself was listed as an avian influenza [H5N1 HPAI] epidemic zone. Kamnuan Ungchusak, director of the epidemiology bureau, said a team of epidemiologists had been dispatched to the district to carry out bird flu surveillance and that disinfectant would be sprayed at all poultry farms, slaughterhouses, and at-risk areas. According to the Bangkok Post, Thailand had experienced its fifth wave of bird flu outbreaks in early Feb. 2008 when the disease re-emerged in Nakhon Sawan and Phichit. The very first outbreak, it said, had struck Thailand in Jan. 2004 when more than 60 million birds were culled. Since then, there have been 25 human cases (17 fatal), although the last was in 2006.
Migratory wild water fowl on the move
These suspected outbreaks in South Korea and Thailand are yet to be confirmed one way or the other. If they do turn out to be H5N1 HPAI, there are all sorts of implications, and not just for the two countries concerned. First and foremost, South Korea and Thailand are among the most diligent of Asian countries when it comes to dealing with H5N1 HPAI. South Korea and Thailand reported episodes of H5N1 HPAI earlier this year in the same areas as these latest suspected outbreaks, and as before, they dealt with it ruthlessly. These new suspected outbreaks both involve ducks, and given their ability to carry the virus without showing symptomatic disease, then residual infection from earlier outbreaks cannot be ruled out.
Pertinent to the suspected South Korea outbreak is that migratory wild birds are on the move right now from northern Asia to warmer southern climes. The virus responsible fo
r the South Korean outbreak in April 2008 was genetically the same as the one identified simultaneously in wild whooper swans in Japan. Recombionics have just said that although the latest report from South Korea lacks detail it is likely that the initial positive readings will be confirmed, and as Fujian H5N1 related to the H5N1 identified in the region in spring 2008.
The outbreak, they say, is in the same area which largely targeted domestic waterfowl. Then the H5N1 was identified as a reassortant, with a clade 2.3.2 HA (haemagluttinin) and clade 2.3.4 for the other seven gene segments. It was the largest H5N1 outbreak in South Korea reported to date and they claim it included a soldier/culler who was H5 PCR positive, but the H5N1 was denied by South Korea. Closely related gene sequences were reported for whooper swans in multiple locations in northern Japan, as well as domestic poultry in Primorie, in south eastern Russia.
Recombionics says the spring 2008 outbreak signaled the movement of H5N1 to the north via wild bird infections, and although H5N1 was not reported in north eastern Siberia or Alaska, excessive poultry deaths were reported in Kamchatka, a 1250km-long peninsula in Russia’s Far East. Birds that migrated north in the spring, would be returning to the region South Korea) at this time, so an outbreak in waterfowl in South Korea at this time of the year would not be unexpected, they say. With similarly timed outbreaks reported in this area in 2003, 2006, and 2007, the current outbreak was expected, they say.
Thai/Laotian border risksFor Thailand, ingress of the virus from neighboring countries, where some experts believe the virus is entrenched in backyard flocks, cannot be ruled out. Phichit is relatively close the border area of Thailand and Laos which has been the scene (both sides of the border) of previous outbreaks. Laotian authorities have previously suggested that outbreaks suffered by them came from neighboring Thailand. However, on balance, and given the wide disparity in veterinary infrastructure and general development status between the two countries, it is more likely to be the other way round. Confirmation would be a particularly big blow for Thailand which, according to the World Health Organization (WHO), recorded its last human case of H5N1 in 2006.
Wider implications If these two outbreaks are confirmed as H5N1 HPAI, and especially if due to residual infection, then implications in the wider world context are serious and disturbing. If countries like South Korea and Thailand cannot completely eradicate the disease there must be many more which claim to be bird flu free but which clearly are not. There are some Asian countries and a whole string in Africa where outbreaks are announced periodically then mysteriously disappear from the radar screen after little or no action, mainly because they do not have the resources and veterinary infrastructure to fight a fast moving versatile virus like H5N1 HPAI.
