Liberty Times: What are the possible sources of the new strains of avian influenza?
Lai Shiow-suey (賴秀穗): The H5N8 subtype had never before been seen domestically. According to the Council of Agriculture, the “H5” hemagglutinin genome sequence of the local H5N8 strain is more than 90 percent similar to the one seen in South Korea, and the South Korean subtype shares the same origin with the ones found in Japan and China. It can be assumed that H5N8 was transmitted from South Korea or China by migratory birds.
H5N8 was found in China in 2013 and in South Korea’s duck farms in early 2014, causing massive death in layer ducks. Sporadic deaths of chicken infected with H5N8 were reported in Japan in April last year, and the subtype has also been found in the UK, Germany, the Netherlands and Italy since November last year.
Photo: Liao Chen-huei, Taipei Times
The World Organization for Animal Health [OIE] subsequently issued a warning by the end of 2014, saying that H5N8 is a highly pathogenic strain that poses a major threat to various birds and even humans.
What worries me is that H5N8 must have existed in Taiwan for more than three months, and its contact with local viruses must have engendered another series of genetic reassortments.
The new strains of H5N2 and H5N3 that are affecting Taiwan have not been seen in neighboring nations, so it is unlikely that the new strains have their origins outside Taiwan.
The “H5” hemagglutinin component of the new strains of H5N2 and H5N3 is almost the same as that of the H5N8 seen in South Korea, which suggests the new strains could result from the mutation prompted by the local viruses’ contact with H5N8 transmitted from abroad.
The new strains of H5N2 and H5N3 have evolved into a highly pathogenic version of their low-pathogenic subtypes due to the introduction of the highly pathogenic H5N8.
LT: Ducks and geese farmers claimed that they had not thought that waterfowl could contract bird flu. Do the new strains have a different way of transmission? Were the measures adopted by the government ineffective?
Lai: Virus-carrying migratory birds usually stay somewhere close to water, so the virus is usually transmitted to the waterfowl first. Yet geese and ducks generally have higher tolerance to virus compared to chickens, so the infection might not necessarily cause massive deaths in geese and ducks.
However, the virus could take a heavy toll in chickens before being transmitted to mammals such as pigs and humans.
The recent subtype has caused a high mortality among waterfowl, with the death rate of geese at about 90 percent. It is obvious that Taiwan is dealing with a highly pathogenic subtype that overshadows anything the nation has ever seen.
However, the outbreaks of H5N8 in neighboring nations clearly indicated that the recent subtype could infect both waterfowl and landfowl. Duck farms in South Korea have seen serious flu epidemics since January last year, and by the end of last year the OIE warned that all kinds of birds are susceptible to H5N8.
H5N3 has infected chickens and ostriches in Germany and France, and a low-pathogenic strain of H5N3 was found in duck farms in Hualien County as early as 2013.
The fact that those new strains of avian influenza could transmit themselves to both waterfowl and landfowl should have alarmed the government and encouraged it to promptly enforce all the necessary measures at every poultry farms.
The latest outbreaks started with a layer hen farm in Pingtung County’s Dawu Mountain (大武山), where hens tested positive for a known strain of H5N2 earlier this month. However, chickens in the farm began dying in droves last month, but the farm did not report the situation to the authorities.
This indicates the failure of the authorities’ infection prevention system and the poultry sector’s slackness in monitoring the disease.
LT: Mammal H5N8 infections have been confirmed overseas. Could the new subtype be transmitted to humans?
Lai: The H5N1 subtype was not considered communicable to humans until 1997, but it has claimed 400 human lives with a mortality rate of more than 50 percent, making it deadlier than SARS.
Every avian flu virus might mutate into a form that could transmit itself to humans. The Ministry of Health and Welfare should therefore carefully monitor the physical conditions of farm staff and epidemic prevention personnel. The ministry should also ensure that no anomalies could go unreported.
Human infection with the avian influenza could be treated with medications such as Tamiflu — an antiviral medication used to prevent and treat flu — but every case of infection should be reported to the authorities to prevent further spread of the disease.
National Taiwan University [Institute of Epidemiology and Preventive Medicine] professor King Chwan-chuen (金傳春) investigated more than 300 employees at a farm where chickens were infected with a known strain of H5N2, and he found that more than 60 people carried the antibody to the subtype, suggesting that human infection with H5N2 is possible.
LT: The government on Jan. 12 imposed a two-day ban on the slaughtering of ducks and geese and demanded culling at farms that were stuck by the H5 subtype and farms where the death rate exceeded 20 percent. Council of Agriculture Minister Chen Bao-ji (陳保基) has promised to contain the outbreak within a month. Is that plausible? What are your recommendations for battling the disease?
Lai: The council’s two-day prohibition on slaughtering ducks and geese was ridiculous in terms of bird flu control. The slaughter prohibition was aimed to minimize the spread by suspending the movement of poultry.
However, two days was not enough, and the prohibition should have applied to chickens as well. It is well known that avian influenza affects chickens, too. The avian flu must have spread to farms other than those having been confirmed to have the infection. The prohibition should have lasted more than two days and should not have been limited just to waterfowl.
All this suggests that the authorities have not been using the highest standards to combat the outbreak.
That a cull is called for only when a farm’s death rate reaches 20 percent is another joke.
A chicken farm in Japan that kept 4,000 chickens immediately reported the deaths of 10 chickens to authorities there. The chickens turned out to be infected with H5N8 and a cull was subsequently enacted. A culling of hundreds of chickens was carried out in a farm in the US, because the death of just two chickens was enough to alarm the authorities.
Vigilance on the part of the government and industry is pivotal to containing infection. However, with response measures as flexible as we have, it is impossible for the government to contain the outbreak within a month, as it promised.
Vice Premier Simon Chang (張善政) even demanded that the authorities shorten the one-month infection control period, which I believe was a very unprofessional.
The government, in view of the approaching Lunar New Year holidays, might be trying to minimize public discontent with a potential hike in poultry prices if a massive culling was carried out. However, that is just political calculations.
To eliminate the causal agents that triggered the latest outbreaks, the government should extend the ban on slaughter from five to 10 days, and the ban should be applied to chickens, ducks and geese alike.
A cull should be implemented at poultry farms where irregular deaths or potential infection have taken place.
The corresponding measures — including compensation for culling, the handling of corpses and confinement — should be well devised and executed. Afflicted farms should be disinfected three to four times a day, followed by a period of enforced idleness before they can resume business.
The government and the poultry industry should respond to the outbreaks with the most stringent measures.
Translated by staff writer Chen Wei-han
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