Health workers in protective gear pack slaughtered chickens at a wholesale market in Cheung Sha Wan yesterday. Edmond Tang

An outbreak of avian influenza has been contained but the government is considering whether to switch the poultry vaccine it has been using for six years.

Government inspectors did not find any more traces of the H5 virus that killed about 200 birds at a farm in Yuen Long Monday.

After finding the dead chickens, the government ordered a mass slaughter of poultry at the farm and a second nearby as well as a wholesale market. Every other farm in Hong Kong tested normal.

The incident sparked concerns of a possible mutation in the virus and about the efficacy of the current vaccine since some of the dead chickens were inoculated.

The government has been using the current poultry vaccine for six years and the virus may have mutated in that time. Hong Kong has been using the Dutch-made H5N2 vaccine since 2003.

"It is a natural trend that the virus would change over the years. It may affect the immunity caused by the vaccination," said Secretary for Food and Health York Chow yesterday.

Yuen Kwok-yung, head of the Department of Microbiology at the University of Hong Kong (HKU), said the outbreak this week is a sign that the time has come to switch vaccines. "It is unavoidable that the efficacy of the current vaccine may wane after six years as the genotype of the virus found on wild birds and in the wet market is different," he said.

Yuen suggested the government consider the H5N1 vaccine currently used in the mainland as the genotype it targets is close to the one found in Hong Kong.

"Hong Kong also needs a vaccine which targets the whole southern China," he said, adding that the most important thing is bio-security in farms.

The government has requested the HKU study whether the H5 virus has mutated. The university would also investigate with mainland authorities to compare the efficacy of H5N1 and H5N2 vaccines. The tests could take one to two months.

"If the H5N1 vaccine can offer more protection to chickens in Hong Kong, we will adopt it in some areas first," Chow said.

Meanwhile authorities continued to cull the 60,000 chickens in the infected farm yesterday. The health chief said the slaughter would be completed today.

Later this week, chickens at the second farm nearby, which houses 20,000 chickens, would also be completed. More than 10 staff from the Agriculture, Fisheries and Conservation Department culled 9,700 chickens in the Cheung Sha Wan Wholesale Poultry Market yesterday.

21-day ban

The government also banned sales of local farm chickens and imports of mainland poultry for 21 days, which left vendors in a difficult position.

Ma Ping-loon, spokesperson for the Hong Kong and Kowloon Poultry Dealers and Workers Association, said business would drop at least 70 percent during the three-week ban.

"The dead chickens were not found in wet markets or wholesale market. It is acceptable to stop trading for three days to do the cleansing, but we can hardly survive under the 21-day ban," Ma said.

The association asked the government to waive rent of their stores for a month to compensate for the loss.

But some vendors considered themselves lucky to have given up their livestock licenses in September.

A vendor surnamed Mok switched to sales of frozen chicken after receiving payments.

"I think I made a right decision. Otherwise I would suffer again now," he said.

Hong Kong Poultry Wholesalers and Retailers Association chairman Wong Wai-chuen also felt relieved despite the fears of bird flu.

"Some members asked if they could surrender the license to get the ex-gratia payments as they can hardly run their businesses after the flu resurfaced," he said.

The government said applications closed in September but it would see what assistance could be offered to vendors of live chickens.

Without any live chickens over the next three weeks, frozen chickens may have to become more accepted but Mok said sales of frozen chickens were also affected by the bird flu, dropping about 30 percent yesterday.

"It's normal. Business will resume a few days later," he said.

Consumers have also accepted the frozen poultry.

A housewife surnamed Chan has refrained from buying live chickens since the Avian flu in 2003.

"We can have frozen chicken for the winter solstice. It's more important to follow the government policy to save lives," she said.

Veteran movie star Chow Yun-fat, who was seen shopping in a Kowloon City market yesterday, also found frozen chicken acceptable.

"Chicken legs in fast food shops are frozen but children love them. Only we traditional people insist on the live ones. Actually frozen chickens are okay," he said.

The health chief estimated that about 100,000 live chickens may be sold before Chinese New Year but lawmaker Wong Yung-kan, from the agriculture and fisheries sector, worried about insufficient stock after the 21-day ban.

(HK Edition 12/11/2008 page1)