How Effective Are Bird Flu Vaccines?

Avian Flu | China | Thailand

By Li Hujun, Southern Weekly, Beijing bureau

China has implemented the compulsory immunization of poultry with government-funded vaccines since the end of 2005. Unfortunately, the weakest link in China's system for preventing animal epidemics still lies at the grassroots level.

(Photo Caption) Mr. Jin’s duck farm is very close to Gao’s hennery, and the ducks were not closed. All ducks in Jin’s farm were vaccinated. However, according to a Hong Kong-US joint research, about 3.3% of ducks in Yunnan and other Southern provinces were H5N1 positive.

(Photo Caption) The price of this gamecock is as high as 100, 000Bahts(more than 2,600 USD). In Thailand, the vaccination is illegal.

Gao Wenbin’s hennery got attention from the State Council.

In November 2005, more than 2,000 chickens in Gao's poultry farm in Lotus Village of Chuxiong city, Yunnan province was wiped out by the deadly H5N1 bird flu virus. The incident prompted special visit and inspection from Vice Premier Hui Liangyu.

Gao had no idea how the chickens caught the virus. He bought over 10,000 chicks and injected them with bird flu vaccines manufactured in Inner Mongolia. The vaccines, however, did not have the Ministry of Agriculture license, so they were deemed as sham.

Now, all the chickens in Gao’s farm have been injected with genuine vaccines provided free by the town's veterinary clinic.

Are these vaccines able to resist avian flu virus?

HIDDEN DANGER

In the one year following poultry deaths in Gao’s farm, there wasn’t any public report on bird flu pandemic in Yunnan. However, calmness on the surface does not mean risks from avian flu have been eliminated.

On Oct. 30, 2006, a research team led by Guan Yi, director of the State Key Laboratory of Emerging Infectious Diseases at the University of Hong Kong, and Rob Webster of St. Jude Children's Research Hospital in Memphis, United States, published a study in the U.S. journal Proceedings of National Academy of Sciences.

The team collected over 50,000 samples from poultry markets in six southern Chinese provinces including Yunnan, and found the rate for H5N1-positive chickens, ducks and geese was 0.5, 3.3 and 3.5 percent respectively.

The team claimed that they first detected a new Fujian-like strain of the H5N1 virus in March 2005, and this type of virus had already been transmitted to Hong Kong, Laos, Malaysia and Thailand. After analyzing some samples of chicken blood serum, the team observed that the bird flu vaccine China now uses was not effective for the Fujian-like breed. They also inferred that large-scale vaccination might, in fact, facilitate the gradual dominance of the Fujian-like virus.

The direct challenge that this study posed to China's compulsory immunization policy led the Ministry of Agriculture to fiercely criticize the article.

Jia Youling, China’s chief veterinary officer with the Ministry of Agriculture' Bureau of Animal Health, appeared at a press conference hold by the State Council Information Office. He accused Guan Yi and his colleagues of unlawfully obtaining samples and questioned the reliability of the team's data and rejected its conclusions.

The World Organization for Animal Health (OIE) and the United Nations Food and Agriculture Organization (FAO), meanwhile, issued a joint statement saying the research team's conclusions would not be too surprising if they were verified, because avian flu viruses, after all, are known to mutate fairly quickly.

While Guan Yi said, “We have kept all the original samples for our data. They could come and check on it. This year, we had a much higher rate of viruses detected from poultry samples than last year. Why is this? Many bird flu patients in China were infected with the Fujian-like strain. Although at the moment chickens are not dying, what if people start to die?”

Jia Youling also revealed that the national veterinary services tested 305,000 pathogenic samples from poultry and wild birds during past ten months. Among poultry samples, 25 turned out to be positive for bird flu, all of which came from Yunnan and two other provinces.

An expert who prefers to remain anonymous noted: “Although there are fewer public reports on the pandemic, it doesn’t mean that we could pay less attention to avian flu prevention.”

Up to the end of November 2006, 21 people had tested positive for bird flu in China. Of this figure, 14 had died. Worldwide, there had been altogether 258 human bird flu cases, with 154 deaths.

Nonetheless, Ms Wang, a villager living near Gao Wenbin’s poultry farm, still does not know that bird flu has already caused human deaths.

UNATTAINABLE TARGET

Under the government’s seemingly lax strategy on bird flu, the role of vaccination has been placed at an unprecedented high level.

Li Jinxiang, deputy chief of the Bureau of Animal Health, once pledged at a press conference an average vaccination rate of over 98 percent for poultry in the country by June 2006.

In reality, that’s a very difficult target.

Song Xuelin, head of Yunnan Provincial Veterinary Epidemic Prevention Station, said only large-scale poultry farms could achieve the 100-percent vaccination target, and small household farmers could hardly achieve it. Thus, the bird flu vaccination rate in the province would stand at over 80 percent higher in more developed areas and lower in remote regions.

According to him, some villagers were not willing to inject vaccines to their poultry, for fear of frightening poultry, or killing the weaker ones. Even if small household farmers were all willing to take vaccination, there are few people or resources to do the job. “Once you have the bullets, you still need to shoot,” he added.

Nonetheless, with the compulsory vaccination policy in China, bird flu vaccines have become a profitable industry. But how was its effect?

Chen Hualan, director of China’s National Avian Influenza Reference Laboratory, said that existing vaccines can protect waterfowl from the virus in southern China quite well, up to almost 100 percent even. She based her observation from laboratory experiments she has done in her laboratory.

However, vaccines are not always so effective. In Chuxiong city, Yunnan Province, the success rate for antibodies against bird flu at the end of 2005 was 93 percent.

Prevention results in autumn 2006 were even less ideal. For instance, the Chuxiong Veterinary Epidemic Prevention Station ordered a vaccine for both bird flu and Newcastle disease, a type of disease that causes mild conjunctivitis and flu-like symptoms in birds. The antidote had been developed by Chen Hualan’s lab.

However, surveillance results gave Li Chaocang, deputy chief for Chuxiong Vet Station, a fright. The results showed only a 14 percent success rate for bird flu antibodies, with some farms having a zero pass rate.

Out of frustration, the Chuxiong Vet Station had to use a vaccine solely meant for avian flu all over again, with a final antibody pass rate of 72 percent. Li quoted experts from provincial level as saying that there was no problem with the joint vaccine itself. Something might have gone wrong when farmers carried out the vaccination, he added.

Prof. Bi Yingzuo from South China Agriculture University said he could not comment since he did not know much about the exact circumstances around the Chuxiong incident. However, he added, immunization is not a one-jab thing. The processing of the vaccines, animal susceptibility and careless immunization practices could all affect the outcome of the exercise. Clearly, the lack of technical support in the grassroots level is a major factor.

In China, a village veterinarian plays a key role in the prevention of a bird flu pandemic. However, Ms. Yang Ke, a technician working for Ziwu Town vet station said, "In places where vaccination is well conducted, there are fewer animal diseases, which means the income of a vet would decline. Therefore, some vets are not very responsible as expected. They might just use a syringe and pretend to inject.”

Lack of technical support and poor pay are juts the tip of the iceberg. According to Song Xuelin, vets are poorly paid and not skillful enough despite increased government support in the last few years.

Yang Peichang, head of the Chuxiong Vet Station, is extremely concerned about the vets’ professional qualifications. “The staff at our station is ageing. While the manning quota is full, new college graduates could not get in. On the other hand, people unqualified for the job have been squeezed into vet stations as an undesired result of township institutional reform.”

THAI STRATEGY

Among the Mekong countries, Vietnam is also doing avian flu vaccinations on a large scale. According to Dr Jeffrey Gilbert, avian flu senior technical coordinator for the FAO in Vietnam, a vaccination drive was launched in Vietnam with FAO support, and it is estimated that 99 percent of the vaccines were from the well-reputed Chinese Institute.

Apart from close cooperation among communities, Gilbert said continued surveillance of all poultry is of vital importance. “People need to understand how the virus spread in vaccinated or unvaccinated poultry and whether mutation has taken place. It is also important to ensure vaccinated birds develop resistance against the virus.”

In sharp contrast, Thailand, another country in the Mekong region, has completely banned bird flu vaccines.

Prof. Porntep Ratanakorn of Mahidol University, believes that whether a country carries out vaccination or not depends on various elements, be it political, economic or technological. One general concern is how vaccination would affect the export of poultry products. Hence, Thailand has put more emphasis on measures other than vaccination to prevent bird flu.

In a gamecock farm in Chiang Saen village, Chiang Rai of northern Thailand,  hundreds of gamecock are separated from each other by barbed fenced, and they have enough space to roam in. Doi, the owner of the farm, said a clean environment is vital for gamecocks to develop better resistance to diseases.

Doi has been in the trade for over 30 years and is quite a figure in cockfighting circles in northern Thailand. He owns a gamecock named Ath Het, which is now worth 100,000 baht (2,600 U.S. dollars). He used to take his gamecocks across the border to Yunnan, China. However, since the outbreak of bird flu three years ago, China has stopped allowing live poultry to cross its borders.

Although Chiang Rai province hasn’t witnessed any bird flu epidemic, the rule in Thailand is for every gamecock to have a “passport” if it fights in another province, an important managerial method on migrating poultry.

Duck King is a duck company located in central Thailand. It practices enclosed farming, which keeps the ducks away from direct contact with people and other fowls. Samples are collected every eight weeks for local vets to check.

According to Anant Singhattha, a local veterinary officer, the number of poultry farms had dropped from 1,200 to 430 since bird flu broke out in Thailand in 2004. Those without bio-safety measures were all closed down. What's more, government orders that poultry farms should be at least five km away from each other.

Dr Supamit Chunsutiwat, senior expert for Thailand’s Health Ministry on disease control, referred the five km distance policy as “compartment”, and it was a new measure in the country’s bird flu prevention. “As to its effect, it might not be clear until five to ten years later,” he added.

A non-governmental organization, Kenan Institute Asia, has been engaged in school education on avian flu prevention in Thailand. James Hopkins, head of the program, said relevant textbooks have been dispatched to 40,000 schools in the country. “This is the first time that a specific public health training textbook was sent out to every school,” he added.

After the Sep 19, 2006 coup in Thailand, there had been renewed discussions on whether the country should follow China’s immunization policy. One group favors vaccinating gamecocks that traveled long distance and free-range poultry without bio-safety measures to reduce the risks of bird flu transmission.

Hopkins is planning to conduct a forum on the prevention of cross-border bird flu among the Mekong countries, “some countries don’t want to publicize the avian flu epidemic, preferring to deal with it internally. But bird flu is no longer a country’s internal affair. Every country has to share information and work together.”

LASTING STRUGGLE

Bird flu prevention has become a long-lasting struggle. Vaccination, said Song Xuelin, is not the only preventive measure. There are, after all, different kinds of bird flu and viruses are constantly mutating. One vaccine could only target one virus. Therefore, improving hygiene and managing enclosed poultry farming are both very important.

Both the OIE and FAO, meanwhile, regard vaccination as one of the measures for bird flu control. The two groups also stressed on disease monitoring and surveillance after vaccination, apart from improved hygienic practices in the farm and efficient management of poultry transport.

However, in Chuxiong, Yunnan Province, prevention measures are not satisfactory even in large-scale farms. At Gao Wenbin’s farm, dozens of chickens still roam out of the enclosed area and stroll in front of the dorms of the farm staff. The air reeked of chicken feces. Dozens of meters away is Old Jin’s duck farm where over 2,000 ducks were raised in the open air, many of them playing in a pond nearby.

In a report on bird flu prevention, Chuxiong Animal Husbandry Bureau advocated a change in poultry farming to scale farming. But Li Haifen, head of the vet section in the bureau, said so far no concrete measures have been mapped out.

In contrast, the monitoring of avian flu in humans is much better. Since vaccines for human bird flu cases have yet to be developed, the health sector has no recourse but to rely more on the monitoring system.

Though there has not been any human bird flu case in Yunnan, the Provincial Centre for Disease Control and Prevention (CDC) director Lu Lin revealed that a preliminary flu and human avian flu monitoring network have been set up, and several hospitals have been collecting samples all year round.

In Yunnan, the provincial health and agriculture departments have initiated a new response mechanism in the wake of a bird flu epidemic, under which the two departments would intervene, report and deal with the pandemic simultaneously.

Lu noted that transparency is a must. Even if only one or two free-range poultry are suspected of carrying the virus, the health department should be notified immediately. “If the health department was notified only after someone got infected, it would be too late.”

(Li Hujun wrote this story under the Avian Flu Series of the Imaging Our Mekong program, 2006-07, coordinated by IPS Asia-Pacific and Probe Media Foundation Inc. The story was published by Southern Weekly on Jan. 11, 2007.)