Sentinel chickens all wiped out by avian flu infection, poultry restocking sentinel defense breached

Avian influenza has dealt a heavy blow to the poultry industry. To help farmers restock, the Livestock Research Institute of the Council of Agriculture (COA) provided "sentinel chickens" for the first time, originally intended to help farmers monitor whether avian influenza virus remained in the environment before restocking. Unexpectedly, before they were even deployed, a new type of avian influenza virus was detected in a chicken house at the Livestock Research Institute, and all 254 were culled. Will this affect the restocking schedule? Chang Shu-hsien, Director-General of the Bureau of Animal and Plant Health Inspection and Quarantine (BAPHIQ), did not answer directly, saying only that the government could not provide sentinel chickens in the short term, but that in the past they had always been raised by the private sector, and the COA would coordinate with breeding-chicken operators to provide free testing. "With everyone working together, it should still be okay."

Sentinel chickens fall, one sample tests positive for new-type H5N2 avian influenza

To confirm whether avian influenza virus still remains on a poultry farm, sentinel chickens that do not carry avian influenza must first be released and observed for 21 days; only after confirming they are not infected can restocking proceed. Each chicken farm needs at least 20 sentinel chickens for confirmation, and if a farm has multiple chicken houses, at least 5 chickens must be placed in each house.

After the avian influenza outbreak in December last year, the COA has already culled 4.45 million chickens, ducks and geese. Recently, reported cases have slowed, and many poultry farms are busy restocking. On February 25, the COA coordinated with the Livestock Research Institute in Xinhua, Tainan, to raise 252 chickens. The first two avian influenza virus test results were both negative, but in the final test before deployment, on March 26, avian influenza antibodies were detected. On the afternoon of the 28th, nucleic acid of H5 subtype avian influenza virus and antibodies of H5 and H6 subtypes were detected. To avoid affecting other chickens, all were culled that day. Yesterday it was confirmed that the chickens carried both old-type and new-type avian influenza viruses.

BAPHIQ Director-General Chang Shu-hsien said that when testing sentinel chickens, the serum of every five chickens is mixed into one sample. Of 50 samples in total, one tested positive for nucleic acid of the new-type H5N2 subtype avian influenza virus, and more than 30 tested positive for old-type H5N2 subtype avian influenza.

Source of the virus still to be clarified

Where exactly did the virus come from? Huang Ying-hao, Director of the Livestock Research Institute, said that the source of the sentinel chickens also came from the Livestock Research Institute, and the first two tests did not detect avian influenza, so the problem should not lie with the source, and it remains to be clarified.

The Livestock Research Institute has 6 chicken houses in total: one is empty and unused, four house 11 rare breeds of conservation chickens, and one is used to raise sentinel chickens. Chang Shu-hsien said that the chicken house raising sentinel chickens had bird-proof netting, but no buffer zone; the Livestock Research Institute has a large yard with many birds roosting, so perhaps avian influenza virus was already present in the environment, or perhaps personnel entering and leaving frequently during sampling brought the virus in. Epidemiological experts have been asked to investigate, and no sentinel chickens can be provided in the short term.

Previously, the COA had repeatedly urged farmers to build bird-proof netting and pay attention to personnel entering and leaving bringing in the virus, yet it was given a heavy slap in the face by its own people. Will closed, environment-controlled chicken houses be built in the future?

Chang Shu-hsien said there is no such plan, because the number of sentinel chickens raised is small. At present, other private chicken houses have been rented to raise sentinel chickens, and the location is not convenient to disclose, though it is still not a fully environment-controlled closed space. He said it would be best not to have poultry farms near where sentinel chickens are raised; there are fully closed chicken houses in the private sector, but due to location and cost considerations, renting closed chicken houses is not currently being considered.

COA foots the entire bill for sentinel chicken testing

As of 6 p.m. yesterday, a total of 117 free-range chicken farms, 31 broiler farms, 5 laying hen farms and 13 turkey farms across Taiwan had tested positive for avian influenza, and the COA is still tallying the demand for sentinel chickens. Based on the minimum standard of 20 per farm, at least 3320 sentinel chickens would be needed for full restocking.

In the past, sentinel chickens were all raised by the private sector and sent to the COA's Animal Health Research Institute for testing; once confirmed qualified, they could be deployed. But this time, to avoid a shortage, the COA provided sentinel chickens for the first time, only to get off to a bad start. Will this affect the restocking schedule? Huang Ying-hao believes that in the past they were always raised privately or from imported hatching eggs and breeding chickens, so the loss of just over 200 chickens from the Livestock Research Institute should not have too great an impact.
Chang Shu-hsien did not answer directly, saying only that farmers can raise sentinel chickens themselves and send them to the Animal Health Research Institute for testing, with all costs covered by the COA. "With everyone working together, it should still be okay."

To conserve precious breeding chickens, avian influenza vaccination not ruled out

The fall of sentinel chickens at the Livestock Research Institute could also affect 6,000 precious conservation breeding chickens. The Livestock Research Institute is the country's most important source bank of breeding stock, having introduced more than 10 rare breeds of chickens. Today all were tested for whether they had contracted avian influenza virus, with results expected by the weekend.

Taiwan currently does not allow avian influenza vaccination, but Chang Shu-hsien said that because these chickens are very precious, if infection with avian influenza is confirmed, vaccination to boost antibodies would not be ruled out. After the hens complete their task of reproducing, they would be culled to avoid the vaccine taking root, and the eggs laid would be fumigated and moved to the Agricultural Research Institute for raising, though how to proceed still depends on the test results.

News Glossary

1. Sentinel chicken:

(1) What is a sentinel chicken?

After a poultry farm or laboratory has been disinfected and cleaned, it must be further confirmed whether any virus remains. At this point, a healthy advance team, namely "sentinel chickens" (Sentinel chicken), must be sent into the poultry farm and observed for 21 days. If virus still remains in the environment, the sentinel chickens may bravely fall; even if they do not develop disease, their serum and tracheal and cloacal fluids must be tested to confirm they are not infected with the virus.

(2) How many sentinel chickens does each chicken farm need?

The COA stipulates that each poultry farm must have at least 20 sentinel chickens, and if the poultry farm has separate chicken houses, each house must have at least 5 sentinel chickens. Taking this avian influenza outbreak as an example, if an operator has one chicken farm with 6 chicken houses, at least 30 sentinel chickens are needed, and only after all are confirmed uninfected can restocking proceed.

(3) Where do sentinel chickens come from? What conditions are required?

Taking avian influenza as an example, since the purpose is to monitor whether avian influenza virus is present in the environment, sentinel chickens must not carry this virus to begin with, but to prevent the sentinel chickens from dying before they grow up, they still need to be vaccinated in accordance with COA regulations. For example, after 1 day of age they must be injected with Newcastle disease vaccine to avoid dying from disease halfway through rearing.

The COA stipulates that sentinel chickens must have Newcastle disease antibody titers of 16 or above, be at least 4 weeks old, and not carry avian influenza. In the past, sentinel chickens were all raised by the private sector and sent to the Animal Health Research Institute for testing; this is the first time the COA has provided them.

2. SPF (specific pathogen free) chickens:

Some people confuse SPF chickens with sentinel chickens, but the two differ in both nature and rearing process. The full term of SPF is specific pathogen free, meaning "free of specific pathogens," that is, not carrying a certain disease. At present, in Taiwan only the Animal Health Research Institute can raise SPF chickens, monitoring 15 kinds of viruses, including Newcastle disease and avian influenza, usually as laboratory animals.

To avoid the intrusion of viruses or microorganisms during rearing, SPF chickens are cared for in every possible way: the water they drink is treated by reverse osmosis, the air is filtered layer by layer and changed regularly, and so on. In the end, however, they still cannot escape death, sacrificing themselves heroically for the development of vaccines and veterinary drugs.