041114 USDA Funds Avian Flu Vaccine for Poultry

Washington - An Iowa company will develop an avian influenza vaccine antigen bank that could produce up to 40 million doses of vaccine for poultry, the US Department of Agriculture's (USDA's) Animal and Plant Health Inspection Service (APHIS) announced recently.

APHIS's Center for Veterinary Biologics (CVB) has awarded a 5-year contract to Fort Dodge Animal Health to manufacture and store killed, frozen bulk viral antigens that can be used to produce vaccine for the H5N2, H5N9, H7N2, and H7N3 subtypes of avian flu, according to an APHIS news release. The company will produce and store the antigens in Charles City, Iowa.

The antigen bank will speed production of poultry vaccine if it is needed, Bruce Carter, DVM, global vaccine manager for the CVB. The vaccine could be produced quickly and used to help contain an outbreak of avian flu in some situations, decreasing shedding and spread of the virus. The bank is to be fully stocked by January 2004, APHIS said.

Vaccine is often used in conjunction with other strategies to control and eradicate the disease. Along with other measures, vaccine was used in the United States as recently as 2003 in a successful effort to eradicate a low-pathogenic virus in layer flocks in Connecticut, Carter said.

Highly pathogenic avian influenza (HPAI) is an extremely infectious and fatal form. Once established, it can spread rapidly among flocks. An HPAI outbreak in 1983- 84 cost the industry nearly $65 million, and an H5N2 outbreak last February in Texas forced the slaughter of 7,000 broiler chickens, according to APHIS.

The new antigen bank is intended to help counter HPAI, APHIS Administrator W. Ron DeHaven said in the press release. "The [avian influenza] vaccine antigen bank will be a great asset in helping APHIS work to keep highly pathogenic avian influenza from becoming established in the US poultry population," he said.

In the event that vaccine from the new bank is administered to a poultry flock, a vaccine that doesn't precisely match the strain affecting the flock could be used intentionally, said Carter. At least 80% of the efficacy of an avian flu vaccine is due to the hemagglutinin (H) antigen, he said. So, for example, using H5N9 vaccine to vaccinate birds exposed to H5N2 flu helps protect the birds while allowing veterinarians to distinguish between vaccinated and infected birds on the basis of the neuraminidase (N) subtype. This procedure is known as DIVA (Differentiating Infected from Vaccinated Animals), he added. APHIS guidelines allow H5 and H7 vaccines to be used as tools in potential outbreaks of HPAI in the United States, but only under APHIS supervision or as part of an official animal disease control program, the news release said.

In the first phase of the project, worth $800,000 to Fort Dodge Animal Health, the company will grow the viruses in eggs, as is done for human flu vaccines, Carter said. Next, the allantoic fluid containing the virus will be harvested from the eggs and the virus inactivated. Then the killed bulk viral antigens will be frozen. The antigens can be thawed and mixed with adjuvants to boost the strength of the vaccine, and the resulting vaccine used to immunize poultry.

Fort Dodge Animal Health will store the frozen antigens for 5 years. If vaccine is needed during that time, Carter said, it can be produced relatively quickly. Completing vaccine production if needed is the second phase of the project.

If the bank is activated, Fort Dodge Animal Health's contract calls for the company to receive an additional 1.2 cents per dose, or $120,000 for 10 million doses of a subtype. The maximum possible value of the contract is $1.28 million, Carter said.

"I can't predict how and when we're going to use the vaccine," Carter added, noting that using avian flu vaccine isn't always the best response, depending on the circumstances of an outbreak. "Some years it seems like we just get hammered with outbreaks of avian influenza."

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