Significant progress in controlling poultry-borne infection was reported recently at the 69th Northeastern Conference on Avian Diseases at Cornell.
Still, two diseases (avian influenza and infectious laryngotracheitis, or ILT) threaten the economic health of the American poultry industry and at least one (Salmonella enteritidis, or SE) worries Americans who eat eggs, conference participants from as near as New York and Pennsylvania and as far as Australia were told.
"When it comes to infectious diseases, there's a lot a stake for an industry that exports up to 20 percent of the 6 billion broilers produced here each year to other countries," said Benjamin Lucio, the poultry extension veterinarian who organized the June 11 to 13 meeting at Cornell's College of Veterinary Medicine. "The general public doesn't know or care when millions of dollars are lost because hundreds of thousands of infected birds must be slaughtered. But the public wants assurances," he said, "that the eggs they consume are not infected with salmonella."
That confidence can come from voluntary egg quality assurance programs, John Mason of Food Safety Consultant Services told the avian disease conference. A successful quality-assurance program in Pennsylvania has producers certifying that whole eggs sold to market come only from salmonella-free flocks (and that eggs from flocks with evidence of SE are diverted to processing plants where the eggs are pasteurized to destroy infectious organisms).
A similar quality-assurance program is expected to start in New York later this year, according to Syed A. Naqi, professor of avian medicine at Cornell. The New York program is the result of combined efforts of the New York State Department of Agriculture and Markets and the Cornell College of Veterinary Medicine's Diagnostic Laboratory.
"We've made tremendous progress in this century in understanding and controlling avian diseases," said Lucio, who along with Cornell poultry scientist Robert C. Baker was the first to prove that SE is transmitted by eggs. He pointed to successful test and control strategies developed for potentially devastating conditions in poultry, such as Marek's disease, mycoplasmosis, infectious bursal disease and infectious bronchitis. "Yet, there continue to be emerging diseases, and in an era of expanding international trade, proving that your animals are disease-free is more important than ever," he said.
One strategy for controlling avian influenza could be a genetically engineered vaccine that is now in use in Mexico, Lucio said. The alternative to prevention is "depopulation," in which entire flocks of birds are slaughtered and buried. Earlier this year, infection by the H7N2 strain of avian influenza cost a Pennsylvania egg producer a flock of 123,000 birds, Susan C. Trock of the U.S. Department of Agriculture reported. In the early 1980s, a different avian influenza strain crippled the Pennsylvania poultry industry, forcing the slaughter of some 17 million birds; the result was an estimated loss to producers of $400 million and expense to American taxpayers of $50 million when the federal government partially compensated poultry producers.
Like avian influenza, infectious laryngotracheitis does not affect humans -- except in the pocketbook -- Lucio said. One out of every six broiler chickens raised in the United States is exported, primarily to China and Russia, the Cornell poultry expert said, "and if we can't eradicate that disease to the satisfaction of our overseas customers, we'll have a big problem. While conventional vaccines protect against clinical ILT, they contribute to perpetuating the infection in vaccinated flocks," Lucio said. He noted that genetically engineered vaccines, now under development, show greater promise.
"By hosting the avian disease conference, Cornell University renewed its long-standing ties to poultry medicine and husbandry," Lucio said. "The exchange of ideas between university researchers, industry representatives and veterinarians from the USDA will influence policies for the control and eradication of these important diseases."
Besides the disease-control strategies with bioengineered vaccines and international embargoes, the conference-goers learned of one type of immunization with which every chicken can identify -- the lowly earthworm. Canadian researchers reported on studies with salmonella and vermicompost, the soil-like material that passes through worms when they eat.
The researchers raised earthworms on feces from disease-free chickens and then fed the vermicompost to newly hatched chicks. In theory, "good" bacteria in the vermicompost were supposed to thrive and displace any "bad" bacteria, including salmonella, in the young birds. Yes, the chicken-worm-chicken connection helps, to some extent, researchers said.
