The highly pathogenic Avian Influenza (AI) strain that has caused so much havoc in Asia and Africa in recent years is unlikely to hit the Western Hemisphere, let alone U.S. shores, experts say.

"For it to come here would require very bad luck or it would have to be intentionally brought in," says Steve Roney, senior staff veterinarian for the National Poultry Improvement Plan in Conyers, Ga.

One key reason why, he says, is that the strain everyone is concerned about H5N1 has not been discovered in any wild bird populations that frequent Western Hemisphere flyways. Every year that goes by without an outbreak makes it less likely that one will occur, Roney says. "For it to come here would require illegal smuggling or have it be intentional," he says.

Good news on the AI front, Roney adds, is that it does not seem to be increasing globally, "It's talked about less than it was a year ago." He notes that there have been 300 cases in people in the past 10 to 11 years, which is actually quite low considering the level of outbreaks in birds and the intermingling of birds and humans in areas affected. "I'm not saying it's not important, but it's not a hugely important disease worldwide," Roney says.

The odds are "very, very, very slim" of high path AI reaching the United States, agrees John Brown, manager of veterinary services for Centurion Poultry Corp., Lexington, Ga. In addition, were an isolated case to occur, government and industry are well prepared "to clear it up." He continues, "We're in good shape for preparation on both a state and national level to react quickly to an outbreak."

Brown says that were a case to occur in the United States, it would likely come here through other than legal channels. Brown adds that globally, H5N1 is down a little compared to year-earlier levels, so if it's going to increase "it will have to start pretty soon." That said, he notes that an outbreak hit a small turkey flock in the United Kingdom in mid-November, but that flock was depopulated, and the outbreak does not pose a risk for the United States.

An important reason why H5N1 is unlikely to hit the United States is that U.S. flocks are segregated from people and other animals. Southeast Asia and Africa, meanwhile, have many backyard chicken flocks, making testing and eradication programs difficult, one veterinarian explains. "It's easy to test large production systems here," she says.

Another reason to be optimistic that no H5N1 will enter the United States is that "there has been no crossover detected from Alaska," says Eric Gingerich, staff veterinarian and adjunct assistant professor at the University of Pennsylvania School of Veterinary Medicine in Kennett Square. And were it to occur, "we have pretty good biosecurity in place," he says. "But my thought all along has been that it wouldn't come here at all."

Still, H5N1 is the No. 1 layer disease problem globally, Gingerich says, and it has spread since it was first discovered in 1996-97.

Other Diseases

While things have been mostly quiet on the AI front, other diseases are not. "In the United States, there has been a slight increase in Salmonella enteriditis (SE ) over the past year," says Roney, for no particular reason. SE seems to run on a five-year cycle, he adds, and overall the industry is doing a good job managing the disease.

There also were some cases of Mycoplasma gallispecticum (Mg) and Mycoplasma synoviae in 2007. "It's always there and a challenge," Roney says. Of respiratory diseases, most important for layers economically is (Mg), says Guillermo Zavala, assistant professor at the University of Georgia. He believes that in the United States, "as a group, respiratory diseases are the most important concern."

"Overall health of the national table egg layer flock is very good," Gingerich said at the U.S. Animal Health Association annual meeting in Reno, Nev., in late October. But some diseases still are of concern. He conducted a poll of Veterinarians in Egg Production, which ranked the following concerns:

No. 1: E. Coli/peritonitis;

No. 2-3-4, a three way tie: coccidiosis/necrondtic enteritis, Mg and calcium depletion/tetany; and

No. 5, respiratory viruses (i.e., Infectious Bronchitis, Infectious Laryngotracheitis) and cannibalism.

Other diseases of concern for the industry, he said, are AI and SE.

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Will Cage-Free Boost Disease Problems?

An important issue is whether diseases will increase as cage-free egg production rises. "When you put birds on the ground, you tend to have more parasites coccidiosis and tapeworms, for example," Roney says, leading to more required medications or vaccinations.

Gingerich expects to see more fowl cholera under cage-free or pasture conditions.

Don Bell, Poultry Specialist (emeritus) at the University of California-Riverside, says that more cage-free production puts hens at additional disease risk. Reducing diseases, he says, "is why we went to cages in the first place." Specifically, he says that cage-free birds are at more risk to intestinal parasites and worms.

Overall, cannibalism is a problem, though stable, Gingerich says, "but we're seeing more cannibalism in cage-free flocks."

Dennis Avery, director of Global Food Diseases and former USDA and Central Intelligence Agency analysts, says there is no question that more cage-free production means more disease and cannibalism by birds.

In the United States and globally, diseases have probably decreased in recent years, experts say. Neoplastic or tumor diseases continue to be of concern, says Zavala, as well as infectious bronchitis.

Globally, he says that Newcastle, in addition to AI, continues to be a concern. In some parts of the world tropical areas with high humidity, he says, infectious coryza is a problem. Another bacterial disease he adds to the list of concerns is peritonitis, a condition caused by bacterial disease that is caused by producing eggs too early.

Overall, he says, layer diseases are down substantially over the past few years. Reasons why, he says, are genetics and stricter bird density regulations, and the fact that birds in the United States are raised in clean environments.

He agrees that cage-free birds might be exposed to more pathogens, which also raises food safety concerns.

One viral disease Brown sees is Marek's, even though he sees it a lot less in the United States than in other parts of the world. He also has been seeing a fair number of infectious bronchitis cases. Another viral disease he has been seeing is infectious laryngotracheitis, which has been on the increase in the United States during the last four years. A high mortality, fall and wintertime disease, he says, "It seems to cycle." Brown agrees that salmonella SE runs in cycles and is a little on the increase. EI