Avian influenza found in Texas

March 2004

Avian influenza, which decimated Asian poultry flocks and infected several people, has been found in U.S. flocks in several states. However, the strains are not related, public health officials said.

One state reported a highly pathogenic strain of H5N2, and the others reported low pathogenic strains. Countries from Russia to Mexico have banned importation of American poultry products. Early this year, Delaware and Pennsylvania reported finding avian influenza in their poultry flocks, but the disease was a low pathogenic strain (H7N2, H2N2, respectively). The birds either died from the disease or were culled.

However, in late February, the Department of Agriculture (USDA) confirmed that the highly pathogenic strain of H5N2 avian influenza was found in a chicken flock in Texas. This was the first U.S. case of highly pathogenic disease in birds in 20 years.

“Avian influenza is a very highly contagious disease. Exposure of poultry to migratory waterfowl seems to be the most likely cause or certainly the ongoing reservoir of infection. But once established, the movement of poultry, poultry equipment and people from one infected premise to another poses the risk of introducing avian influenza into other premises and certainly into commercial poultry,” said W. Ron DeHaven, DVM, MBA, deputy administrator for the USDA veterinary services program. “Once it’s in a flock, the spread of the disease can occur from bird to bird by direct contact and then as I mentioned typically from farm to farm through people, equipment and other mechanical means of transmitting the virus.” DeHaven spoke at a press briefing held in Washington D.C.

The flock was found in Gonzales County, Texas, about 50 miles east of San Antonio. This establishment is under state quarantine, and approximately 6,600 broiler chickens were depopulated by Texas authorities. In addition, an epidemiological investigation determined that infected birds were sent to two live bird markets in Houston, so those are also under quarantine.

The original birds were found during routine surveillance, DeHaven said. “Samples that were sent to the Texas Veterinary Medical Diagnostic Laboratory where they received a preliminary positive for an H5 virus, avian influenza virus. That then prompted follow-up on-site investigation at the premises.”

Samples were submitted to the National Veterinary Services Laboratories (NVSL), where H5N2 was confirmed, and the lab also did DNA sequencing. “Since H5 and H7 avian influenza strains can either be low path or high path, we initiated the additional tests,” he said, including genetic sequencing.

Public health officials are encouraging poultry producers and others in the industry to make sure that equipment, such as manure-spreading equipment, vehicles, egg flats, crates, people and their clothing and footwear are properly cleaned and disinfected between coops on the same poultry premise or before traveling to another poultry area. “Any poultry producer that notices an increase to mortality, we would encourage them to report those losses to their veterinarian, to the appropriate USDA extension agent, to their state animal health agency, or certainly they can contact us as well,” he said.

To date, no human cases have been reported in the United States. “Avian influenza viruses usually do not infect humans. And the ability of avian influenza viruses to transmit from person to person appears to be very limited, even if humans do become infected with an avian influenza virus. And past experience with H5N2 viruses have indicated that there is a low threat to public health,” assured Nancy Cox, PhD, chief of the influenza branch, CDC.

Nevertheless, Cox said, “We must keep an open mind and really monitor the situation as we go.” She said people who come in contact with infected birds should contact their doctor if they develop influenza-like illness like fever or respiratory symptoms. Anyone who has been involved in the culling should monitor his or her health for 10 days.

USDA is working closely with the CDC to forestall any human outbreak. There is no evidence to date of any human transmission of this virus in Texas.

The Texas premises in Gonzales County, Texas, were under quarantine when Infectious Disease News went to press, and the flock was depopulated.

In other news, nearly 100 million birds have died or been culled to stop the spread of the H5N1 strain of avian influenza in Asia. The Asian reports led to a CDC ban on the importation of poultry from Asian countries because public health officials are afraid the virus might spread to those living in this country.

“Introduction of influenza A (H5N1) infected birds into the United States could lead to outbreaks of disease in the human population, a significant public health threat,” explained CDC Director Julie L. Gerberding, MD, in the order banning the birds.

Until further notice, birds, poultry products and eggs are banned from Cambodia, Indonesia, Japan, Laos, Hong Kong and China, South Korea, Thailand and Vietnam. According to the U.S. Fish and Wildlife Service, the United States imports more than 20,000 live birds from countries affected by avian influenza.

WHO reported stability among the number of countries in Asia that reported avian influenza in Asia and said the disease appears to have stopped spreading to new countries.