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Veterinarians, farmers eliminate LT threat

By Laura Whelan

MISSISSIPPI STATE -- By employing vaccinations and biosecurity measures, Mississippi veterinarians and the poultry industry have brought a devastating disease under control.

Laryngotracheitis, a viral infection of the chicken respiratory tract, was suspected on at least 70 Mississippi farms from December 2002 through March 2003. Six of the nine poultry companies in the state had at least one diagnosed case of LT.

"The consequences of LT make it a significant threat," said Dr. Danny Magee, clinical professor of avian medicine at Mississippi State University's College of Veterinary Medicine. "The mortality rate for chickens that contract this disease has negative effects on production efficiency, including meat and egg production."

That's why the state veterinarian's office in Jackson, MSU-CVM veterinarians and the poultry industry joined forces to combat the disease, which infects chickens through their upper respiratory tract and eyes, causing respiratory distress.

"LT occurs sporadically in the U.S. poultry industry," Magee said. "But it has been about 20 years since we had an outbreak in Mississippi."

Since the poultry industry in Mississippi is quite large and involves a great deal of farm-to-farm movement, the first step toward defeating the disease was to minimize contact between poultry populations. The industry implemented biosecurity measures on chicken farms, including washing boots, wearing coveralls and stopping unnecessary visits to reduce the risk of spreading LT.

Utility companies responded to industry requests to distribute biosecurity information to farmers and implement biosecurity precautions for their employees who made service calls at chicken houses.

Scientists at CVM performed testing to confirm LT diagnosis, while the CVM Poultry Research and Diagnostic Laboratory in Pearl collected samples and performed case evaluations. They found that biosecurity measures were helpful, but the seriousness of the disease required a more powerful weapon. The state veterinarian's office and CVM veterinarians worked with the industry to develop a vaccination protocol.

"Birds were vaccinated with a modified live-virus vaccine administered through drinking water, coarse spray or eye drops," Magee said. "All birds received the first vaccination at 2 weeks of age. Breeder birds were commonly re-vaccinated at 10 and 18 weeks of age."

The state veterinarian's office reported that the vaccinations have controlled the outbreak.

"Having gone through several months of vaccinations, we feel LT is under control," said Dr. Jim Watson, state veterinarian. "As of May 9 we discontinued vaccinations in Mississippi."

To prevent further problems with LT, Watson said the state has adopted a proactive protocol.

"We are taking stringent steps to ensure LT doesn't persist. This summer, chicken houses will be heated to high levels and cleaned thoroughly to eliminate infectious agents before new chickens come in," he said.

"We're using our experience with this disease to reinforce the importance of always being on our toes where animal health is concerned and always having an active biosecurity plan," Watson said. "We have to have safety measures in place all the time because once a disease hits, it's too late to implement them."

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Released: May 19, 2003
Contact: Dr. Danny Magee, (601) 932-6771

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