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Poultry - 2004
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"Minnesota produces and processes more turkeys than any other state in the U.S. Animal health (disease and nutrition) and regulations are the most important issues to the industry. Of turkey diseases, APV is of the most concern to not only the state’s turkey industry but also the broiler and egg layer sectors. The annual estimated cost tot the turkey industry alone is $15 million."
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| Project Contact: | K.V. Nagaraja | Funding: | $50,000 |
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District:
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| • The Problem • Background • Objectives • Mid-Year Progress Report • |
Researchers designed a laboratory experiment to simulate the stressful field conditions. Sixty, one day-old APV-antibody-free commercial turkey poults were divided into two equal groups. At 2 weeks of age, poults in one group were infected with APV. Poults in the second group were maintained as an APV non-infected group. After three weeks, poults in the infected group were further divided into two subgroups of 15 birds each and housed separately. Poults from one subgroup were treated with intramuscular injection of Dexamethasone and Cyclophosphamide to induce immunosuppression. Post-treatment, researchers collected tracheal and choanal swabs from individual birds at weekly intervals for virus detection by RT-PCR and real time quantitative RT-PCR.
Persistence of APV infection in turkey flocks in barn environment
Researchers carried out this study with the collaboration of a turkey producer in Minnesota. They examined the length of persistence of APV in flocks and in the barn environment following a post clinical outbreak. So far they have analyzed birds from three APV-positive flocks. The birds showed clinical signs of APV at the age of 8-12 weeks. The results were confirmed by RT-PCR and APV-ELISA. They collected nasal turbinate and blood samples from the birds selected at random from these flocks. Samples were collected at four week intervals starting from the time of their first APV exposure till they were sent for processing. The last set of samples was collected at the processing plant to investigate the effect of transport stress if any on the appearance of APV in birds. Results: In two flocks out of three, APV persisted in infected turkeys up to 18 weeks of age. APV-RNA could be detected in the nasal turbinate up to 18 weeks. In the third flock, APV persisted up to 21 weeks (until the birds were sent for processing). All the three flocks were serologically positive for APV antibodies when tested by APV-ELISA throughout the flock cycle.
Researchers collected litter samples at four-week intervals from each barn from the three APV infected flocks. These were processed to detect APV by RT-PCR. Results: Of the three barn environments examined, researchers detected APV-RNA from the litter in one facility up to 9.5 weeks post clinical infection of APV and up to 6 weeks post infection in the second facility. The third facility remained negative for the presence of APV in the litter, though the birds were positive for APV up to 21 weeks of age.
Pathogenesis of APV infection in domestic turkeys
Researchers have conducted an experiment to investigate the pathogenesis of APV in two-week old turkey poults. Two-week-old turkey poults were divided into two groups. One group was inoculated with APV (MN 19). Birds in the second group were maintained as controls. The birds were monitored daily for clinical signs. Five birds each from group 1 and 2 were sacrificed and samples such as nasal turbinates, trachea, conjunctiva, lungs and liver were collected at 1, 3, 5, 7, 9, 11, and 14 days post-inoculation, and analyzed. Results: Birds showed severe clinical signs of infection from 4 day PI to 12 day PI. Viral RNA could be detected for 14 days post infection from nasal turbinate and for 9 days from trachea.