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Avian - 2001
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| (Print Friendly Version) |
| Project Contact: | David A. Halvorson | Funding: | $44,000 |
| Kakambi Nagaraja |
District:
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Unknown |
| • The Problem • Background • Mid-Year Progress Report • |
Respiratory diseases of turkeys are responsible for more than $35 million in losses to Minnesota’s turkey producers each year. This is a small but significant slice of a Minnesota poultry industry that employs more than 25,000 people and annually contributes more than $1 billion to Minnesota’s economy.
A respiratory disease caused by an avian pneumovirus (APV) has been spreading across the turkey production areas of Minnesota. It has caused losses of more than $20 million to Minnesota turkey growers since first diagnosed in 1996. This disease has not been reported in any other major turkey producing state. Thus, one of the greatest potential risks of this disease is the increased condemnation of birds and a ban of birds from Minnesota for foreign markets.
This year’s Rapid Response funding continues to build on emergency funding appropriated by the State Legislature in FY98 to:
Using this knowledge, a plan is being developed to constrain the disease from spreading to uninfected flocks.
Three interrelated problems have plagued researchers in this area: the inability to grow avian pneumovirus (APV) in sufficient amounts, the inability to obtain APV isolates from field infections, and the inability to determine the natural reservoir of APV.
January 2001
Problem 1. Growing sufficient amounts of APV
Background: University researchers have been struggling with a virus that grows to only about 100,000 virus particles per ml. This is about a tenth of a percent of what’s needed to make a vaccine, improve a test or study the virus. This goal is to develop techniques to increase virus yield in the laboratory.
Results: We have tried to grow APV in different tissue culture systems, at different temperatures, under different conditions, in chicken eggs, in turkey eggs, etc. We have shown APV grows most consistently in embryos inoculated by the yolk sac. Many cell-lines have been eliminated from further consideration for a variety of reasons. Work continues with others.
Problem 2. Establish a Center for Isolation and Characterization of APV
Background: More than 800 flocks in Minesota were found to have APV in teh first two years we knew about APV in the state. Only a handful of APV isolates could be identified despite intensive efforts to retrieve and process samples quickly.
Isolating APVs from different flocks is necessary to determine how the virus gets from farm to farm, whether all the infections are due to a single virus clone and whether one vaccine will protect against all outbreaks.
Results: A new Center for Isolation and Characterization of APV is coordinating many laboratories’ procedures for submitting, receiving, and processing samples, isolating viruses and subjecting them to tests for molecular, epidemiological, pathological and serological characterization.
Sixteen virus isolates have been retrieved from 110 submissions received between October 1999 and July 2000. The submissions accounted for thousands of sampled turkeys and hundreds of PCRs and virus isolation attempts. Preliminary indications are that 1997 isolates are different from 1999 isolates.
Problem 3. Seek the natural reservoir of APV
Background: Circumstantial evidence supports a wild bird reservoir for APV. Ducks have been shown susceptible to APV. To examine the role of waterfowl in APV epidemiology, isolation-reared sentinel ducks were allowed contact with wild waterfowl, and monitored weekly for APV infection. APV was detected in the sentinels.
With other birds, 60 percent of 270 Canada geese nabbed during a metropolitan goose roundup were found positive, and one-third of 155 blue winged teal caught during a North Dakota DNR banding operation were positive.
Impact: APV is clearly found in wild waterfowl! The role of waterfowl as a reservoir and in transmission of APV remains to be elucidated.
Other specific results: