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Avian - 2001
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| Project Contact: | Moses Njenga | Funding: | $16,000 |
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| • The Problem • 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.
January 2001
This project is trying to develop a reliable enzyme-linked immunosorbent assay (ELISA) for diagnosis of avian pneumovirus (APV) infection.
Trials are comparing the detection rates for APV found, in experimentally infected turkeys, with a "routine" ELISA versus use of a recombinant M protein based ELISA. The M protein ELISA is identifying infected birds at a much higher rate (97.1% vs. 52.9% at 28 days after infection) while also reducing the number of false positive readings. In another trial, of 184 samples received from commercial turkey flocks suspected of APV infection, 133 samples (72.3%) were positive by M protein ELISA, whereas only 99 samples (53.8%) were positive by routine APV ELISA.
The M protein ELISA has been found to be more than six times more sensitive than virus isolation in detecting infections from samples obtained from cases showing clinical signs of APV infection. Taken together, these results showed that ELISA based on recombinant M protein is a highly sensitive and specific test for detecting antibodies to APV.
Impact: Results have been published in the Journal of Clinical Microbiology (volume 38, pages 4010-4014) and a US Patent application based on the results has been filed. Presently, we have obtained sera for APV subgroup A and subgroup B strains from Dr Richard Gough of Veterinary Laboratory Agency, New Haw, England. The sera are being tested for cross-reactivity with US APV using both the routine ELISA and M-based ELISA. We are also generating polyclonal antibodies to purified APV and M protein. The competitive ELISA test should be complete in the next 6 months.
Details: Sera from APV-infected turkeys consistently contained antibodies to a 30 kDa protein (M protein). An ELISA based on recombinant M protein generated in E. coli was compared with the routine APV ELISA that utilizes inactivated virus as antigen. In experimentally infected turkeys, 33 of 34 (97.1%) were positive by M protein ELISA, whereas only 18 (52.9%) were positive by routine APV ELISA 28 days after infection. None of the serum samples from uninfected experimental turkeys (n=41) were positive by M protein ELISA. Of 184 field sera from turkey flocks suspected of APV infection, 133 samples (72.3%) were positive by M protein ELISA, whereas only 99 samples (53.8%) were positive by routine APV ELISA. Twelve (12) serum samples, which were negative by M protein ELISA, but positive by routine APV ELISA were not reactive with either recombinant M protein or denatured purified APV proteins by western analysis. This indicates that the samples were false positives by routine APV ELISA. The M protein ELISA was over six times more sensitive than virus isolation (11.5%) in detecting infections from samples obtained from cases showing clinical signs of APV infection.