2018-19 Rapid Ag: Re-emerging Turkey Arthritis Reovirus in Minnesota turkeys: Development of Novel Diagnostic Assays and Control Strategies
Sunil Kumar Mor
Veterinary Population Medicine
- 2018 Fiscal Year: $125,000
- 2019 Fiscal Year: $125,000
At the Minnesota Veterinary Diagnostic Lab, we have seen an increase in submission of 12-18 week-old turkeys that are recumbent with wing tip bruises (“wing walkers”), uni- or bilateral swelling of the hock (tibiotarsal) joints, and increased fluid in the tendon sheath and hock joint. Lately, another change has been seen in the clinical picture of some cases e.g., cartilage erosions, which have not been previously described and clinical lameness in young turkeys at the age of 6-8 weeks. In some instances, lameness affects 35-70% of a flock resulting in huge economic losses to turkey producers from excessive culling, diminished carcass quality (male drums) and reduced market weights in addition to raising animal welfare concerns.
A turkey company in Pennsylvania lost an estimated $3 million in 2014 due to re-emerging TARV-associated lameness1. Custom autogenous vaccines made with 2011 strains helped slow down the infection initially, but now is ineffective against the newly evolved strains. This failure appears to be due to the use of inappropriate strains, which in turn is due to lack of information on mutation of TARVs circulating in the field. This was confirmed by the fact that viruses isolated in 2014 were antigenically different from 2011 isolates based on virus neutralization assays2.
Anticipated benefits: Analyzing the complete genome of TARVs from Minnesota and neighboring states will help in characterizing newly emerging TARVs, their relationship with 2011 isolates, and with those used in autogenous vaccines. Currently, no molecular or serological test is available for specific detection of pathogenic TARVs and anti-TARV antibodies. We intend to find molecular markers that can differentiate TERVs from TARVs, which will help in the development of diagnostic tools for early detection of TARVs leading to implementation of preventive and control measures. Also, empirical approach of strain selection for vaccine development needs to be replaced with scientifically-based criteria by studying the types of strains (and the relationships among them, if any) circulating in the population. Recently, Goldenberg et al.3developed a polypeptide vaccine against chicken arthritis reovirus (CARV) in which a fragment of sigma C protein (SC122-326) was found to induce strong mucosal immunity, which resulted in elimination of infection with virulent strains to a higher extent than that produced in response to whole virus. This fragment includes globular head, shaft and hinge domains while eliminating intra-capsular region, which means that this segment folds correctly and exposes epitopes that are identical to those of the native protein. Since TARVs are similar to CARVs in terms of the genomic structure, segment sizes and open reading frames, this fragment (SC122-326) of TARV should be useful in the development of uni- or multi-valent virus vectored vaccine against TARV.
To study the evolution and genomic constellations of newly re-emerging, lameness-associated turkey arthritis reoviruses (TARV) with a view to develop highly sensitive and specific diagnostic assays and to develop and evaluate safe and effective vaccines. Specific aims:
- To sequence the complete genomes of a representative number of TARVs in order to determine space-time distribution of variant viruses, to determine genetic changes associated with tissue tropism of these re-emerging viruses, and to identify specific strains for the development of safe and effective vaccines with wide spectrum immunity
- To develop highly sensitive and specific molecular and serological diagnostic assays
- To generate recombinant Pichinde virus-based vaccines that express the sigma C or sigma B and sigma C proteins of TARV using strains identified in Aim 1
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