By Rob Porter DVM, PhD, Sunil Mor, DVM, PhD, and Sagar Goyal, DVM, PhD
University of Minnesota
This is the 1st article in a series of 4.
Should I keep my turkeys away from chicken farms to prevent transmission of TARV? Our research indicates that the reovirus isolated from turkey tendons is quite different from that isolated from chickens. However, good biosecurity always means following protocols to keep turkey flocks separated from other turkey and chicken flocks. The chicken arthritis reovirus (CARV) isolated from field cases does not cause arthritis in turkeys and TARV does not cause arthritis in chickens when inoculated into the mouth or trachea. There is no evidence at this time that turkeys developing reovirus arthritis can contract the infection from chicken egg layers or meat-type birds.
How is TARV infection diagnosed? Most cases are observed in tom turkeys after 12 weeks of age, but hens are occasionally affected. Lameness is associated with (intertarsal) joint swelling with edema in one or both legs (Figure 1A). Fibrosis of skin and hock joint capsule is commonly observed (Figure 1B). The gastrocnemius and digital flexor tendon sheaths can contain increased synovial fluid and flecks of white exudate. This condition can affect 5-40% of the flock. The condition when first described was associated with rupture of the gastrocnemius tendon (Figure 1C). However, this occurs in a relatively small percentage of infected turkeys. Stretched or ruptured digital flexor tendons can be observed as well. Severe lameness results in culling of birds as the primary cause of death; however, flocks with TARV-induced lameness often die from aortic rupture.
University of Minnesota
This is the 1st article in a series of 4.
What is turkey arthritis reovirus and where did it come from?
Avian reoviruses (ARVs) are RNA viruses that are ubiquitous in domestic poultry with 80% of them being non-pathogenic. However, ARVs have also been associated with enteritis, hepatitis, neurological disease, myocarditis, respiratory distress and viral arthritis/tenosynovitis in chickens and turkeys. Clinical disease associated with ARV is mostly dependent on age, and immune status of the bird, virus pathotype, and route of exposure (oral, intratracheal, footpad, or subcutaneous). Reovirus was isolated from joints and ruptured tendons of turkeys with tenosynovitis/arthritis as early as 1980; however, experimental infection of turkey reoviruses failed to reproduce the disease. After, a hiatus of >20 years, the problem of reovirus-associated lameness in turkeys re-emerged in the Midwestern and Eastern states by 2011. Turkey reoviral arthritis is now recognized as a significant cause of lameness in U. S. turkeys and the associated reovirus is referred to as turkey arthritis reovirus (TARV). Because TARV grows well in the small intestine, just like turkey enteric reovirus (TERV), and there is 98% genetic similarity (homology) of TARV with TERV, we believe that TARV has mutated from TERV and has developed the capacity to invade tendons.What are UMN Researchers learning?
Turkey arthritis reoviruses have been isolated from the gastrocnemius tendons and hock joints of lame male turkeys in the Midwest. Affected flocks often show lameness after 12 weeks of age. From 2011-2018, the Minnesota Veterinary Diagnostic Laboratory received whole turkeys or turkey legs from flocks with history of lameness and swollen hock joints. All samples were largely negative for aerobic and anaerobic bacteria as well as for Mycoplasma. Reovirus was isolated from tendon tissues in approximately 52% of these cases; the presence of virus was confirmed by multiple testing methods.Should I keep my turkeys away from chicken farms to prevent transmission of TARV? Our research indicates that the reovirus isolated from turkey tendons is quite different from that isolated from chickens. However, good biosecurity always means following protocols to keep turkey flocks separated from other turkey and chicken flocks. The chicken arthritis reovirus (CARV) isolated from field cases does not cause arthritis in turkeys and TARV does not cause arthritis in chickens when inoculated into the mouth or trachea. There is no evidence at this time that turkeys developing reovirus arthritis can contract the infection from chicken egg layers or meat-type birds.
How is TARV infection diagnosed? Most cases are observed in tom turkeys after 12 weeks of age, but hens are occasionally affected. Lameness is associated with (intertarsal) joint swelling with edema in one or both legs (Figure 1A). Fibrosis of skin and hock joint capsule is commonly observed (Figure 1B). The gastrocnemius and digital flexor tendon sheaths can contain increased synovial fluid and flecks of white exudate. This condition can affect 5-40% of the flock. The condition when first described was associated with rupture of the gastrocnemius tendon (Figure 1C). However, this occurs in a relatively small percentage of infected turkeys. Stretched or ruptured digital flexor tendons can be observed as well. Severe lameness results in culling of birds as the primary cause of death; however, flocks with TARV-induced lameness often die from aortic rupture.
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| Figure 1A-C. Fifteen-week-old tom turkey positive for reovirus: A. - TARV-infected turkeys often have periarticular swelling of one or both hock joints. B. - The swollen hock joint from Figure 1A has the skin removed to reveal marked accumulation of scar tissue (fibrosis) around the joint. C. - Fifteen-week-old tom turkey from same flock has enlarged hock with rupture of the gastrocnemius tendon (arrow). |
Assessment of legs from lame turkeys should include observing and sampling longitudinal section of leg bones to rule out the presence of bumblefoot (bacterial pododermatitis), dyschondroplasia, bacterial osteomyelitis, Mycoplasma infection, femoral spiral fractures, skeletal muscle rupture, and tendon rupture from other causes. Virus isolation remains the gold standard for definitive diagnosis of TARV.
Are there confirmatory tests for diagnosis of turkey reoviral arthritis? Again, virus isolation remains the gold standard for definitive diagnosis of turkey reoviral arthritis. This isolation can take up to two months depending on the amount of virus within the affected tendons.
Virus isolation can take weeks to complete. Is there anything faster for diagnosis?
Real-time PCR is now available at the Minnesota Veterinary Diagnostic Laboratory and is combined with virus isolation for a total fee of $60.00. The cost of real-time PCR alone is $35. Cost for leg necropsy is $75 plus 10.00 accession fee on Minnesota cases.
2. Pack on ice or frozen gel packs and ship overnight in Styrofoam cooler.
For more information, please contact Dr. Rob Porter, Minnesota Veterinary Diagnostic Laboratory (61) 624-7400 or by email porte349@umn.edu.
Are there confirmatory tests for diagnosis of turkey reoviral arthritis? Again, virus isolation remains the gold standard for definitive diagnosis of turkey reoviral arthritis. This isolation can take up to two months depending on the amount of virus within the affected tendons.
Virus isolation can take weeks to complete. Is there anything faster for diagnosis?
Real-time PCR is now available at the Minnesota Veterinary Diagnostic Laboratory and is combined with virus isolation for a total fee of $60.00. The cost of real-time PCR alone is $35. Cost for leg necropsy is $75 plus 10.00 accession fee on Minnesota cases.
What should I send the veterinary diagnostic laboratory if I suspect turkey reoviral arthritis?
1. In lieu of whole birds, select six fresh, not frozen, turkey legs excised at the hip joint (acetabulum)2. Pack on ice or frozen gel packs and ship overnight in Styrofoam cooler.
For more information, please contact Dr. Rob Porter, Minnesota Veterinary Diagnostic Laboratory (61) 624-7400 or by email porte349@umn.edu.
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