Browsing by Subject "Turkey arthritis reovirus"
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Item Diagnosis, Pathogenesis And Control Of Chicken And Turkey Arthritis Reoviruses(2021-10) Kumar, RahulAvian reoviruses are the causative agent of arthritis/tenosynovitis in broilers and turkeys. Recently, variants of chicken arthritis reovirus (CARV) and turkey arthritis reovirus (TARV) have occurred worldwide leading to vaccine failures, causing huge economic loses, and increasing animal welfare concerns. Whole genome sequencing of 35 and 14 isolates of CARV from the US and Germany, respectively, indicated significant divergence in these strains. In fact, US strains had more divergence among themselves than the German strains. The US strains clustered in six previously established genotype clusters (GCs) while the German strains clustered in only four of the six GCs. Strains from both countries were highly divergent from the currently used vaccine strains. Based on distinct evolutionary trees of each gene, we discovered that all genes evolve in an independent manner and contribute to the evolutionary process. The S1 (σC) genome segment showed noticeably higher divergence followed by M2 (μB) and L3 (λC) genes. Congruent topologies of these isolates indicated frequent genetic re-assortment among multiple co-circulating variants. We believe that the genetic variability among CARVs is due to a combination of evolutionary mechanisms involving multiple cocirculating lineages and genetic reassortments.We developed a recombinant pichinde virus-vectored vaccine (rPICV-CARV) that expresses the sigma C (SC) and sigma B (SB) antigenic proteins of CARVs. Several combinations of monovalent and bivalent rPICV-CARV vaccines were developed carrying codon-optimized SC and SB genes from two divergent CARV strains. The S1 and S3 genes and antigens were found to be expressed in virus-infected cells via reverse transcriptase polymerase chain reaction (RT-PCR) and direct fluorescent antibody (DFA) technique, respectively. We conducted an in vivo study to determine safety and efficacy of two vaccine formulations against a wide spectrum of virus challenges. The vaccinated birds produced serum-neutralizing antibodies, which were responsible for early clearing of the virus from the host, inhibited virus replication in intestine and tendons, and decreased fecal shedding of the virus relative to non-vaccinated controls. The vaccine is a promising candidate that needs to be further evaluated in breeders. The survival of bivalent codon optimized rPICV-CARV vaccine was studied in poultry litter and water at room temperature (approx. 25°C). In spiked samples, it was found that the vaccine virus survived for approximately six hours in litter and drinking water. Reoviruses have been isolated from three different disease syndromes in turkeys, e.g., turkey enteric reovirus (TERV) from cases of turkey enteritis, turkey arthritis reovirus (TARV) from cases of tenosynovitis/arthritis in turkeys, and turkey hepatitis reovirus (THRV) from cases of hepatitis in turkeys. The comparative pathogenesis of these viruses, and correlation with their genetic make-up (if any), is not known. All nine viruses were found to be enterotropic; the virus gene copy number in the intestine reached a peak at 5 dpi followed by a sharp decline at 7 dpi. All viruses caused significant decrease in body weight gain of birds compared to the negative control group. Both TARV and THRV strains replicated in tendons and produced histologic lesions consistent with tenosynovitis. Hepatic lesions were produced by THRV only and the virus was re-isolated from liver and spleen of inoculated birds thereby fulfilling Koch’s postulates. We then conducted a study to determine the age at which turkey poults become susceptible to infection with TARV. All turkeys were susceptible to TARV infection at all ages studied. However, virus replication was more pronounced in the intestine and gastrocnemius tendons of turkeys at 2-weeks of age or less. Additionally, turkeys at all ages of TARV challenge developed typical lesions of lymphoplasmacytic tenosynovitis, shed TARV in feces, and transmitted TARV to sentinels. The sentinels, in turn, also showed virus replication in their intestines and tendons leading to histological lesions of arthritis/tenosynovitis. These findings indicate that turkeys at the age of 28 days or less are susceptible to infection with TARV following oral challenge. It was also found that TARV-infected birds could transmit the infection to naïve sentinel turkeys of the same age. We also created a recombinant live pichinde virus-vectored bivalent subunit vaccine that expresses Sigma C and Sigma B proteins of TARV SKM121. The efficacy of this vaccine was tested against both homologous (TARV SKM121) and heterologous (TARV O’Neil) virus challenges. Immunized poults produced serum-neutralizing antibodies that neutralized both viruses. The body weights of vaccinated and non-vaccinated birds were similar indicating no adverse effect of the vaccine on feed efficiency. Comparison of virus gene copy numbers in intestine and histologic lesion scores in tendons of vaccinated and non-vaccinated birds showed a decrease in the replication of challenge viruses in the intestines and tendons of vaccinated birds. These results indicate the potential usefulness of this vaccine. In addition, the vaccine virus was found to be transmissible horizontally to non-vaccinated pen mates of vaccinated birds inducing serum neutralizing antibodies.Item Turkey Arthritis Reovirus Diagnostic Submission Analysis And Development Of A Serological Test(2019-04) Barrera Vaca, MariaTurkey reovirus (TRV) has been associated with several clinical syndromes including lameness, enteritis, myocarditis, and immunosuppression in turkey flocks. Lameness and enteritis are the current field problems and an increase in cases of lameness has been reported, possibly due to the emergence of novel genotypes of the virus. It is, therefore, important to understand factors responsible for this increase and to devise methods for the rapid detection of the virus and its antibodies. Currently, TRV is detected through RT-PCR and virus isolation but no specific serological test is available to detect anti-TRV antibodies in turkeys. In this thesis, I report a retrospective analysis of lameness submissions to the University of Minnesota Veterinary Diagnostic Laboratory (UMN-VDL) in the last eight years and confirm that submission of TRV positive cases has indeed increased. There were some months during which the probability of positive cases was numerically high. In addition, the submission of reovirus-positive lameness cases came from many different states indicating that the problem is widespread. There was a positive correlation between age of the turkey and TRV-related lameness; the number of TRV positive cases increased as the flocks aged. In addition, I developed a whole-virus ELISA (enzyme-linked immunosorbent assay) to detect anti-TRV antibodies. The TRV isolate used for this ELISA was a representative of several TRV genotypes based on Sigma C and B conserved epitopes. The test was validated using serum samples from experimental and clinical cases of TRV. At 0.4 cut-off, the diagnostic sensitivity and specificity of this ELISA were 0.92. In summary, the development of an ELISA with high sensitivity and specificity should provide an opportunity for early diagnosis of reovirus exposure and to follow the dynamics of reovirus immune response over time.Item Turkey arthritis reovirus: pathogenesis and immune response(2015-01) Sharaf Eldin, Tamer Ahmed IbrahimIn 2011, turkey reoviruses were isolated from tendons and synovial fluids of >15-week-old lame turkeys displaying swollen joints and occasionally ruptured leg tendons in Midwest, USA. These reoviruses were tentatively called turkey arthritis reoviruses (TARV) to differentiate them from reoviruses isolated from intestinal contents and feces of turkeys namely turkey enteric reoviruses (TERV). TARV were found to be genetically distinct from chicken arthritis reoviruses (CARV). Five experiments were conducted to test the pathogenicity of TARV in turkeys and in chickens and to compare it with that of TERV and CARV. Additionally, this work investigated the virus pathogenesis and cytokine immune responses. TARV showed unique capability to induce significantly higher tenosynovitis scores in turkeys as compared with TERV and CARV which induced minimal scores. Clinical lameness was first displayed at 8 weeks of age in TARV-inoculated turkeys at 1 week of age. Lameness in infected group reached approximately 50% at 16 weeks of age. TARV did not induce any lesions in chickens via intratracheal or oral route. TARV inoculation via footpad route induced tenosynovitis in chickens at 2 and 3 weeks PI with no clinical lameness. In pathogenesis study, TARV displayed the greatest replication in intestines and bursa of Fabricius than in leg tendons of turkeys. Viral infection mediated effective antiviral cytokines immune response that limited virus replication in the intestines. Furthermore, viral infection mediated a significantly elevated T helper-1(Th1) cytokine response in intestines and tendons and minimal Th2 and Th17 cytokine response during the early stage (2 weeks) of infection. This work established an experimental model to study TARV which provides early end points that are indicative of disease pathogenicity. Additionally this work developed a new grading system for histologic tenosynovitis which can be used in a wide variety of experimental models. For lameness evaluation in turkeys, this work developed a grading system for gait scores. In summary, this work showed unique pathogenicity of the newly isolated TARV and added significant knowledge to TARV pathogenesis and immune response using the newly established reproducible experimental model and the newly developed grading systems for evaluation of tenosynovitis and clinical lameness.