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ThesisItem Open Access Studies on pathology of respiratory viral diseases in bovine calves(palampur, 2022-09-24) Singh, Rahul; Patil, R. DThe present investigation was conducted to study the pathology of pneumonia and to identify the possible respiratory viral etiology in bovine calves under one year of age during 1st June 2021 to 30th June 2022. A total of 30 calves were necropsied for studying pathology of pneumonia by help of cytological, gross, histopathological and immunohistochemical examination. To detect viral agents, 228 samples were collected from necropsy (30 tissues), clinically sick calves (130 including 121 nasal and 9 ocular swabs) and apparently healthy calves (68 nasal swabs). In addition, 221 samples were gathered from clinically sick calves (121 nasal swabs), apparently healthy calves (68 nasal swabs) and necropsy (32 including 30 nasal and 2 lung swabs) for isolation and identification of associated bacteria. Pneumonia was found to be the main cause of death in bovine calves under one year of age. Male calves showed maximum mortality i.e., 80%. Maximum mortality was observed in 3-12 months of age group with 24/30 (80%) cases followed by 1-3 months of age group with 4/30 (13.33%) cases and least mortality was observed in <1 month of age with 2/30 (6.67%) cases. Pneumonia present in all of 30 necropsied calves revealed different pattern with bronchointerstitial pneumonia in 14/30 (46.67%), suppurative bronchopneumonia in 4/30 (13.33%), fibrinous bronchopneumonia in 5/30 (16.67%) and interstitial pneumonia 7/30 (23.33%) cases. In bovine respiratory syncytial virus (BRSV) and bovine parainfluenza virus type 3 (BPIV3) positive cases necrotising bronchiolitis and bronchitis, multiple number of syncytial cells in alveolar lumen and infiltration of inflammatory cells mainly lymphocytes were seen. Using AgELISA, the prevalence of each of the bovine herpes virus-1 (BoHV) and BRSV was 56.67%, BPIV3 46.67% and bovine viral diarrhoea virus (BVDV) 26.67% in necropsy cases. Using AgELISA, 5/33 (15.15%) samples tested positive for all the 4 tested viruses, 4/33 (12.12%) tested positive for the concomitant 3 viruses and 11/33 (33.33%) were positive for 2 viruses. The prevalence of BRSV was found to be 50% (15/30) in necropsy cases and 23.73% (47/198) in clinical samples using nested RT-PCR of Nucleoprotein (N) giving a product size of 435 bp after secondary PCR. The maximum positivity in necropsy cases was seen in 3-12 months age group with 13/30 (43.33%) cases and in clinical samples the highest prevalence was observed in 1-3 months age group with 23/198 (11.61%) samples. The prevalence of BPIV3 was found to be 40% (12/30) in necropsy cases with maximum positivity rate in 3-12 months age group having 10/30 (33.33%) cases using RT-PCR of Matrix (M) protein having product size of 127bp. In addition, 13 different bacterial isolates from clinical samples and 9 different bacterial isolates from necropsy samples were isolated and identified. Staphylococcus aureus was the most prevalent bacteria in both clinical (15.87%) as well as necropsy samples (12.50%). Other bacterial isolates including Staphylococcus epidermidis, Streptococcus mutans, Streptococcus pyogenes, Streptococcus uberis, Klebsiella oxytoca, Klebsiella pneumoniae, Citrobacter koseri, Citrobacter freundii, Pasteurella spp., Salmonella spp., Escherichia coli and Proteus spp. were also isolated and identified. Pathogenic S. aureus and S. epidermidis were also identified. 3/5 (60%) isolates of C. freundii were found to be positive for shiga toxin pathotype. Different pathotypes of E. coli such as enteroaggregative, enterotoxigenic, enteropathogenic and enterohaemorrhagic were also detected. This study concludes that correlation of cytological findings and pathological findings coupled with molecular techniques aids in accurate diagnosis of respiratory viral diseases.
