STUDIES ON PATHOLOGY OF RESPIRATORY DISEASES IN BOVINE CALVES WITH SPECIAL EMPHASIS ON BOVINE RESPIRATORY SYNCYTIAL VIRUS AND PARAINFLUENZA-3 VIRUS INFECTION.
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Date
2019-07-23
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CSK HPKV, Palampur
Abstract
The present study was conducted to determine the prevalence and the factors responsible for respiratory diseases in bovine calves during April, 2018 to May, 2019. A total 210 nasal swabs were collected from the necropsy (18), clinically sick (130) and apparently healthy calves (62). Besides, 24 tracheal and 12 lung swabs from necropsy cases were also collected. 33 calves were examined at necropsy. Pneumonia was recorded in all 33(100%) calves and was considered an important contributor to death. Out of 33 cases, gross lesions suggestive of bronchopneumonia seen in 7/33 (21.2%), interstitial pneumonia in 4/33 (12.1%) and bronchointerstitial pneumonia in 22 (66.7%). Bronchointerstitial pneumonia revealed mixed characteristic features of suppurative bronchopneumonia and interstitial pneumonia. Staphylococcus aureus was detected in 30.3 % of the clinical samples. E. coli comprised 23.6% of the isolates in necropsy. Bacterial isolates seen in nasal tract were different from the bacterial isolates obtained from lungs / trachea. Single bacterial infection was detected in 51.5% (17/33) cases and polymicrobial infection in 45.5% (15/33) cases. Total 41 lung tissues from necropsy and 104 nasal samples from clinical cases were screened for BRSV using RT-PCR with glycoprotein gene (246bp) primers and showed overall prevalence of 50.4%. BRSV infected lung showed consolidation at the cranioventral and fibrinous pleuritis with range of changes in airways histopathologically multinucleated syncytial cells was seen. Total of 145 cases were screened for BPIV-3 using RT-PCR, no sample was found positive for primer having HN gene. In necropsy, most frequent E.coli pathotype categories were found to be enterotoxigenic (80%) & enteroaggregative (80%). In clinically sick cases frequent pathotype categories found were enterotoxigenic (63.6%). Four (33.3%) of Citrobacter freundii isolates were pathogenic with shiga toxin on PCR analysis. 17.9% Staphylococcus aureus and 15.4% Staphylococcus epidermidis were recorded as pathogenic. Male and female calves showed 20/33 (60.7%) and 13/33 (39.4%) mortalities respectively. Maximum mortality was recorded in <1 M (42.2%) old calves. Most number of deaths were recorded during the summer (36.4%) season. Combination of molecular detection (PCR) along with clinical, gross & histopathology helped in better confirmatory diagnosis of BRSV infection in calves. The present study concluded co-infection of bacterial and BRSV in respiratory infection of young calves.
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