Thumbnail Image

Kerala Veterinary and Animal Sciences University, Wayanad

Browse

2022 - 20232
Reset filters
Subject: Veterinary Microbiology × End date: 2023 × Start date: 2020 × Type: Thesis × Thesis Type: Ph.D ×
Reset filters

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    ThesisItemOpen Access
    COMPARATIVE EFFICACY OF DIFFERENT TESTS FOR ANTE-MORTEM DIAGNOSIS OF BOVINE TUBERCULOSIS
    (COLLEGE OF VETERINARY AND ANIMAL SCIENCES, MANNUTHY, THRISSUR, KERALA VETERINARY AND ANIMAL SCIENCES UNIVERSITY, 2022-11-07) SARIKA N; Dr. Binu K. Mani
    Blood and nasal swab samples, 50 each and 17 milk samples were collected from animals with symptoms suggestive of bTB, presented for slaughter, at Thrissur corporation slaughterhouse, Kuriachira. The samples were subjected to detection by ZN staining, IS6110 insertion element specific PCR to detect MTBC, 12.7 kb fragment specific mPCR to differentiate M. bovis and M. tuberculosis, real-time PCR specific for a region upstream of p34 gene to detect the presence of M. bovisand M. tuberculosis, bovine gamma interferon immuno assay of blood and isolation and further characterisation. Histopathology was also performed on post-mortem tissue samples. The presence of drug resistance genes (viz., rpoB for rifampicin, pncA for pyrazinamide and katG for isoniazid) were detected in the isolates obtained using mPCR. Further, comparison of the results of different ante-mortem tests to that of isolation from the tissue samples, which being the gold-standard for confirmative diagnosis of TB, was made and analysed statistically. Finally, in order to confirm efficacy of the various ante-mortem diagnostic methods assessed in the study, 118 apparently healthy dairy cattle, maintained in organised farms and households in and around Thrissur were screened for TB. In the present study, ZN staining on nasal swab/milk/tissue samples was found to be highly specific, but showed poor sensitivity. The sensitivity of the PCR (nasal swab), real-time PCR (nasal swab), isolation (nasal swab) and gamma interferon assay was 100, 100, 100 and 50 per cent, respectively. The specificity of PCR (nasal swab), PCR (blood), real-time PCR (nasal swab), isolation (nasal swab) and gamma interferon assay was 95.83, 85.42, 97.92, 100 and 91.67 per cent, respectively. The sensitivity and specificity of PCR and real-time PCR from tissue samples was 100. None of the molecular methods could detect mycobacteria in any of the milk samples. Visible lesions were absent in the tissue samples. The HP of PCR positive tissue samples revealed multiple areas of mononuclear infiltration, epitheloid cells and mildchanges in lung samples. Present study revealed that, nasal swabs were found to be a better choice for ante-mortem diagnosis of bTB, than milk. Isolation of bacteria from nasal swab and PCR of the nasal swab were found to have maximum sensitivity and specificity for diagnosing bTB. Screening of 118 cattle maintained in organised and unorganised farms in Thrissur district, revealed a positivity rate of 2.54, 7.63 and 2.54 respectively for PCR, gamma interferon immuno assay and isolation, respectively. Drug resistance genes were detected in five of the isolates obtained, of which, all the M. bovis isolates amplified all three genes namely rpoB, pncA and katG. However, the M. tuberculosis isolates showed discordant results and failed to amplify all genes. In conclusion, a single method alone did not specifically detect mycobacteria in the present study. Therefore, a combination of tests could be used for screening and accurate diagnosis of bTB, considering other factors like, availability of samples, cost of the test and diagnostic facilities available in the laboratory.
  • Thumbnail Image
    ThesisItemOpen Access
    DETECTION AND CHARACTERISATION OF BACTERIAL AND VIRAL AGENTS ASSOCIATED WITH NEONATAL DIARRHOEA IN CALVES
    (COLLEGE OF VETERINARY AND ANIMAL SCIENCES POOKODE, WAYANAD , LERALA VETRINARY AND ANIMAL SCIENCES UNIVERSITY, 2023-03-25) SARITHA BABY; Dr. Chintu Ravishankar
    Neonatal calf diarrhea (NCD) is a major threat to cattle farmersworldwide. It causes huge financial losses mainly due to morbidity andmortality of the calves. The etiology of NCD is complex disease in which both infectious agents and non infectious factors are involved. A comprehensiveanalysis was carried out to detect the major bacterial and viral agentsresponsible for NCD in Kerala and also to assess non-infectious factors thatcontribute to the condition. A total of 120 diarrhoeic faecal samples collected from different cattle farms in Thrissur and Wayanad districts of Kerala duringthe period from October 2019 to September 2022 were used for the study.Each farm has its own management practices that were found to influence the onset of diarrhoea. In the study it was observed that unhygienic conditions, overcrowding and changes in nutrition were the major predisposing factors for NCD. The incidence of diarrhoea was higher in farms housing large number of animals. Calves below one month of age were affected the most and the maximum number of diarrhoeic calves (26 per cent) was found in the 22-30 days age group. Among the infectious agents, E. coli, Salmonella, rotavirus and coronavirus were focused in the current investigation. The isolated bacteria were characterized by biochemical testing and E. coli was found to be the main infectious agent associated with the condition with a prevalence of 84.17 per cent. From the 120 samples, a total of 101 isolates of E. coli could be isolated. None of the samples were found to be positive for Salmonella. Antibiotic sensitivity testing revealed that the all E. coli. isolates were resistant to Penicillin G, Cefotaxime/Clavulanic acid and Cefpodoxime. The percentage of isolates resistant to Amoxicillin/sulbactam and Enrofloxacin, Ciprofloxacin, Co-Trimoxazole and Tetracycline, Gentamicin, and Nitrofuratonin were 92.08 per cent, 85.15 per cent, 80.2 per cent, 77.23 per cent, and 72.25 per cent respectively. Only 53.47 and 51.49 per cent of the isolates were resistant to chloramphenicol and streptomycin, respectively. When the E. coli isolates were subjected to phylogrouping using a quadruplex PCR, it was observed that B1 was the most prevalent group in this study with 28 isolates. Group A, D, C, E, F and clade I were also detected but with a lower prevalence. The fimbrial genes are responsible for virulence of E. coli and played a role in causing diarrhoea. The presence of fimbrial genes F5, F41 and F17 was also tested employing PCR. Of the isolates tested ten were detected as positive for F17 with a positivity of 16.13 per cent. Fimbrial genes F5 and F41 were not detected in any of the isolates. Reverse transcriptase polymerase chain reaction (RT-PCR) was employed for the detection of the viral agents. For rotavirus and coronavirus, VP6 gene and N gene were targeted respectively. Out of the 120 samples, 14 (11. 67 per cent) were found to be positive for rotavirus. The diarrhoeic faeces of calves infected with rotavirus were gray or creamy white and watery and all the affected calves were above one week of age. Coronavirus could not be detected in any of the samples. The results of the study indicate that diarrhoea in calves in Kerala was caused by both bacterial and viral agents. Varying degrees of antibiotic resistance were also detected against the common antibiotics. Good care of the new born calves and hygienic practices in farms will go a long way in control of the condition