PATHOTYPING OF NEWCASTLE DISEASE VIRUS BY MEAN DEATH TIME AND REAL-TIME PCR ASSAY: AN EMPIRICAL COMPARISON

Newcastle disease (ND) remains the most significant disease in the poultry sector and contributes to huge economic loss. Early detection and pathotyping of Newcastle disease virus associated with field infection are highly crucial. In vivo pathogenicity assaying is a sensitive and specific pathotyping tool used for the detection and identification of NDV was used until the recent past. Genome-based sequence analysis yields promising results in virulence determination. Keeping the above facts, the present study was designed to compare the efficacy of conventional and molecular assays in NDV virulence determination. In this study twelve NDV isolates (Isolate numbers 463, 464, 475, 476, 122-17C, 122-17D, 122-17E, 128-17A, 128-17D, 137, 139, 141) available in the Department of Veterinary Microbiology, Madras Veterinary College (MVC), Chennai was subjected to differentiation of virulent and avirulent strains using mean death time (MDT) in specific pathogen-free (SPF) embryonated eggs and TaqMan minor groove binding (MGB) probe real-time PCR assay. Pathotyping based on the MDT revealed two NDV isolates (isolate no. 476 and 128-17D) as velogenic strains and the remaining ten NDV isolates as lentogenic strains. Pathotyping based on TaqMan MGB probe real-time PCR assay revealed six NDV isolates (476, 128-17D, 463, 464, 475, 137) as velogenic/mesogenic strains and remaining six NDV isolates (122-17C, 122-17D, 122-17E 128-17A, 139, 141) as lentogenic strains. Using a TaqMan MGB probe in real-time PCR assay, four NDV isolates (463, 464, 475, 137) which were MDT pathotyped as lentogenic strains were re-pathotyped as velogenic/mesogenic strains, which indicates the greater sensitivity of TaqMan MGB probe real-time PCR assay in pathotyping of NDV over conventional MDT

MOLECULAR PREVALENCE OF PORCINE CIRCOVIRUS 2 INFECTION: FOREMOST REPORT IN SOUTHERN STATES OF INDIA

Porcine circovirus 2 (PCV2) is the emerging viral pathogen in the swine associated with multi-systemic clinical and subclinical outcomes. This study aimed to detect the molecular and serological prevalence of PCV2 infection in the southern states of India. A total of 434 random samples comprising serum (n=273), pooled postmortem tissues (n=109) and rectal, vaginal, and nasal swabs (n=52) and were collected from PCV2 suspected and healthy swine populations of Tamil Nadu, Kerala, Andhra Pradesh, Telangana, and Puducherry states in India from 2019 to 2021 were screened for PCV2 by specific polymerase chain reaction (PCR) assay. Of 434 samples screened, 12.2% (n=53) showed positivity to PCV2 genome. Statistical analysis of the molecular prevalence of PCV2 within breed, age, sex, and vaccination status revealed no significant (p>0.05) difference but there was a significant (p<0.05) difference in the prevalence of PCV2 among healthy and suspected swine populations. Suspected pigs had a significantly higher prevalence of PCV2 in comparison to healthy. ELISA-based PCV2 antibody screening in 176 non-vaccinated serum samples revealed a seropositivity of 44.8% (n=79). The molecular and seroprevalence of PCV2 is alarming in southern states of India, which necessitates the need for genotypic characterization and phylogenetic analysis and development of candidate vaccine for implementation of suitable prevention and control measures

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Not AvailableThe coding sequence of NP gene was amplified by RT-PCR, cloned and expressed in prokaryotic expression system-E. coli. The crude extract of expressed protein was purified, extensively dialyzed and further purified by expanded bed adsorption chromatography. Three indirect ELISA using recombinant NP were standardized and the antibody titres against NDV in serum samples were found to correlate among these three ELISAs. The correlation coefficient values were 0.3 to 0.6 which were higher than table values for correlation coefficient at 1% level. The empirical ROC values were observed to be 0.929, 1.0 and 1.0 for comparisons between RP-ELISA versusHI, RP-ELISA versus WVP-ELISA and R P-ELISA versus PEPELISA respectively which are more than the standard value of 0.8.Not Availabl