DETECTION AND MOLECULAR CHARACTERIZATION OF EMERGING VIRAL PATHOGENS OF PIGS
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Date
2016
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COLLEGE OF VETERINARY AND ANIMAL SCIENCES, POOKODE WAYANAD
Abstract
An array of viruses cause economically important diseases in pigs. The important
viruses affecting pigs include classical swine fever virus (CSFV), porcine reproductive and
respiratory syndrome virus (PRRSV), African swine fever virus, transmissible gastro
enteritis virus, porcine circovirus 2 (PCV2), porcine parvovirus (PPV), and porcine
rotavirus (PRV) to name few. A comprehensive study was done to detect the presence of
CSFV, PCV2, PPV and PRV in pigs in Kerala. A total of 52 samples, collected from
domestic and wild pigs of different districts of the State, were utilized for the study. Of
these, 38 samples were tested for CSFV, PPV and PCV2. For CSFV detection nested
reverse transcription polymerase chain reaction (RT PCR) targeting E2 gene region was
carried out. Of the samples tested, five samples were detected as positive giving a
percentage positivity of 13.56 per cent. These samples were from wild pigs. Sequencing
and subsequent phylogenetic analysis of the isolates revealed that it belonged to serotype
2.2 which was having close sequence similarity to other Indian isolates and to isolates from
Thailand. For PPV detection PCR targeting NS1 gene region was done and two samples
were detected as positive with percentage positivity of 5.26. Of the two positive samples,
one was from a wild pig. For PCV2 detection PCR and TaqMan real time PCR targeting
ORF2 gene were carried out. Only two samples were detected as positive in PCR while
real time PCR detected 15 samples (39.47 per cent) as positive. In one of the samples,
mixed infection with PCV2 and PPV was detected. On phylogenetic analysis, isolates of
PCV2 and PPV were found to be more similar to Chinese strains indicating a probable
entry of these viruses from that country. For PRV detection RT-PCR targeting Seg 6 gene
was carried out and none of the 14 samples were detected as positive. Attempts were
carried out to isolate CSFV, PPV and PCV2 in PK-15 cell lines. The presence of the virus
in the infected cells could not be detected by RT PCR and direct immunofluorescence test
for CSFV and by PCR for PCV2 and PPV after three blind passages.
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