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|Advisor:||Dr. P. KALYANI|
|Title:||MOLECULAR TYPING OF BLUETONGUE VIRUS (BTV) ISOLATES OBTAINED FROM FIELD OUTBREAKS OF BT DURING 2016-18|
|Abstract:||Bluetongue virus (BTV, family Reoviridae, genus Orbivirus) causes the hemorrhagic disease bluetongue (BT) in both domestic and wild ruminants and is one of the main veterinary diseases worldwide. BTV is non-contagious and is transmitted by bites of certain species of Culicoides midges. At least 29 BTV serotypes are known with widespread geographic distribution, causing sometimes significant economic losses. BT is endemic in India, where most of the 29 serotypes of BTV have been reported at one time or another. The present study was taken up with objective of molecular typing of BTV isolates obtained from field outbreaks of BT during 2016-18 from the states of Telangana and Andhra Pradesh by using cell culture and molecular diagnostic techniques. Blood was collected from sheep exhibiting BT symptoms like pyrexia, oral lesions, nasal discharges, frothy salivation and torticollis. The samples were processed in KC cell line followed by BHK-21 cell line. Samples exhibiting BTV-specific CPE were proceeded for RNA isolation and segmented pattern of dsRNA characteristic of BTV by agarose gel electrophoresis (1%), followed by confirmation of BTV by NS3 group-specific RT-PCR, and subsequent molecular typing by real-time PCR based technique using primers specific to VP2 gene of 29 known serotypes. A total of 144 samples were processed and a total of 109 isolates were obtained during the study period (2016-18). The analysis of each of the 109 isolates for individual primer pairs of 29 serotypes revealed that serotypes BTV-1E (38%), 2E (63%), 4W (37%), 5W (02%), 9E (03%), 10W (01%), 12W (32%), 16E (48%), 21E (06%) and 24W (06%) seem to be circulating in the tested period. It is noted that more than one serotype are involved in an area in the disease period. Mixed serotype infections (69%) involving 2 to 5 serotypes affecting individual animal were also observed. The presence of viruses belonging to same serotypes that have been circulating during different years in the study area (BTV – 1E, 2E, 9E, 10W, 12W, 16E and 21E), along with the prevalence of recently isolated serotypes (BTV-5W & 24W) and also emergence of serotype BTV-4W has been observed. From the current study, it may be concluded that to control the BT disease, it is important to regularly monitor the serotypes circulating in particular area. Seromonitoring the susceptible species, to estimate immunity against different serotypes circulating in particular area is also needed. This knowledge can be applied in designing appropriate vaccination strategies to include particular serotypes of virus as part of a multivalent vaccine for a particular period in a particular area.|
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