Infection kinetics and antibody responses in Deccani sheep during experimental infection and superinfection with bluetongue virus serotypes 4 and 16.

Kalyani Putty,Y Narasimha Reddy,M Shreekanth Reddy,Sunil R Patil,P P Rao,Abdul Muzeer Shaik,Shaik Jahangeer Peera,J Shiva Jyothi,B Susmitha

doi:10.14202/vetworld.2019.41-47

Kalyani Putty, Y Narasimha Reddy + Show 7 more

Open Access

https://doi.org/10.14202/vetworld.2019.41-47

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Abstract

Aim:The current study was designed to understand the infection kinetics and antibody responses of major circulating serotypes of bluetongue virus (BTV) in India, i.e., BTV-4 and BTV-16 through experimental infection and superinfection of Deccani sheep, a popular breed of sheep found in the southern states of India.Materials and Methods:Experimental infection with 106 TCID50/ml BTV-4 was followed by superinfection with BTV-16 and vice versa. Along with observing for clinical signs and immunological responses in the experimentally infected sheep, the effect of infection of one specific serotype on the outcome of superinfection with a different serotype was also studied.Results:Certain interesting findings have been made in the course of experimental infection, such as prominent signs of infection in BTV-4 infection, mild or no clinical signs in BTV-16-infected and superinfected animals, and non-seroconversion of one of the BTV-16-superinfected animals. In addition, BTV was isolated from infected sheep in all the experimental conditions except BTV-16 superinfection. Furthermore, it was observed that immune response in the form of type-specific antibodies was slower with BTV-16 superinfection.Conclusion:Superinfection of a sheep with more than one serotype of BTV is a common phenomenon in BT endemic countries like India. Such situation was replicated in an experimental infection in the current study, and the findings to our knowledge are first of a kind and are likely to aid in unfolding the newer aspects of BTV pathogenesis and virulence.

Highlights

Bluetongue (BT) is an infectious disease of wild and domestic ruminants, caused by BT virus (BTV), a double-stranded RNA virus of the genus Orbivirus within the family Reoviridae [1]
Rectal temperatures were recorded for all the bluetongue virus (BTV)-inoculated as well as control animals every day for 60 days. Both BTV-4 and BTV-16 infected as well as superinfected animals showed a rise in the rectal temperatures, whereas the control animals exhibited no pyrexia
All the infected sheep showed a rise in rectal temperatures 5-8 days post-infection in BTV-4 infection ranging from 103.7oF to 105.4oF and 4-8 days post-superinfection with BTV-16 ranging from 103.3oF to 105oF

Summary

Introduction

Bluetongue (BT) is an infectious disease of wild and domestic ruminants, caused by BT virus (BTV), a double-stranded RNA virus of the genus Orbivirus within the family Reoviridae [1]. Twenty nine serotypes of BTV have been recognized to date [2,3], and a total of 24 serotypes have been reported from India [4,5]. A very flexible reassortment involving any of the genomic segments contributes majorly to the observed phenotypic variations in the BTV strains [6]. VP2 protein encoded by the highly variable segment 2 is the determinant of serotype, the other viral protein VP5 is known to codetermine serotype along with VP2 [7]. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/ publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated

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