Published Date: 2017-11-11 16:25:04
Subject: PRO/AH/EDR> Bluetongue - Asia: India (AD, TG), ruminants, st 4, evolutionary analysis
Archive Number: 20171111.5438141
BLUETONGUE - ASIA: INDIA (ANDHRA PRADESH, TELANGANA), RUMINANTS, SEROTYPE 4, EVOLUTIONARY ANALYSIS
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Date: Fri 10 Nov 2017
Source: Transbound EmergDis. 2017;00:1-10.[edited]
Citation: Reddy YV, Susmitha B, Patil S, et al. Isolation and evolutionary analysis of Australasian topotype of bluetongue virus serotype 4 from India.
Bluetongue (BT) is a Culicoides-borne disease caused by several serotypes of bluetongue virus (BTV). Similar to other insect-borne viral diseases, distribution of BT is limited to distribution of Culicoides species competent to transmit BTV. In the tropics, vector activity is almost year long, and hence, the disease is endemic, with the circulation of several serotypes of BTV, whereas in temperate areas, seasonal incursions of a limited number of serotypes of BTV from neighbouring tropical areas are observed. Although BTV is endemic in all the 3 major tropical regions (parts of Africa, America and Asia) of the world, the distribution of serotypes is not alike. Apart from serological diversity, geography-based diversity of BTV genome has been observed, and this is the basis for proposal of topotypes. However, evolution of these topotypes is not well understood. In this study, we report the isolation and characterization of several BTV-4 isolates from India. These isolates are distinct from BTV-4 isolates from other geographical regions. Analysis of available BTV seg-2 sequences indicated that the Australasian BTV-4 diverged from African viruses around 3500 years ago, whereas the American viruses diverged relatively recently (1684 CE). Unlike Australasia and America, BTV-4 strains of the Mediterranean area evolved through several independent incursions. We speculate that independent evolution of BTV in different geographical areas over long periods of time might have led to the diversity observed in the current virus population.
EpiCore Surveillance Project member
Hyderabad, Telangana, India
[Bluetongue is endemic in India. According to a 1992 OIE review (Ref 1), the 1st Indian outbreak had been recorded in 1964 in Maharashtra State. Exotic sheep were found to be more susceptible than indigenous and cross-bred sheep. Though serological survey indicated the presence of BTV antibodies in cattle and buffalo in several states in India, clinical BT had not been observed in cattle or buffalo as of 1992. Of the total of 24 serotypes of BTV, known worldwide as of 1992, 18 were identified in India on the basis of serum neutralising antibodies or virus isolation. These were serotypes 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 15, 16, 17, 18, 20.
1.Prasad G., Jain N.C.& Gupta A.Y. Bluetongue virus infection in India: a review. Rev. sci. tech. Off. int. Epiz., 1992, 11 (3), 699-711. - Mod.AS
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