Researchers at The Pirbright Institute have developed field tests for Indian strains of bluetongue virus (BTV) that are reliable, rapid and simple to use.
Bluetongue is a viral disease transmitted by biting midges (Culicoides) that infects cattle, goats, sheep and wild animals such as deer, although sheep tend to be the most severely affected. In India, BTV impacts directly on subsistence level sheep farmers in southern states and is a key limiting factor in development.
There are currently 27 different types of bluetongue virus, or serotypes. Each serotype can vary depending on the area it was isolated from. These serotype variations - or topotypes, can be split into two groups: eastern and western. In India, several serotypes are circulating that belong to both the eastern and the western topotypes. This makes vaccination against BTV especially difficult as a vaccine for one serotype or topotype usually does not protect against the others.
Tests that can accurately diagnose these different types of BTV have previously been confined to the laboratory, which causes inevitable delays in diagnosing which strains are circulating and causing disease. Scientists have therefore been keen to identify a diagnostic test that is both rapid and accurate to ensure that the appropriate disease control policies can be implemented quickly; so saving animal lives and reducing the wider impact.
Joint research by Professor Peter Mertens and his group at The Pirbright Institute and scientists from the LLR University of Veterinary and Animal Sciences (LUVAS), in India, has produced two new tests which are able to tell the difference between both the serotypes and the topotypes that are currently circulating in India.
The technique used by the researchers; called loop-mediated isothermal amplification (LAMP), is a portable test which can be used in the field and is rapid and easy to use. The study, published in Transboundary and Emerging Diseases, was funded by the Biotechnology and Biological Sciences Research Council (BBSRC). This new LAMP test is similar to one for African horse sickness which was recently developed by another team of scientists at the Institute.
The BTV research group said this test is expected to be, “Particularly suitable for use in front-line diagnostic facilities and mobile diagnostic units. It has potential for adaptation as a pen-side test to help in early diagnosis and containment of field outbreaks caused by eastern or western topotypes of BTV in India”.
Bluetongue virus is able to re-organise its genetic material very quickly; generating yet more differences between the virus serotypes and topotypes. Research into quick diagnosis of all these types is therefore urgently needed to control this fast spreading and devastating disease.
Dr Simon Carpenter, Head of the vector-borne disease programme at The Pirbright Institute said, "This test paves the way for accurate and effective targeting of vaccination that will play a significant role in helping improve livestock productivity for some of the poorest people in India".