Video transcript: Midges tracked by new Indian Bluetongue Vector Network

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April 2013

India Bluetongue Vector Network.

Dr Simon Carpenter, The Pirbright Institute
Hello my name is Simon Carpenter and I am a BBSRC-funded scientist working at The Pirbright Laboratory in Surrey. At Pirbright we work on viruses of livestock and among these the viruses are transmitted by arthropods such as biting midges, mosquitoes and ticks. One of these viruses, bluetongue virus, was recently found in the southeast of the UK in 2007. While this outbreak was eventually eradicated through vaccination, bluetongue remains a global problem to livestock producers worldwide.

As part of a new project the Indian Bluetongue Vector Network, or IBVNet, we are addressing the problems that are common to UK and India dealing with outbreaks of bluetongue. To accomplish this we rely upon a wide range of collaborators in both the UK and India, and in particular the India Council for Agriculture for Research and the all Indian national network programme for bluetongue virus. These links not only strengthen the science we carry out, but also enable direct translation of our studies in the field.

Video shows biting midge eggs and larva.

Biting midges are one of the smallest files that feed on livestock and the eggs you can see here are just a couple of millimetres long. The larva that emerges from the eggs are extremely vulnerable to drying out and hence favour damp habitat such as soil or animal dung. Seasonal availability in abundance of such sites therefore often drives the adult abundance for a particular species. Pupation usually occurs just over a day or two and mating occurs when adults emerge. Only female biting midges blood feed and hence are responsible for bluetongue virus transmission.

Video shows images of infected cattle.

Bluetongue virus causes a hemorhetic disease in affected sheep both in the EU and India. Common clinical science include fever, swelling of head and neck, lameness, respiratory problems and mortality rates can exceed 30% of cases. While considered an exotic virus in the UK, bluetongue virus circulates almost continuously in India with periodordic explosions of disease cases. These are particularly serious on subsistence farms in the southern states of Andhra Pradesh, Karnataka and Tamil Nadu.

Video shows madra red sheep in field.

In these three southern states sheep, such as these madras red, represent a vital resource for small holders and landless workers and are usually grazed on common land. Owners often make daily movements with their flocks of up to 7 kilometres a day to water sources returning to their villages to house them at dusk. Additionally in some areas of southern India, seasonal migrations occurs that follow monsoon related changes in the availability of grazing and can entail journeys of up to 200 miles. As India supports a wide range of diverse habitats and livestock breeds this makes tracking and predicting the movements of strains of bluetongue virus extremely challenging. One aspect of IBVNet is to gain a clearer understanding of the factors that drive bluetongue outbreaks across these habitats. To do this we are establishing Culicoides trapping networks across southern India to identify species transmitting bluetongue virus and to monitor their seasonal abundance.

Video shows project partners setting up an ultraviolet light trap.

Here some of the project partners are learning how to set up a standard ultraviolet light trap that is used to collect Culicoides in the field. Like moths and other insects active at dusk, Culicoides are attracted to the light and are blown by a fan into the collecting pot, shown being attached to the bottom of a trap. By hanging these traps in close proximity to livestock we can gain an understanding of the abundance of Culicoides populations and also which species are feeding on livestock most often and hence most likely to transmit bluetongue virus. Through collaboration with the Indian Council for Agricultural Research, IBVNet will enable a network of traps to be run at weekly intervals across southern Indian. The data produced from this network will then be used to compare Culicoides abundance with monsoon conditions which may influence the availability of larva breeding sites. Identifying these drivers of Culicoides populations could eventually lead to tools that can be used to predict occurrence of major bluetongue virus outbreaks. This would mean that the farmers would be warned in advance of outbreaks of bluetongue virus to employ vaccination. This project compliments a wider effort being conducted by the Indian Council for Agricultural Research to vaccinate for bluetongue in India. In addition we are also examining ways in which outbreaks of bluetongue virus can be controlled by subsistence farmers. This includes characterising how farms currently combat outbreaks using traditional techniques as well as producing cost neutral methods to reduce Culicoides abundance. This will not only assist in reducing the impact of bluetongue but may also lead to a reduction in untargeted control techniques in the form of insecticides.

The CIDLID programme is funded by BBSRC, DFID and the Scottish Government. Highlights of our progress are to be presented by members of IBVNet throughout the project. You can also learn more about our project from the website ibvnet.com and Culicoides.net.



This video may be reproduced in its entirity with due credit and copyright to IBVNet.

Contact: Dr Simon Carpenter, The Pirbright Institute, simon.carpenter@pirbright.ac.uk