A researcher at Swansea University has discovered that a strain of fungus could be used to control the insect-borne bluetongue virus (BTV) common in livestock, potentially preventing thousands of losses to farmers each year.
Dr Minshad Ali Ansari who works in one of the leading insect mycopathology (insect pest control) teams in the UK – based at Swansea University’s College of Science – has conducted a study that shows for the first time that the strain of fungus known as Metarhizium anisopliae V275 can effectively kill adult Culicoides (biting midges) in the family of insects that carry BTV.
Dr Ansari explained: “Although insecticides have proved effective in killing Culicoides species, they have been harmful to a range of beneficial insects”.
“As a result, the range of available insecticides has diminished as the chemical-based products are withdrawn from the market – because of the perceived risk to humans and the environment – and farmers face a growing challenge to control the population of biting midges.”
BTV is an arbovirus, a group of viruses transmitted by arthropod vectors, invertebrates that carry and transmit an infectious agent, in this case the Culicoides biting midge.
The control of bluetongue (BT) disease, which mainly affects sheep and cattle, is of growing importance in Europe due to the influence of climate change. Before 1998, there had only been a few small outbreaks, but increasing temperatures mean the virus is starting to survive further north over the winter.
As a result, BT outbreaks have had a major economic impact in European countries in recent years, through livestock losses and restrictions imposed on cattle movements.
This new study made possible with 400K€ (Euro), of funding from INTERREG 4A is the first to demonstrate the efficacy of fungus against the adult midges responsible for transmitting BTV. The study is particularly timely as new EU directives are encouraging member states to develop integrated pest management programmes which use benign plant protection products.
Dr Ansari conducted trials using adult male and female midges and found the fungal susceptibility test identified the fungus Metarhizium anisopliae V275 as highly virulent in both the laboratory and under greenhouse trials – killing the insects within 24 hours.
The tests also revealed that increasing the dose of fungus decreased the number of midges that survived. Encouragingly, the efficiency of the fungus was shown to increase when applied to certain substrates such as manure – as opposed to tissue paper – suggesting success in future field tests.
Although the fungi tested in the study appears to present little risk to people or the environment, widespread use of the fungi will be dependent on rigorous field trials to establish the best formulations and methods of delivery, and to evaluate potential risks.
While earlier research, undertaken by the research team, found that use of the control agent Metarhizium anisopliae is effective when applied to the larval stages of insects yet remained safe for fish, birds and mammals, field experiments of the newly developed strain of fungi (Metarhizium anisopliae V275) will need to thoroughly investigate potential effects on non-target species.
Professor Tariq Butt, who leads the insect mycopathology at Swansea University’s College of Science concluded: “The development of Metarhizium anisopliae V275 – as a control agent for Culicoides biting midges – is a significant step forward for the research team.
“The fungi can, potentially, be applied cost-effectively to the places where adult midges rest, such as animal housing and livestock, to effectively target known problem areas.
“The next step is to test the fungus in large-scale field trials with the eventual aim of developing protocols for its simple and economical application in BTV endemic countries.”
