PYNAMITE

Mode of action and selectivity of pyrethroids on economically important mites and ticks

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 Obiettivo del progetto (Objective)

'There are over 45,000 species of mites/ticks (class: Arachnida, taxon: Acari). Amongst these are a number of important agricultural, horticultural, domestic animal and human pests. Economic losses inside the European Union caused by several of these species can reach hundreds of million euros every year. In the UK, mites have been reported in 72 % of farm stores, 81 % of commercial grain stores, 89 % of animal feed mills and 89 % of oilseed rape stores. The damage caused by a mite infestation can lead to direct financial loss through the deterioration of food quality, downgrading of products, customer complaints and rejection of stock. Synthetic pyrethroid compounds are frequently used as acaricides to control tick/mite infestations in agricultural, veterinary and domestic (home/garden) settings, and command a large market share. Understanding their mechanism of action and selectivity on mites/ticks is clearly important for the design of next generation compounds. Selectivity may be highly desirable in situations where there is a need to target one species only, leaving a second species unharmed - a good example being the control of varroa mites on honeybees. This proposal entails the characterization of pyrethroids interactions with tick/mite Na channels at the molecular level since it is important to be able to establish why certain pyrethroid acaricides are more lethal than others, and why some have differing effects on different species. In addition, as resistance development in pest populations threatens the long-term success of currently effective compounds, it is urgent to screen field populations of ticks/mites to identify novel resistance mutations. Eventually, with the information generated from the screening performed, it will be feasible to develop rapid, high throughput DNA-based assays for diagnosing the presence/absence of resistance mutations in field populations of ticks/mites.'

Introduzione (Teaser)

An EU-funded project has elucidated the mechanism of resistance to pyrethroids in the bee mite, Varroa destructor, and has developed a test for a rapid and accurate identification of resistant mites in populations across Europe.

Descrizione progetto (Article)

Mites and ticks are agricultural, domestic animal and human pests responsible for major economic losses every year. These pests can be controlled with high efficacy using pyrethroid insecticides, but resistance to these chemicals has been evolving in mite and tick populations in the last decades.

The 'Mode of action and selectivity of pyrethroids on economically important mites and ticks' (PYNAMITE) project set out to better understand the pyrethroids mechanism of action. At the same time, the project looked for pyrethroid resistance in several pest species, and investigated why resistance differs between species.

Researchers began by studying the structure of voltage-gated sodium channels (VGSCs), a protein targeted by pyrethroid insecticides on the membrane of insect cells. They found many differences in the areas directly in contact with pyrethroids, giving a reason for the wide variation in susceptibility among species.

Another aspect of PYNAMITE used molecular techniques to analyse the genetic sequences associated with VGSCs in a wide range of mites and ticks. This work also identified species-specific differences that could be used to design targeted insecticides.

Finally, PYNAMITE collected Varroa destructor mites (partly responsible for the worldwide decline in bee health) from bee colonies around Europe, and searched for pyrethroid resistance. Researchers narrowed down the resistance to a specific mutation in the VGSC gene. From this work, scientists designed a rapid assay that can detect pyrethroid resistance in V. destructor populations.

Research into pyrethroid resistance in mites and ticks has produced new knowledge and tools that can help in controlling these damaging pests. With time, these results will translate into more effective pest control around the world.