Bloodsucking flies with a taste for cannabis plants identified by scientists

Disease-spreading insects could be controlled using extracts from illegal shrubs

Josh Gabbatiss
Science Correspondent
Monday 29 October 2018 20:00 GMT
Sand flies transmit diseases such as leishmaniasis to humans
Sand flies transmit diseases such as leishmaniasis to humans (CDC/ Frank Collins)

Flies known to carry diseases to humans appear to have an unusual taste for cannabis – a habit that may help scientists target these pests.

Sand flies suck human blood, and in doing so they can transmit unpleasant infections such as the ulcer-causing leishmaniasis.

They also need to drink sugary sap in order to survive, and a group of scientists set out to find which plants these tiny creatures favoured in order to better understand their movements.

To their surprise, they found that in sites from Brazil to the Middle East, these flies appeared to be seeking out cannabis plants.

Due to the illegality of cannabis in all the countries where the scientists were working, they did not come across the plants in the wild except for a few shrubs in Kazakhstan, where they grow naturally.

The fact that cannabis was the most commonly consumed plant for sand flies trapped in four of the five regions they visited therefore suggested that the insects were actively seeking these plants out.

“We conclude that cannabis comprised but a small fraction of the available sugar sources in any particular habitat and that its ample representation among sand fly plant meals signifies bona fide attraction,” the scientists wrote in their Proceedings of the National Academy of Sciences paper.

After trapping insects across five international sites, the team led by professor Alon Warburg from the Hebrew University of Jerusalem identified which plants they had been eating by extracting DNA from inside the flies.

As insects seem to lack receptors to detect and respond to the active ingredients in cannabis, the scientists were unsure what benefit the flies were taking from its sap besides a sugary meal.

However, they noted that sugar baits are being used as a means to catch and control mosquitoes and other insects that carry deadly diseases.

Cannabis could therefore be used to produce sand fly-specific baits to control their numbers in problem regions.

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