Advertisement

Synthetic chemical more effective in curbing malaria

Friday January 20 2017
TEAMcKinstry13

Pyrethroids are used in insecticide-treated bed nets and indoor residual sprays that are major interventions for combating malaria in East Africa and other world regions grappling with the disease. PHOTO | FILE

Mosquitoes are increasingly developing resistance to the insecticides (made from pyrethroids) that are used in bednets to kill them.

Numerous studies conducted in Kenya, Tanzania Uganda, Ethiopia and Burundi show that Anopheles female mosquitoes are becoming increasingly resistant to pyrethroids.

A new study published in this month’s issue of PLOS Pathogens journal shows that a type of chemical that disrupts biological processes of the female Anopheles mosquito may be just as effective as insecticides in reducing the spread of malaria.

During the research, scientists found that mosquitoes treated with a synthetic chemical known as DBH (dibenzoylhydrazine) died more quickly compared with those not exposed to the chemical.

Aside from producing and laying fewer eggs, the mosquitoes were unable to mate successfully and thus multiply to increase their numbers.

They were also less likely to be infected by malaria parasites, which they usually harbour and transmit to human beings while sucking their blood. And the higher the DBH dose was, the greater these effects became.

Advertisement

“As insecticide resistance is spreading, new intervention methods to control mosquitoes are needed urgently,” said Flaminia Catteruccia, senior author of the study and associate professor of immunology and infectious diseases at Harvard’s T.H Chan School of Public Health.

“Our study provides a new strategy based on the use of a non-toxic compound that prevents transmission of malaria parasites,” she added.

This DBH chemical mimics the action of the steroid hormone 20E (20-hydroxyecdysone), which plays a key role in the reproductive cycle of the female Anopheles mosquito. It can therefore be manipulated for malaria control purposes.

Since its compounds are not toxic to mammals, the researchers noted that DBH could be used in bed nets, where low toxicity is essential to safeguard the health of those sleeping under them.

“The study demonstrates the importance of basic research on mosquito biology for developing new tools against malaria,” said Caroline Buckee, an assistant professor of epidemiology at the T.H Chan School who co-authored the study.

The researchers said the chemical could provide an alternative to pyrethroids whose efficacy in malaria control has been waning over the years globally.

Pyrethroids are used in insecticide-treated bed nets and indoor residual sprays that are major interventions for combating malaria in East Africa and other world regions grappling with the disease.

According to the World Health Organisation, sub-Saharan Africa continues to suffer from a disproportionately high share of the global malaria burden.

The continent is home to 90 per cent of malaria cases and 92 per cent of malaria deaths. But the death rates have been falling in recent years as a result of several malaria control interventions such as bed nets and indoor residual sprays.

Of the four classes of insecticides available for malaria control, pyrethroids are the only compounds approved for use in bed nets, due to their relatively low toxicity.

They are also heavily used in indoor residual sprays (IRS) that kill mosquitoes resting on house walls, before they can attack humans.

Advertisement