Olyset® Plus epidemiologoical data leads to WHO endorsing new interim PBO LLIN class
- NMCPs should consider using PBO nets in areas of moderate resistance
- Performance of PBO LLINs may vary depending on PBO net design
- Interim guidance provided after large scale epidemiological trial using Olyset Plus as the sole PBO LLIN
Following consideration at WHO of epidemiological data from the randomised controlled trial in Muleba, Tanzania where Sumitomo Chemical’s Olyset Plus and Olyset Nets were used exclusively as the test products, WHO has established a new interim class for pyrethroid PBO long lasting insecticide nets (LLINs).
The epidemiological data from the Muleba trial conducted by the London School of Hygiene and Tropical Medicine was reviewed by WHO. This data ‘suggests that pyrethroid–PBO net products may have additional public health value when compared to pyrethroid only LLIN products in areas with confirmed moderate levels of pyrethroid resistance’.
With growing pyrethroid resistance reported across countries with on-going malaria transmission, WHO acknowledges ‘…. the need to deploy products that are effective against pyrethroid resistant mosquitoes’, concluding that ‘pyrethroid-PBO nets are being given an interim endorsement as a new WHO class of vector control products’.
WHO highlights the differences between different PBO LLINs …. ’the entomological and epidemiological impact of pyrethroid PBO nets may vary depending on the bio-availability and retention of PBO in the net and on the design of the net’. This underlines the need for care in extrapolating data generated with Olyset Plus to other brands of PBO bed net. The appropriate side by side entomological tests will be needed to ensure that other PBO nets are providing at least equivalent bio-efficacy to be able to have the confidence to ensure that these would also provide an epidemiological impact. We await guidance from WHO on details of what these tests should be.
Full endorsement can only follow after a second set of positive epidemiological data is generated according to current VCAG guidelines. This could well follow with the recently started trial in Uganda which again includes Olyset Plus. In the meantime, National Malaria Control Programmes are being advised by WHO to consider deploying PBO LLINs in areas where pyrethroid resistance has been confirmed in the main malaria vector.
Ms Atsuko Hirooka, Executive Officer of Sumitomo Chemical’s Environmental Health Division responded to the news: “Sumitomo Chemical welcomes this interim guidance which reflects the impact we had expected from Olyset Plus – we trust this will provide added protection to vulnerable populations and allow us to stay one step ahead of insecticide resistance.”