PMI VectorLink Implements SOP Bioassays For New Nets
Somebody has to be first for something new, right? When it came to field testing the effectiveness of a new generation of insecticide-treated bed nets (ITNs), it was our President’s Malaria Initiative (PMI) Vector Link Burkina Faso team.
It was an important breakthrough. As mosquitoes become more resistant to pyrethroid ITNs, demand for other options, including piperonyl butoxide (PBO)-synergist and dual active ingredient Interceptor G2 (IG2) nets, will grow. That in turn requires entomologists to test vector resistance to the new nets.
The PMI Vector Link Project implemented bioassay standard operating procedures (SOPs) for both PBO and IG2 nets. Bioassays are critical for understanding ITN effectiveness. They test effectiveness by measuring mosquito knockdown and mortality, among other variables. SOPs outline how labs should perform bioassays for different types of nets.
IG2 is the first World Health Organization-recommended mosquito net that is not based solely on conventional chemistry. It combines two active ingredients, chlorfenapyr and alpha-cypermethrin, which protect sleepers from malaria and combat resistant mosquitoes. Some studies show that PBO added to pyrethroid nets makes them more effective than pyrethroid-only nets.
PBO and IG2 nets were first distributed in Burkina Faso in 2019. The President’s Malaria Initiative and Centers for Disease Control and Prevention developed the SOPs to monitor the durability of the nets. PMI Vector Link partner Research Institute of Health Sciences (IRSS) located in Bobo-Dioulasso conducted cone bioassays of pyrethroid and PBO nets and tunnel tests with IG2 nets using pyrethroid resistant and susceptible colonies of An. gambiae s.l. The baseline tests led to SOP revisions. They included a standardized approach to characterization of pyrethroid-resistant Anopheles for use in bioassays and an increase in the number of positive control new nets to quantify any loss of efficacy more accurately in field nets.
Data collection for the 12-month monitoring round ended in November 2020. VectorLink Burkina Faso visited 510 households, assessed 723 nets for damage, and collected 90 IG2, Interceptor, and PermaNet 3.0 nets to undergo chemical content testing and bioassays using the revised SOPs.
