It has been confirmed that two mosquito species spreading malaria - anopheles funestus and anopheles arabiensis – can penetrate some treated and untreated bed nets. Now, Ifakara Health Institute scientists recommend modifications to the bed net – a tool widely used in malaria endemic countries to control the disease.

Meanwhile, recent studies found the funestus species with “a high ability to penetrate all nets types compared to the other species. After learning this, scientists have also cautioned on the ability of this species to penetrate even intact nets, saying this could be an additional risk for sustained malaria transmission across Africa.

“This phenomenon signals an alarming situation for malaria mosquito control efforts that heavily relies on the use of LLINs (long-lasting insecticide-treated nets), which its ability to prevent mosquito bites that exceed 80% come from the physical barrier and integrity,” the scientists pointed out in the study published the Wellcome Open Research journal.

Fact confirmed after over 20 years of research
Ifakara scientists who contributed to the study include Felician Meza, Letus Muyaga, Alex Limwagu and Dickson Lwetoijera.

They carried out experiments inside a semi-field system (SFS) of the Ifakara Health Institute located at Kining’ina village in Kilombero Valley, southern Tanzania where a notable scale-up of long-lasting insecticide-treated nets coverage was made over the past two decades.

From the study findings, the two-mosquito species could penetrate treated and untreated bed nets and contact their preferred host due to their small size which is relative to net mesh hole sizes. For this reason, the scientists recommended modifications to the bed nets.

The current net-mesh limitations
“This study highlights the limitation of current net-mesh size in offering biting proof against A. funestus and A. arabiensis, the dominant malaria vector. The findings point out the importance of considering future modifications of mesh sizes that offer complete bite protection by preventing mosquitoes to penetrate the net without compromising ventilation.”

Additionally, the scientists also acknowledged that the ability of the two species to feed successfully on human volunteers during the study could result in noticeable effects on malaria transmission across mosquito populations in real-life settings.

“Although the number of both mosquito species that penetrated the nets was relatively low, the fact that the majority that did successfully blood fed on the volunteers, its effect on malaria transmission is likely to be noticeable if these numbers are magnified across mosquito populations under real-life settings.”

>> Read full article: https://pubmed.ncbi.nlm.nih.gov/36974127/