Background
malaria, deaths, malaria infection
MALARIA
Globally, significant progress has been made controlling malaria through the scale-up of pyrethroid long-lasting insecticidal nets (LLINs), indoor residual spraying (IRS) and other prevention, diagnostic and treatment tools. The World Health Organization (WHO) estimated that due to the implementation of large-scale interventions, 1.5 billion malaria cases and 7.6 million malaria deaths were averted, 68% of which being attributed to the use of insecticide-treated nets (ITNs) [Until 2017, pyrethroids were the only chemical recommended by the WHO for use in LLINs. The first new class of dual-active-ingredient LLINs were treated with a mixture of a pyrethroid insecticide and a synergist, piperonyl butoxide (PBO), which enhances pyrethroid toxicity by inhibiting the activity of metabolic enzymes, commonly over-expressed in resistant vector populations. PBO-Pyrethroid-LLINs received a WHO recommendation following evidence from the present study on the efficacy of those nets against malaria infection over 2 years of use [Net deployment regimens currently assume three years of functional survival for LLINs under field conditions [Overall, there is a paucity of field data evaluating the effectiveness of PBO-Pyrethroid-LLINs to prevent malaria over longer periods of time. Their superiority and potential for cost-effectiveness over pyrethroid-only LLINs, while evident after 2 years in some endemic settings, may decline rapidly thereafter. In a recent CRT conducted in Misungwi a different district of Tanzania, the reduction in malaria infection prevalence between PBO-Pyrethroid-LLINs compared to standard LLINs was 45% after 1 year, while there was no further reduction observed in the second year [This paper reports on the effectiveness of PBO-Pyrethroid-LLINs compared to pyrethroid-only LLINs against malaria infection after 3 years of continuous community-use in an area of intense pyrethroid resistance.