Two types of malaria-transmitting mosquitoes in Mali — Anopheles gambiae and Anopheles coluzzii — have interbred to create a new hybrid “super” mosquito resistant to insecticide treated bed nets [1]. A recent publication in the Proceedings of the National Academy of Sciences, provides convincing evidence that man-made changes in the environment — in particular, the introduction of insecticides — have impacted the mosquito’s evolutionary relationship and has removed the “reproductive isolation that separates them” [2]. Prof. Gregory Lanzaro — a medical entomologist and professor at the University of California, Davis — the leader of the study’s research group, states that the results of the study is “an example of one unusual mechanism that has promoted the rapid evolution of insecticide resistance in one of the major malaria mosquito species” [2]. Given the recent findings, there may be a few implications regarding its impact on malaria, particularly in endemic areas.
What are the Implications?
Malaria, a mosquito-borne disease caused by a parasite, impacts mostly developing tropical and subtropical areas of the world [3]. According to the Center for Disease Control (CDC), approximately 627,000 people died from malaria in 2012, with the majority being young children in sub-Saharan Africa [3]. Young children are the most vulnerable to malaria, because they have yet to develop immunity to the disease [3]. Additionally, pregnant women are also vulnerable, because their immunity decreases as a result of their pregnancy [3].
Malaria-control efforts have curbed the disease’s impact, cutting mortality by 45% and saving 3.3 million lives globally [3]. The most common preventive measures include indoor residual spraying (IRS), vector control, anti-malarials, and insecticide-treated bed nets (ITNs) [4]. It has been shown in community-wide trials across Africa that ITNs can reduce child mortality from all diseases by 20% [4]. An estimated 214 million long-lasting ITNs were distributed to malaria countries across Africa in 2014 — this has brought the distributed regional total to 427 million long-lasting ITNs since 2012 [5].
With the introduction of a new hybrid species of mosquito that is resistant to ITNs, the impact that ITNs have had in the battle against malaria may truly be a figment of the past. This issue will only get worse if left unaddressed. Mosquito insecticide resistance isn’t novel. According to the WHO, 49 countries reported mosquito resistance to at least one insecticide between 2010 and 2013, and the number seems to be growing [5]. Prof. Lanzaro reports that, "it has reached a level at some localities in Africa where it is resulting in the failure of the nets to provide meaningful control, and it is my opinion that this will increase" [2]. Without new means to combat insecticide resistance, a rise in mosquito-borne diseases such as malaria, is imminent.
Sources
[2] http://www.medicalnewstoday.com/articles/287907.php
[3] http://www.cdc.gov/malaria/malaria_worldwide/index.html
[4] http://www.cdc.gov/malaria/malaria_worldwide/reduction/itn.html
[5] http://www.who.int/malaria/media/world_malaria_report_2014/en/
