{"id":350198,"date":"2026-03-27T07:35:15","date_gmt":"2026-03-27T07:35:15","guid":{"rendered":"https:\/\/www.newsbeep.com\/nz\/350198\/"},"modified":"2026-03-27T07:35:15","modified_gmt":"2026-03-27T07:35:15","slug":"a-new-challenge-in-malaria-control","status":"publish","type":"post","link":"https:\/\/www.newsbeep.com\/nz\/350198\/","title":{"rendered":"A New Challenge in Malaria Control"},"content":{"rendered":"

The fight against infectious disease is a race against evolution. Bacteria become\u00a0resistant to antibiotics<\/a>. Viruses\u00a0adapt to spread more quickly<\/a>. Diseases transmitted by insects present another evolutionary front: Insects themselves can evolve resistance to the poisons that people use to kill them.<\/p>\n

In particular, the mosquito-borne disease malaria\u00a0kills over 600,000 people annually<\/a>.\u00a0Since World War II<\/a>, people have battled malaria with insecticides \u2014 chemical weapons intended to kill\u00a0Anopheles\u00a0mosquitoes infected with the\u00a0Plasmodium\u00a0parasites that cause the disease.<\/p>\n

However, mosquitoes are\u00a0quickly evolving counterstrategies<\/a>\u00a0that make these insecticides ineffective, putting millions of people at greater risk of deadly infection. My colleagues and I have newly published research showing how.<\/p>\n

Insecticide resistance threatens public health<\/p>\n

As an evolutionary geneticist<\/a>, I study\u00a0natural selection<\/a>\u00a0\u2014 the basis for adaptive evolution. Genetic variants that best promote survival can replace less advantageous versions, causing species to change.\u00a0Anopheles\u00a0mosquitoes are frustratingly adept at evolving.<\/p>\n

In the mid-1990s, most African\u00a0Anopheles\u00a0were\u00a0susceptible to pyrethroids<\/a>, a popular type of insecticide originally derived from chrysanthemums.\u00a0Anopheles\u00a0control relies on\u00a0two pyrethroid-based methods<\/a>: Insecticide-treated bed nets to protect sleepers, and indoor residual spraying of insecticide against the walls of homes. These two methods alone likely\u00a0prevented over a half-billion cases of malaria<\/a>\u00a0between 2000 and 2015.<\/p>\n

However, mosquitoes today\u00a0from Ghana<\/a>\u00a0to Malawi<\/a>\u00a0are often able to survive insecticide concentrations 10 times the previously lethal dose. Along with\u00a0Anopheles\u00a0control efforts, agriculture also inadvertently\u00a0exposes mosquitoes to pyrethroids<\/a>\u00a0and contributes to insecticide resistance.<\/p>\n

In some African locales,\u00a0Anopheles\u00a0is already showing\u00a0resistance to all four main classes of insecticide<\/a>\u00a0used for malaria control.<\/p>\n

Adaptation in Latin American mosquitoes<\/p>\n

Anopheles\u00a0mosquitoes and the malaria-causing\u00a0Plasmodium\u00a0also occur outside Africa, where insecticide resistance is less well-researched.<\/p>\n

In much of South America, the main malaria vector is\u00a0Anopheles darlingi. This mosquito species has diverged evolutionarily from the African vectors so extensively that it might be a\u00a0different genus, <\/a>Nyssorhynchus<\/a>. Along with colleagues from eight countries, I\u00a0analysed over 1,000 <\/a>Anopheles darlingi<\/a> genomes<\/a>\u00a0to understand its genetic diversity, including any recent changes due to human activity. My collaborators collected these mosquitoes at 16 locations ranging from the Atlantic coast of Brazil to the Pacific side of the Andes in Colombia.<\/p>\n

We found that, like its African counterparts,\u00a0Anopheles darlingi\u00a0shows extremely high genetic diversity \u2014\u00a0more than 20 times that of humans<\/a>\u00a0\u2014 indicating that very large populations of this insect exist. A species with such a vast gene pool is well poised to adapt to new challenges. The right mutation giving it the advantage it needs is more likely to pop up when there are so many individuals. And once that mutation starts to spread, it\u2019s protected by numbers since it won\u2019t be wiped out if a few mosquitoes die by chance.<\/p>\n

In contrast,\u00a0bald eagles in the contiguous US<\/a>\u00a0were never able to evolve resistance against the insecticide DDT and approached extinction. Evolution is more efficient among millions of insects than mere thousands of birds. And indeed, we saw\u00a0signals of adaptive evolution<\/a>\u00a0in the resistance-related genes of\u00a0Anopheles darlingi\u00a0occurring over the past few decades.<\/p>\n

Mosquitoes evolve to detoxify poisons<\/p>\n

Insecticides like pyrethroids and DDT share the same molecular target: channels in nerve cells that can open and close. When open, the nerve cell stimulates other cells. These insecticides force the channels to remain open and continuously fire,\u00a0causing paralysis and death<\/a>. However, insects can evolve resistance by changing the shape of the channel itself.<\/p>\n

Earlier genetic scans performed by other researchers\u00a0had not detected this type of resistance<\/a>\u00a0in\u00a0Anopheles darlingi, and neither did ours. Instead, we found that resistance is evolving in another way: A group of genes encoding enzymes that break down toxic compounds. High activity of these\u00a0enzymes, called P450<\/a>, frequently underlies resistance to insecticides in other mosquitoes. The same cluster of P450 genes has changed independently at least seven times across South America since insecticide use began in the mid-20th century.<\/p>\n

In French Guiana, a different set of P450 genes exhibits a\u00a0similar evolutionary pattern<\/a>, cementing the clear connection between these enzymes and adaptation. Moreover, when we exposed mosquitoes to pyrethroids in sealed bottles, differences among the P450 genes of individual mosquitoes were linked to the length of time they stayed alive.<\/p>\n

Insecticide-heavy campaigns against malaria have been only sporadic in South America and may not be the main driver behind this evolution. Instead, it\u2019s possible that mosquitoes are being exposed indirectly to agricultural insecticides. Intriguingly, we saw the strongest signs of evolution in places where farming is prevalent.<\/p>\n

Toward more sophisticated vector control<\/p>\n

Despite\u00a0new vaccines and other recent advances against malaria<\/a>, mosquito control remains essential for reducing disease.<\/p>\n

Some countries are launching trials of\u00a0gene drives<\/a>\u00a0to control<\/a>\u00a0malaria<\/a>, which involve forcing a genetic modification into a mosquito population to reduce their numbers or their tolerance for\u00a0Plasmodium. Such prospects are exciting, though the relentless adaptability of mosquitoes could be an obstacle.<\/p>\n

I and others are revising methods to\u00a0efficiently test for emerging insecticide resistance<\/a>. Genome-scale sequencing remains important to detect new or unexpected evolutionary responses. The risk of adaptation is highest under a continuous, strong selection pressure, so minimizing, switching and staggering pesticides can help thwart resistance.<\/p>\n

Success in the fight against evolving resistance will require a coordinated effort of monitoring, and reacting accordingly. Unlike evolution, humans can think ahead.<\/p>\n","protected":false},"excerpt":{"rendered":"The fight against infectious disease is a race against evolution. Bacteria become\u00a0resistant to antibiotics. Viruses\u00a0adapt to spread more…\n","protected":false},"author":2,"featured_media":350199,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[10],"tags":[185788,185787,6567,134,6474,185793,185789,6512,185791,9695,139585,111,139,69,185792,185790],"class_list":{"0":"post-350198","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-health","8":"tag-anopheles","9":"tag-disease-vectors","10":"tag-evolution","11":"tag-health","12":"tag-infectious-diseases","13":"tag-insecticide-resistance","14":"tag-insecticides","15":"tag-malaria","16":"tag-mosquito-borne-diseases","17":"tag-mosquitoes","18":"tag-new-research","19":"tag-new-zealand","20":"tag-newzealand","21":"tag-nz","22":"tag-plasmodium","23":"tag-pyrethroids"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/350198","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/comments?post=350198"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/350198\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media\/350199"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media?parent=350198"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/categories?post=350198"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/tags?post=350198"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}