Interbreeding of two malaria mosquito species in the West African country of Mali has resulted in a "super mosquito" hybrid that's resistant to insecticide-treated bed nets. 
 
 "It's 'super' with respect to its ability to survive exposure to the insecticides on treated bed nets," said medical entomologist Gregory Lanzaro of UC Davis, who led the research team. 
 
 The research, published Jan. 6 in the Proceedings of the National Academy of Sciences, "provides convincing evidence indicating that a man-made change in the environment -- the introduction of insecticides -- has altered the evolutionary relationship between two species, in this case a breakdown in the reproductive isolation that separates them," said Lanzaro, who is director of the Vector Genetics Laboratory and professor in the Department of Pathology, Microbiology and Immunology in the School of Veterinary Medicine. 
 
 "What we provide in this new paper is an example of one unusual mechanism that has promoted the rapid evolution of insecticide resistance in one of the major malaria mosquito species." 
 
 Anopheles gambiae, a major malaria vector, is interbreeding with isolated pockets of another malaria mosquito, A. coluzzii. Entomologists initially considered them as the "M and S forms" of Anopheles gambiae. They are now recognized as separate species. 
 
 Interbreeding of two malaria mosquito species in the West African country of Mali has resulted in a "super mosquito" hybrid that's resistant to insecticide-treated bed nets. 
 
 "It's 'super' with respect to its ability to survive exposure to the insecticides on treated bed nets," said medical entomologist Gregory Lanzaro of UC Davis, who led the research team. 
 
 "What we provide in this new paper is an example of one unusual mechanism that has promoted the rapid evolution of insecticide resistance in one of the major malaria mosquito species." 
 
 Anopheles gambiae, a major malaria vector, is interbreeding with isolated pockets of another malaria mosquito, A. coluzzii. Entomologists initially considered them as the "M and S forms" of Anopheles gambiae. They are now recognized as separate species. 
 
 The insecticide resistance came as no surprise. "Growing resistance has been observed for some time," Lanzaro said. "Recently 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." 
 
 Lanzaro credits insecticide-treated nets with saving many thousands, probably tens of thousands of lives in Mali alone. The World Health Organization's World Malaria Report indicates that deaths from malaria worldwide have decreased by 47 percent since 2000. Much of that is attributed to the insecticide-treated bed nets. However, it was just a matter of time for insecticide resistance to emerge, medical entomologists and epidemiologist agree. 
 
 Now there's "an urgent need to develop new and effective malaria vector control strategies," Lanzaro said. A number of new strategies are in development, including new insecticides, biological agents -- including mosquito-killing bacteria and fungi -- and genetic manipulation of mosquitoes aimed at either killing them or altering their ability to transmit the malaria parasite. 
 
 ### 
 
 First author on the paper is Laura Norris, a postdoctoral scholar in the UC Davis Department of Entomology and Nematology who was supported by a National Institutes of Health training grant awarded to Lanzaro. She has since accepted a position with the President's Malaria Initiative in Washington, D.C. 
 
 Other co-authors include, at UC Davis, Anthony Cornel, Yoosook Lee, Bradley Main and Travis Collier; and Abdrahamane Fofana of the Malaria Research and Training Center at the University of Bamako, Mali. Three grants from the National Institutes of Health funded the research. 
 
 Lanzaro has researched mosquitos in Mali for 24 years with Cornel, who is an associate professor in the UC Davis Department of Entomology and Nematology and headquartered at the UC Kearney Agriculture and Research Center, Parlier. Both are graduate student advisors in the department, training medical entomologists of tomorrow. ||||| Fact sheet on the World Malaria Report 2014 
 
 Malaria is an entirely preventable and treatable mosquito-borne illness. In 2014, 97 countries and territories had ongoing malaria transmission. 
 
 An estimated 3.3 billion people are at risk of malaria, of whom 1.2 billion are at high risk. In high-risk areas, more than one malaria case occurs per 1000 population. 
 
 Disease burden in 2013 
 
 There were an estimated 198 million cases of malaria worldwide (range 124–283 million) in 2013, and an estimated 584 000 deaths (range 367 000–755 000). 90% of all malaria deaths occur in Africa. 
 
 In 2013, an estimated 437 000 African children died before their fifth birthday due to malaria. Globally, the disease caused an estimated 453 000 under-five deaths in 2013. 
 
 Between 2000 and 2013, an expansion of malaria interventions helped to reduce malaria incidence by 30% globally, and by 34% in Africa. 
 
 During the same period, malaria mortality rates decreased by an estimated 47% worldwide and by 54% in Africa. In the under-five age group, mortality rates have declined by 53% globally, and by 58% in Africa. 
 
 New analysis reveals that the prevalence of malaria parasite infection (including both symptomatic and asymptomatic infections) has decreased significantly in Africa since 2000. The number of people infected fell from 173 million in 2000 to 128 million in 2013 – a reduction of 26%. This has occurred despite a 43% increase in the African population living in malaria transmission areas. 
 
 Trends in the scale-up of malaria interventions 
 
 During the past 10 years, coverage with vector control interventions increased substantially in Africa. In 2013, almost half of the population at risk in Africa (49%) had access to an insecticide-treated mosquito net, compared to 3% in 2004. 
 
 In 2014, an estimated 214 million long-lasting insecticidal nets (LLINs) were delivered to malaria-endemic countries in Africa, bringing the total number of LLINs delivered to that region since 2012 to 427 million. 
 
 In 2013, 124 million people were protected from malaria by indoor residual spraying around the world. In Africa, 55 million people, or 7% of the population at risk, lived in households that were regularly sprayed. 
 
 Access to rapid diagnostic tests (RDTs) and quality-assured artemisinin-based combination therapies (ACTs) has been increasing around the world. 
 
 The volume of RDT sales to the public and private sectors of endemic countries has increased from 46 million in 2008 to 319 million in 2013. 
 
 The number of patients tested by microscopic examination increased to 197 million in 2013, with India accounting for over 120 million slide examinations. 
 
 Globally, 392 million courses of ACTs were procured by endemic countries in 2013, up from 11 million in 2005. 
 
 In 2013, for the first time, the total number of diagnostic tests (RDTs and microscopy combined) provided in the public sector in Africa exceeded the total number of ACTs distributed. This indicates a prominent shift away from presumptive treatment and is thus an encouraging sign. 
 
 In Africa, the proportion of women who receive intermittent preventive treatment in pregnancy (IPTp) for malaria has been increasing over time, although the levels remain below national targets. An estimated 15 million of the 35 million pregnant women did not receive a single dose of IPTp in 2013. 
 
 Progress in adopting and rolling out preventive therapies for children has been even slower. As of 2013, only six of the 16 countries where WHO recommends preventive therapies for children under five have adopted the treatment as national policy. Only one country has adopted the recommended preventive therapy for infants, but has not yet started rolling out the programme. 
 
 Drug and insecticide resistance 
 
 Emerging parasite resistance to antimalarial medicines and mosquito resistance to insecticides, if left unaddressed, could render some of the current tools ineffective and trigger a rise in global malaria mortality. 
 
 In recent years, parasite resistance to artemisinin has been detected in five countries of the Greater Mekong subregion: Cambodia, the Lao People’s Democratic Republic, Myanmar, Thailand and Viet Nam. In areas along the Cambodia–Thailand border, P. falciparum has become resistant to most available antimalarial medicines, and multi-drug resistance is a major concern. 
 
 Between 2010 and 2013, 53 countries globally have reported mosquito resistance to at least one insecticide. Of these, 41 have reported resistance to two or more insecticide classes. The most commonly reported resistance is to pyrethroids, the most frequently used insecticide in malaria vector control. 
 
 Progress towards global targets 
 
 The malaria-specific Millennium Development Goal (MDG 6 target C: to have halted by 2015 and begun to reverse the incidence of malaria) has already been met. 
 
 In terms of country-level progress, a total of 64 countries are currently on track to reverse the incidence of malaria nationally by 2015. 
 
 Of these, 55 are on track to meet the World Health Assembly and Roll Back Malaria Partnership target of reducing malaria incidence by 75% by 2015. 
 
 Funding remains inadequate 
 
 International and domestic funding for malaria control and elimination totalled US$ 2.7 billion in 2013. Although this represents a threefold increase since 2005, it is still significantly below the US$ 5.1 billion that is required to achieve global targets for malaria control and elimination. ||||| We report that during a recent period of hybridization between two major African malaria mosquitoes, Anopheles gambiae and Anopheles coluzzii, an island of divergence on chromosome 2 introgressed from the A. gambiae into the A. coluzzii genome and its frequency subsequently increased. This introgression was coincident with the start of a major insecticide-treated bed net campaigns in Mali. These observations suggest that increased insecticide exposure acted as a selective force sufficient to drive introgression of an entire genomic island of divergence across the reproductive barrier separating these two species. This study provides a rare example of adaptive introgression in an animal species and elucidates the dynamics of how insecticide resistance evolved in A. coluzzii. 
 
 Abstract 
 
 Animal species adapt to changes in their environment, including man-made changes such as the introduction of insecticides, through selection for advantageous genes already present in populations or newly arisen through mutation. A possible alternative mechanism is the acquisition of adaptive genes from related species via a process known as adaptive introgression. Differing levels of insecticide resistance between two African malaria vectors, Anopheles coluzzii and Anopheles gambiae, have been attributed to assortative mating between the two species. In a previous study, we reported two bouts of hybridization observed in the town of Selinkenyi, Mali in 2002 and 2006. These hybridization events did not appear to be directly associated with insecticide-resistance genes. We demonstrate that during a brief breakdown in assortative mating in 2006, A. coluzzii inherited the entire A. gambiae-associated 2L divergence island, which includes a suite of insecticide-resistance alleles. In this case, introgression was coincident with the start of a major insecticide-treated bed net distribution campaign in Mali. This suggests that insecticide exposure altered the fitness landscape, favoring the survival of A. coluzzii/A. gambiae hybrids, and provided selection pressure that swept the 2L divergence island through A. coluzzii populations in Mali. We propose that the work described herein presents a unique description of the temporal dynamics of adaptive introgression in an animal species and represents a mechanism for the rapid evolution of insecticide resistance in this important vector of human malaria in Africa. ||||| Scientist have discovered the most advanced mosquito repellent. Dirty socks. 
 
 The smell of sweaty socks signals “feast” to the blood-sucking insects. 
 
 And scientists fighting malaria may soon be wafting that odor of stinky socks over poor villages throughout Africa as a potent anti-malarial weapon, thanks to a Canadian foreign aid grant, according to Healthzone.ca. 
 
 Mosquitoes, including the malaria-carrying anopheles, choose their targets for blood entirely on their sense of smell. 
 
 And the mosquitoes find the smell of sweaty socks irresistible. 
 
 So worn socks will be employed as bait in traps that can kill thousands of the malaria-bearing parasites each night, said the Tanzanian scientist who invented the device. 
 
 “We bait them indeed with dirty socks,” said Fredros Okumu, 29, a research scientist with the Ifakara Health Institute in southeastern Tanzania. Okumu is leading the two-year project funded by the Bill and Melinda Gates Foundation and Grant Challenges Canada. 
 
 “The sock is attractive to us, not just because it’s attractive to mosquitoes, but also because it’s readily available,” said Okumu, who is completing a PhD at the London School of Hygiene & Tropical Medicine. 
 
 Okumu has also used simple cotton pads worn for a day in villagers’ shoes as an alternative to the actual sock. 
 
 “If you’re using socks, you’re going to have to get a lot of socks to do this,” he said. “It’s not going to be acceptable for people to take all their socks and put them in traps.” 
 
 Mosquitoes are particularly attracted to feet because they are a key source of the odor that allows them to distinguish us as humans, Okumu said. 
 
 Socks trap this scent, a volatile fatty acid smell created by the bacteria that teem on our skin throughout the day, he said. 
 
 The stinky sock trap is a solution to the serious problem of malaria. Nearly 1 million people die of malaria every year from 250 million cases of the disease, according to the World Health Organization. 
 
 Malaria is especially serious in Africa, where one in every five (20 percent) of childhood deaths is from the effects of the disease. An African child has on average between 1.6 and 5.4 episodes of malaria fever each year. And every 30 seconds a child dies from malaria. 
 
 Okumu’s smelly sock trap will be used alongside mosquito nets to put over beds, which are being distributed across malarial regions of the continent. Many experts working to eliminate malaria in Africa and around the world say that the most effective method is to spray the inside of homes with a weak solution of the insecticide, DDT. 
 
 “But we can’t eliminate malaria by just focusing inside the house, we have to go outside as well,” said Okumu. 
 
 The trap is a louvered box about the size of a garbage can. Once drawn inside by the smell, the mosquitoes are poisoned by a powerful insecticide. 
 
 Okumu also uses a black box that contains the stinky socks, or a synthetic bait, and is coated with a fungal insecticide. Mosquitoes are attracted to the box and die when they land on it. 
 
 They persuaded a number of volunteers to donate socks they had worn for at least ten hours. They then placed them inside canvas and wooden boxes hung with insecticide-laced drapes outside people's homes in rural southeast Tanzania. 
 
 "In their attempts to get blood from these devices, between 74 to 95 percent of all of those who landed in them got killed," he said. "We're hoping this will be a worthwhile and significant addition to the malaria control arsenal." 
 
 The research team plans to simplify the devices so they can be made and sold by the rural villagers themselves. 
 
 Using a $400,000 grant from Toronto-based Grand Challenges Canada, Okumu is also developing a synthetic attractant that mimics the sock smell and the other human emissions that mosquitoes zero in on. 
 
 These chemical scents will also reproduce the breath and sweat odors that attract mosquitoes. Okumu said these chemical attractants are four times more seductive to mosquitoes than socks alone. If the chemical is unavailable, however, villagers can fall back on the sock or cotton pad bait, he said. 
 
 The project has also received $500,000 in funding from the Bill and Melinda Gates Foundation. The combined funds will be used for several initiatives, including proper placement of the traps around villages. 
 
 Okumu said he expects that 20 traps for every 1,000 people would suffice, but that villagers themselves would be consulted to locate prime mosquito locations. 
 
 The traps spread their foot odor with fans that run on solar powered batteries, which could also help light homes and make them more desirable. ||||| In global public health, disease-fighting tools that are cheap, available and sustainable are the Holy Grail. It might be hard to top the one being tested in Tanzania as a way to prevent malaria: smelly socks. 
 
 Experiments in three villages where people get about 350 bites a year from malaria-infected mosquitoes are using dirty socks to lure the insects into traps, where they become contaminated with poisons and ultimately die. 
 
 Researchers hope that if the strategy works, it will eventually complement insecticide-treated bed nets as a low-tech way to prevent malaria, which kills nearly 900,000 people a year worldwide, most of them children. 
 
 “It’s a bold idea. Who would have thought there was a life-saving technology working in your laundry basket?” said Peter A. Singer, a physician who heads Grand Challenges Canada, a development agency of the Canadian government that is helping fund the research. 
 
 Previous lab studies have shown that smelly socks work well in attracting mosquitoes. Field experiments have shown that synthetic bait is more attractive than people, at least until the insects get close enough to realize there’s no blood waiting for them. 
 
 The new experiments, however, are the first head-to-head field tests of footwear vs. chemistry. The researchers hope the footwear wins. 
 
 “It is simply a cost issue and an expediency issue,” said Fredros O. Okumu, the Tanzanian entomologist leading the research. “Socks are more readily available, and you don’t have to mix any chemicals. It is the sort of thing that could be set up in a cottage factory.” 
 
 The traps are square boxes that look a little like commercial beehives. Some will contain the human-odor bait, which consists of simple chemicals (including lactic acid, ammonia and propionic acid) that are exuded by people, especially from the legs and feet. Some will contain socks worn for a day by adults. Others will contain cotton pads that schoolchildren will put inside their socks for a day and then deliver to researchers. 
 
 The researchers will compare the number of mosquitoes caught with each method. 
 
 Earlier work by Okumu and his colleagues at the Ifakara Health Institute in Tanzania showed that the chemical bait attracted four times as many mosquitoes as live people and that dirty socks worked just as well, at least in the lab. If the sock pads prove adequate, they will be the preferred bait. 
 
 The inside surfaces of some traps are coated with an organophosphate pesticide. Mosquitoes that land there will die within 24 hours. Other traps contain a fungus that infects the insects and kills them in five days — roughly half the time needed for the complicated cycle that enables a newly infected mosquito to transmit the malaria parasite to a person. 
 
 The bait-and-kill strategy is a new one in malaria prevention efforts. 
 
 Normally, attempts to prevent malaria by controlling mosquitoes, known as vector control, have aimed at driving the insects away from people or killing them once natural attraction has brought them into proximity. 
 
 Insecticide-treated bed nets, millions of which have been sold or given away in Africa in the past decade, have a long-acting repellant, permethrin. In many malaria-endemic areas, people spray the inside walls of dwellings with insecticide that kills mosquitoes when they land. 
 
 Bed nets have cut childhood deaths by about 20 percent in malaria-endemic areas. Modeling suggests that traps could reduce malaria transmission about as much as bed nets do in villages where half the households use them. 
 
 Despite its low-tech appearance, the strategy Okumu is testing is far more complicated, and potentially fraught with hazard, than it seems. 
 
 A key question is where to place traps. They need to be close enough to dwellings to attract mosquitoes, but not so close that they will increase people’s exposure to the disease-carrying insects. Okumu’s research suggests that the traps should be at least 100 feet from houses. 
 
 Another question is how many traps a village might need. Okumu has calculated the minimum number at 20 per 1,000 people, although in places where malaria transmission is especially intense and in certain village configurations, 130 traps per 1,000 people might be needed. 
 
 Despite these challenges, Singer said, projects such as these are what Grand Challenges Canada is looking to support. It is providing $388,000 for the research, and the Bill and Melinda Gates Foundation is providing a similar amount. The Gates Foundation gave Okumu $100,000 for preliminary studies, as well. 
 
 “We are inspired by people like Fredros,” Singer said. “We strongly believe that innovators in low-income countries are best situated to solve their own problems. He is an African researcher with an African innovation for an African problem.” 
 
 Okumu, who is a doctoral candidate at the London School of Hygiene and Tropical Medicine, said he is “working on the premise that this is a global problem — a global problem in a flat world.” 
 
 He said he doubted that there might be an application for his strategy — should it prove successful — in non-malarious places such as the United States. A pair of socks from a recent 10K run at the corner of a patio will only briefly divert mosquitoes. They’ll soon find the bare legs under the picnic table. 
 
 “Mosquitoes are still fairly clever animals,” he said. “What they are looking for is blood. They might be attracted to the socks, but they will not spend much time there.”
– For years, campaigns such as Nothing But Nets have been trying to control the scourge of malaria—a blood disease spread by mosquito bites—by sending insecticide-laced nets to hard-hit regions (mostly in Africa). But a University of California-Davis study has some bad news: Researchers have discovered a hybrid "super mosquito" that seems to be resistant to the treated nets. The study published in Proceedings of the National Academy of Sciences indicates that Anopheles coluzzii mosquitoes in Mali that cross-bred with the A. gambiae variety created the superinsect—"'super' with respect to its ability to survive exposure to the insecticides," says Gregory Lanzaro, the study's lead author, in a press release. Although he's not surprised insecticide resistance is rising, it's still worrisome: "It is resulting in the failure of the nets to provide meaningful control." There were about 584,000 deaths from malaria in 2013, 90% of them occurring in Africa, according to the World Health Organization; every 60 seconds a child there dies from the disease, Nothing But Nets adds. But inroads have been made: Intervention tactics, including insecticide-treated nets, helped cut the mortality rate 54% in Africa between 2000 and 2013, the WHO notes—and in 2013, 49% of all African residents at risk for the disease (up from a mere 3% in 2004) had access to insecticide-laced nets. This new finding could throw a wrench in that progress, and new preventative measures will need to be explored. (Another study: Pantyhose help reveal why mosquitoes prefer humans.)