text: Malaria is a mosquito-borne disease caused by a parasite. People with malaria often experience fever, chills, and flu-like illness. Left untreated, they may develop severe complications and die. In 2016 an estimated 216 million cases of malaria occurred worldwide and 445,000 people died, mostly children in the African Region. About 1,700 cases of malaria are diagnosed in the United States each year. The vast majority of cases in the United States are in travelers and immigrants returning from countries where malaria transmission occurs, many from sub-Saharan Africa and South Asia. 
   
   CDC’s Malaria Program ||||| 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. ||||| 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. ||||| Progress 
   
   Who needs your help? 
   
   We work with our UN partners to protect refugees and families who are most vulnerable to malaria. Some have fled conflict, others have been displaced by natural disasters or political unrest and have left everything behind. After all they have endured, these families shouldn’t have to fear a deadly mosquito bite. ||||| 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.
target: – 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.)