Diseases spread by ticks are on the rise around the world, spurred by a combination of factors, including shifting climates and population sprawl into rural areas. Reported cases of Lyme, the most common US tick-borne illness, have nearly tripled in the country since 1992, although some of the increase could be due to heightened awareness. Lyme is also a growing problem in parts of Europe, Mongolia and China. Yet as bad as it is, there are nastier threats on the rise. In parts of Africa, the Middle East, Asia and southern Europe, ticks can spread Crimean–Congo haemorrhagic fever, which is fatal in 40% of cases. And a tick-borne relapsing fever afflicts as many as 1 in 20 residents in parts of Senegal. In the United States, ticks spread at least 16 illnesses, including anaplasmosis, babesiosis, ehrlichiosis and Rocky Mountain spotted fever, all “serious, life-threatening infections”, Beard says. And many are increasing in incidence more quickly than Lyme. In a July 2015 position statement, the Entomological Society of America argued for a national strategy to combat tick-borne diseases. “The recent confluence of environmental, ecological, sociological, and human demographic factors,” it said, “has created a near 'perfect storm' leading to more ticks in more places throughout North America.”
A. gambiae has been called the world’s most dangerous animal, although strictly speaking that applies only to the female of the species, which does the bloodsucking and harms only indirectly. Its bite is a minor nuisance, unless it happens to convey the malaria parasite, Plasmodium falciparum, for which it is a primary human vector. Although a huge international effort has cut malaria mortality by about half since 2000, the World Health Organization still estimates there were more than 400,000 fatal cases in 2015, primarily in Africa. Children are particularly susceptible. The Bill and Melinda Gates Foundation prioritized malaria in its more than $500 million commitment to fight infectious disease in developing countries. ... Humans have been at war with members of the family Culicidae for over a century, since the pioneering epidemiologist Sir Ronald Ross proved the role of Anopheles in malaria and U.S. Army Maj. Walter Reed made a similar discovery about Aedes aegypti and yellow fever. The war has been waged with shovels and insecticides, with mosquito repellent, mosquito traps and mosquito-larvae-eating fish, with bed nets and window screens and rolled-up newspapers. But all of these approaches are self-limiting. Puddles fill up again with rain; insects evolve resistance to pesticides; predators can eat only so much. ... If Crisanti’s approach works, you could, in theory, wipe out an entire species of mosquito. You could wipe out every species of mosquito, although you’d need to do them one at a time, and there are around 3,500 of them, of which only about 100 spread human disease. You might want to stop at fewer than a dozen species in three genera—Anopheles (translation: “useless,” the malaria mosquito), Aedes (translation: “unpleasant,” the principal vector for yellow fever, dengue and Zika) and Culex (translation: “gnat,” responsible for spreading West Nile, St. Louis encephalitis and other viruses).