National Geographic : 2016 Aug
+100% No change NORTH AMERICA SOUTH AMERICA EUROPE TROPIC OF CANCER TROPIC OF CAPRICORN EQUATOR ASIA AFRICA AUSTRALIA –100% the mosquito world, males live off plants. The female is the biter, the worker, the source of hu- man peril; she lives off plants too, but all those blood nutrients are for her eggs, the nourishing and laying of which are the great project of her short, purposeful, and somewhat solitary life. A single mating may be all an Ae. aegypti needs; she stores sperm inside her body, fertilizing sep- arate batches of eggs as needed, up to several hundred at a time. Five or six occasions of egg laying are common for an Ae. aegypti that es- capes extermination by swat or insecticide and reaches her expected month-long life span. The multiplication possibilities are staggering. Ask biologists what natural advantage dif- ferent mosquito species might have gained by spreading disease—why Aedes became the pri- mary carrier of the Zika virus, for example, and Anopheles the carrier of malaria parasites—and they’re likely to tell you that you’re thinking about the question backward. It’s the patho- gens, those disease-causing organisms driven to multiply in mammalian bodies, that over Aedes aegypti Found in cities, this insect feeds almost exclusively on human blood. Aedes albopictus The aggressive, adapt- able species can easily colonize the habitats of other mosquitoes. Anopheles* The only genus that transmits malaria, it is known for its long front feelers. Haemagogus* These forest vectors of yellow fever can be identified by their metallic sheen. Mosquito Maladies Pathogens have adapted to thrive in different species of mosquitoes with characteristics that make them good hosts. Culex quinquefasciatus These night feeders, common around the world, prefer to lay eggs in dirty water. LYMPHATIC FILARIASIS This tropical disease alters the lymphatic system and causes devastating disfigurement and enlargement of body parts. MALARIA The parasitic disease killed more than 400,000 people in 2015. Most of the fatalities were in sub-Saharan Africa. WEST NILE FEVER In 1999, the appearance of this virus in the U.S. highlighted the threat of vector-borne diseases outside native ranges. DENGUE FEVER Spreading since the 1970s, the potentially fatal virus now threatens 50 percent of the world’s population. YELLOW FEVER Nearly 60,000 deaths a year are attributed to this skin- yellowing disease, which can be prevented with a vaccine. ZIKA VIRUS DISEASE This rapidly spreading virus can cause defects in the unborn babies of infected pregnant women. CHIKUNGUNYA Named after a Kimakonde word meaning “to be contorted,” the virus, discovered in Tanzania, causes severe joint pain. JASON TREAT, RYAN WILLIAMS, AND CHARLES PREPPERNAU, NGM STAFF SOURCES: WORLD HEALTH ORGANIZATION; CENTERS FOR DISEASE CONTROL AND PREVENTION (GRAPHIC); YIANNIS PROESTOS, CYPRUS INSTITUTE (MAP) millennia “learned,” evolutionarily speaking, what excellent transport and delivery services some mosquitoes happen to provide. It’s not an easy ride for the pathogens: They have to survive being sucked into a mosquito’s gut, ex- posed to digestive enzymes, and then pushed through membranes into a mosquito salivary gland before being injected into the next warm- blooded host. The injectors, on the other hand, are simply perpetuating their family line. “It’s such a rare confluence of evolution that has allowed this to happen,” says Karl Malamud- Roam, a mosquito research scientist who helps direct a pest management program based at Rutgers University. “It’s hard to be a successful germ or mosquito.” A modicum of respect seems in order, then, for this remarkable confluence and the very resourcefulness of the flying vampires. Con- sider the reproductive strategies of Aedes aegypti, which because of Zika has been the subject of international symposia and plans of attack. An Ae. aegypti will lay her eggs in the * Many species within the genus can transmit the disease.