Here are some things parasites will do to survive.
The hairworm makes infected crickets commit suicide in water so it can find a mate. Parasitic barnacles invade the bodies of crabs, sterilize them, and then trick them into caring for baby parasitic barnacles. Toxo makes rats so fearless that they run straight to cats, whose feces spread the parasite.
In other words, parasites sometimes possess not just the bodies of their hosts. They seem to possess their minds.
Malaria, which sickens more than 200 million people a year, seems to have some mind-altering powers over mosquitoes, too. The parasites that causes malaria, which belong to the genus Plasmodium, spread to humans through mosquito bites. A handful of studies have found that female mosquitoes infected with a certain stage of the parasite are more eager for blood. And conversely, humans infected with malaria seem to emanate signals that attract more mosquitoes.
A new study in Science actually illuminates how the parasite in human blood draws mosquitoes, manipulating the bugs into flying malaria-dispersal machines.
The discovery came by accident. Ingrid Faye, a molecular biologist at Stockholm University, was curious about a particular molecule made by malaria parasites called HMBPP. She wanted to drill into the details of how HMBPP affects mosquito immune systems, but her team ended up noticing some behavior too odd to ignore: The mosquitos—specifically, the species Anopheles gambiae they were studying—would go crazy for human blood with HMBPP. “The difference it made was just astounding,” says Faye. When given a choice between normal human blood and that either laced with the HMBPP or infected with malaria parasites, almost all the mosquitoes went for the latter two.