Aliens in the Backyard: Plant and Animal Imports into America

Bad Air and Worse Science: Malaria’s Gifts to America

67 Bad Air and Worse Science Malaria’s Gifts to America Malaria may well be the deadliest disease humanity has ever encountered. Experts guesstimate that the disease has killed more people throughout history than have wars. Today 250 to 300 million people worldwide are infected, and 2.5 million of these die each year. Prior to World War II, the United States was also cursed with malaria. During the Civil War 50 percent of white and 80 percent of black Union troops are estimated to have contracted malaria. The Centers for Disease Control estimated that six hundred thousand Americans contracted the disease in 1914. Only the government’s concerted efforts and the miracle pesticide DDT eradicated malaria in the States. Before drugs and drainage conquered it, people desperate to prevent or cure malaria imported plants purportedly capable of combating the disease. Their descendants are still with us.1 Malaria is a gift from Old World to the New, there being no record of its having been present in the Americas prior to the arrival of Europeans. Not that malaria leaves any telltale skeletal signs. Nevertheless, none of the preColumbian Central American written records describes an illness similar to malaria. Within a few generations of 1492, however, malaria spread throughout the Americas, helping to kill off native peoples who were not immune and spurring white Europeans to import allegedly immune black Africans into malarial districts. Microscopic parasitic protozoans called plasmodia cause malaria. The plasmodia infect not only people, but also a variety of mammals, birds, reptiles, and mosquitoes. Four kinds of plasmodia infect humans: Plasmodium vivax, P. malariae, P. ovale, and P. falciparum—and each causes a different response in its human host. Plasmodium vivax and the relatively rare P. ovale cause similar symptoms known as benign tertian malaria, since it doesn’t kill and its fevers reappear every other, or third, day. Plasmodium malaria causes quartan malaria, with fevers repeating every fourth day. Plasmodium falciparum is the deadliest plasmodium, causing malign tertian malaria, whose fevers’ timing resembles that 68 Aliens in the Backyard of benign tertian malaria, but whose intensity often results in death. Mosquitoes carry the plasmodia from one infected person to another, injecting them into the blood stream along with anticoagulants in their saliva when they bite us. Only female mosquitoes, which need blood to produce eggs, bite; the males are inoffensive nectar feeders. Only members of the Anopheles mosquito species infect humans. Other animals have their own plasmodia and mosquito species. Pre-Columbian America had Anopheles mosquitoes. They may have been annoying, but, without malaria, they were not dangerous. However,when these mosquitoes bit Europeans and Africans infected with malaria, they acquired the plasmodia and passed them on to other humans, and an American epidemic ensued.2 Not that anyone understood then the connection between mosquitoes and malaria. That was a nineteenth century medical triumph. Indeed, at least one person thought mosquitoes helped prevent malaria. Harper’s Weekly told its readers in 1875, “According to the recent revelations of a physician, the mosquito has been shamefully abused, and instead of being a plague, should be regarded as a public benefactor. The mosquito was created for the purpose of driving man from malarial districts. Its presence is a warning; but if man will not heed the warning, what does this public benefactor do? Why, it injects hypodermically a little liquid, which serves a double purpose—it renders the blood thin enough to be drawn up by the hungry insect, thus affording him a good meal; and as this liquid contains the principles of quinine, a useful homeopathic dose is thus administered.”3 Both popular and scientific opinion held that malaria was caused by “miasmas ” that arose from decaying organic material in stagnant or polluted water. These miasmatic vapors—bad air, or, in Italian, mala aria—were said to cause fevers in humans. The Pontine Marshes outside Rome were so notoriously malarial that the Italian-derived word malaria won out over earlier terms, such as ague and fever, in the English language. Eighteenth-century writer Horace Walpole’s 1740 observation about “a horrid thing called the mal’aria, that comes to Rome every summer and kills one,” is the first known use of the word in English.4 Malarial control consisted of eliminating standing or noxious water, avoiding or countering miasmas, and counteracting malarial fevers with a variety of drugs. Anopheles mosquitoes prefer to feed at dusk and after dark, so “night air” was considered especially dangerous. None...