Malaria, Poems

II. How It Happens

57 I. TYPES “Plasmodium is a tiny, single-celled parasite that infects cells.” There are over 120 species of the parasite genus Plasmodium. These five infect humans: 1. Plasmodium falciparum: causes the most serious disease; this is the killer. 2. Plasmodium vivax: the most common but infections rarely fatal. 3. Plasmodium ovale: restricted to West Africa; causes mild illness. 4. Plasmodium malariae: isolated and scattered over globe, severe fever, rarely fatal. 5. Plasmodium knowlesi: recently discovered in Southeast Asia, potentially fatal. (Wellcome Collection, “The Malaria Parasite at a Glance” and A. Kantele and S. Jokiranta, Plasmodium knowlesi—the fifth species causing human malaria) II. HOW IT HAPPENS “The female Anopheles mosquito, hungry for blood, lands on a patch of warm human skin. “She plants four of her six hairy legs as she dips her head and thorax. She probes with her long, tube-like proboscis, bending back her labium, the lip that sheathes the proboscis. At the end of the proboscis, knife-like stylets move rapidly like electric carving knives to split the skin. She gently jabs at different angles in the hole until she nicks an arteriole that spouts a subcutaneous pool of blood that she can draw from. Exquisitely evolved, the female vampire will squirt into the cut a small amount of saliva full of anticoagulants to prevent the blood from clotting. . . . “Within a couple minutes, her translucent belly bloats and shifts from waxy gray to cherry red. She sucks a few micrograms M I S C . M A T T E R S 58 of blood—more than her own body weight. Unlike other mosquitoes, the female Anopheles doesn’t wait until after feeding to start the digestion process . She excretes water from the blood as she feeds. This allows her to pack into her stomach more of the blood’s protein while getting rid of what she doesn’t need. She lifts in a slow, tottering flight and moves to a nearby vertical surface. There, sluggish from gorging the blood meal, she continues digesting the blood that will provide the nutrients and proteins necessary for her eggs to develop. “In her blood meal, she has ingested red blood cells, white blood cells, platelets, and other constituents of human blood. And she sucked up something else as well: some protozoan stowaways. “The mosquito, in a simple act essential for reproduction, ensures the reproduction and spread of another species:” Falciparum. “The malaria cycle begins once more.” —Brian W. Simpson, “Putting the Bite on Malaria,” Johns Hopkins Public Health, 2001 III. BIO BATTLE I Sickle Cell: “evidence indicating that persons with sickle cell trait are protected against the most serious form of malaria.” —Michael Woods, “Detection Center Set for Sickle Cell Anemia” Thalassemia: “disease may account for much lower malaria mortality.” —“Decreased Malaria Morbidity in the Tharu People Compared to Sympatric Populations in Nepal” G6PD: “the common African form of G6PD . . . deficiency is associated with a 46–58% reduction in risk of severe malaria” —“Natural selection of hemi- and heterozygotes for G6PD” Duffy: “The resistance factor to Plasmodium vivax in blacks. The Duffyblood -group genotype, FyFy” —title of an article in The New England Journal of Medicine ...