parasite

This photomicrograph depicts Leishmania donovani parasites contained within a canine bone marrow cell. One of the more dangerous of 20 different species of Leishmania, L. donovani is endemic to parts of India, Africa, and South-West Asia. Dr. Francis W. Chandler/CDC hide caption

A female adult head louse holds onto human hairs, as it is filmed under a microscope. The brown line visible inside the louse, on the left side of its body, is the blood meal it took when it lived on a human host's scalp. Josh Cassidy/KQED hide caption

These mitochondria, in red, are from the heart muscle cell of a rat. Mitochondria have been described as "the powerhouses of the cell" because they generate most of a cell's supply of chemical energy. But at least one type of complex cell doesn't need 'em, it turns out. Science Source hide caption

A colored-in microscopic image of the parasite that causes African sleeping sickness (teal) among red blood cells. Georg Gerster/Science Source hide caption

The giant roundworm, Ascaris lumbricoides, shows its three serrated lips. Eye of Science/Science Source hide caption

A mosquito bed net keeps the bugs out. The photo was taken in Pailin province, Cambodia. Paula Bronstein/Getty Images hide caption

An Aka man smokes hemp while hunting in the Central African Republic. Veronique Durruty/Gamma-Rapho via Getty Images hide caption

Does this little guy look familiar? Clean up his feces in your yard to avoid infection from his parasites. iStockphoto hide caption

A health official takes a blood sample from a child's finger for a malaria test at a clinic in Bong Ti Lang village on the Thai-Myanmar border. Narong Sangnak/EPA /LANDOV hide caption