Parasites are organisms that live off other organisms, or hosts, to survive. Some parasites don’t noticeably affect their hosts. Others grow, reproduce, or invade organ systems that make their hosts sick, resulting in a parasitic infection.
Anyone can get a parasitic infection. But some people are at greater risk than others. You’re more likely to contract a parasitic infection if you:
have a compromised immune system or are already sick with another illness
live or travel in tropical or subtropical regions of the world
lack a clean supply of drinking water
swim in lakes, rivers, or ponds where Giardia or other parasites are common
work in childcare, work with soil regularly, or work in other contexts where you come into contact with feces on a consistent basis
Human scabies is caused by an infestation of the skin by the human itch mite (Sarcoptes scabiei var. hominis). The microscopic scabies mite burrows into the upper layer of the skin where it lives and lays its eggs. The most common symptoms of scabies are intense itching and a pimple-like skin rash. The scabies mite usually is spread by direct, prolonged, skin-to-skin contact with a person who has scabies. Scabies occurs worldwide and affects people of all races and social classes. Scabies can spread rapidly under crowded conditions where close body contact is frequent. Institutions such as nursing homes, extended-care facilities, and prisons are often sites of scabies outbreaks.
- Cutaneous Larva Migrans
Cutaneous larva migrans is caused by Ancylostoma, a hookworm that normally inhabits the intestines of dogs and cats. The eggs of the parasite are in dog and cat feces and develop into larvae when left in warm, moist soil or sand. When bare skin touches the ground, for example, when a person walks barefoot or sunbathes, the hookworm gets into the skin. Cutaneous larva migrans occurs worldwide but is most common in tropical environments.Cutaneous Larva Migrans on the Foot Cutaneous Larva Migrans on the Foot.Starting from the site of infection—usually the feet, legs, buttocks, or back—the hookworm burrows along a haphazard tract, leaving a winding, threadlike, raised, reddish brown rash. The rash itches intensely. Small bumps and blisters may also occur. Often, scratching of the bumps or blisters results in a bacterial infection of the skin.
The infection goes away by itself after a few weeks to months, but treatment relieves the itching and reduces the risk of bacterial infection that sometimes results from scratching. A liquid or cream preparation of thiabendazole applied to the affected area effectively treats the infection. Albendazole or ivermectin given by mouth also is effective.