A parasite is an organism that lives on or inside another organism (called a host) and causes harm. Humans can play "host" to over 100 different kinds of parasites ranging from microscopic to long tapeworms.
Parasites generally enter the body through the mouth or skin. Parasites that enter through the mouth are swallowed and can remain in the intestine or burrow through the intestinal wall and invade other organs.
Most skin parasites are tiny insects or worms that burrow into the skin and make their home there. Some parasites live in the skin for part of their life cycle; others would be permanent residents.
Scabies is a mite infestation that produces tiny reddish bumps and itching. Scabies is caused by the itch mite Sarcoptes scabei. The infestation spreads easily from person to person by physical touch, often spreading though an entire household. The hallmark of scabies is intense itching, which is usually worse at night. The burrows of the mites are often visible as very thin linesup to 1/2 inch long. The burrows can be anywhere on the body except the face. Common sites are the webs between the fingers and toes, the wrists, ankles, buttocks.
Scabicides are drugs that kill scabies and mites. They include:
Permethrin (Elimite) 5% cream is recommended by CDC as a first-line agent. Permethrin is the treatment of choice for children and for pregnant women. According to the Cochrane Review that focused on scabies, topical permethrin is considered the most effective treatment, more effective than lindane and crotamiton3.
Itching may persist for up to 2 weeks because of a continued allergic reaction to the mite bodies, which remain in the skin for a while.
Today the use of lindane (Kwell, gamma benzene hexachloride) for lice or scabies is considered outmoded due to increasing resistance, lack of efficacy, and toxicity to the nervous system. In many countries it is no longer available.
Sulfur in petrolatum is the oldest treatment for scabies, however not FDA approved for this use. Sulfur is one of the few choices that may be used safely in very small children and in pregnant women. However, it is messy, malodorous, stains clothes, and requires repeat applications.
Crotamiton 10% cream or lotion (Eurax) is approved by the FDA for scabies in adults. This agent is not approved for use in children.
Benzyl benzoate is not available in the United States, but is used in Europe.
Ivermectin (Mectizan, Stromectol) is an oral agent used for other parasites. It is currently not approved by the FDA for scabies, but several studies have shown that it is effective. Ivermectin may be convenient for people with skin conditions who should not use topical lotions and creams.
Parasitic helminthic infections are caused by parasitic worms of the helminth class. The most common worm parasites include hookworm, pinworm, threadworm, whipworm, tapeworm, and Ascaris lumbricoides (common roundworm).
Anthelmintics (also called antihelminthics) work by killing the worms.
Virtually all of the worm infections can be treated with one of anthelmintics currently available: albendazole (Albenza), mebendazole (Vermox), diethylcarbamazine (Hetrazan), ivermectin (Stromectol), praziquantel (Biltricide), and thiabendazole (Mintezol)1. They have broad spectrum coverage with high cure rates.
Mebendazole and albendazole are benzimidazole derivatives. These agents are most effective against intestinal roundworms (e.g. pinworms), but are contraindicated during the first trimester of pregnancy.
Mebendazole and albendazole are useful in single doses for various intestinal worm infections as they have a broad spectrum coverage. Cure rate with single doses of albendazole and mebendazole is about 88-95% for ascariasis2. For hookworm infections, albendazole is more effective than mebendazole. Cure rates for trichuriasis with single-dose are low (28% for albendazole and 36% for mebendazole).
Albendazole is active against a wider range of worms than mebendazole, including strongyloidiasis, toxocariasis, hydatid disease, and cysticercosis. Therefore albendazole is a choice in mixed worm infections.
Praziquantel is the better choice for schistosomiasis. It is also effective for intestinal tapeworms infections (taeniasis) and neurocysticercosis.
Last updated: October 20, 2012