Helminth infections -- worm infections -- are a major cause of illness worldwide. Even though public sanitation has led to a decreasing rate of helminth infections in the United States, worms can still cause infection when you travel, eat undercooked meats, or fall victim to poor sanitation. There are a variety of medications available to treat helminth infections, and most are very effective with few side effects.
Albendazole and Mebendazole
Albendazole and mebendazole work by preventing synthesis of microtubules in the worms, blocking the ability of worms to shuttle proteins through their cells. They carry a very low risk of side effects with short treatment; with longer treatment, patients must be monitored for changes in blood cell counts and liver enzymes. Pregnant women should avoid these drugs. Albendazole is the drug of choice for treating ascariasis and only one dose is required. Both drugs are effective against hookworms, pinworms, and whipworm. Albendazole can also be used to treat strongyloidiasis, trichinella, neurocystercosis, and cutaneous and visceral larva migrans.
Diethylcarbamazine interferes with the protective surface of the worms, allowing the patient's immune system a better chance to fight the worms. It has few side effects, but is usually given with an antihistamine to reduce the risk of having an allergic reaction to the dying worms. It is primarily used for filariasis and is a second-line drug for onchocerciasis.
Ivermectin causes paralysis of worms by increasing gamma-aminobutyric acid, or GABA, and should not be used with other drugs that also increase GABA, such as benzodiazepines and valproic acid. Mild side effects include upset stomach, dizziness, and headache. It is the drug of choice for onchocerciasis, requiring only one dose, and strongyloidiasis, which may require repeated doses. It is also useful for ascariasis and pinworms, and it can be given with albendazole to shorten the treatment course for trichuriasis.
Praziquantel affects the metabolism of calcium, causing paralysis and damage to the cell membranes of the worms. Headaches, dizziness, and drowsiness are common and frequent side effects. It is the preferred drug for schistosomiasis and fluke infections, but can also effectively treat tapeworms and neurocystercosis.
This antihelminthic blocks acetylcholine, causing paralysis of the worms. Pyrantel pamoate causes mild side effects such as nausea, headaches, fevers, and rash. If you have liver disease and need to take pyrantel pamoate, you should have your liver enzymes checked regularly, because it may stress the liver. This drug is very effective in treating ascariasis, curing all but 5 percent of infections, and is also effective against hookworms and pinworms.
Tetracycline and Doxycycline
McLauren and other researchers reported in the 1970s that a bacteria called Wolbachia can live inside of filarial worms, creating an endosymbiotic relationship. A study published in 1993 in the "Journal of Parasitology" showed that treatment with tetracycline was effective in filarial infections due to its ability to kill these endosymbiotic bacteria. Because of this, filarial infections are often treated with tetracycline, or the similar drug doxycycline, in addition to an antihelminthic agent.
Helminth infections usually trigger an immune response in healthy persons. Sometimes the immune response is out of proportion to the infection, and can lead to more problems than the infection itself. In these situations, it is sometimes useful to dampen the immune response by using steroids in addition to an antihelminthic medicine. In particular, they may be useful for trichinella and cerebral fluke infections.
Is This an Emergency?
- “Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases," 7th ed.; Diseases Due to Helminths; James H. Maguire, M.D.; 2010.
- “Basic and Clinical Pharmacology”; Clinical Pharmacology of the Antihelminthic Drugs; Philip J. Rosenthal, M.D.; 2009.
- “Journal of Parasitology”; Prophylactic Activity of Tetracycline against Brugia pahangi Infection in Jirds (Meriones unguiculatus). SC Bosshardt, et. al.; 1993.
- “Transactions of the Royal Society of Tropical Medicine and Hygiene”; Micro-organisms in Filarial Larvae (Nematoda); D.J. McLaren, et. al.; 1975.
- World Health Organization
- Centers for Disease Control and Prevention