Roundworms, or nematodes, are parasites that can infect humans, usually by residing in the intestines. Several different species of worm can cause infection, and worms can range in length from 1 millimeter to 1 meter. As with other parasitic diseases, roundworm infections are more common in warm, tropical climates than in cooler, temperate areas of the world. The most common roundworm infection is Ascariasis (caused by the worm Ascaris lumbricoides), which affects as many as 1 billion people worldwide.

The signs and symptoms of roundworm infection include:

• Passage of worm by mouth, rectum, or, with certain species (particularly dracun culosis), through skin ulcers; worm eggs may also be passed in feces
• Abdominal cramps
• Loss of appetite
• Diarrhea or constipation
• Flatulence
• Weight loss
• Anemia
• Cough, chest pain, or difficultly breathing
• Nausea and vomiting
• Fever
• Skin lesions, rashes, hives, itching
• Muscle aches
• Swelling of lymph nodes
• Visual impairment with certain species (particularly onchocerciasis)

According to the National Institute of Allergy and Infectious Diseases, many roundworm parasitic diseases result from a lack of appropriate personal hygiene and sanitation measures. Most roundworms or their eggs are found in the soil and can be picked up on the hands and transferred to the mouth or can enter through the skin. Different species of roundworms cause different infections.

The various roundworm infections include:

• Ascariasis

Ascariasis is an infection caused by the roundworm Ascaris lumbricoides. Infection occurs when an individual consumes food or drink contaminated with fecal matter that contains mature worm eggs. Adult worms can reside in the small intestine and produce eggs for a year or more.

• Whipworm (trichuriasis)

A whipworm infection occurs when an individual consumes food or drink contaminated with fecal matter containing the roundworm Trichuris trichiura. After eggs are ingested, larvae hatch in the small intestine and mature in the large intestine.

• Hookworm (ancylostomiasis) 

A hookworm infection occurs when larvae of the roundworms Ancylostoma duodenale or Necator americanus penetrate human skin, making their way through the lungs to the small intestine, where they attach and mature into adults, laying more eggs. Children are particularly susceptible to this kind of infection. Once infected, children become weak and experience delayed growth patterns. These roundworms infect about 25% of the world's population.

• Threadworm (strongyloidiasis)

Threadworm is an infection caused by the roundworm Strongyloides stercorali. This type of roundworm infects humans in the same way as Ancylostoma duodenale. About half of the population of some African countries has been infected with Strongyloides stercorali.

• Pinworm (enterobiasis)

A pinworm infection occurs when an individual consumes food or drink contaminated with fecal matter containing the roundworm Enterobius vermicularis. After being ingested, eggs hatch in the small intestine and adult worms ultimately inhabit the large intestine. The pregnant female worms migrate to the anus and deposit large numbers of eggs in the skin around that area. Pinworm, which is commonly spread in day care centers, schools, and camps, affects as many as one-third of all American children.

• Visceral larva migrans, or VLM (toxocariasis) 

VLM is an infection caused by the roundworms Toxocara canis, Toxocara cati, or Baylisascaris procyonis. These parasites ordinarily infect dogs, cats, and raccoons, respectively, but a human can become infected by consuming soil contaminated by infected animal feces. While the larvae do not mature to adults in humans, they penetrate the intestinal wall and migrate to various parts of the body, particularly the lungs and liver.

• Trichinosis (trichiniasis)

Trichinosis an infection caused by the roundworm Trichinella spiralis. These larvae live in pigs and other wild carnivores, such as bears, but humans can become infected with Trichinella spiralis when they eat such meat (particularly pork) that is undercooked. The larvae mature in small intestines and migrate to muscle cells where they can live for months or years.

• Guinea worm disease (dracunculosis)

Humans can become infected with Guinea worm disease when they consume drinking water contaminated with the roundworm Dracunculus medinensis. Larvae penetrate the intestinal wall, where they mature and migrate to connective tissues. This type of roundworm infects 10 to 40 million people annually worldwide, primarily in the Indian subcontinent, West and Central Africa, and some Middle Eastern countries.

• Lymphatic filariasis

A lymphatic filariasis infection occurs when an individual is bitten by a mosquito containing the roundworms Wucheria bancrofti, Brugia malayi, or Brugia timori. Over a period of 6 to 12 months, adult worms mature and live in human lymph vessels and nodes and can eventually circulate through the blood. About 90 million people worldwide have been infected with these roundworms.

• River blindness (onchocerciasis) 

River blindness is an infection caused by the roundworm Onchocerca volvulus. Onchocerciasis, which is spread by day-biting flies, is the leading cause of blindness worldwide, affecting about 20 million people, mostly in Africa.

• Loiasis

Loiasis is an infection caused by the roundworm Loa loa. Like river blindness, loiasis is spread by day-biting flies. An estimated 3 to 13 million people in equatorial Africa have been infected with Loa loa.

The risk factors for roundworm infection include:

• Living in or visiting a warm, tropical climate
• Poor sanitation
• Poor personal hygiene
• Crowded conditions, such as day care or institutional settings
• Frequent practice of anal intercourse
• Compromised immune system
• Malnutrition
• Eating undercooked meat from carnivorous animals
• Eating dirt or clay (children and especially boys tend to become infected this way)
• Contact with animal feces
• Multiple insect bites

Diagnosing roundworm infection involves identifying the species of worm causing the infection. If a worm passes through the mouth or rectum, it should be brought to the physician for analysis and identification. Other steps in diagnosis may include:

• Physical exam
• Stool and urine samples – identify microorganisms in the stool and urine
• Blood tests – detect infection in the blood
• Muscle and/or skin biopsy – reveals infections that affect the muscle and/or skin
• Ultrasound – reveals worms in lymph nodes
• X ray – reveals large worms in abdominal region
• Sampling of contents of small intestine may reveal presence of roundworms
• Tape test – used particularly for pinworm infections; physician applies cellulose acetate tape to the skin around the anal region, removes the tape, and then examines it for pinworm under a microscope

Probably the best solution to the problem of roundworms rests in preventing these infections rather than in curing them. The steps to preventing roundworm infection include:

• Good personal hygiene (such as washing hands and avoiding contact with fecal matter)
• Avoid uncooked or unwashed fruits and vegetables in areas where sanitation is poor
• Avoid mosquito or fly-infested areas, unfiltered water, and direct skin contact with soil in areas where roundworm infections are prevalent
• Wear protective clothing and use insect repellant
• Cook or freeze meat thoroughly
• Keep children away from pet feces
• Consult a veterinarian about deworming pets
• Public health measures in areas where roundworm infections are prevalent include improving general sanitation, especially sewage disposal, and reducing mosquito and fly populations

The use of antiparasitic medications is the primary therapy for roundworm infections; the medication prescribed depends on the specific roundworm identified. Surgical procedures may be necessary under certain circumstances; such procedures are not always readily available, however, in areas where roundworm infections are prevalent. Roundworm infections can inflame the lining of the gut and limit the absorption of and/or compete with many essential nutrients, including vitamins A and B6. Vitamin A deficiencies are believed to increase the risk of parasitic infections, so some researchers speculate that vitamin A supplementation may help prevent or reduce symptoms associated with roundworm infections. In addition, some herbal remedies, particularly fig, have been shown to limit roundworm egg production or destroy roundworms altogether. Some other studies suggest that Traditional Chinese Medicine may prove more effective than placebo in improving the symptoms of roundworm infection.

Antiparasitic drugs and other medications used to treat roundworm infections and certain complications include:

• Mebendazole – for ascariasis, whipworm, hookworm, and pinworm
• Albendazole – for ascariasis, whipworm, and hookworm
• Thiabendazole – for threadworm
• Pyrantel pamoate – for ascariasis, hookworm, and pinworm
• Prednisone – for severe VLM and at certain times in cases of trichinosis
• Diethylcarbamazine (DEC) – for lymphatic filariasis
• Ivermectin – for river blindness; may also be effective for threadworm
• Oral iron – if anemia is present
• Analgesics, anti-inflammatories, antihistamines, and antibiotics – for relief of symptoms or to treat bacterial infection

See Warnings and Precautions for certain medications that an individual with roundworm infection should avoid.

Surgical removal of worms from Guinea worm disease and river blindness are possible but are usually not available in many areas where roundworm infection is prevalent. Surgery may be necessary in some cases when the infection causes obstructions in the intestines or other organs. To alleviate soft tissue swelling from lymphatic filariasis, measures such as bandaging, physical therapy, careful skin care, as well as drainage of excess fluids may be taken.

Malnutrition is associated with roundworm infection, so maintaining optimal nutritional status may be helpful in preventing and treating roundworm infection. The following nutrients may be particularly useful in this regard:

Vitamin A 

Some studies have suggested that vitamin A deficiency may be associated with roundworm infection. Parasites may deplete stores of vitamin A, leaving the infected individual with inadequate levels to fight off infection. Parasites may also impair an individual's ability to absorb fat, thereby interfering with the intestinal absorption of fat-soluble vitamins such as vitamin A. At this time, however, there is not enough scientific evidence to suggest that vitamin A supplementation is effective at preventing or treating malnutrition associated with roundworm infection.

Vitamin B6 (Pyridoxine)

Animal studies have suggested that vitamin B6-deficient rats recover from trichinosis significantly slower than rats with normal vitamin B6 status. No studies have investigated whether vitamin B6 is effective at preventing or treating roundworm infection in humans, however.

Some herbal remedies have properties that are destructive to parasites such as roundworm. While many of these herbal remedies have been used traditionally by certain cultures, few have been scientifically tested for their safety and effectiveness. These herbal remedies include:

Fig (Ficus glabrata)

Studies of individuals with roundworm infections, including ascariasis, threadworm, whipworm, and hookworm, have suggested that daily doses of Ficus glabrata (an extract from a species of fig tree) may reduce roundworm egg production by up to 85 percent.

Andrographis root (Andrographis paniculata)

Animal studies indicate that this herb may reduce the presence of Wucheria bancrofti, Brugia malayi, or Brugia timori (lymphatic filariasis infections) by 84% to 93% in infected dogs. The safety and effectiveness of this herb has yet to be investigated in humans, however.

Garlic (Allium sativum)

Laboratory studies suggest that large quantities of fresh, raw garlic may have antiparasitic properties against the roundworm, Ascaris lumbricoides; this herbal remedy has not yet been tested clinically in humans.

Wormseed (Chenopodium ambrosioides) 

Although wormseed has not gone through rigorous scientific testing, this herb is used throughout the world as an effective antiparasitic agent against hookworm and whipworm.

Wormwood (Artemisia absinthium) 

Various species of wormwood are reported to have antiparasitic properties and have been used traditionally to treat parasites. The safety and efficacy of this herb, however, has not been established in clinical trials.

Turmeric (Curcuma longa) 

Laboratory studies suggest that curcuminoids, the active components of turmeric, may work together with wormwood to reduce the destructive activity of parasites. Clinical trials with humans are warranted.

Rangoon creeper (Quisqualis indica) 

The seeds of this tropical vine are frequently used throughout Southeast Asia for treating infections associated with roundworms, particularly ascariasis and pinworm. Results of clinical studies suggest that this herb may eliminate between 30% and 86% of roundworms in infected individuals.

Other herbs with a substantial history of treating roundworms include pumpkin seeds and husks (Curcubita pepo), Punica granatum (Pomegranate bark), and quassia (Picraena excelsa). The clinical safety and effectiveness of these herbs have not been scientifically studied, however.

One randomized, controlled study of 92 individuals infected with the roundworm Ascaris lumbricoides demonstrated that people treated with acupuncture combined with traditional Chinese herbs had significantly greater improvement in symptoms compared with people who were treated with conventional medication.

Most antiparasitic drugs used to treat roundworm infection should not be used during pregnancy.

• Ivermectin – this medication, sometimes used to treat roundworm infections, should not be given to nursing mothers, the severely ill, children under 5 years old, or those weighing less than 15 kg (6.8 lb).

• Antioxidant supplements – some antioxidant supplements, such as selenium and vitamins C and E, should be avoided during the treatment of roundworms. In theory, these antioxidants may enhance the activity of roundworms. In one study, the effectiveness of the medication, mebendazole, appeared to be diminished when these supplements were taken at the same time.

There are several possible complications associated with roundworm infections. They include:

• Intestinal obstruction (caused by the roundworm itself)
• Inflammation of the intestines or gall bladder
• Kidney disease
• Pus accumulation in the liver
• Inflammation of the pancreas
• Appendicitis
• Peritonitis (inflammation of the sac surrounding the abdomen; generally with fluid accumulation)
• Encephalopathy (disorder of the brain)
• Cardiomyopathy (disease of the cardiac muscle of the heart)
• Malnutrition
• Distorted, abnormal growth of the skin and surrounding soft tissue
• Blindness (from onchocerciasis)

The course of some roundworm infections can be long and unpleasant, and there are many possible complications. Individuals living in areas where roundworm infections are prevalent may become infected more than once. Fortunately, most roundworm infections can be successfully treated with antiparasitic medications. For example, the prognosis in cases of ascariasis and pinworm is generally excellent.

Beers MH, Berkow R, eds. The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories; 1999. Section 13, Chapter 161.

Bennett A, Guyatt H. Reducing intestinal nematode infection: efficacy of albendazole and mebendazole. Parasitol Today. 2000;16(2):71-74.

Brabin L. Sex differentials in susceptibility to lymphatic filariasis and implications for maternal-child immunity. Epidemiol Infect. 1990;105(2):335-353.

Bensky D, Gamble A. Chinese Herbal Medicine - Materia Medica. Seattle, Wash: Eastlands Press; 1986.

Bundy DA, Grenfell BT, Rajagopalan PK. Immunoepidemiology of lymphatic filariasis: the relationship between infection and disease. Immunol Today. 1991;12(3):A71-A75.

Carman JA, Pond L, Nashold F, Wassom DL, Hayes CE. Immunity to Trichinella spiralis infection in vitamin A-deficient mice. J Exp Med. 1992;175(1):111-120.

Chandrashekar R. Recent advances in diagnosis of filarial infections. Indian J Exp Biol. 1997;35(1):18-26.

Comley JC. New macrofilaricidal leads from plants? Trop Med Parasitol. 1990;41(1):1-9.

de Padua LS, et al. Plant Resources of South-East Asia (PROSEA) 12 - Medicinal and Poisonous Plants. Leiden, The Netherlands: Backhuys Publishers; 1999.

Daoud AA, Abdel-Ghaffar AE, Deyab FA, Essa TM. The effect of antioxidant preparation (antox) on the course and efficacy of treatment of trichinosis. J Egypt Soc Parasitol. 2000;30(1):305-314.

Dutta A, Sukul NC. Filaricidal properties of a wild herb, Andrographis paniculata. J Helminthol. 1982;56(2):81-84.

Fenwick PK, Aggett PJ, Macdonald D, Huber C, Wakelin Dl. Zinc deficiency and zinc repletion: effect on the response of rats to infection with Trichinella spiralis. Am J Clin Nutr. 1990;52(1):166-172.

Frydas S, Papaioanou N, Vlemmas I, et al. Vitamin B₆-deficient diet plus 4-deoxypyridoxine (4-DPD) reduces the inflammatory response induced by T. spiralis in diaphragm, masseter and heart muscle tissue of mice. Mol Cell Biochem. 1999;197(1-2):79-85.

Hansson A, Veliz G, Naquira C, Amren M, Arroyo M, Arevalo G. Preclinical and clinical studies with latex from Ficus glabrata HBK, a traditional intestinal anthelminthic in the Amazonian area. J Ethnopharmacol. 1986;17(2):105-138.

Harnett W, Bradley JE, Garate T. Molecular and immunodiagnosis of human filarial nematode infections. Parasitol. 1998;117(suppl):S59-S71.

Heron S, Yarnell E. Treating parasitic infections with botanical medicines. Altern Complement Ther. 1999;8:214-224.

Jalal F, Nesheim MC, Agus Z, Sanjur D, Habicht JP. Serum retinol concentrations in children are affected by food sources of beta-carotene, fat intake, and anthelmintic drug treatment. Am J Clin Nutr. 1998;68(3):623-629.

Kightlinger LK, Seed JR, Kightlinger MB. Ascaris lumbricoides aggregation in relation to child growth status, delayed cutaneous hypersensitivity, and plant anthelmintic use in Madagascar. J Parasitol. 1996;82(1):25-33.

Kilian HD, Jahn K, Kraus L, Buttner DW. In vivo and in vitro effects of extracts from Cassia aubrevillei in onchocerciasis. Acta Leiden. 1990;59(1-2):365-371.

Kiuchi F. Studies on the nematocidal constituents of natural medicines. Natural Medicines. 1995;49(4):364-372.

Kiuchi F, Goto Y, Sugimoto N, Akao N, Kondo K, Tsuda Y. Nematocidal activity of turmeric: synergistic action of curcuminoids. Chem Pharm Bull. 1993;41(9):1640-1643.

Liangmin L. Clinical observation on combined use of herbal medicine and acupuncture for treatment of 50 cases of biliary ascariasis complicated by infection. J Tradit Chin Med. 1996;16(3):194-197.

Persson V, Ahmed F, Gebre-Medhin M, Greiner T. Relationships between vitamin A, iron status and helminthiasis in Bangladeshi school children. Public Health Nutr. 2000;3(1):83-89.

Public Health Service. Parasitic Roundworm Diseases. NIAID Fact Sheet. October, 1998.

Rai SK, Nakanishi M, Upadhyay MP, et al. Effect of intestinal helminth infection on retinol and beta-carotene status among rural Nepalese. Nutr Res. 2000;20(1):15-23.

Rajan TV, Gundlapalli AV. Lymphatic filariasis. Chem Immunol. 1997;66:125-158.

Rajan TV. Molecular biology of human lymphatic filariasis. Exp Parasitol. 1990;70(4):500-503.

Sherif A, Hall RG, El-Amamy M. Drugs, insecticides and other agents from Artemisia. Med Hypotheses. 1987;23:187-193.

Storey DM. Filariasis: nutritional interactions in human and animal hosts. Parasitology. 1993;107(suppl):S147-S158.

Tietze PE, Tietze PH. The roundworm, Ascaris lumbricoides. Prim Care. 1991;18(1):25-41.

Weiss EL. Ascaris lunbricoides. In: Adler J, Brenner B, Dronen S, et al., eds. Emergency Medicine: An On-line Medical Reference. Accessed at http://www.emedicine.com/emerg/contents.htm (see Infectious Diseases) on July 10, 2000.

Wenk P. The vector-host link in filariasis. Ann Trop Med Parasitol. 1991;85(1):139-147.

Wolff KM, Scott AL. Brugia malayi: retinoic acid uptake and localization. Exp Parasitol. 1995;80(2):282-290.

Zambou NF, Mbiapo TF, Lando G, Tchana KA, Gouado I. Effect of Onchocerca volvulus infestation on plasma vitamin A concentration in school children in a rural region of Cameroon [in French]. Cahiers Santé. 1999;9:151-155.