The two major classes of intestinal parasites are helminths and protozoa. Helminths are multicellular worms (with the exceptions of Strongyloides and Hymenolepis nana) with complex life cycles. Helminths cannot multiply in the host and will eventually clear up without reinfection. Protozoa are single-cell organisms capable of multiplying within the host. There is usually a direct fecal–oral transmission, with direct person-to-person transmission uncommon. Intestinal parasites affect 5% to 30% of the U.S. population, dependent on geographic and socioeconomic factors. Less than 10% of parasitologic reports routinely identify helminths.

• Helminth pathogens include cestodes (tapeworms), trematodes (flukes), hookworms, and various nematodes (roundworms).
• Protozoan pathogens include Entamoeba histolytica (amebiasis), Giardia lamblia (giardiasis), Cryptosporidium, Isospora belli, Enterocytozoon bieneusi (microsporidiosis), and free-living amebas and blood/tissue protozoa (e.g., Plasmodium [malaria]).

• Demographics—endemic areas
• International travel
• Poor sanitation (food and water)
• Poor personal hygiene
• Age—children at a higher risk
• Child and institutional care facilities
• Acquired immunodeficiency syndrome (AIDS)

Symptoms vary depending upon the intestinal parasite and may include the following.

• Malodorous diarrhea Midepigastric pain/tenderness
• Nausea/vomiting Fatigue
• Gas/bloating Weight loss
• Dysentery (e.g., amebiasis) Passing a worm
• Perirectal or vulvar rash/pruritus

• Food poisoning/bacterial diarrhea (e.g., Escherichia coli) Pyogenic abscesses
• Typhoid Inflammatory bowel disease Hemorrhoids
• Peptic ulcer Influenza

The patient may appear anorexic. There may be abdominal bloating and/or tenderness to palpation. Increased bowel sounds are often present with auscultation. Perirectal or vulvar rash or rectal prolapse may be visible.

Tests for some intestinal parasites should be based on an assessment of the risk profile for the patient.

• Fecal testing—identifies ova, larvae, or adult helminths and trophozoites or cysts of protozoa. Collect sample before use of antidiarrheal agents, antibiotics, or barium for X ray to avoid detection problems. Prompt examination or use of preservative is necessary; three (five for pinworm) samples required for accurate detection. Complete exam includes use of wet mounts, permanent stains (for laboratory's records), and concentration techniques.
• Serological testing—reliable tests available for only a few parasitic diseases (e.g. amebiasis).
• Eosinophilia—associated with degree of mucosal invasion
• Biopsy of tissue to detect helminths in tissue or parasites in mucosa

• Gross or occult blood with amebic colitis
• Ulceration and inflammation of bowel, rarely a lesion
• Trophozoites invade tissue, most parasites do not

Rarely required for diagnosis. X ray with barium, ultrasound, or CT are sometimes used to diagnose amebomas, liver abscesses, and colitis.

• String test—samples duodenal contents (e.g., for Giardia lamblia, Cryptosporidium, Strongyloides), rarely used
• "Scotch tape" test—identifies pinworm ova on perianal skin.
• Sigmoidoscopy—may show mucopurulent colitis and ulceration.
• Endoscopy of upper intestinal tract—can extract fluid or tissue for biopsy, impression smear, and microscopic examination; usually for Giardia lamblia and Strongyloides.

Medication, diet, and patient education for personal hygiene and to avoid reinfection. Some of the most effective drugs with the least side effects are not available in this country (e.g., tinidazole for giardia or amebiasis) or are available only from the Centers for Disease Control and Prevention (e.g., ivermectin for various nematodes).

Symptomatic treatment—initiate after drug therapy has begun. Drug therapy for helminths, selected examples (adult dosages):

• Albendazole—for various roundworms and tapeworms; 400 mg once, three days in severe cases; for pinworms repeat dose after two weeks. Used with glucocorticoids for neurocysticercosis (prevents complications from dying cysticerci) 15 mg/kg/day in three doses, 8 to 28 days.
• Mebendazole—for various roundworms; 100 mg bid for three days, longer periods for echinococcosis (tapeworm). Mild side effects (e.g., diarrhea) except with long administration.
• Pyrantel pamoate—for various roundworms; 11 mg/kg up to 1 g, once, but several times for hookworm. Available over-the-counter for pinworms; is well-tolerated.
• Praziquantel—for most flukes and tapeworms; 40 mg/kg/day in 2 doses once, to 75 mg/kg/day in 3 doses for 2 days. Mild side effects— headache, dizziness, nausea, abdominal pain. Use with glucocorticoids for neurocysticercosis; 50 mg/kg/day in 3 doses for 15 days.

Drug therapy for protozoa, selected examples (adult dosages):

• Metronidazole (Flagyl)—250 mg tid for five days commonly used for giardia, but not FDA approved for this use; use for B. hominis concurrently eradicates giardia. Use 750 mg tid for 10 days for liver abscesses and cysts of Enta histolytica, follow with iodoquinol for severe amebiasis and abscesses, E. coli, Trichomonas vaginalis; avoid all alcohol, disulfiram-like reaction can occur. Side effects—nausea, metallic taste, dry mouth, headache, and rarely encephalopathy, pancreatitis, ataxia, seizures, and peripheral neuropathy.
• Trimethoprim–sulfamethoxazole—for I. belli; 160/800 mg qid for 10 days, then bid for three weeks. Side effects—self-limited diarrhea (severe with AIDS), possible liver, skin, or bone marrow toxicity from sulfamethoxazole.
• Chloroquine—oral therapy for malaria; 600 mg, then 300 mg at 6, 24, and 48 hours.

Identification of the organism is imperative before initiating any therapy. The following nutritional guidelines will help to inhibit organism growth. Many of the herbs suggested have toxic side effects and should only be used under the supervision of a qualified practitioner. It is important to maintain good bowel elimination during treatment.

• Avoid simple carbohydrates such as refined foods, fruits, juices, dairy products (contain lactose sugar), and all sugars.
• Eliminate caffeine and alcohol.
• Increase intake of raw garlic, pumpkin seeds, pomegranates, beets, and carrots, all of which have vermifuge properties. Ensure adequate intake of water and dietary fiber to promote good bowel elimination.
• Digestive enzymes will help to normalize digestion and restore the local environment to its normal state which is inhospitable to parasites. Papain taken 30 minutes before and after meals helps to kill worms. Acidophilus supplements will help normalize bowel flora.
• Vitamin C (1,000 mg tid to qid), zinc (20 to 30 mg/day), and beta-carotene (100,000 IU/day) support the immune system.

Ascertain a diagnosis before pursuing treatment. Herbs may be used as dried extracts (capsules, powders, teas), glycerites (glycerine extracts), or tinctures (alcohol extracts). Unless otherwise indicated, teas should be made with 1 tsp. herb per cup of hot water. Steep covered 5 to 10 minutes for leaf or flowers, and 10 to 20 minutes for roots. Drink 2 to 4 cups/day. Tinctures may be used singly or in combination as noted.

The following herbs are listed according to increasing strength and toxicity. Use only under the supervision of a qualified practitioner. The most gentle herb that is effective should be used for treatment.

Vermifuges include the following.

• Garlic (Allium sativum) 1 clove tid.
• Thyme (Thymus vulgaris) or oregano (Oreganum vulgare) oil, 1 to 2 enteric-coated capsules tid to qid.
• Wormwood (Artemisia absinthum) may be used as a tea (3 cups/day) or tincture (1 to 2 tsp. tid).
• Quassia (Picrasma excelsor) is specifically for threadworms. Prepare a cold infusion tea (1 heaping tbsp. soaked in 1 qt. of water overnight) and drink throughout the day.
• Black walnut (Juglans nigra) may be used as a tea (3 cups/day) or tincture (30 drops tid to qid).
• Male fern (Dryopteris filix-mas) is specific for tapeworm. Large doses are extremely poisonous and may induce toxic liver damage.
• Tansy (Tanacetum vulgare) may be used in combination with wormwood for treatment of roundworm and threadworm. Drink 1 cup of tea one to two times/day, or use tincture at 30 to 60 drops bid to tid. Large doses of this herb can be highly toxic.

Antiparasitic herbs include the following. Use together in a tea (1 cup tid) or tincture (30 to 60 drops tid).

• Barberry (Berberis vulgaris)
• Oregon grape (Berberis aquafolium)
• Goldenseal (Hydrastis canadensis)
• Wormseed (Chenopodium ambrosoides)

Topical applications for roundworm include oils of garlic (use with a carrier oil such as olive oil to avoid skin irritation), thyme, or lavender.

An experienced homeopath should assess individual constitutional types and severity of disease to select the correct remedy and potency. For acute prescribing use 3 to 5 pellets of a 12X to 30C remedy every one to four hours until acute symptoms resolve.

• Cina is specific for pinworms; with restless agitation and itching rectum
• Rumex crispus for marked itching immediately on uncovering or undressing
• Spigellia for worm infestations with piercing and sharp pains

May help stimulate bowel function and elimination.

The patient must receive adequate hydration and diet. Patient education prevents transmission or reinfection. Retesting must take into account the lifecycle of the parasite (usually three to four weeks for protozoa and five to six weeks for helminths) and the likelihood of reinfection.

The best prevention is good community sanitation and personal hygiene.

Complications occur more frequently in the elderly, AIDS patients, or immunocompromised patients. Complications involving the central nervous system may be severe.

The course and prognosis vary with the specific intestinal parasite.

Treatment for intestinal parasites during pregnancy should be closely followed by a qualified practitioner.

Fauci AS, Braunwald E, Isselbacher KJ, et al., eds. Harrison's Principles of Internal Medicine. 14th ed. New York, NY: McGraw-Hill; 1998.

Morrison R. Desktop Guide to Keynotes and Confirmatory Symptoms. Albany, Calif: Hahnemann Clinic Publishing; 1993:128, 329, 353.

Rakel RE, ed. Conn's Current Therapy. 50th ed. Philadelphia, Pa: WB Saunders; 1998.