Chloroquine was used unsuccessfully in attempts to treat opisthorchiasis in 1951-1968. Control of opisthorchiasis relies predominantly on antihelminthic treatment with praziquantel. The single dose of praziquantel of 40 mg/kg is effective against opisthorchiasis (and also against schistosomiasis). Despite the efficacy of this compound, the lack of an acquired immunity to infection predisposes humans to reinfections in endemic regions. In addition, under experimental conditions, the short-term treatment of "Opisthorchis viverrini"-infected hamsters with praziquantel (400 mg per kg of live weight) induced a dispersion of parasite antigens, resulting in adverse immunopathological changes as a result of oxidative and nitrative stresses following re-infection with "Opisthorchis viverrini", a process which has been proposed to initiate and/or promote the development of cholangiocarcinoma in humans. Albendazole can be used as an alternative.

A randomised-controlled trial published in 2011 showed that the broad-spectrum anti-helminthic, tribendimidine, appears to be at least as efficacious as praziquantel. Artemisinin was also found to have anthelmintic activity against "Opisthorchis viverrini".

Parasitic infections can usually be treated with antiparasitic drugs.

Albendazole and mebendazole have been the treatments administered to entire populations to control hookworm infection. However, it is a costly option and both children and adults become reinfected within a few months after deparasitation occurs raising concerns because the treatment has to repeatedly be administered and drug resistance may occur.

Another medication administered to kill worm infections has been pyrantel pamoate. For some parasitic diseases, there is no treatment and, in the case of serious symptoms, medication intended to kill the parasite is administered, whereas, in other cases, symptom relief options are used. Recent papers have also proposed the use of viruses to treat infections caused by protozoa.

Effective prevention could be readily achieved by persuading people to consume cooked fish (via education programs), but the ancient cultural custom to consume raw, undercooked or freshly pickled fish persists in endemic areas. One community health program, known as the "Lawa" model, has achieved success in the Lawa Lakes region south of Khon Kaen. Currently, there is no effective chemotherapy to combat cholangiocarcinoma, such that intervention strategies need to rely on the prevention or treatment of liver fluke infection/disease.

Cooking or deep-freezing (-20 °C for 7 days) of food made of fish is sure method of prevention. Methods for prevention of "Opisthorchis viverrini" in aquaculture fish ponds were proposed by Khamboonruang et al. (1997).

The drug of choice to treat paragonimiasis is praziquantel, although bithionol may also be used.

One strategy to control the disease in areas where it is common is the treatment of entire groups of people regardless of symptoms via mass drug administration. This is often done among school-age children and is known as deworming. While testing and treating children who are infected looks like it is effective, there is insufficient evidence to conclude that routine deworming, in the absence of a positive test, improves nutrition, haemoglobin, school attendance or school performance.

For this purpose, broad-spectrum benzimidazoles such as mebendazole and albendazole are the drugs of choice recommended by WHO. These anthelminthics are administered in a single dose are safe, relatively inexpensive, and effective for several months. Mebendazole can be given with a single dose twice a day for three consecutive days. Albendazole is given at a single dose. WHO recommends annual treatment in areas where between 20 and 50% of people are infected, and a twice a year treatment if it is over 50%; and in low risk situation (i.e. less than 20% prevalence) case-by-case treatment. In addition to these, pyrantel pamoate is also equally effective on ascaris. However, it has been reported that albendazole, mebendazole, and pyrantel pamoate are not entirely effective against "T. trichiura" with single oral doses in population-based control.

In cases of coinfection, combination therapy with ivermectin and diethylcarbamazine is advocated. However coinfection with malaria and HIV, especially among African women, does not respond well to the current combination therapies. It is more pressing for trichuriasis that the recommended drugs fail to provide positive results. A novel drug tribendimidine, which was approved in China by the CCDC for human use in 2004, has been subjected to clinical trials showing that they are highly effective against major human flukes, ascaris (>90% cure rate) and hookworm (>82%); however with low cure rate for whipworm (<37%).

Tapeworms are treated with medications taken by mouth, usually in a single dose. The drug of choice for tapeworm infections is praziquantel. Niclosamide can also be used.

Several drugs are effective for fascioliasis, both in humans and in domestic animals. The drug of choice in the treatment of fasciolosis is triclabendazole, a member of the benzimidazole family of anthelmintics. The drug works by preventing the polymerization of the molecule tubulin into the cytoskeletal structures, microtubules. Resistance of "F. hepatica" to triclabendazole has been recorded in Australia in 1995 and Ireland in 1998.

Praziquantel treatment is ineffective.

There are case reports of nitazoxanide being successfully used in human fasciolosis treatment in Mexico. There are also reports of bithionol being used successfully.

More recently, Mirazid, an Egyptian drug made from myrrh, has been investigated as an oral treatment of trematode-caused ailments including fascioliasis.

Nitazoxanide has been found effective in trials, but is currently not recommended. The life cycle includes freshwater snails as an intermediate host of the parasite.

Broad-spectrum benzimidazoles (such as albendazole and mebendazole) are the first line treatment of intestinal roundworm and tapeworm infections. Macrocyclic lactones (such as ivermectin) are effective against adult and migrating larval stages of nematodes. Praziquantel is the drug of choice for schistosomiasis, taeniasis, and most types of food-borne trematodiases. Oxamniquine is also widely used in mass deworming programmes. Pyrantel is commonly used for veterinary nematodiasis. Artemisinins and derivatives are proving to be candidates as drugs of choice for trematodiasis.

Medications that are used to kill roundworms are called ascaricides. Those recommended by the World Health Organization for ascariasis are: albendazole, mebendazole, levamisole and pyrantel pamoate. Other effective agents include tribendimidine and nitazoxanide. Pyrantel pamoate may induce intestinal obstruction in a heavy worm load. Albendazole is contraindicated during pregnancy and children under two years of age. Thiabendazole may cause migration of the worm into the esophagus, so it is usually combined with piperazine.

Piperazine is a flaccid paralyzing agent that blocks the response of Ascaris muscle to acetylcholine, which immobilizes the worm. It prevents migration when treatment is accomplished with weak drugs such as thiabendazole. If used by itself, it causes the worm to be passed out in the feces and may be used when worms have caused blockage of the intestine or the biliary duct.

Corticosteroids can treat some of the symptoms, such as inflammation.

Oral anti-parasitic drugs such as praziquantel are the treatment of choice. Treatment with praziquantel has been approved by the U.S. Food and Drug Administration and is quite effective against these parasites. Usual treatments are with praziquantel (5–10 mg/kg, single-administration) or niclosamide (adults and children over 6 years: 2 g, single-administration after a light breakfast, followed after 2 hours by a laxative; children aged 2–6 years: 1 g; children under 2 years: 500 mg). Albendazole is also highly effective. Atrabine is quite effective but has adverse effects in humans.

Amphistomiasis is considered a neglected tropical disease, with no prescription drug for treatment and control. Therefore, management of infestation is based mainly on control of the snail population, which transmit the infective larvae of the flukes. However, there are now drugs shown to be effective including resorantel, oxyclozanide, clorsulon, ivermectin, niclosamide, bithional and levamisole. An in vitro demonstration shows that plumbagin exhibits high efficacy on adult flukes. Since the juvenile flukes are the causative individuals of the disease, effective treatment means control of the immature fluke population. Prophylaxis is therefore based on disruption of the environment (such as proper drainage) where the carrier snails inhabit, or more drastic action of using molluscicides to eradicate the entire population. For treatment of the infection, drugs effective against the immature flukes are recommended for drenching. For this reason oxyclozanide is advocated as the drug of choice. It effectively kills the flukes within a few hours and it effective against the flukes resistant to other drugs. The commercially prescribed dosage is 5 mg/kg body weight or 18.7 mg/kg body weight in two divided dose within 72 hours. Niclosamide is also extensively used in mass drenching of sheep. Successfully treated sheep regain appetite within a week, diarrhoea stops in about three days, and physiological indicators (such as plasma protein and albumin levels) return to normal in a month.

Praziquantel is recommended in both adult and pediatric cases with dosages of 75 mg/kg/d in 3 doses for 1 day. Praziquantel is a Praziniozoquinoline derivative that alters the calcium flux through the parasite tectum and causes muscular paralysis and detachment of the fluke. Prizaquantel should be taken with liquids during a meal and as provided commercially as Biltricide. Praziquantel is not approved by the U.S. Food and Drug Administration (FDA) for treatment of metagonimiasis, but is approved for use on other parasitic infections.

Praziquantel has some side effects but they are generally relatively mild and transient and a review of evidence shows it overall a well-tolerated drug. Possible side effects include abdominal pain, allergy, diarrhea, headache, liver problems, nausea or vomiting, exacerbation of porphyries, pruritis, rash, somnolence, vertigo, or dizziness. In fact, in 2002, the World Health Organization recommended the use of Praziquantel in pregnant and lactating women, though controlled trials are still needed to verify this.

Another possible drug option is Tetrachloroethylene, a chlorinated hydrocarbon, but its use has been superseded by new antihelminthic drugs (like Praziquantel). A 1978 study also looked at the efficacy of several drugs on metagonimiasis infection, including bithionol, niclosamide, nicoflan, and Praziquantel. All drugs showed lower prevalence of eggs in feces, however only Praziquantel showed complete radical cure. Therefore, the authors concluded Praziquantel was the most highly effective, was very well tolerated, and was the most promising drug against metagonimiasis.

Medication is the primary treatment for pinworm infection. They are so effective that many medical scientists regard hygienic measures as impractical. However, reinfection is frequent regardless of the medication used. Total elimination of the parasite in a household may require repeated doses of medication for up to a year or more. Because the drugs kill the adult pinworms, but not the eggs, the first retreatment is recommended in two weeks. Also, if one household member spreads the eggs to another, it will be a matter of two or three weeks before those eggs become adult worms and thus amenable to treatment. Asymptomatic infections, often in small children, can serve as reservoirs of infection, and therefore the entire household should be treated regardless of whether or not symptoms are present.

The benzimidazole compounds albendazole (brand names e.g., "Albenza", "Eskazole", "Zentel" and "Andazol") and mebendazole (brand names e.g., "Ovex", "Vermox", "Antiox" and "Pripsen") are the most effective. They work by inhibiting the microtubule function in the pinworm adults, causing glycogen depletion, thereby effectively starving the parasite. A single 100 milligram dose of mebendazole with one repetition after a week, is considered the safest, and is usually effective with cure rate of 96%. Mebendazole has no serious side effects, although abdominal pain and diarrhea have been reported. Pyrantel pamoate (also called pyrantel embonate, brand names e.g., "Reese's Pinworm Medicine", "Pin-X", "Combantrin", "Anthel", "Helmintox", and "Helmex") kills adult pinworms through neuromuscular blockade, and is considered as effective as the benzimidazole compounds and is used as a second-line medication. Other medications are piperazine, which causes flaccid paralysis in the adult pinworms, and pyrvinium pamoate (also called pyrvinium embonate), which works by inhibiting oxygen uptake of the adult pinworms. Pinworms located in the genitourinary system (in this case, female genital area) may require other drug treatments.

The standard of care is administration of antifilarial drugs, most commonly Ivermectin or diethyl-carbamazine (DEC). The most efficacious dose in all nematode and parasitic infections is 200 µg/kg of ivermectin. There has also been other various anthelminthic drugs used, such as mebendazole, levamisole, albendazole and thiabendazole. In worst-case scenarios, surgery may be necessary to remove nematodes from the abdomen or chest. However, mild cases usually do not require treatment.

Toxocariasis will often resolve itself, because the "Toxocara" larvae cannot mature within human hosts. Corticosteroids are prescribed in severe cases of VLM or if the patient is diagnosed with OLM. Either albendazole (preferred) or mebendazole (“second line therapy”) may be prescribed. Granulomas can be surgically removed, or laser photocoagulation and cryoretinopexy can be used to destroy ocular granulomas.

Visceral toxocariasis in humans can be treated with antiparasitic drugs such as albendazole or mebendazole, tiabendazole or diethylcarbamazine usually in combination with anti-inflammatory medications. Steroids have been utilized with some positive results. Anti-helminthic therapy is reserved for severe infections (lungs, brain) because therapy may induce, due to massive larval killing, a strong inflammatory response. Treatment of ocular toxocariasis is more difficult and usually consists of measures to prevent progressive damage to the eye.

Currently, no therapeutic drugs are prescribed for the disease. Therefore, prevention is the sole mode of treatment. This disease can only be prevented by quarantining sick birds and preventing migration of birds around the house, causing them to spread the disease. Deworming of birds with anthelmintics can reduce exposure to the cecal nematodes that carry the protozoan. Good management of the farm, including immediate quarantine of infected birds and sanitation, is the main useful strategy for controlling the spread of the parasitic contamination. The only drug used for the control (prophylaxis) in the United States is nitarsone at 0.01875% of feed until 5 days before marketing. Natustat and nitarsone were shown to be effective therapeutic drugs. Nifurtimox, a compound with known antiprotozoal activity, was demonstrated to be significantly effective at 300–400 ppm, and well tolerated by turkeys.

Parasitic worms and nematodes regulate many immune pathways of their host in order to increase their chances of survival. For example, molecules secreted by "Acanthocheilonema vitae" actually limit host effective immune mechanisms. These molecules are called excretory-secretory products. An effective excretory-secretory product released from "Acanthochelionema vitae" is called ES-62, which can affect multiple immune system cell types. ES-62 has anti-inflammatory effects when subjected to mice. The anti-inflammatory effect occurs because of a phosphorylcholine (PC)-containing moiety and signal transduction. More research needs to be completed; however there is some evidence that "Acanthocheilonema vitae" may have anti-inflammatory effects, and should be researched further.

In some cases with severe infestation the worms may cause bowel obstruction, requiring emergency surgery. The bowel obstruction may be due to all the worms or twisting of the bowel. During the surgery the worms may be manually removed.

The highest clearance rates are obtained by combining mebendazole or albendazole with ivermectin. Ivermectin's safety in children under and pregnant women has not yet been established.

People with diarrhea may be treated with loperamide to increase the amount of drug contact with the parasites.

Mebendazole is 90% effective in the first dose, and albendazole may also be offered as an anti-parasitic agent. Adding iron to the bloodstream helps solve the iron deficiency and rectal prolapse. Difetarsone is also an effective treatment.

Drugs are frequently used to kill parasites in the host. In earlier times, turpentine was often used for this, but modern drugs do not poison intestinal worms directly. Rather, anthelmintic drugs now inhibit an enzyme that is necessary for the worm to make the substance that prevents the worm from being digested.

For example, tapeworms are usually treated with a medicine taken by mouth. The most commonly used medicine for tapeworms is praziquantel.

There are two drugs available, praziquantel and oxamniquine, for the treatment of schistosomiasis. They are considered equivalent in relation to efficacy against "S. mansoni" and safety. Because of praziquantel's lower cost per treatment, and oxaminiquine's lack of efficacy against the urogenital form of the disease caused by "S. haematobium", in general praziquantel is considered the first option for treatment. The treatment objective is to cure the disease and to prevent the evolution of the acute to the chronic form of the disease. All cases of suspected schistosomiasis should be treated regardless of presentation because the adult parasite can live in the host for years.

Schistosomiasis is treatable by taking by mouth a single dose of the drug praziquantel annually.

The WHO has developed guidelines for community treatment based on the impact the disease has on children in villages in which it is common:

- When a village reports more than 50 percent of children have blood in their urine, everyone in the village receives treatment.

- When 20 to 50 percent of children have bloody urine, only school-age children are treated.

- When fewer than 20 percent of children have symptoms, mass treatment is not implemented.

Other possible treatments include a combination of praziquantel with metrifonate, artesunate, or mefloquine. A Cochrane review found tentative evidence that when used alone, metrifonate was as effective as praziquantel.

Another agent, mefloquine, which has previously been used to treat and prevent malaria, was recognised in 2008–2009 to be effective against "Schistosoma".

For alveolar echinococcosis, surgical removal of cysts combined with chemotherapy (using albendazole and/or mebendazole) for up to two years after surgery is the only sure way to completely cure the disease. However, in inoperable cases, chemotherapy by itself can also be used. In treatment using just chemotherapy, one could use either mebendazole in three doses or albendazole in two doses. Since chemotherapy on its own is not guaranteed to completely rid the patient of disease, patients are often kept on the drugs for extended periods of times (i.e. more than 6 months, years). In addition to surgery and chemotherapy, liver transplants are being looked into as a form of treatment for alveolar echinococcosis although it is seen as incredibly risky since it often leads to echinococcosis re-infection in the patient afterwards.

For simple cases of cystic echinococcosis, the most common form of treatment is open surgical removal of the cysts combined with chemotherapy using albendazole and/or mebendazole before and after surgery. However, if there are cysts in multiple organs or tissues, or the cysts are in risky locations, surgery becomes impractical. For inoperable cases such as these, chemotherapy and/or PAIR (puncture-aspiration-injection-reaspiration) become alternative options of treatment. In the case of alternative treatment using just chemotherapy, albendazole is preferred twice a day for 1–5 months. An alternative to albendazole is mebendazole for at least 3 to 6 months. The other alternative to surgery is PAIR with chemotherapy. PAIR is a minimally invasive procedure that involves three steps: puncture and needle aspiration of the cyst, injection of a scolicidal solution for 20–30 min, and cyst-re-aspiration and final irrigation. Patients who undergo PAIR typically take albendazole or mebendazole from 7 days before the procedure until 28 days after the procedure. While open surgery still remains as the standard for cystic echinococcosis treatment, there have been a number of studies that suggest that PAIR with chemotherapy is more effective than surgery in terms of disease recurrence, and morbidity and mortality. In addition to the three above mentioned treatments, there is currently research and studies looking at new treatment involving percutaneous thermal ablation (PTA) of the germinal layer in the cyst by means of a radiofrequency ablation device. This form of treatment is still relatively new and requires much more testing before being widely used. An alternative to open surgery is laparoscopic surgery, which provides excellent cure rates with minimal morbidity and mortality.

If complications of helminthiasis, such as intestinal obstruction occur, emergency surgery may be required. Patients who require non-emergency surgery, for instance for removal of worms from the biliary tree, can be pre-treated with the anthelmintic drug albendazole.