In regions where helminthiasis is common, mass deworming treatments may be performed, particularly among school-age children, who are a high-risk group. Most of these initiatives are undertaken by the World Health Organization (WHO) with positive outcomes in many regions. Deworming programs can improve school attendance by 25 percent. Although deworming improves the health of an individual, outcomes from mass deworming campaigns, such as reduced deaths or increases in cognitive ability, nutritional benefits, physical growth, and performance, are uncertain or not apparent.

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.

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.

Good hygiene is necessary to avoid reinfection. The Rockefeller Foundation's hookworm campaign in Mexico in the 1920s was extremely effective at eliminating hookworm from humans with the use of anthelmintics. However, preventative measures were not adequately introduced to the people that were treated. Therefore, the rate of reinfection was extremely high and the project evaluated through any sort of scientific method was a marked failure. More education was needed to inform the people of the importance of wearing shoes, using latrines (better access to sanitation), and good hygiene.

Intestinal parasite prevention methods are not isolated to specific geographical areas; however, many of the research-based interventions have primarily taken place in underdeveloped countries and regions, where sanitation is a large concern for spreading disease.Current best practice behaviors that prevent intestinal parasites include: using proper hand washing practices, using correctly-built latrines with ample ventilation, having a piped water source, and wearing shoes. Currently, in some parts of Ethiopia where disease prevalence is high, up to 80% of people in a population lack access to washing facilities. While is this high, 93% did have access to a latrine, but only 29.2% of those latrines had proper construction to decrease parasitic infections.Behavioral interventions have focused on promoting washing, sometimes with soap, in context of education at schools and child care facilities. In recent studies, the best interventions follow a multidisciplinary approach by:

- Increasing environmental sanitation to promote hand washing and shoe wearing habits

- Educating children at young ages at school and at home

Specific evidence-based interventions that may lower disease prevalence include:

- Interventions at schools, focusing on the construction of pit latrines (ventilated and improved), providing clean drinking water and educating the students about hygiene

- The SAFE (surgery, antibiotics, facial cleanliness, environmental sanitation) strategy to address trachoma, primarily the facial cleanliness and the environmental sanitation components

- Hand-washing with soap at critical times and nail clipping to decrease reinfection rates, although further research is needed to develop and implement similar interventions at scale

- Programs combining anthelmintic drug administration with interventions to increase environmental sanitation (such as decreasing fecal contamination)

Prevention and control measures to prevent soil-transmitted helminthiasis are the following: availability of clean water for personal and domestic uses, improved access to sanitation which includes the use of properly functioning and clean toilets by all community members, education on personal hygiene such as hand washing and hygienic and safe food preparation; eliminating the use of untreated human faeces as fertilizer.

The World Health Organizations recommended albendazole or mebendazole for treatment.

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.

Prevention is by improved access to sanitation which includes the use of properly functioning and clean toilets by all community members as one important aspect. Handwashing with soap may be protective; however, there is no evidence it affects the severity of disease. Eliminating the use of untreated human faeces as fertilizer is also important.

In areas where more than 20% of the population is affected treating everyone is recommended. This has a cost of about 2 to 3 cents per person per treatment. This is known as mass drug administration and is often carried out among school-age children. For this purpose, broad-spectrum benzimidazoles such as mebendazole and albendazole are the drugs of choice recommended by WHO.

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.

Limited access to essential medicine poses a challenge to the eradication of trichuriasis worldwide. Also, it is a public health concern that rates of post-treatment re-infection need to be determined and addressed to diminish the incidence of untreated re-infection. Lastly, with mass drug administration strategies and improved diagnosis and prompt treatment, detection of an emergence of antihelminthic drug resistance should be examined.

Mass Drug Administration (preventative chemotherapy) has had a positive effect on the disease burden of trichuriasis in East and West Africa, especially among children, who are at highest risk for infection.

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.

Control of this parasite should be directed against reducing the level of

environmental contamination. Treatment of heavily infected individuals is one

way to reduce the source of contamination (one study has estimated that 60% of

the total worm burden resides in less than 10% of the population). Other

obvious methods are to improve access to sanitation, e.g. toilets, but also

convincing people to maintaining them in a clean, functional state, thereby making

them conducive to use.

Education, improved sanitation, and controlled disposal of human feces are critical for prevention. Nonetheless, wearing shoes in endemic areas helps reduce the prevalence of infection.

An infection of "N. americanus" parasites can be treated by using benzimidazoles: albendazole or mebendazole. A blood transfusion may be necessary in severe cases of anemia. Light infections are usually left untreated in areas where reinfection is common. Iron supplements and a diet high in protein will speed the recovery process. In a case study involving 56-60 men with "Trichuris trichiura" and/or "N. americanus" infections, both albendazole and mebendazole were 90% effective in curing "T. trichiura". However, albendazole had a 95% cure rate for "N. americanus", while mebendazole only had a 21% cure rate. This suggests albendazole is most effective for treating both "T. trichiura" and "N. americanus".

Cryotherapy by application of liquid nitrogen to the skin has been used to kill cutaneous larvae migrans, but the procedure has a low cure rate and a high incidence of pain and severe skin damage, so it now is passed over in favor of suitable pharmaceuticals. Topical application of some pharmaceuticals has merit, but requires repeated, persistent applications and is less effective than some systemic treatments.

The two drugs that have been well-described for the treatment of hymenolepiasis are praziquantel and niclosamide. Praziquantel, which is parasiticidal in a single dose for all the stages of the parasite, is the drug of choice because it acts very rapidly against "H. nana". Although structurally unrelated to other anthelminthics, it kills both adult worms and larvae. "In vitro", the drug produces vacuolization and disruption of the tegument in the neck of the worms, but not in more posterior portions of the strobila. Praziquantel is well absorbed when taken orally, and it undergoes first-pass metabolism and 80% of the dose is excreted as metabolites in urine within 24 hours.

Repeated treatment is required for "H. nana" at an interval of 7–10 days.

Praziquantel as a single dose (25 mg/kg) is the current treatment of choice for hymenolepiasis and has an efficacy of 96%. Single-dose albendazole (400 mg) is also very efficacious (>95%).

A three-day course of nitazoxanide is 75–93% efficacious. The dose is 1 g daily for adults and children over 12; 400 mg daily for children aged 4 to 11 years; and 200 mg daily for children aged 3 years or younger.

Mammals can get parasites from contaminated food or water, bug bites, or sexual contact. Ingestion of contaminated water can produce Giardia infections.

Parasites normally enter the body through the skin or mouth. Close contact with pets can lead to parasite infestation as dogs and cats are host to many parasites.

Other risks that can lead people to acquire parasites are walking barefeet, inadequate disposal of feces, lack of hygiene, close contact with someone carrying specific parasites, and eating undercooked foods, unwashed fruits and vegetables or foods from contaminated regions.

Parasites can also be transferred to their host by the bite of an insect vector, i.e. mosquito, bed bug, fleas.

Abdominal discomfort and, in case of prolonged diarrhea, dehydration are possible complications.

In 2015 an unusual complication was noted in a man whose immune system had been compromised by HIV. He developed multiple tumors of malignant cell nests within his body that had originated from a tapeworm in his intestines.

The drug of choice for the treatment of hookworm disease is mebendazole which

is effective against both species, and in addition, will remove the intestinal

worm Ascaris also, if present. The drug is very efficient, requiring only a

single dose and is inexpensive. However, treatment requires

more than giving the anthelmintic, the patient should also receive dietary

supplements to improve their general level of health, in particular iron

supplementation is very important. Iron is an important constituent of a

multitude of enzyme systems involved in energy metabolism, DNA synthesis and

drug detoxification.

An infection of "N. americanus" parasites can be treated by using benzimidazoles, albendazole, and mebendazole. A blood transfusion may be necessary in severe cases of anemia. Light infections are usually left untreated in areas where reinfection is common. Iron supplements and a diet high in protein will speed the recovery process. In a case study involving 56–60 men with "Trichuris trichiura" and/or "N. americanus" infections, both albendazole and mebendazole were 90% effective in curing "T. trichiura". However, albendazole had a 95% cure rate for "N. americanus", while mebendazole only had a 21% cure rate. This suggests albendazole is most effective for treating both "T. trichiura" and "N. americanus".

The CDC recommends hand-washing and avoiding potentially contaminated food and untreated water.

Boiling suspect water for one minute is the surest method to make water safe to drink and kill disease-causing microorganisms such as "Giardia lamblia" if in doubt about whether water is infected. Chemical disinfectants or filters may be used.

According to a review of the literature from 2000, there is little evidence linking the drinking of water in the North American wilderness and Giardia. CDC surveillance data (for 2005 and 2006) reports one outbreak (6 cases) of waterborne giardiasis contracted from drinking wilderness river water in Colorado. However, less than 1% of reported giardiasis cases are associated with outbreaks.

Person-to-person transmission accounts for the majority of "Giardia" infections and is usually associated with poor hygiene and sanitation. "Giardia" is found on the surface of the ground, in the soil, in undercooked foods, and in water, and on hands without proper cleaning after handling infected feces. Water-borne transmission is associated with the ingestion of contaminated water. In the U.S., outbreaks typically occur in small water systems using inadequately treated surface water. Venereal transmission happens through fecal-oral contamination. Additionally, diaper changing and inadequate hand washing are risk factors for transmission from infected children. Lastly, food-borne epidemics of "Giardia" have developed through the contamination of food by infected food-handlers.

Anthelmintics such as mebendazole and albendazole have been reported to eliminate infestation of humans more effectively than thiabendazole.

Prevention is as simple as avoiding eating small, whole, uncooked fish. However, in "C. philippinensis" endemic areas, such dietary habits are common and have been practiced for many generations.

Parasitic worms have been used as a medical treatment for various diseases, particularly those involving an overactive immune response. As humans have evolved with parasitic worms, proponents argue they are needed for a healthy immune system. Scientists are looking for a connection between the prevention and control of parasitic worms and the increase in allergies such as hay-fever in developed countries. Parasitic worms may be able to damp down the immune system of their host, making it easier for them to live in the intestine without coming under attack. This may be one mechanism for their proposed medicinal effect.

One study suggests a link between the rising rates of metabolic syndrome in the developed worlds and the largely successful efforts of Westerners to eliminate intestinal parasites. The work suggests eosinophils (a type of white blood cell) in fat tissue play an important role in preventing insulin resistance by secreting interleukin 4, which in turn switches macrophages into "alternative activation". Alternatively-activated macrophages are important to maintaining glucose homeostasis (i.e., blood sugar regulation). Helminth infection causes an increase in eosinophils. In the study, the authors fed rodents a high-fat diet to induce metabolic syndrome, and then injected them with helminths. Helminth infestation improved the rodents' metabolism. The authors concluded:

Although sparse in blood of persons in developed countries, eosinophils are often elevated in individuals in rural developing countries where intestinal parasitism is prevalent and metabolic syndrome rare. We speculate that eosinophils may have evolved to optimize metabolic homeostasis during chronic infections by ubiquitous intestinal parasites….

The drug of choice for the treatment of uncomplicated strongyloidiasis is ivermectin. Ivermectin does not kill the "Strongyloides" larvae, only the adult worms, therefore repeat dosing may be necessary to properly eradicate the infection. There is an auto-infective cycle of roughly two weeks in which Ivermectin should be re-administered however additional dosing may still be necessary as it will not kill "Strongyloides" in the blood or larvae deep within the bowels or diverticula. Other drugs that are effective are albendazole and thiabendazole (25 mg/kg twice daily for 5 days—400 mg maximum (generally)). All patients who are at risk of disseminated strongyloidiasis should be treated. The optimal duration of treatment for patients with disseminated infections is not clear.

Treatment of strongyloidiasis can be difficult and "Strongyloides" has been known to live in individuals for decades; even after treatment. Continued treatment is thus necessary even if symptoms resolve.

Because of the high cost of Stromectol, the veterinary formula Ivomec can be used. Government programs are needed to help citizens finance lifelong medication.

Clothes and sheets must be washed with enzyme washing powder and dried on hot daily.

In cats, giardiasis responds to metronidazole, although this should not be administered to pregnant cats as it can cause developmental malformations. An alternative and effective drug is febendazole.

There are 21.4 million people infected with trachoma, of whom 2.2 million are partially blind and 1.2 million are blind. It is found in Africa, Asia, Central and South America, Middle East, and Australia. The disease disproportionately affects women and children. The mortality risk is very low, although multiple re-infections eventually lead to blindness. The symptoms are internally scarred eyelids, followed by eyelids turning inward. Trachoma is caused by a micro-organism that spreads through eye discharges (on hands, cloth, etc.) and by "eye-seeking flies".

It is treated with antibiotics. The only known prevention method is interpersonal hygiene.

Snakebite was added to the list in 2017, after years of criticism of the WHO by activists for not making it a priority. The greatest burden of snakebite morbidity is in India and Southeast Asia. Globally, there are an estimated 421,000 envenomings each year (about 1 in 4 snakebites) and 20,000 deaths, but snakebites often go unreported.