Malaria is treated with antimalarial medications; the ones used depends on the type and severity of the disease. While medications against fever are commonly used, their effects on outcomes are not clear.

Simple or uncomplicated malaria may be treated with oral medications. The most effective treatment for "P. falciparum" infection is the use of artemisinins in combination with other antimalarials (known as artemisinin-combination therapy, or ACT), which decreases resistance to any single drug component. These additional antimalarials include: amodiaquine, lumefantrine, mefloquine or sulfadoxine/pyrimethamine. Another recommended combination is dihydroartemisinin and piperaquine. ACT is about 90% effective when used to treat uncomplicated malaria. To treat malaria during pregnancy, the WHO recommends the use of quinine plus clindamycin early in the pregnancy (1st trimester), and ACT in later stages (2nd and 3rd trimesters). In the 2000s (decade), malaria with partial resistance to artemisins emerged in Southeast Asia. Infection with "P. vivax", "P. ovale" or "P. malariae" usually do not require hospitalization. Treatment of "P. vivax" requires both treatment of blood stages (with chloroquine or ACT) and clearance of liver forms with primaquine. Treatment with tafenoquine prevents relapses after confirmed "P. vivax" malaria.

Severe and complicated malaria are almost always caused by infection with "P. falciparum". The other species usually cause only febrile disease. Severe and complicated malaria are medical emergencies since mortality rates are high (10% to 50%). Cerebral malaria is the form of severe and complicated malaria with the worst neurological symptoms.

Recommended treatment for severe malaria is the intravenous use of antimalarial drugs. For severe malaria, parenteral artesunate was superior to quinine in both children and adults. In another systematic review, artemisinin derivatives (artemether and arteether) were as efficacious as quinine in the treatment of cerebral malaria in children. Treatment of severe malaria involves supportive measures that are best done in a critical care unit. This includes the management of high fevers and the seizures that may result from it. It also includes monitoring for poor breathing effort, low blood sugar, and low blood potassium.

Drug resistance poses a growing problem in 21st-century malaria treatment. Resistance is now common against all classes of antimalarial drugs apart from artemisinins. Treatment of resistant strains became increasingly dependent on this class of drugs. The cost of artemisinins limits their use in the developing world. Malaria strains found on the Cambodia–Thailand border are resistant to combination therapies that include artemisinins, and may, therefore, be untreatable. Exposure of the parasite population to artemisinin monotherapies in subtherapeutic doses for over 30 years and the availability of substandard artemisinins likely drove the selection of the resistant phenotype. Resistance to artemisinin has been detected in Cambodia, Myanmar, Thailand, and Vietnam, and there has been emerging resistance in Laos.

As with many diseases in developing nations, (including trypanosomiasis and malaria) effective and affordable chemotherapy is sorely lacking and parasites or insect vectors are becoming increasingly resistant to existing anti-parasite drugs. Possibly due to the lack of financial return, new drugs are slow to emerge and much of the basic research into potential drug targets takes place in universities, funded by charitable organizations. Product Development Partnerships (PDPs) like Drugs for Neglected Diseases "initiatives" also work on the development of new treatments (combination treatments and new chemical entities) for visceral leishmaniasis.

The traditional treatment is with pentavalent antimonials such as sodium stibogluconate and meglumine antimoniate. Resistance is now common in India, and rates of resistance have been shown to be as high as 60% in parts of Bihar, India.

The treatment of choice for visceral leishmaniasis acquired in India is now Amphotericin B in its various liposomal preparations. In East Africa, the WHO recommended treatment is SSG&PM (sodium stibogluconate and paromomycin) developed by Drugs for Neglected Diseases "initiative" (DNDi)in 2010.

Miltefosine is the first oral treatment for this disease. The cure rate of miltefosine in Phase III clinical trials is 95%; Studies in Ethiopia show that is also effective in Africa. In HIV immunosuppressed people which are coinfected with leishmaniasis it has shown that even in resistant cases 2/3 of the people responded to this new treatment.

Miltefosine has received approval by the Indian regulatory authorities in 2002, in Germany in 2004 and in U.S.A. in 2014. It is now registered in many countries.

The drug is generally better tolerated than other drugs. Main side effects are gastrointestinal disturbance in the first or second day of treatment (a course of treatment is 28 days) which does not affect the efficacy. Because it is available as an oral formulation, the expense and inconvenience of hospitalization is avoided, and outpatient distribution of the drug becomes an option, making Miltefosine a drug of choice.

Incomplete treatment has been cited as a major reason of death from visceral leishmaniasis.

The nonprofit Institute for OneWorld Health has adopted the broad spectrum antibiotic paromomycin for use in treating VL; its antileishmanial properties were first identified in the 1980s. A treatment with paromomycin costs about $15 USD. The drug had originally been identified in the 1960s. The Indian government approved paromomycin for sale and use in August 2006.

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.

There are no treatment modalities for acute and chronic chikungunya that currently exist. Majority of treatment plans use supportive and symptomatic care like analgesics for pain and anti-inflammatories for inflammation caused by arthritis. In acute stages of this virus, rest, antipyretics and analgesics are used to subside symptoms. Most use non-steroidal anti-inflammatory drugs (NSAIDs). In some cases, joint pain may resolve from treatment but stiffness remains.

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.

Dengue infection's therapeutic management is simple, cost effective and successful in saving lives by adequately performing timely institutionalized interventions. Treatment options are restricted, while no effective antiviral drugs for this infection have been accessible to date. Patients in the early phase of the dengue virus may recover without hospitalization. However, ongoing clinical research is in the works to find specific anti-dengue drugs.

The treatment is antimalarial chemotherapy, intravenous fluid and sometimes supportive care such as intensive care and dialysis.

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".

Neonatal infection treatment is typically started before the diagnosis of the cause can be confirmed.

Neonatal infection can be prophylactically treated with antibiotics. Maternal treatment with antibiotics is primarily used to protect against group B streptococcus.

Women with a history of HSV, can be treated with antiviral drugs to prevent symptomatic lesions and viral shedding that could infect the infant at birth. The antiviral medications used include acyclovir, penciclovir, valacyclovir, and famciclovir. Only very small amounts of the drug can be detected in the fetus. There are no increases in drug-related abnormalities in the infant that could be attributed to acyclovir. Long-term effects of antiviral medications have not been evaluated for their effects after growth and development of the child occurs. Neutropenia can be a complication of acyclovir treatment of neonatal HSV infection, but is usually transient. Treatment with immunoglobulin therapy has not been proven to be effective.

There are no vaccines or preventive drugs for visceral leishmaniasis. The most effective method to prevent infection is to protect from sand fly bites. To decrease the risk of being bitten, these precautionary measures are suggested:

- Outdoors:

1. Avoid outdoor activities, especially from dusk to dawn, when sand flies generally are the most active.

2. When outdoors (or in unprotected quarters), minimize the amount of exposed (uncovered) skin to the extent that is tolerable in the climate. Wear long-sleeved shirts, long pants, and socks; and tuck your shirt into your pants.

3. Apply insect repellent to exposed skin and under the ends of sleeves and pant legs. Follow the instructions on the label of the repellent. The most effective repellents generally are those that contain the chemical DEET (N,N-diethylmetatoluamide).

- Indoors:

1. Stay in well-screened or air-conditioned areas.

2. Keep in mind that sand flies are much smaller than mosquitoes and therefore can get through smaller holes.

3. Spray living/sleeping areas with an insecticide to kill insects.

4. If you are not sleeping in a well-screened or air-conditioned area, use a bed net and tuck it under your mattress. If possible, use a bed net that has been soaked in or sprayed with a pyrethroid-containing insecticide. The same treatment can be applied to screens, curtains, sheets, and clothing (clothing should be retreated after five washings)."

On February 2012, the nonprofit Infectious Disease Research Institute launched a clinical trial of the visceral leishmaniasis vaccine. The vaccine is a recombinant form of two fused Leishmania parasite proteins with an adjuvant. Two phase 1 clinical trials with healthy volunteers are to be conducted. The first one takes place in Washington (state) and is followed by a trial in India.

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.

It is suggested that splenectomized persons receive the following vaccinations, and ideally prior to planned splenectomy surgery:

- Pneumococcal polysaccharide vaccine (not before 2 years of age). Children may first need one or more boosters of pneumococcal conjugate vaccine if they did not complete the full childhood series.

- Haemophilus influenzae type b vaccine, especially if not received in childhood. For adults who have not been previously vaccinated, two doses given two months apart was advised in the new 2006 UK vaccination guidelines (in the UK may be given as a combined Hib/MenC vaccine).

- Meningococcal conjugate vaccine, especially if not received in adolescence. Previously vaccinated adults require a single booster and non-immunised adults advised, in UK since 2006, to have two doses given two months apart. Children too young for the conjugate vaccine should receive meningococcal polysaccharide vaccine in the interim.

- Influenza vaccine, every winter, to help prevent getting secondary bacterial infection.

Because of the increased risk of infection, physicians administer oral antibiotics as a prophylaxis after a surgical splenectomy (or starting at birth, for congenital asplenia or functional asplenia).

Those with asplenia are also cautioned to start a full-dose course of antibiotics at the first onset of an upper or lower respiratory tract infection (for example, sore throat or cough), or at the onset of any fever.

They are treated with antiprotozoal agents. Recent papers have also proposed the use of viruses to treat infections caused by protozoa.

All persons suspected of Lassa fever infection should be admitted to isolation facilities and their body fluids and excreta properly disposed of.

Early and aggressive treatment using ribavirin was pioneered by Joe McCormick in 1979. After extensive testing, early administration was determined to be critical to success. Additionally, ribavirin is almost twice as effective when given intravenously as when taken by mouth. Ribavirin is a prodrug which appears to interfere with viral replication by inhibiting RNA-dependent nucleic acid synthesis, although the precise mechanism of action is disputed. The drug is relatively inexpensive, but the cost of the drug is still very high for many of those in West African states. Fluid replacement, blood transfusion, and fighting hypotension are usually required. Intravenous interferon therapy has also been used.

When Lassa fever infects pregnant women late in their third trimester, induction of delivery is necessary for the mother to have a good chance of survival. This is because the virus has an affinity for the placenta and other highly vascular tissues. The fetus has only a one in ten chance of survival no matter what course of action is taken; hence, the focus is always on saving the life of the mother. Following delivery, women should receive the same treatment as other Lassa fever patients.

Work on a vaccine is continuing, with multiple approaches showing positive results in animal trials.

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.

Treatment of asymptomatic carriers should be considered if parasites are still detected after 3 months. In mild-to-moderate babesiosis, the treatment of choice is a combination of atovaquone and azithromycin. This regimen is preferred to clindamycin and quinine because side effects are fewer. The standard course is 7 to 10 days, but this is extended to at least 6 weeks in people with relapsing disease. Even mild cases are recommended to be treated to decrease the chance of inadvertently transmitting the infection by donating blood. In life-threatening cases, exchange transfusion is performed. In this procedure, the infected red blood cells are removed and replaced with uninfected ones.

Imizol is a drug used for treatment of babesiosis in dogs.

Extracts of the poisonous, bulbous plant "Boophone disticha" are used in the folk medicine of South Africa to treat equine babesiosis. "B. disticha" is a member of the daffodil family Amaryllidaceae and has also been used in preparations employed as arrow poisons, hallucinogens, and in embalming. The plant is rich in alkaloids, some of which display an action similar to that of scopolamine.

To reduce neonatal infection, routine screening of pregnant women for HIV, hepatitis B, syphilis, and rubella susceptibility is required in the UK.

Treatment with an vaginal antibiotic wash prior to birth does not prevent infection with group B streptococcus bacteria. Breast milk protects against necrotizing enterocolitis.

Because GBS bacteria can colonize the lower reproductive tract of 30% of women, typically pregnant women are tested for this pathogen from 35 to 37 weeks of pregnancy. Before delivery treatment of the mother with antibiotics reduces the rate of neonatal infection. Prevention of the infection of the baby is done by treating the mother with penicillin. Since the adoption of this prophylatic treatment, infant mortality from GBS infection has decreased by 80%.

Mothers with symptomatic HSV and who are treated with antiviral prophylaxis are less prone to have an active, symptomatic case at the time of birth and it may be able to reduce the risk of passing on HSV during birth. Cesarean delivery reduces the risk of infection of the infant.

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.

The disease results from the aggregation of erythrocytes infected by "Plasmodium falciparum" which have been shown to adhere to chondroitin sulfate A (CSA) on placental proteoglycans causing them to accumulate in the intervillous spaces of the placenta, blocking the crucial flow of nutrients from mother to embryo.

If the splenomegaly underlies hypersplenism, a splenectomy is indicated and will correct the hypersplenism. However, the underlying cause of the hypersplenism will most likely remain; consequently, a thorough diagnostic workup is still indicated, as, leukemia, lymphoma and other serious disorders can cause hypersplenism and splenomegaly. After splenectomy, however, patients have an increased risk for infectious diseases.

Patients undergoing splenectomy should be vaccinated against "Haemophilus influenzae", "Streptococcus pneumoniae", and "Meningococcus". They should also receive annual influenza vaccinations. Long-term prophylactic antibiotics may be given in certain cases.

In cases of infectious mononucleosis splenomegaly is a common symptom and health care providers may consider using abdominal ultrasonography to get insight into a person's condition. However, because spleen size varies greatly, ultrasonography is not a valid technique for assessing spleen enlargement and should not be used in typical circumstances or to make routine decisions about fitness for playing sports.

Women experiencing PAM may exhibit normal symptoms of malaria, but may also be asymptomatic or present with more mild symptoms, including a lack of the characteristic fever. This may prevent a woman from seeking treatment despite the danger to herself and her unborn child.

Most people with sickle-cell disease have intensely painful episodes called vaso-occlusive crises. However, the frequency, severity, and duration of these crises vary tremendously. Painful crises are treated symptomatically with pain medications; pain management requires opioid administration at regular intervals until the crisis has settled. For milder crises, a subgroup of patients manage on NSAIDs (such as diclofenac or naproxen). For more severe crises, most patients require inpatient management for intravenous opioids; patient-controlled analgesia (PCA) devices are commonly used in this setting. Diphenhydramine is also an effective agent that doctors frequently prescribe to help control itching associated with the use of opioids.

For many years from the 1950s onwards, vast dams and irrigation schemes were constructed, causing a massive rise in water-borne infections from schistosomiasis. The detailed specifications laid out in various UN documents since the 1950s could have minimized this problem. Irrigation schemes can be designed to make it hard for the snails to colonize the water and to reduce the contact with the local population. Even though guidelines on how to design these schemes to minimise the spread of the disease had been published years before, the designers were unaware of them. The dams appear to have reduced the population of the large migratory prawn "Macrobrachium". After the construction of fourteen large dams, greater increases in schistosomiasis occurred in the historical habitats of native prawns than in other areas. Further, at the 1986 Diama Dam on the Senegal River, restoring prawns upstream of the dam reduced both snail density and the human schistosomiasis reinfection rate.