One strategy for the prevention of infection transmission between cats and people is to better educate people on the behaviour that puts them at risk for becoming infected.

Those at the highest risk of contracting a disease from a cat are those with behaviors that include: being licked, sharing food, sharing kithchen utensils, kissing, and sleeping with a cat. The very young, the elderly and those who are immunocompromised increase their risk of becoming infected when sleeping with their cats (and dogs). The CDC recommends that cat owners not allow a cat to lick your face because it can result in disease transmission. If someone is licked on their face, mucous membranes or an open wound, the risk for infection is reduced if the area is immediately washed with soap and water. Maintaining the health of the animal by regular inspection for fleas and ticks, scheduling deworming medications along with veterinary exams will also reduce the risk of acquiring a feline zoonosis.

Recommendations for the prevention of ringworm transmission to people include:

- regularly vacuuming areas of the home that pets commonly visit helps to remove fur or flakes of skin

- washing the hands with soap and running water after playing with or petting your pet.

- wearing gloves and long sleeves when handling cats infected with.

- disinfect areas the pet has spent time in, including surfaces and bedding.

- the spores of this fungus can be killed with common disinfectants like chlorine bleach diluted 1:10 (1/4 cup in 1 gallon of water), benzalkonium chloride, or strong detergents.

- not handling cats with ringworm by those whose immune system is weak in any way (if you have HIV/AIDS, are undergoing cancer treatment, or are taking medications that suppress the immune system, for example).

- taking the cat to the veterinarian if ringworm infection is suspected.

There is a negative association between an infection with the parasite "T. gondii" and multiple sclerosis, therefore, researchers have concluded that toxoplasmosis infection could be considered a protective factor.

Congenital toxoplasmosis is a specific form of toxoplasmosis in which an unborn fetus is infected via the placenta. Congenital toxoplasmosis is associated with fetal death and abortion, and in infants, it is associated with neurologic deficits, neurocognitive deficits, and chorioretinitis. A positive antibody titer indicates previous exposure and immunity, and largely ensures the unborn fetus' safety. A simple blood draw at the first prenatal doctor visit can determine whether or not a woman has had previous exposure and therefore whether or not she is at risk. If a woman receives her first exposure to "T. gondii" while pregnant, the fetus is at particular risk.

Not much evidence exists around the effect of education before pregnancy to prevent congenital toxoplasmosis. However educating parents before the baby is born has been suggested to be effective because it may improve food, personal and pet hygiene. More research is needed to find whether antenatal education can reduce congenital toxoplasmosis.

For pregnant women with negative antibody titers, indicating no previous exposure to "T. gondii", serology testing as frequent as monthly is advisable as treatment during pregnancy for those women exposed to "T. gondii" for the first time dramatically decreases the risk of passing the parasite to the fetus. Since a baby's immune system does not develop fully for the first year of life, and the resilient cysts that form throughout the body are very difficult to eradicate with antiprotozoans, an infection can be very serious in the young.

Despite these risks, pregnant women are not routinely screened for toxoplasmosis in most countries, for reasons of cost-effectiveness and the high number of false positives generated; Portugal, France, Austria, Uruguay, and Italy are notable exceptions, and some regional screening programmes operate in Germany, Switzerland and Belgium. As invasive prenatal testing incurs some risk to the fetus (18.5 pregnancy losses per toxoplasmosis case prevented), postnatal or neonatal screening is preferred. The exceptions are cases where fetal abnormalities are noted, and thus screening can be targeted.

Pregnant women should avoid handling raw meat, drinking raw milk (especially goat milk) and be advised to not eat raw or undercooked meat regardless of type. Because of the obvious relationship between "Toxoplasma" and cats it is also often advised to avoid exposure to cat feces, and refrain from gardening (cat feces are common in garden soil) or at least wear gloves when so engaged. Most cats are not actively shedding oocysts, since they get infected in the first six months of their life, when they shed oocysts for a short period of time (1–2 weeks.) However, these oocysts get buried in the soil, sporulate and remain infectious for periods ranging from several months to more than a year. Numerous studies have shown living in a household with a cat is not a significant risk factor for "T. gondii" infection, though living with several kittens has some significance.

In 2006, a Czech research team discovered women with high levels of toxoplasmosis antibodies were significantly more likely to have baby boys than baby girls. In most populations, the birth rate is around 51% boys, but women infected with "T. gondii" had up to a 72% chance of a boy. In mice, the sex ratio was higher in early latent toxoplasmosis and lower in later latent toxoplasmosis.

Cryptosporidiosis is a parasitic disease that is transmitted through contaminated food or water from an infected person or animal. Cryptosporidiosis in cats is rare, but they can carry the protozoan without showing any signs of illness. Cryptosporidiosis can cause profuse, watery diarrhea with cramping, abdominal pain, and nausea in people. Illness in people is usually self-limiting and lasts only 2–4 days, but can become severe in people with weakened immune systems. Cryptosporidiosis (Cryptosporidium spp.) Cats transmit the protozoan through their feces. The symptoms in people weight loss and chronic diarrhea in high-risk patients. More than one species of this genus can be acquired by people. Dogs can also transmit this parasite.

Areas with the highest prevalence of helminthiasis are tropical and subtropical areas including sub-Saharan Africa, central and east Asia, and the Americas.

Even in areas of high prevalence, the frequency and severity of infection is not uniform within communities or families. A small proportion of community members harbour the majority of worms, and this depends on age. The maximum worm burden is at five to ten years of age, declining rapidly thereafter. Individual predisposition to helminthiasis for people with the same sanitation infrastructure and hygiene behavior is thought to result from differing immunocompetence, nutritional status, and genetic factors. Because individuals are predisposed to a high or a low worm burden, the burden reacquired after successful treatment is proportional to that before treatment.

Infection of "T. trichiura" is most frequent in areas with tropical weather and poor sanitation practices. Trichuriasis occurs frequently in areas in which untreated human feces is used as fertilizer or where open defecation takes place. Trichuriasis infection prevalence is 50 to 80 percent in some regions of Asia (noted especially in China and Korea) and also occurs in rural areas of the southeastern United States.

Infection can be avoided by proper disposal of human feces, avoiding fecal contamination of food, not eating dirt, and avoiding crops fertilized with untreated human feces. Simple and effective proper hygiene such as washing hands and food is recommended for control.

Improved facilities for feces disposal have decreased the incidence of whipworm. Handwashing before food handling, and avoiding ingestion of soil by thorough washing of food that may have been contaminated with egg-containing soil are other preventive measures. Improvement of sanitation systems, as well as improved facilities for feces disposal, have helped to limit defecation onto soil and contain potentially infectious feces from bodily contact.

A study in a Brazillian urban centre demonstrated a significant reduction in prevalence and incidence of soil-transmitted helminthiasis, including trichuriasis, following implementation of a citywide sanitation program. A 33% reduction in the prevalence of trichuriasis and a 26% reduction in the incidence of trichuriasis was found in a study performed on 890 children ages 7–14 years old within 24 different sentinel areas chosen to represent the varied environmental conditions throughout the city of Salvador, Bahia, Brazil. Control of soil fertilizers has helped eliminate the potential for contact of human fecal matter and fertilizer in the soil.

Deworming treatments in infected children may have some nutritional benefit, as worms are often partially responsible for malnutrition. However, in areas where these infections are common, there is strong evidence that mass deworming campaigns do not have a positive effect on children's average nutritional status, levels of blood haemoglobin, cognitive abilities, performance at school or survival. To achieve health gains in the longer term, improvements in sanitation and hygiene behaviours are also required, together with deworming treatments.

Experimental infection in immunocompetent and immunocompromised mice has produced intestinal inflammation, altered bowel habits, lethargy and death. Chronic diarrhea has been reported in non-human higher primates.

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.

Amphistomiasis in farm and wild mammals is due to infection of paramphistomes, such as the species of "Paramphistomum", "Calicophoron", "Cotylophoron", "Pseudophisthodiscus", etc. These are essentially rumen flukes, of which "Paramphistomum cervi" is the most notorious in terms of prevalence and pathogenicity. Infection occurs through ingestion of contaminated vegetables and raw meat, in which the viable infective metacercaria are deposited from snails, which are the intermediate hosts. The immature flukes are responsible for destroying the mucosal walls of the alimentary tract on their way to growing into adults. It is by this fervent tissue obliteration that the clinical symptoms are manifested. The adult flukes, on the other hand, are quite harmless, as they merely prepare for reproduction.

The zoonotic infection in human is caused by "G. discoides" and "W. watsoni" which are essentially intestinal flukes. The disease due to "G. discoides" is more specifically termed gastrodiscoidiasis. In their natural hosts such as pigs and monkeys, their infection in asymptomatic, but human infection is prevalent, by which they cause serious health problems, characterised by diarrhoea, fever, abdominal pain, colic, and an increased mucous production. In extreme situations such as in Assam, India, a number of mortality among children is attributed to this disease.

It is estimated that a third of all pregnant women in developing countries are infected with hookworm, 56% of all pregnant women in developing countries suffer from anemia, 20% of all maternal deaths are either directly or indirectly related to anemia. Numbers like this have led to an increased interest in the topic of hookworm-related anemia during pregnancy. With the understanding that chronic hookworm infection can often lead to anemia, many people are now questioning if the treatment of hookworm could effect change in severe anemia rates and thus also on maternal and child health as well. Most evidence suggests that the contribution of hookworm to maternal anemia merits that all women of child-bearing age living in endemic areas be subject to periodic anthelmintic treatment. The World Health Organization even recommends that infected pregnant women be treated after their first trimester. Regardless of these suggestions, only Madagascar, Nepal and Sri Lanka have added deworming to their antenatal care programs.

This lack of deworming of pregnant women is explained by the fact that most individuals still fear that anthelmintic treatment will result in adverse birth outcomes. But a 2006 study by Gyorkos et al. found that when comparing a group of pregnant women treated with mebendazole with a control placebo group, both illustrated rather similar rates in adverse birth outcomes. The treated group demonstrated 5.6% adverse birth outcomes, while the control group had 6.25% adverse birth outcomes. Furthermore, Larocque et al. illustrated that treatment for hookworm infection actually led to positive health results in the infant. This study concluded that treatment with mebendazole plus iron supplements during antenatal care significantly reduced the proportion of very low birth weight infants when compared to a placebo control group. Studies so far have validated recommendations to treat infected pregnant women for hookworm infection during pregnancy.

A review of effects of antihelminthics (anti-worm drugs) given in pregnancy found that there was not enough evidence to support treating pregnant women in their second or third trimesters. The women who were treated in the second trimester and the women who had no treatment showed no difference in numbers of maternal anemia, low birth weight, preterm birth or deaths of babies.

The intensity of hookworm infection as well as the species of hookworm have yet to be studied as they relate to hookworm-related anemia during pregnancy. Additionally, more research must be done in different regions of the world to see if trends noted in completed studies persist.

Humans contract "Blastocystis" infection by drinking water or eating food contaminated with feces from an infected human or animal. "Blastocystis" infection can be spread from animals to humans, from humans to other humans, from humans to animals, and from animals to animals. Risk factors for infection have been reported as following:

- International travel: Travel to less developed countries has been cited in development of symptomatic Blastocystis infection. A 1986 study in the United States found that all individuals symptomatically infected with "Blastocystis" reported recent travel history to less developed countries. In the same study, all hospital employees working in New York who were screened for "Blastocystis" were found to have asymptomatic infections.

- Military service: Several studies have identified high rates of infection in military personnel. An early account described infection of British troops in Egypt in 1916 who recovered following treatment with emetine. A 1990 study published in "Military Medicine" from Lackland AFB in Texas concluded symptomatic infection was more common in foreign nationals, children, and immunocompromised individuals. A 2002 study published in "Military Medicine" of army personnel in Thailand identified a 44% infection rate. Infection rates were highest in privates who had served the longest at the army base. A follow-up study found a significant correlation between infection and symptoms, and identified the most likely cause as contaminated water. A 2007 newspaper article suggested the infection rate of US military personnel returning from the Gulf War was 50%, quoting the head of Oregon State University's Biomedicine department.

- Consumption of Untreated Water (well water): Many studies have linked "Blastocystis" infection with contaminated drinking water. A 1993 study of children infected symptomatically with "Blastocystis" in Pittsburgh indicated that 75% of them had a history of drinking well water or travel in less developed countries. Two studies in Thailand linked "Blastocystis" infection in military personnel and families to drinking of unboiled and untreated water. A book published in 2006 noted that in an Oregon community, infections are more common in winter months during heavy rains. A research study published in 1980 reported bacterial contamination of well water in the same community during heavy rainfall. A 2007 study from China specifically linked infection with "Blastocystis sp. subtype 3" with drinking untreated water. Recreational contact with untreated water, for example though boating, has also been identified as a risk factor. Studies have shown that "Blastocystis" survives sewage treatment plants in both the United Kingdom and Malaysia. "Blastocystis" cysts have been shown to be resistant to chlorination as a treatment method and are among the most resistant cysts to ozone treatment.

- Contaminated Food: Contamination of leafy vegetables has been implicated as a potential source for transmission of "Blastocystis" infection, as well as other gastrointestinal protozoa. A Chinese study identified infection with "Blastocystis sp. subtype 1" as specifically associated with eating foods grown in untreated water.

- Daycare facilities: A Canadian study identified an outbreak of "Blastocystis" associated with daycare attendance. Prior studies have identified outbreaks of similar protozoal infections in daycares.

- Geography: Infection rates vary geographically, and variants which produce symptoms may be less common in industrialized countries. For example, a low incidence of "Blastocystis" infection has been reported in Japan. A study of individuals infected with "Blastocystis" in Japan found that many (43%, 23/54) carried "Blastocystis sp. subtype 2", which was found to produce no symptoms in 93% (21/23) of patients studied, in contrast to other variants which were less common but produced symptoms in 50% of Japanese individuals. Studies in urban areas of industrialized countries have found "Blastocystis" infection associated with a low incidence of symptoms. In contrast, studies in developing countries generally show "Blastocystis" to be associated with symptoms. In the United States, a higher incidence of "Blastocystis" infection has been reported in California and West Coast states.

- Prevalence over Time: A 1989 study of the prevalence of "Blastocystis" in the United States found an infection rate of 2.6% in samples submitted from all 48 states. The study was part of the CDC's MMWR Report. A more recent study, in 2006, found an infection rate of 23% in samples submitted from all 48 states. However, the more recent study was performed by a private laboratory located in the Western US, and emphasized samples from Western states, which have previously been reported to have a higher infection rate.

Research studies have suggested the following items are not risk factors for contracting "Blastocystis" infection:

- Consumption of municipal water near water plant (not a risk factor): One study showed that municipal water was free of "Blastocystis", even when drawn from a polluted source. However, samples taken far away from the treatment plant showed cysts. The researchers suggested that aging pipes may permit intrusion of contaminated water into the distribution system.

- Human-to-Human transmission among adults (not a risk factor): Some research suggests that direct human-to-human transmission is less common even in households and between married partners. One study showed different members of the same household carried different subtypes of Blastocystis.

Moderate hookworm infections have been demonstrated to have beneficial effects on hosts suffering from diseases linked to overactive immune systems. This is possibly explained by the hygiene hypothesis. Research at the University of Nottingham conducted in Ethiopia observed a small subset of people with hookworm infections were half as likely to experience asthma or hay fever. Potential benefits have also been hypothesized in cases of multiple sclerosis, Crohn's Disease and diabetes.

Some research conducted has shown favourable results using hookworms to treat coeliac disease. Though research points to anti-allergenic properties associated with hook worm infections, the FDA does not currently recognize hookworms as a treatment.

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.

Estimates regarding the number of deaths vary. Worldwide, the Global Burden of Disease Study issued in 2010 estimated 12,000 direct deaths while the WHO in 2014 estimated more than 200,000 annual deaths related to schistosomiasis. Another 20 million have severe consequences from the disease. It is the most deadly of the neglected tropical diseases.

Amphistomiasis or paramphistomiasis (alternatively spelled amphistomosis or paramphistomosis) is a parasitic disease of livestock animals, more commonly of cattle and sheep, and humans caused by immature helminthic flatworms belonging to the order Echinostomida. The term amphistomiasis is used for broader connotation implying the disease inflicted by members of Echinostomida including the family Paramphistomidae/Gastrodiscidae (to be precise, the species "Gastrodiscoides hominis"); whereas paramphistomiasis is restricted to that of the members of the family Paramphistomatidae only. "G. discoides" and "Watsonius watsoni" are responsible for the disease in humans, while most paramphistomes are responsible in livestock animals, and some wild mammals. In livestock industry the disease causes heavy economic backlashes due to poor production of milk, meat and wool.

Parasitic pneumonia is an infection of the lungs by parasites. It is a rare cause of pneumonia, occurring almost exclusively in immunocompromised persons (persons with a weakened or absent immune system). This is a respiratory infection that may or may not be serious.

There are a variety of parasites which can affect the lungs. In general, these parasites enter the body through the skin or by being swallowed. Once inside the body, these parasites travel to the lungs, most often through the blood. There, a similar combination of cellular destruction and immune response causes disruption of oxygen transportation. Depending on the type of parasite, antihelmynthic drugs can be prescribed.

The most common parasites involved:

- Ascariasis

- Schistosoma

- Toxoplasma gondii

Various strategies targeting the mollusc and avian hosts of schistosomes, have been used by lakeside residents in recreational areas of North America to deal with outbreaks of swimmer's itch. In Michigan, for decades, authorities used copper sulfate as a molluscicide to reduce snail host populations and thereby the incidence of swimmer's itch. The results with this agent have been inconclusive, possibly because:

- Snails become tolerant

- Local water chemistry reduces the molluscicide's efficacy

- Local currents diffuse it

- Adjacent snail populations repopulate a treated area

More importantly, perhaps, copper sulfate is toxic to more than just molluscs, and the effects of its use on aquatic ecosystems are not well understood.

Another method targeting the snail host, mechanical disturbance of snail habitat, has been also tried in some areas of North America and Lake Annecy in France, with promising results. Some work in Michigan suggests that administering praziquantel to hatchling waterfowl can reduce local swimmer's itch rates in humans. Work on schistosomiasis showed that water-resistant topical applications of the common insect repellent DEET prevented schistosomes from penetrating the skin of mice. Public education of risk factors, a good alternative to the aforementioned interventionist strategies, can also reduce human exposure to cercariae.

Humans usually become infected after swimming in lakes or other bodies of slow-moving fresh water. Some laboratory evidence indicates snails shed cercariae most intensely in the morning and on sunny days, and exposure to water in these conditions may therefore increase risk. Duration of swimming is positively correlated with increased risk of infection in Europe and North America, and shallow inshore waters may harbour higher densities of cercariae than open waters offshore. Onshore winds are thought to cause cercariae to accumulate along shorelines. Studies of infested lakes and outbreaks in Europe and North America have found cases where infection risk appears to be evenly distributed around the margins of water bodies as well as instances where risk increases in endemic swimmer's itch "hotspots". Children may become infected more frequently and more intensely than adults but this probably reflects their tendency to swim for longer periods inshore, where cercariae also concentrate. Stimuli for cercarial penetration into host skin include unsaturated fatty acids, such as linoleic and linolenic acids. These substances occur naturally in human skin and are found in sun lotions and creams based on plant oils.

Dientamoebiasis is a medical condition caused by infection with "Dientamoeba fragilis", a single-cell parasite that infects the lower gastrointestinal tract of humans. It is an important cause of traveler's diarrhea, chronic abdominal pain, chronic fatigue, and failure to thrive in children.

The preventative measure of keeping cats inside in areas with high infection rates can prevent infection. Approved tick treatments for cats can be used but have been shown not to fully prevent tick bites.

The most often used treatments for cytauxzoonosis are imidocarb dipropionate and a combination of atovaquone and azithromycin. Although imidocarb has been used for years, it is not particularly effective. In a large study, only 25% of cats treated with this drug and supportive care survived. 60% of sick cats treated with supportive care and the combination of the anti-malarial drug atovaquone and the antibiotic azithromycin survived infection.

Quick referral to a veterinarian equipped to treat the disease may be beneficial. All infected cats require supportive care, including careful fluids, nutritional support, treatment for complications, and often blood transfusion.

Cats that survive the infection should be kept indoors as they can be persistent carriers after surviving infection and might indirectly infect other cats after being themselves bitten by a vector tick.

Fever and sickness behavior and other signs of infection are often taken to be due to them. However, they are evolved physiological and behavioral responses of the host to clear itself of the infection. Instead of incurring the costs of deploying these evolved responses to infections, the body opts to tolerate an infection as an alternative to seeking to control or remove the infecting pathogen.

Subclinical infections are important since they allow infections to spread from a reserve of carriers. They also can cause clinical problems unrelated to the direct issue of infection. For example, in the case of urinary tract infections in women, this infection may cause preterm delivery if the person becomes pregnant without proper treatment.

Organisms similar to "D. fragilis" are known to produce a cyst stage that is able to survive outside the host and facilitate infection of new hosts. However, the exact manner in which it is transmitted is not yet known, as the organism is unable to survive outside its human host for more than a few hours after excretion, and no cyst stage has been found.

Early theories of transmission suggested "D. fragilis" was unable to produce a cyst stage in infected humans, but some animal existed that in which it did produce a cyst stage, and this animal was responsible for spreading it. However, no such animal has ever been discovered. A later theory suggested the organism was transmitted by pinworms, which provided protection for the parasite outside the host. DNA has been detected in surface-sterilized eggs of "Enterobius vermicularis" eggs, thus suggesting the latter may harbor the former. Experimental ingestion of pinworm eggs established infection in two investigators. Numerous studies reported high rates of coinfection with helminthes. However, recent study has failed to show any association between "D. fragilis" infection and pinworm infection. Parasites similar to "D. fragilis" are transmitted by consuming water or food contaminated with feces. The high rate (40%) of concomitant infection with other protozoa reported by at St. Vincent's Hospital, Sydney, Australia, supports the oral-fecal route of transmission.