Parasitic Diseases

Also known as African sleeping sickness, this illness is caused by two parasites that are carried by the tsetse fly, which is found only in Africa. The East African illness is acute, while West African (Gambian) is chronic. Both are fatal if left untreated. The disease is endemic to sub-Saharan Africa, but travelers to the region are not at high risk and few cases have been reported outside Africa.

Infection of humans or other animals by a nematode of the family Anisakidae. Humans typically are infected after eating undercooked infected marine fish (e.g., herring) such as often appears in sashimi, sushi and ceviche. The larvae burrow into the stomach wall and cause a mass to form. Symptoms include nausea and vomiting, diarrhea or abdominal pain within 12 hours of consuming the infected food.

Disease caused by a one-celled parasite known as Entamoeba histolytica. It most often is found in developing countries but sometimes is found in the United States in immigrants from areas where the disease is common. Symptoms usually are mild and include loose stools, stomach pain and stomach cramping. A severe form of this illness called amebic dysentery features stomach pain, bloody stools and fever.

Also known as Chagas disease, this parasitic disease is caused by the protozoan Trypanosoma cruz, which occurs mainly in Central and South America, although sometimes in the United States. It typically is transmitted to humans by insects called triatomine bugs that live in cracks and holes of substandard housing. Chagas disease has symptoms such as swelling or fever at the time of infection. In some people, it may enter a chronic stage and produce cardiac or digestive complications 20 to 30 years after the infection.

Infection by the intestinal roundworm, Ascaris lumbricoides, which looks like a common earthworm. These parasites can grow to about a foot long and become as thick as a pencil. Contact with infected feces (especially in areas with poor sanitation) spreads the disease. Up to 100 worms can infect a single person. The greater the number of worms in the body, the more severe the symptoms. Symptoms range from none at all to severe abdominal pain, vomiting and insomnia. The worms may be visually identifiable in an infected person’s vomit or stool. Ascariasis is a common worm infection, although it is not frequently seen in the United States.

Any of several tickborne diseases due to infection with protozoa of the genus Babesia. More than 100 species have been reported, but only a few infect humans and they generally do not produce symptoms. Infections are transmitted from animals to humans.

A parasitic disease caused by infection with species of the roundworm Capillaria.

Also known as swimmer’s itch, this patchy, red skin rash causes itching on the parts of the body that have been in the water. It is caused by a larval parasite known as a cercaria. Typically, it is not serious and clears without treatment.

A diarrheal disease caused by the parasite Cryptosporidium parvum. It can live in the intestines of humans and animals before being passed in the stool. It is a significant cause of waterborne illness throughout the world, including the United States, where it is sometimes found in drinking water and recreational water (e.g., swimming pools, waterparks). Symptoms may include diarrhea, nausea, cramping and a slight fever. The health risk associated with this infection is greatest in people with compromised immune systems, such as HIV and AIDSAIDS. In these patients, cryptosporidiosis can have long-lasting and potentially fatal consequences. All cases of cryptosporidiosis in the United States are required to be reported to the CDC.

Infection with the Cyclospora cayetanensis parasite that occurs when a person ingests food or water contaminated by the parasite. Symptoms may include diarrhea, nausea, cramping, vomiting, muscle aches, a low fever and fatigue. The infection was previously confined to developing areas but cases now occur worldwide.

Also known as Guinea worm disease, this painful, debilitating infestation with the parasite Dracunculus medinensis is contracted by drinking stagnant water contaminated with Guinea worm larvae. The larvae matures inside a person's abdomen until the worm emerges through a blister. International efforts are under way to eradicate Guinea worm disease in the African nations where it still exists.

Infection caused by the trematodes Fasciola hepatica (the sheep liver fluke) and Fasciola gigantica. Human infections are sometimes found where sheep and cattle are raised, generally in sporadic outbreaks in Africa and South America.

A parasitic infection from consuming contaminated water or food. It may cause diarrhea, nausea, cramping and bloating. Giardiasis is one of the most common waterborne illnesses in the United States and is responsible for most cases of childhood diarrhea in developing nations. It is a highly contagious parasitic infection and may be spread through drinking or swimming in contaminated water, consuming contaminated food and person-to-person contact.

A common roundworm infection in which parasites generally enter the body through the skin. It is commonly spread through unsanitary conditions (e.g., walking barefoot on contaminated soil). An itchy patch typically develops where the parasite entered the body. Symptoms depend on the number of worms in the body, and may range from minor abdominal pain and diarrhea to serious anemia.

Infection with the dwarf tapeworm, it is the most commonly diagnosed tapeworm infection throughout the world, and the leading source of tapeworm infections in the United States.

Infection of the epithelial cells of the small intestine with the coccidian parasite Isospora belli. It causes diarrhea and has been the source of some diarrheal outbreaks in daycare centers and nursing homes. In Africa, isosporiasis is commonly the first infection experienced by people infected with HIV.

A parasitic disease spread by the bite of infected sandflies. There are several different forms, including cutaneous (causes skin sores) and visceral (affects some internal organs). It occurs in tropical and subtropical areas where sandflies are common.

Illness caused by tiny, wingless, parasitic insects that feed on a person’s blood. The major symptom associated with lice is extreme itchiness. Forms of lice include head lice, body lice and pubic lice. Lice are highly contagious and are spread through personal contact or sharing personal items. For example, outbreaks of head lice among school children are commonplace.

A potentially fatal disease caused by a parasite that is marked by high fevers, shaking, chills and flu-like illness. Five types of malaria parasites infect humans - Plasmodium falciparum, P. vivax, P. ovale, P. malariae and P. knowlesi. All cases of malaria in the United States are required to be reported to the U.S. Centers for Disease Control and Prevention.

An intestinal infection that causes diarrhea and wasting in people with HIV. Two species of the single-celled parasite microsporidia cause the illness -- Enterocytozoon and Septata.

Infection of the biliary tract with trematodes of the genus Opisthorchis. Transmission occurs through ingesting raw or inadequately cooked fish infected with the parasites. It generally occurs in parts of Europe and Asia.

Infestation with a worm of the genus Paragonimus. It typically invades the lung, producing chronic bronchitis with cough and reddish or brownish sputum. Most cases are native to areas of Asia, Africa and Latin America.

A parasitic infection by a small, white roundworm called Enterobius vermicularis that lives in the human rectum. Females exit the anus and deposit eggs on the surrounding skin. Itching in the area is common. According to the National Institutes of Health, pinworm infection is the most common of all roundworm infections in the United States. It is mainly spread by children.

Infection caused by Pneumocystis jiroveci (formerly known as Pneumocystis carinii), a fungus that lives in the lungs. Healthy people usually do not experience symptoms, but it can cause pneumonia in people who have compromised immune systems. It is the most common serious infection in people with advanced HIV disease in the United States.

A contagious and itchy skin disease caused by a species of mite. The mites burrow under the skin and deposit their eggs, forming a burrow that resembles a pencil mark. Scabies is spread by direct contact with infected individuals. Scabies is found worldwide.

An infection caused by one of the five species of parasite known as Schistosoma. Transmission occurs through contact with contaminated fresh water in Africa, Asia, South America and the Caribbean.

Infection caused by the roundworm Strongyloides stercoralis. It is fairly common in warm, moist regions and is transmitted through exposure to contaminated soil. In many cases, it does not cause symptoms. Moderate infections may include symptoms of burning pain in the abdomen, nausea, vomiting, as well as alternating diarrhea and constipation. Severe infections may cause anemia, weight loss and chronic diarrhea.

Infection with pork or beef tapeworms. It is typically transmitted by consuming undercooked pork or beef contaminated with tapeworm eggs or larvae. Humans are the definitive hosts of these tapeworms, and the organisms’ eggs are passed in human feces. Symptoms may include abdominal pain, weight loss, digestive problems and itching near the anus.

Infection with the parasite Toxoplasma gondii. Cats are the definitive host of the parasite. Transmission methods include ingestion of contaminated soil, careless handling of cat litter or ingestion of undercooked meat. It may also be transmitted from an infected mother to her fetus. Most people with toxoplasmosis exhibit no symptoms. Minor symptoms may resemble the flu. Severe symptoms include encephalitis (inflammation of the brain), eye diseases and respiratory failure. Infants born with an infection may develop problems later in life, such as blindness, hearing loss, as well as mental and learning difficulties.

Also known as an ova and parasite test (O&P), it is used to identify the presence of infectious parasites or parasite eggs in a patient’s stool. Patients may collect multiple samples over a period of days. These samples are specially stored until they can be delivered to a healthcare provider or laboratory, where the samples are examined. Use of certain medications may make it difficult to detect parasites in a stool sample. Such medications include antacids, antibiotics and laxatives.

Used when a fecal exam fails to reveal the source of a patient’s diarrheal illness. During the procedure, a tube is inserted into the patient’s mouth or rectum and through the intestines to allow a physician (e.g., a gastroenterologist) to examine the area. If a parasitic infection is suspected, endoscopy will be used to identify the presence of parasites within the intestines.

Some parasites can also be found through this method, but only if the test is designed to identify a specific type of parasitic infection. There is no blood test that can identify all parasite infections. Serology tests look for certain types of antibodies produced by the body’s immune system in response to infection by a particular parasite. Serology tests can also find antigens associated with a specific type of parasite. Another test known as a blood smear uses microscopic examination to reveal the presence of parasites found in the blood, including those that cause malaria, filariasis or babesiosis.

Patients may wish to ask their doctor the following questions related to parasitic diseases:

• What are the signs of parasitic disease?
• How will you diagnose my parasitic disease?
• What type of parasite do you suspect caused my infection?
• How serious is my parasitic disease?
• What are my treatment options?
• What are the risks associated with these treatments?
• How long will I have to take my medication?
• How will I know if treatment has been effective?
• What tips do you suggest for preventing parasitic disease?
• What steps can I take to protect myself while traveling?