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Trypanosomiasis

TRYPANOSOMIASIS

Trypanosomiasis, also known as African sleeping sickness, is an infection endemic to sub-Saharan Africa. It is caused by protozoan parasites called trypanosomes, which are spread by the bite of the tsetse fly. There are two subspecies of trypanosomes that infect humans, each causing a different form of the disease. Trypanosoma brucei rhodesiense, found in eastern and southern Africa, causes an acute illness leading to death within weeks or months. Trypanosoma brucei gambiense, found in western and central Africa, causes a more chronic form of the illness which may last several years. Both forms of sleeping sickness are fatal if left untreated.

It is estimated that approximately 60 million people are at risk for the disease. Accurate assessment of the extent of the disease is made difficult by the remoteness of the areas in which it is found and the variability in the tests used for diagnosis. Trypanosomiasis often occurs focally, so scattered pockets of infection will be found within an endemic region.

Following the bite of an infected tsetse fly, a scab, or chancre, often forms. After an incubation period of days to weeks, the trypanosomes enter the blood and lymphatic systems and multiply. During this stage, patients may experience headaches, fevers, sweating, rash, and malaise. Enlargement of lymph glands occurs, particularly at the back of the neck. The enlarged nodes may be the only visible sign during this phase of the infection. Eventually the trypanosomes will invade the central nervous system, giving rise to neurological symptoms. This stage, aptly called "sleeping sickness," is characterized by headache, apathy, lethargy, and somnolence. Patients may experience personality and cognitive changes, tremors, and coordination problems. They become increasingly wasted and drowsy, and eventually fall into a coma and die. This progression to death usually occurs in months with T. b. rhodesiense and in years with T.b. gambiense.

Diagnosis is made by microscopic identification of the parasite, which may be found in the chancre, lymph glands, blood, or cerebral spinal fluid, depending on the stage of the disease. There are several serologic assays available. The sensitivity and specificity of these tests are variable. They are used mainly for epidemiological surveys, but they do have some clinical utility as well.

The form of treatment depends on whether the central nervous system (CNS) is involved. If the disease has not affected the CNS, suramin or pentamidine may be used. In cases of CNS involvement, melarsoprol is the drug of choice. This is a very toxic drug which may have severe side effects, including a fatal encephalopathy. Another effective medication for the treatment of T. b. gambiense is eflornithine. Unfortunately, this drug is not currently readily available.

Human beings are the main hosts of T. b. gambiense. Control of this infection involves routine screening of at-risk populations, treatment of infected individuals, and control of exposure to tsetse flies, which often inhabit riverine areas. T. b. rhodesiense is found in savannah areas in antelopes, other wild game, and domestic cattle, so control of infection is more complicated and involves the coordination of medical, veterinary, agricultural, entomological, and other services.

Martha Fulford

Jay Keystone

(see also: Comunicable Disease Control; Vector-Borne Diseases )

Bibliography

Burri, C. et al. (2000). "Efficacy of New, Concise Schedule for Melarsoprol in Treatment of Sleeping Sickness Caused by Trypanosoma brucei gambiense : A Randomised Trial." Lancet 355:14191425.

Neva, F. A., and Brown, W. (1994). Basic Clinical Parasitology. Englewood Cliffs, NJ: Prentice Hall.

Smith, D. H.; Pepin, J.; and Stich, A. H. R. (1998). "Human African Trypanosomiasis: An Emerging Public Health Crisis." British Medical Bulletin 54:341355.

World Health Organization (1998). "Control and Surveillance of African Trypanosomiasis." World Health Organization Technical Report Series 881(vi):1114.

(2000). "African Trypanosomiasis." WHO Report on Global Surveillance of Epidemic-Prone Infectious Diseases. Geneva: Author.

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trypanosomiasis

trypanosomiasis (trəpăn´əsōmī´əsis), infectious disease caused by a protozoan organism, the trypanosome, which exists as a parasite in the blood of a number of vertebrate hosts. The three variations of the disease that predominate in humans are transmitted by an insect vector. Two types of African sleeping sickness are caused, respectively, by Trypanosoma brucei rhodesiense and T. brucei gambiense, both transmitted by the bite of the tsetse fly. South American trypanosomiasis, or Chagas' disease, is caused by T. cruzi, which is the most common cause of heart disease in South America. It is transmitted by certain species of bugs; the parasite enters the skin when infected bug feces are rubbed into the site of the bite.

The characteristic symptoms of Chagas' disease are edema; hard, red nodular outbreaks of the skin; and damage to the heart muscle. There is no effective treatment. Symptoms of African sleeping sickness may appear at once, after several weeks, or even after years in the Gambian type, which is the most common form. Early disturbances include inflammation at the site of the bite, intermittent fever, enlargement of the spleen; in the Gambian variety the lymph nodes are enlarged. Subsequent signs of heart damage, personality changes, and headache develop. The final stages are marked by tremor, disturbed speech and gait, emaciation, and a prolonged comatose state. African trypanosomiasis is treated with pentamidine or suramin, which are effective when injected in early stages of the disease; in the second stage, when the nervous system is affected, treatment involves melarsoprol or nifurtimox and eflornithine. Even with treatment, organ damage appears irreversible and the disease is often fatal; the prognosis becomes grave after the nervous system is invaded. Prevention involves the use of insecticides and the clearing of vegetation that harbors the tsetse fly. A form of trypanosomiasis known as nagana affects cattle, leading to enormous annual economic losses.

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Trypanosomiasis

Trypanosomiasis

What Is Trypanosomiasis?

What Causes Trypanosomiasis?

How Common Is Trypanosomiasis?

Is Trypanosomiasis Contagious?

What Are the Symptoms of the Disease?

How Do Doctors Diagnose Trypanosomiasis?

Can Trypanosomiasis Be Treated Successfully?

What Happens to People with Trypanosomiasis?

Can Trypanosomiasis Be Prevented?

Resources

Trypanosomiasis (trih-pan-o-so-MY-uh-sis) is a disease found in Africa and the American continents that is caused by infection with a parasite. Forms of the disease may persist for many years and have several phases, with symptoms that can vary from one stage to the next.

KEYWORDS

for searching the Internet and other reference sources

Chagas disease

Chagoma

Protozoa

Reduviid bug

Sleeping sickness

Trypanosoma brucei

Trypanosoma cruzi

Tsetse fly

What Is Trypanosomiasis?

Trypanosomiasis refers to three types of infections caused by protozoa* and spread to humans through insect bites. There are two kinds of African trypanosomiasis, East African and West African. Both of these varieties also are known as sleeping sickness. The disease can affect people living on the African continent south of the Sahara Desert. American trypanosomiasis also is called Chagas (SHAH-gus) disease. It occurs only on the American continents, from Mexico to Argentina.

*protozoa
(pro-tuh-ZOH-uh) are single-celled microorganisms (tiny organisms), some of which are capable of causing disease in humans.

What Causes Trypanosomiasis?

The bite of an infected tsetse (SET-see) fly usually transmits the organisms that cause the African forms of trypanosomiasis. These flies live in the countryside in Africa, especially in bushes and thick vegetation near rivers and lakes. Tsetse flies infected with the protozoan Trypanosoma brucei rhode-siense (trih-pan-o-SO-mah BRU-see-eye ro-dee-see-EN-see) spread East African trypanosomiasis, the most severe form of the disease, to humans. The West African variety comes from a fly infected with Trypanosoma brucei gambiense (trih-pan-o-SO-mah BRU-see-eye gam-be-EN-see).

Reduviid (rih-DO-vee-id) bugs (also called assassin, cone-nose, or kissing bugs) carry the Trypanosoma cruzi (trih-pan-o-SO-mah KROO-zee) protozoa that cause the American variety of trypanosomiasis, or Chagas disease, named for the Brazilian doctor who discovered it. These bugs hide during the day in the cracks in mud and adobe homes. At night they crawl across sleeping people and bite them, usually on the face but sometimes on the arms, legs, or trunk. They also leave behind their feces*, which contain the protozoa. Without knowing it, people can rub the infected feces into the bite, a cut or open sore, or even into their noses, mouths, or eyes.

*feces
(FEE-seez) is the excreted waste from the gastrointestinal tract.

How Common Is Trypanosomiasis?

Trypanosomiasis can infect people of every age and race, though it is uncommon in the United States. Since the late 1960s, fewer than 30 cases have been reported among U.S. citizens traveling to areas where the infection is found. In other parts of the world, however, the disease affects thousands of people. The World Health Organization estimates that as many as 500,000 people could have African trypanosomiasis, but because of poor monitoring most of these cases are not reported. Between 16 million and 18 million people in the Americas currently have Chagas disease. Approximately 50,000 may die from the disease each year.

Is Trypanosomiasis Contagious?

People cannot catch any form of trypanosomiasis in the same way that they catch a cold or the flu from other people. Only the tsetse fly spreads the African varieties, and the reduviid bug spreads Chagas disease. Rarely, a mother infected with the West African variety of trypanosomiasis or with Chagas disease can pass the illness to her unborn child. People who receive a transfusion* of blood or an organ transplant from an infected person also may contract the disease; this form of transmission tends to happen more often with Chagas disease than with the African types.

*transfusion
(trans-FYOO-zhun) is a procedure in which blood or certain parts of blood, such as specific cells, is given to a person who needs it because of illness or blood loss.

What Are the Symptoms of the Disease?

African trypanosomiasis

People who contract the African varieties of trypanosomiasis may start sleeping more, though this usually does not happen until the later stages of the disease. Sleeping sickness may start with the appearance of a sore called a chancre (SHANG-ker) at the spot where the person received the tsetse fly bite. Later symptoms include fever, extreme tiredness, severe headaches, rashes, itching, joint pain, and swelling of the hands and feet. The lymph nodes* on the back of the neck may become swollen as well. These signs typically appear 2 to 4 weeks after infection with East African trypanosomiasis.

*lymph
(LIMF) nodes are small, bean-shaped masses of tissue that contain immune system cells that fight harmful microorganisms. Lymph nodes may swell during infections.

Other symptoms can follow quickly, as the protozoa cross the blood-brain barrier* and start affecting a patients mental functions. The later stages of sleeping sickness may bring mental confusion, changes in personality, problems with walking and talking, weight loss, and seizures*. The spleen and liver may become enlarged. Sleeping sickness gets its name from the later part of the disease, when the sick person has nighttime insomnia (in-SOM-nee-uh, an inability to sleep) but sleeps for long periods during the day. If the person does not receive treatment, the heart muscles may become inflamed or weakened, causing death from heart failure.

*blood-brain barrier
is a biological shield in the body that helps prevent germs or other potentially harmful materials in the blood from entering the brain and spinal cord.
*seizures
(SEE-zhurs) are sudden bursts of disorganized electrical activity that interrupt the normal functioning of the brain, often leading to uncontrolled movements in the body and sometimes a temporary change in consciousness.

The early symptoms in West African trypanosomiasis are similar but may take longer to appear. Months or years may pass before an infected person becomes sick, and the disease develops more slowly, though it still can cause death if it is left untreated. The gap between infection and the start of symptoms can make this form of sleeping sickness difficult to diagnose.

Global Warming

The bite of an insect can transmit bacteria, protozoa, or even worms into a persons bloodstream, leading to a variety of illnesses. Trypanosomiasis is just one example of a tropical insect-borne disease. Here are a few others, along with the insects that spread them:

Malaria mosquitoes
(mah-LAIR-e-uh) 
Yellow fever mosquitoes
Elephantiasis mosquitoes
(eh-luh-fan-TIE-uh-sis) 
Leishmaniasis sandflies
(leesh-muh-NYE-uh-sis) 
Onchocerciasis, black flies
(on-koh-sir-KYE-us-sis) 
or river blindness  

Why are these diseases common to the tropics? It is because the hot and often rainy climate makes the tropics an ideal breeding ground for insects. Green-peace, among other organizations dedicated to protecting the environment, has warned that global warming could create new breeding grounds for insects throughout the world. At the same time, rising temperatures could raise insect reproductive rates, increasing their numbers. As the climate in the United States and Europe becomes more tropical, diseases such as yellow fever and malaria may become more common, bringing the tropics into our own backyards.

Chagas disease

The first sign of Chagas disease may show up a few hours after infection, when a raised red spot called a chagoma (chuh-GO-mah) appears at the site of the insect bite. Most people have no other symptoms during the early, or acute, phase of the disease, which begins a few weeks later. People who experience symptoms may have fevers, rashes, extreme tiredness, vomiting, loss of appetite, or swollen lymph nodes. The side of the face where the infected feces were rubbed into an eye or a bug bite may swell. In most people these symptoms usually disappear within 4 to 8 weeks without causing problems, but infants can die in this early stage from brain swelling. About 10 to 20 years after this first phase, approximately one-third of infected people can show symptoms of the chronic* phase of Chagas disease. They may become constipated and experience trouble swallowing. The heart may become enlarged, and patients may have altered heart rhythms or heart failure leading to death.

*chronic
(KRAH-nik) means continuing for a long period of time.

How Do Doctors Diagnose Trypanosomiasis?

Because all types of trypanosomiasis are rare in the United States, it is important for people who have any symptoms of the disease to let their doctor know right away if they have been traveling in areas where the disease is common. To diagnose sleeping sickness or Chagas disease, a doctor will order blood tests to look for protozoa or antibodies* to the organism. In cases where the doctor suspects sleeping sickness, a sample drawn from fluid surrounding the brain and spinal cord or tissue from swollen lymph nodes may be examined for evidence of the disease. If a patient has a suspicious-looking skin lesion*, a biopsy* will be performed to test for Trypanosoma cruzi protozoa.

*antibodies
(AN-tih-bah-deez) are protein molecules produced by the bodys immune system to help fight specific infections caused by microorganisms, such as bacteria and viruses.
*lesion
(LEE-zhun) is a general term referring to a sore or a damaged or irregular area of tissue.
*biopsy
(BI-op-see) is a test in which a small sample of skin or other body tissue is removed and examined for signs of disease.

Can Trypanosomiasis Be Treated Successfully?

There are medications available to treat all types of the disease. Doctors recommend that people with trypanosomiasis receive treatment as soon as possible. Treatment is given in a hospital. After leaving the hospital, patients typically are watched closely by a doctor for at least 2 years, to see whether they show any signs that they still have the infection.

What Happens to People with Trypanosomiasis?

East African sleeping sickness can move through the body quickly, progressing in just weeks or months to the most serious phase of illness. West African sleeping sickness takes longer to develop. People may not reach the critical phase for months or even years. People who do not receive treatment for African trypanosomiasis can die from heart failure, and those who wait to start treatment may have permanent brain damage. Long-term complications of Chagas disease, which may not appear for 20 or more years after infection, include damage to the digestive and nervous systems, heart problems, and sudden death.

Can Trypanosomiasis Be Prevented?

There is no vaccine or medication that can prevent any form of the disease, so it is wise for people who travel in areas where the disease is common to take precautions. In Africa this includes wearing clothes of thick material, with long sleeves and long pants. Neutral colors, such as tan, are best because tsetse flies are attracted to dark and bright colors. Doctors recommend that travelers to Africa sleep under netting and avoid riding in the backs of open trucks, because dust from moving vehicles attracts the flies. It is also advisable to not walk through brush. In areas where Chagas disease is found, it is a good idea for people to avoid sleeping in mud, adobe, or thatch houses; to sleep under netting; and to use insect repellent.

See also

Leishmaniasis

Travel-related Infections

Resources

Organizations

U.S. Centers for Disease Control and Prevention (CDC), 1600 Clifton Road, Atlanta, GA 30333. The CDC publishes fact sheets on all three types of trypanosomiasis at its website.

Telephone 800-311-3435 http://www.cdc.gov

World Health Organization (WHO), Avenue Appia 20, 1211 Geneva 27, Switzerland. WHO publishes information on sleeping sickness and Chagas disease at its website.

Telephone 011-41-22-791-2111 http://www.who.int

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"Trypanosomiasis." Complete Human Diseases and Conditions. . Encyclopedia.com. 17 Aug. 2017 <http://www.encyclopedia.com>.

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"Trypanosomiasis." Complete Human Diseases and Conditions. . Retrieved August 17, 2017 from Encyclopedia.com: http://www.encyclopedia.com/medicine/encyclopedias-almanacs-transcripts-and-maps/trypanosomiasis

trypanosomiasis

trypanosomiasis (trip-ă-nŏ-sŏ-my-ă-sis) n. any disease caused by the presence of parasitic protozoans of the genus Trypanosoma. The two most important diseases are Chagas' disease (South American t.), caused by T. cruzi, and sleeping sickness (African t.), caused by T. rhodesiense or T. gambiense.

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