CDC - African Trypanosomiasis - General Information - East African Trypanosomiasis FAQs East African Trypanosomiasis FAQs To receive email updates about this page, enter your email address: Enter Email Address How can I prevent African trypanosomiasis and prevent other insect bites? What is East African trypanosomiasis? There are two types of African trypanosomiasis (also called sleeping sickness); each is named for the region of Africa in which they were found historically. East African trypanosomiasis is caused by the parasite Trypanosoma brucei rhodesiense, which is carried by the tsetse fly. Each year, a few hundred cases of East African trypanosomiasis are reported to the World Health Organization. However, many cases are not recognized or reported and the true number of new cases is higher. Since 1967, 40 cases of East African trypanosomiasis have been diagnosed or treated in the United States, all among individuals who had traveled to eastern Africa. More on: West African Trypanosomiasis FAQs How is East African trypanosomiasis spread?

A person will get East African trypanosomiasis if he or she is bitten by a tsetse fly infected with the Trypanosoma brucei rhodesiense parasite. The proportion of tsetse flies that are infected with this parasite is low. The tsetse fly is found only in rural Africa. Is East African trypanosomiasis a serious illness? Yes. If a person fails to receive medical treatment for East African trypanosomiasis, death will occur, usually within months. Where can you become infected with East African trypanosomiasis? East African trypanosomiasis is found in parts of Eastern and Southeastern Africa. More than 95% of cases are reported from Uganda, Tanzania, Malawi, and Zambia. What are the signs and symptoms of East African trypanosomiasis? A bite by the tsetse fly is often painful and can develop into a red sore, also called a chancre. Fever, severe headaches, irritability, extreme fatigue, swollen lymph nodes, and aching muscles and joints are common symptoms of sleeping sickness. Some people develop a skin rash.

Progressive confusion, personality changes, and other neurologic problems occur after infection has invaded the central nervous system. If left untreated, infection becomes worse and death will occur within months. How soon after infection will I have symptoms of East African trypanosomiasis? Symptoms usually within 1 to 3 weeks after an infective bite. Back To Top What should I do if I think I may have African trypanosomiasis? If you suspect that you may have East African trypanosomiasis, immediately consult with your health care provider, who will order several tests to look for the parasite. A skin biopsy may be done if you have a chancre. Blood tests will be done and a spinal tap may also be performed. What is the treatment for East African trypanosomiasis? Medical treatment of East African trypanosomiasis should begin as soon as possible and is based on the infected person’s laboratory results. Medication for the treatment of East African trypanosomiasis is available through CDC. Hospitalization for treatment is usually necessary. Periodic follow-up exams that include a spinal tap are required for 2 years. Once infected, am I immune to East African trypanosomiasis?

Even if you had the disease once, you can get re-infected. Who is at risk for contracting East African trypanosomiasis? Tsetse flies are found in woodland and savannah areas and they bite during daylight hours. Travelers to urban areas are not at risk. The persons most likely to be exposed to the infection are tourists, hunters, and others working in or visiting game parks. Villagers with infected cattle herds are also at risk. Can I take a medication to prevent East African trypanosomiasis? There is neither a vaccine nor recommended drug available to prevent East African trypanosomiasis. How can I prevent African trypanosomiasis and prevent other insect bites? Wear protective clothing, including long-sleeved shirts and pants. The tsetse fly can bite through thin fabrics, so clothing should be made of medium-weight material. Wear neutral-colored clothing. The tsetse fly is attracted to bright colors and very dark colors. Inspect vehicles for tsetse flies before entering. The flies are attracted to moving vehicles. Avoid bushes. The tsetse fly is less active during the hottest period of the day. It rests in bushes but will bite if disturbed.

Use insect repellant. Though insect repellants have not proven effective in preventing tsetse fly bites, they are effective in preventing other insects from biting and causing illness. Back To Top This information is not meant to be used for self-diagnosis or as a substitute for consultation with a health care provider. If you have any questions about the parasites described above or think that you may have a parasitic infection, consult a health care provider. Get Email Updates To receive email updates about this page, enter your email address: Enter Email Address Parasites - humans, examples, body, water, process, life, plants, type, form Parasites Parasites Photo by: 3drenderings A parasite is an organism that depends on another organism, known as a host, for food and shelter. As an example, tapeworms live in the digestive system of a large variety of animals. The tapeworms have no digestive system of their own, but absorb nutrients through their skin from partially digested food as it passes through the host. A parasite usually gains all the benefits of this relationship. In contrast, the host may suffer from various diseases, infections, and discomforts as a result of the parasitic attack.

In some cases, however, the host may show no signs at all of infection by the parasite. The life cycle of a typical parasite commonly includes several developmental stages. During these stages, the parasite may go through two or more changes in body structure as it lives and moves through the environment and one or more hosts. Words to Know Arthropod: A phylum of organisms characterized by exoskeletons and segmented bodies. Definitive host: The organism in which a parasite reaches reproductive maturity. Helminths: A variety of wormlike animals. Intermediate host: An organism infected by a parasite while the parasite is in a developmental form, not sexually mature. Nematodes: A type of helminth characterized by long, cylindrical bodies; commonly known as roundworms. Protozoa: Single-celled animal-like microscopic organisms that must live in the presence of water. Trematodes: A class of worms characterized by flat, oval-shaped bodies; commonly known as flukes. Vector: Any agent, living or otherwise, that carries and transmits parasites and diseases. Parasites that remain on a host's body surface to feed are called ectoparasites, while those that live inside a host's body are called endoparasites.

Parasitism is a highly successful biological adaptation. More parasitic species are known than nonparasitic ones. Parasites affect just about every form of life, including nearly all animals, plants, and even bacteria. The study of parasites Parasitology is the study of parasites and their relationships with host organisms. Throughout history, people have coped with over 100 types of parasites affecting humans. Parasites have not, however, been systematically studied until the last few centuries. With his invention of the microscope in the late 1600s, the Dutch scientist Anton von Leeuwenhoek (1632–1723) was perhaps the first person to observe microscopic parasites. As Westerners began to travel and work more often in tropical parts of the world, medical researchers had to study and treat a variety of new infections, many of which were caused by parasites. By the early 1900s, parasitology had developed as a specialized field of study. Typically, a parasitic infection does not directly kill a host. The stress placed on the organism's resources can affect its growth, ability to reproduce, and survival. This stress can sometimes lead to the host's premature death.

Parasites, and the diseases they cause and transmit, have been responsible for tremendous human suffering and loss of life throughout history. The majority of parasitic infections occur within tropical regions and among low-income populations. However, almost all regions of the world sustain parasitic species, and all humans are susceptible to infection. Infectious diseases An infectious disease, or infection, is a condition that results when a parasitic organism attacks a host and begins to multiply. As the parasite multiplies, it interferes with the normal life functions of the host more and more. The host begins to feel ill as a symptom of the parasite's invasion and activities. In many cases, the host's immune system (which fights foreign bodies in the body) may be able to respond to the parasite and destroy it. In many other cases, however, the parasitic infection may over-whelm the immune system, resulting in serious disease and even death. Until a century ago, infections were the primary means of human "population control" worldwide, often killing enormous numbers of people in epidemics of diseases such as bubonic plague and typhoid fever. Even today, infections actually cause more deaths during war and famine than do actual injuries and starvation.

Fortunately, many infectious diseases can now be treated by means of antibiotics and other drugs and by a variety of preventative methods. Almost all infections contracted by humans pass from other humans or animals. Some infections originate from outside the body, among them a cold from kissing someone with a cold; rabies from a dog bite; hepatitis B from a contaminated needle entering the bloodstream; hepatitis A from germs transferred from fingers to mouth after touching a dirty toilet seat; measles, mumps, and the flu from tiny moisture particles that exit the mouth and nose when a person sneezes, coughs, or talks; syphilis from an infected sex partner; tetanus from a soil-contaminated wound; salmonella from ingesting undercooked eggs, meat, and poultry; and many diseases ranging from the relatively innocent to the fatal—such as gastroenteritis, cholera, and dysentery—from drinking or bathing in contaminated water. Endogenous (caused by factors within the organism) infections occur when the host's resistance is lowered, perhaps by malnutrition, illness, trauma, or immune depression. Weakening of the host's immune system may permit normally harmless organisms already present in or on the host or in the environment to cause illness.

Types of parasites The major types of organisms that cause parasitic infections include species of protozoa, helminths or worms, and arthropods. Protozoa. Protozoa are single-celled organisms that carry out most of the same physiological functions as more complex organisms. More than 45,000 species of protozoa are known, many of which are parasitic. As parasites of humans, this group of organisms has historically been the cause of more suffering and death than any other category of diseasecausing organisms. Intestinal protozoa occur throughout the world. They are especially common in areas where food and water sources are subject to contamination from animal and human waste. Typically, protozoa that infect their host through water or food do so while in an inactive state, called a cyst. A cyst consists of a protozoan encased in a protective outer membrane. The membrane protects the organism as it travels through the digestive tract of a previous host. Once inside a new host, the parasite develops into a mature form that feeds and reproduces. Amebic dysentery is one of the most common parasitic diseases. It often afflicts travelers who visit tropical and subtropical regions.

The condition is characterized by diarrhea, vomiting and weakness. It is caused by a protozoan known as Entamoeba histolytica. Another protozoan that causes severe diarrhea is Giardia lamblia. This organism was originally discovered by Leeuwenhoek and has been well-publicized as a parasite that can infect hikers who drink untreated water. Other types of parasitic protozoa infect the blood or tissues of their hosts. These protozoa are typically transmitted through another organism, called a vector. A vector is an organism that carries a parasite from one host to another host. In many cases, the vector is an invertebrate, such as an insect that itself feeds on a host and then passes the protozoan on through the bite wound. Some of the most infamous of these protozoa are the ones that cause malaria and African sleeping sickness. Helminths. Helminths are wormlike organisms including nematodes (roundworms), cestodes (tapeworms), and trematodes (flukes). Leeches are also helminths and are considered ectoparasitic, since they attach themselves to the outside skin of their hosts.

One of the most infamous nematodes is Trichinella spiralis. At one stage of its life cycle, this nematode lives in the muscle tissue of animals, including swine. Eventually, these organisms make their way into the intestinal tissue of humans who happen to ingest infected, undercooked pork. The largest parasitic roundworm, common among humans living in tropical developing countries, is Ascaris lumbricoides. This roundworm can grow to a length of 35 centimeters (15 inches) within the small intestine of its host. A parasitic roundworm that affects dogs is Dirofilaria immitus, or heartworm. This worm infects the heart tissues and eventually weakens A liver fluke seen from above. There are more than 6,000 species of parasitic flatworms. (Reproduced by permission of JLM Visuals .) the cardiac (heart) muscles to the point of failure. If left untreated, heart-worm can kill a dog. Tapeworms are a class of worms characterized by their flat, segmented bodies. The segments hold both male and female reproductive organs, allowing self-fertilization.

Segments that contain fertilized eggs break off or dissolve, passing the eggs out of the host. Adult tapeworms typically reside in the intestinal tract of vertebrates, attaching themselves to the stomach lining with hooks or suckers on their head. Common tapeworms that attack humans are Taenia saginata, Taenia solium, and Diphyllobothrium latum. These parasites use intermediate hosts, such as cattle, swine, and fish respectively, before entering the human body. Parasites such as these infect an intermediate host organism while in a early developmental form. But they do not grow to maturity until they have been transmitted to the final host. In the case of Taenia species, for example, tapeworm eggs are passed into cattle or swine through infected soil. They develop into an intermediary Entwined pair of male and female schistosomes. Adult pairs live in the small veins of human hosts, where the female produces about 3,500 eggs per day. (Reproduced by permission of Phototake .) stage that embeds in the muscle and connective tissue of the animal.

Infected animals that are processed for meat but improperly cooked still harbor the parasite, which are passed on when consumed by humans. The tapeworms develop into adults that attach to the intestinal lining of the host. Trematodes, or flukes, are another class of helminths that have parasitic species. Adult flukes are typically flat, oval-shaped worms that have a layer of muscles just below the skin. These muscles allow the worm to expand and contract its shape and, thus, move its body. Flukes usually have an oral sucker, sometimes ringed with hooks. They use the sucker to attach themselves to the host's tissues. Some of the most infamous flukes are species of the genus Schistosoma that cause the often-fatal disease known as schistosomiasis. These flukes infect human hosts directly by burrowing into the skin of a person wading or swimming in infected water. One species, S. mansoni, enters the bloodstream as an immature worm and can be carried through various organs, including the lungs and heart, before maturing in the liver. Arthropods. Arthropods are organisms characterized by exterior skeletons and segmented bodies. Examples include the crustaceans, insects, and arachnids.

The arthropods are the most diverse and widely distributed animals on the planet. Many arthropod species serve as carriers of bacterial and viral diseases, as intermediate hosts for protozoan and helminth parasites, and as parasites themselves. Certain insect species are the carriers of some of humanity's most dreaded diseases, including malaria, typhus, and plague. As consumers of agricultural crops and parasites of our livestock, insects are also humankind's number-one competitor for resources. Mosquitoes are the most notorious carriers of disease and parasites. Female mosquitoes rely on warm-blooded hosts to serve as a blood meal to nourish their eggs. During the process of penetrating a host's skin with their long, sucking mouth parts, saliva from the mosquito is transferred into the bite area. Any viral, protozoan, or helminth infections carried in the biting mosquito can be transferred directly into the blood stream of its host. Among these diseases are malaria, yellow fever, filariasis, elephantiasis, and heartworm. Flies also harbor diseases that can be transmitted to humans and other mammals when they bite to obtain a blood meal for themselves.

For example, black flies can carry Onchocerciasis (which causes river blindness), sandflies can carry leishmaniasis and kala-azar, and tsetse flies can carry the trypanosomes that cause sleeping sickness. Livestock, such as horses and cattle, can be infected with a variety of botflies and warbles that infest and feed on the skin, throat, nasal passages, and stomachs of their hosts. Fleas and lice are two of the most common and irritating parasitic insects of humans and livestock. Lice commonly live among the hairs of their hosts, feeding on blood. Some species are carriers of typhus fever. Fleas usually infest birds and mammals, and can feed on humans when they are transferred from pets or livestock. Fleas are known to carry a variety of devastating diseases, including the plague. Another prominent class of arthropods that contains parasitic species is the arachnids. Included in this group are spiders, scorpions, ticks, and mites. Mites are very small arachnids that infest both plants and animals. One common type of mite is the chigger, which lives in grasses.

As larvae, they may grab onto passing animals and attach themselves to the skin, often leading to irritating rashes or bite wounds. Scabies are another A photo of a flea magnified 50 times. Fleas are common parasitic insects that are known to carry a variety of devastating diseases, including the plague. (Reproduced by permission of The Stock Market .) mite that causes mange in some mammals by burrowing into the skin and producing severe scabs, lesions, and loss of hair. Ticks also live their adult lives among grasses and short shrubs. They are typically larger than mites. The adult female tick attaches itself to an animal host for a blood meal. Tick bites themselves can be painful and irritating. More importantly, ticks can carry a number of diseases that affect humans. The most common of these diseases include Rocky Mountain spotted fever, Colorado tick fever, and Lyme disease. Control of parasites Many parasitic infections can be treated by a variety of medical procedures, such as the use of antibiotics. The best way of controlling infection, however, is prevention. Scientists have developed and continue to test a number of drugs that can be taken as a barrier to certain parasites.

Other measures of control include improving sanitary conditions of water and food sources, proper cooking techniques, education about personal hygiene, and control of intermediate and vector host organisms. What is a Parasite? What do Parasites do? - Medical News Today What is a Parasite? What do Parasites do? Written by Christian Nordqvist 4.5 133 2 A parasite is an organism that lives in another organism, called the host, and often harms it. It is dependent on its host for survival - it has to be in the host to live, grow and multiply. A parasite cannot live independently. Although a parasite rarely kills the host, in some cases it can happen. To a certain extent, if a parasite does kill its host it has failed as this means it will need to find a new home. The parasite benefits at the expense of the host - the parasite uses the host to gain strength, and the host loses some strength as a result. Contents of this article: Fast facts on parasites Here are some key points about parasites. More detail and supporting information is in the main article.

Parasites live within other organisms and thrive to the detriment of their host Malaria is caused by a parasite There are at least 1,000 species of parasite capable of living in or on humans Parasites that live on the surface of their hosts are known as ectoparasites Sleeping sickness is caused by a parasite transmitted by the tsetse fly Some parasitic worms can grow to over 30 m in length Epiparasites are parasites that live on other parasites Babesiosis is a parasitic disease that affects the red blood cells Trichomonas vaginalis is a sexually transmitted parasite Humans can become infected with clonorchiasi after ingesting contaminated ants. What is a parasite? Malaria is caused by a Plasmodium parasite. The word "parasite" comes from the Greek "parasitos", with para meaning "alongside", and sitos meaning "food" - therefore meaning "eating at the side of, as one would when seated at the same table". It was in the 18th century that the word parasite entered the English language as a biologic term; before that it referred to humans, such as a relative or friend who lived at the expense of another person.

In general, a parasite is an organism that live within another, using the resources of the host to fuel its life cycle. Parasites are an incredibly varied group of organisms. Around 70% of parasites are microscopic in size, such as the malarial parasite; however, some worm parasites can reach over 30 m in length. There are three main types of parasitic diseases: Protozoa: a single-celled organism. Plasmodium, which causes malaria, is an example. A protozoa can only multiply (divide) within the host Helminths: worm parasites. Schistosomiasis is caused by a helminth. Other examples include roundworm, pinworm, trichina spiralis, tapeworm , and fluke Ectoparasites: these live on, rather than in their hosts, these include lice and fleas. Parasites, unlike predators, are usually much smaller than their host and they reproduce at a faster rate. Symptoms of parasitic diseases Because there are so many species of parasite there is a wide array of potential symptoms. Sometimes the symptoms may appear similar to hormone deficiency, pneumonia or food poisoning .

These are some of the potential symptoms that might occur: Itchy anus or vagina Types of parasite There are over 1,000 known parasite species that can infect humans. These are some examples: Endoparasite: live inside the host (as opposed to ectoparasites), examples include heartworm, tapeworm, and flatworms. Those that inhabit the spaces within the host's body are called intercellular parasites, while an intracellular parasite live within the host's cells. Intracellular parasites include bacteria and viruses; they rely on a third organism, known as the vector (carrier). The vector transmits the endoparasite to the host. The mosquito is a vector for many parasites including the protozoan of the genus Plasmodium that causes malaria. Epiparasite: these feed on other parasites, a relationship known as hyperparasitism. A flea which lives on a dog may have a protozoan in its digestive tract, the protozoan is the hyperparasite. Parasitoid: the larval development takes place in or on another organism, the host usually dies. In this case there are characteristics of predation, because the host dies.

Human parasites Head lice are called ectoparasites because they live on the exterior of their host. Acanthamoeba: (Acanthamoeba). Affects the eye and/or brain. It exists all over the world. Individuals can become infected if they clean contact lenses with tap water. Babesiosis: (Babesia B. divergens, B. bigemina, B. equi, B. microfti, B. duncani). Affects the red blood cells. Different species live in various parts of the world. Transmitted by tick bites. Balantidiasis: (Latin name: Balantidium coli). Lives in the intestinal mucosa. Blastocystosis: (Blastocystis). Affects the intestines. Enters humans through ingested food contaminated with human/animal feces. Coccidia: (Cryptosporidium). Affects the intestines. Exists worldwide. Enters humans through ingested food contaminated with human/animal feces. Amoebiasis: (Entamoeba histolytica). Affects the intestines. More likely in areas with high population density, poor sanitation, and tropical regions.

Fecal oral transmission. Giardia: (Giardia lamblia). Affects the lumen of the small intestine. If humans ingest food/water contaminated with feces, dormant cysts may infect the body. Isosporiasis: (Isospora belli). Affects the epithelial cells of the small intestine. Exists all over the world. Fecal oral route. Leishmaniasis: (Leishmania) - Affects the skin and/or viscera. Exists worldwide in various forms. Transmitted by types of sandflies. Primary amoebic meningoencephalitis: (PAM) - (Naegleria fowleri). Affects the brain. Insufflation of contaminated soil, swimming pools and contaminated water. Malaria: (Plasmodium falciparum (80% of cases), Plasmodium vivax, Plasmodium ovale, Plasmodium malariae. Affects the red blood cells. Exists in tropical regions. Transmitted by the anopheles mosquito. Rhinosporidiosis: (Rhinosporidium seeberi). Affects the nose and nasopharynx. Exists in India and Sri Lanka.

People who are bathing in common ponds can become contaminated when the nasal mucosa is in contact with infected material. Toxoplasmosis - Parasitic pneumonia: (Toxoplasma gondii). Affects the liver, heart, eyes and brain. Widespread worldwide. People can become infected after ingesting raw/undercooked pork, lamb, goat or milk. Also may exist in contaminated food or soil with cat feces. Trichomoniasis: (Trichomonas vaginalis). Affects the female urogenital tract. Can exist in males, but without symptoms. This is an STI ( sexually transmitted infection ). Sleeping sickness: (Trypanosoma brucei). Affects the central nervous system , blood and lymph. Transmitted by the tsetse fly. Chagas disease: (Trypanosoma cruzi). Affects the blood, muscle, nerves, heart, esophagus and colon. Transmitted through an insect bite. On the next page, we look at helminth organisms and ectoparasites. What is African sleeping sickness? | Facts | yourgenome.org In: Facts Targeting Disease What is African sleeping sickness?

African trypanosomiasis is a parasitic disease transmitted by the tsetse fly. It gets its nickname ‘sleeping sickness’ because symptoms can include a disturbed sleep pattern. What is trypanosomiasis? Trypanosomiasis refers to a group of diseases caused by Trypanosoma parasites . There are two types of trypanosomiasis that affect humans, they are divided according to their geographical location: African trypanosomiasis, or sleeping sickness, is caused by Trypanosoma brucei parasites in sub-Saharan Africa and is transmitted by the tsetse fly (Glossina). American trypanosomiasis, or Chagas disease, is caused by Trypanosoma cruzi parasites in Latin America and is transmitted by the triatomine or ‘kissing’ bug. Trypanosomiasis can also affect animals. Nagana disease is a form of trypanosomiasis that affects vertebrate animals such as cattle. It is caused by several kinds of Trypanosoma including Trypanosoma brucei and Trypanosoma vivax.

Animals, such as wild game and domestic animals, can also act as a reservoir host for the human trypanosome parasites. While wild animals are mostly tolerant to the disease, for domestic animals, the infection can be severe and sometimes fatal. Scanning electron micrograph (SEM) of a Trypanosoma brucei parasite. Image credit: Gull Lab courtesy of Sue Vaughan, Wellcome Images What is human African trypanosomiasis (sleeping sickness)? African trypanosomiasis occurs in 36 countries in sub-Saharan Africa. Around 10,000 new cases of African trypanosomiasis are reported each year. However, it is estimated that many cases go undiagnosed. African trypanosomiasis is caused by two species of Trypanosoma brucei: Trypanosoma brucei gambiense (West African) and Trypanosoma brucei rhodesiense (East African). Trypanosoma brucei gambiense is responsible for more than 98 per cent of all reported cases of human African trypanosomiasis and causes chronic infection.

Trypanosoma brucei rhodesiense is responsible for under 2 per cent of all reported cases of human African trypanosomiasis and causes acute infections that develop rapidly over a few weeks. Another type of trypanosome, Trypanosome brucei brucei, does not affect humans. How is African trypanosomiasis transmitted? Both species of Trypanosoma are transmitted from human to human through the bite of the tsetse fly (Glossina) which is only found in rural parts of Africa. However, trypanosomes can also be transmitted from mother to child as the parasite can cross the placenta in the blood and infect the baby while it is still in the womb . Contaminated needles can also contribute to the spread of trypanosomes, but this is rare. Communities most at risk of trypanosomiasis live in rural areas where the tsetse fly is found. These communities often depend primarily on agriculture, fishing and hunting to survive and have limited access to health services and education. As a result, many cases of trypanosomiasis go undiagnosed. The tsetse fly.

Image credit: Wellcome Library, London Trypanosome life cycle The trypanosome parasite is first introduced into the mammalian host when a tsetse fly takes a blood meal and secretes parasite-filled saliva into the host’s skin. At this stage of the life cycle the parasites are in their infective form, called metacyclic trypomastigotes, which have a short, free flagellum . Once in the bloodstream, the parasites transform into slender trypomastigotes with a longer flagellum which then spread rapidly to other areas of the body in the blood. The trypomastigotes multiply in the blood, lymph or spinal fluid . In the mammalian bloodstream, the trypomastigotes have different forms: a long slender form a short, stumpy form an intermediate form between the two. The short stumpy form is pre-adapted for survival in the tsetse fly so is the form that differentiates into the next stage of the life cycle when the fly takes a blood meal from an infected mammalian host.

Once inside the midgut of the tsetse fly, the trypomastigotes transform into procyclic trypomastigotes, which multiply in the gut. After multiplying, the procyclic trypomastigotes move to the front (anterior) of the midgut en route to the tsetse fly’s salivary gland. On this journey, the procyclic trypomastigotes then develop into epimastigotes which migrate to the tsetse fly’s salivary gland and attach to the wall of the gland by their flagella. Finally, the epimastigotes transform into short, infective metacyclic trypomastigotes and detach from the wall of the salivary gland, ready to be injected into a new host when the fly takes another blood meal. Illustration of the life cycle of the trypanosome parasite that causes African sleeping sickness. Image credit: Genome Research Limited What are the symptoms of African trypanosomiasis?

The symptoms of African trypanosomiasis are divided into two key stages: First stage or haemolymphatic phase: shortly after the metacyclic trypomastigotes enter the body and multiply under the skin an inflammatory reaction occurs. This causes swelling of the skin and enlargement of the lymph nodes in the neck. This immune response results in symptoms such as fever, headaches, joint pains and itching. Second stage or neurological phase: this stage begins when the trypanosome parasites cross from the blood-brain barrier into the spinal fluid, infecting the central nervous system including the brain. Once the brain is affected it results in changes in behaviour, confusion, poor coordination, difficulties with speech and disturbance of sleep (sleeping through the day and insomnia at night), hence the term ‘sleeping sickness’. Without treatment, African trypanosomiasis is fatal. Screening and diagnosis of African trypanosomiasis Diagnosis of African trypanosomiasis must be made as early as possible to prevent the disease from progressing into the second stage. Trypanosomiasis is a disease of rural areas, where there is limited access to medical help or education about the symptoms to look out for.

As a result many sufferers go undiagnosed and consequently do not receive the treatment they need. To try and avoid this happening, screening programmes have been put in place for some at-risk populations. Screening involves two steps: Checking for clinical signs, such as swollen lymph glands in the neck and neurological signs such as an altered mental state or extended daytime sleeping. Examining blood smears for signs of the parasite. Blood smear taken from an individual with trypanosomiasis (pink circles are red blood cells; purple swirls are trypanosome parasites). Image credit: CDC/Dr. Myron G. Schultz. Centers for Disease Control and Prevention's Public Health Image Library (PHIL) #613 If these tests are inconclusive, individuals may have a blood test for specific antibodies that signify the parasite is present. If these test results come back positive and show that an individual has trypanosomiasis then there is a further assessment to find out which stage the disease has progressed to. This involves taking a sample of spinal fluid via a lumbar puncture and examining the sample for parasites. If parasites are present this indicates that the disease has progressed to the neurological phase.

Screening of at-risk populations is a major investment, both in terms of the number of people needed to do them and the materials required (which are often scarce in the areas of Africa where trypanosomiasis is found). However, it is a necessary investment as many people infected with trypanosomiasis are undiagnosed and do not receive treatment. This increases the level of transmission and could eventually lead to the disease reaching epidemic levels. There have been several epidemics of trypanosomiasis in Africa over the last century. In 1920, an epidemic was controlled as a result of screening millions of people at risk. This resulted in less than 5,000 cases of the disease by the mid-1960s. However, as a result of this success, screening was relaxed. The disease soon started to reappear again in several areas, highlighting the need for ongoing surveillance. How is trypanosomiasis treated? Trypanosomiasis is curable if treatment is given quickly, however if left untreated the disease is fatal. The type of treatment given depends on the stage of the disease. Generally, the earlier the disease is identified, the easier it is to treat.

The drugs that are used to treat trypanosomiasis when it is in the first stage of the disease, generally have milder side effects and are easier to administer, usually in the form of a series of injections. Once in the second stage of the disease, when the parasite has crossed the blood-brain barrier, treatment becomes much more aggressive with more toxic drugs needed to kill the parasite. These drugs are also more complicated to administer, usually requiring several weeks of drugs being given intravenously (directly into the veins). Currently, four drugs are registered for treating African trypanosomiasis and are administered free of charge to countries where the disease is a problem. These include: Pentamidine – used to treat first stage Trypanosoma brucei gambiense, it generally has no adverse side effects. Suramin – used to treat first stage Trypanosoma brucei rhodesiense, it causes some side effects such as urinary tract infections and allergic reactions. Melarsoprol – used to treat second stage Trypanosoma brucei rhodesiense. It is derived from arsenic and has many unwanted side effects.

In extreme cases, it has been seen to cause reactive encephalopathy (disorder of the brain) which can be fatal. There has also been a spread of resistance to melarsoprol in trypanosomes found in central Africa. Eflornithine – originally developed as an anti- cancer drug, it is used to treat second stage Trypanosoma brucei gambiense. It is less toxic than melarsoprol but can cause vomiting, diarrhoea and anaemia . How can trypanosomiasis be prevented? There is currently no vaccine or preventative drug to help protect against African trypanosomiasis. Prevention is therefore generally aimed at minimising contact with the tsetse fly vector . Measures include: wearing long-sleeved shirts and long trousers to limit the amount of exposed skin wearing clothes in neutral colours as tsetse flies are attracted to bright colours avoiding bushes where the tsetse fly rest during the hottest part of the day as they will bite if disturbed using insect repellent such as DEET.

Control of African trypanosomiasis currently centres around two key strategies: Population screening to ensure early treatment of infected people and help reduce the number of people carrying trypanosomiasis. Fewer people carrying the parasite means the tsetse fly is less likely to become infected when they take a blood meal and less likely to pass the parasite on to another individual at their next blood meal. Reducing transmission via the tsetse fly by using insecticides to kill the insect and deploying fly traps and/or screens in homes to reduce the number of flies entering. Insecticidal spraying against tsetse fly in Nigeria. Image credit: Wellcome Library, London WHO | Trypanosomiasis, human African (sleeping sickness) Trypanosomiasis, human African (sleeping sickness) Updated February 2016 Key facts Sleeping sickness occurs in 36 sub-Saharan Africa countries where there are tsetse flies that transmit the disease. The people most exposed to the tsetse fly and therefore the disease live in rural areas and depend on agriculture, fishing, animal husbandry or hunting.

Human African trypanosomiasis takes 2 forms, depending on the parasite involved: Trypanosoma brucei gambiense accounts for more than 98% of reported cases. Sustained control efforts have reduced the number of new cases. In 2009 the number reported dropped below 10 000 for the first time in 50 years, and in 2014 there were 3796 cases recorded. Diagnosis and treatment of the disease is complex and requires specifically skilled staff. Definition of the disease Human African trypanosomiasis, also known as sleeping sickness, is a vector-borne parasitic disease. It is caused by infection with protozoan parasites belonging to the genus Trypanosoma. They are transmitted to humans by tsetse fly (Glossina genus) bites which have acquired their infection from human beings or from animals harbouring human pathogenic parasites. Tsetse flies are found just in sub-Saharan Africa though only certain species transmit the disease. For reasons that are so far unexplained, in many regions where tsetse flies are found, sleeping sickness is not.

Rural populations living in regions where transmission occurs and which depend on agriculture, fishing, animal husbandry or hunting are the most exposed to the tsetse fly and therefore to the disease. The disease develops in areas ranging from a single village to an entire region. Within an infected area, the intensity of the disease can vary from one village to the next. Forms of human African trypanosomiasis Human African trypanosomiasis takes 2 forms, depending on the parasite involved: Trypanosoma brucei gambiense is found in 24 countries in west and central Africa. This form currently accounts for over 98% of reported cases of sleeping sickness and causes a chronic infection. A person can be infected for months or even years without major signs or symptoms of the disease. When more evident symptoms emerge, the patient is often already in an advanced disease stage where the central nervous system is affected. Trypanosoma brucei rhodesiense is found in 13 countries in eastern and southern Africa. Nowadays, this form represents under 2% of reported cases and causes an acute infection. First signs and symptoms are observed a few months or weeks after infection.

The disease develops rapidly and invades the central nervous system. Only Uganda presents both forms of the disease, but in separate zones. Another form of trypanosomiasis occurs mainly in Latin America. It is known as American trypanosomiasis or Chagas disease. The causal organism belongs to a different Trypanosoma subgenus and is transmitted by a different vector. Animal trypanosomiasis Other parasite species and sub-species of the Trypanosoma genus are pathogenic to animals and cause animal trypanosomiasis in wild and domestic animals. In cattle the disease is called Nagana. Trypanosomiasis in domestic animals, particularly in cattle, is a major obstacle to the economic development of affected rural areas. Animals can host the human pathogen parasites, especially T.b. rhodesiense, of which domestic and wild animals are an important reservoir. Animals can also be infected with T.b. gambiense and act as a reservoir to a lesser extent. However the precise epidemiological role of the animal reservoir in the gambiense form of the disease is not yet well known.

Major human epidemics There have been several epidemics in Africa over the last century: one between 1896 and 1906, mostly in Uganda and the Congo Basin; one in 1920 in a number of African countries; and the most recent epidemic started in 1970 and lasted until the late 1990s. The 1920 epidemic was controlled thanks to mobile teams which carried out the screening of millions of people at risk. By the mid-1960s, the disease was under control with less than 5000 cases reported in the whole continent. After this success, surveillance was relaxed, and the disease reappeared, reaching epidemic proportions in several regions by 1970. The efforts of WHO, national control programmes, bilateral cooperation and nongovernmental organizations (NGOs) during the 1990s and early 21st century reversed the curve. Since the number of new human African trypanosomiasis cases reported between 2000 and 2012 dropped by 73%, the WHO neglected tropical diseases roadmap targeted its elimination as a public health problem by 2020.

Disease burden Sleeping sickness threatens millions of people in 36 countries in sub-Saharan Africa. Many of the affected populations live in remote rural areas with limited access to adequate health services, which complicates the surveillance and therefore the diagnosis and treatment of cases. In addition, displacement of populations, war and poverty are important factors that facilitate transmission. In 1998, almost 40 000 cases were reported, but estimates were that 300 000 cases were undiagnosed and therefore untreated. During the most recent epidemic the prevalence reached 50% in several villages in Angola, the Democratic Republic of the Congo, and South Sudan. Sleeping sickness was the first or second greatest cause of mortality in those communities, even ahead of HIV/AIDS. In 2009, after continued control efforts, the number of cases reported dropped below 10 000 (9878) for the first time in 50 years. This decline in number of cases has continued with 3796 new cases reported in 2014, the lowest level since the start of systematic global data-collection 75 years ago.

The estimated number of actual cases is below 20 000 and the estimated population at risk is 65 million people. Current disease distribution The disease incidence differs from one country to another as well as in different parts of a single country. In the last 10 years, over 70% of reported cases occurred in the Democratic Republic of the Congo (DRC). The DRC is the only country that currently reports more than 1000 new cases annually and accounts for 85% of the cases reported in 2014. Central African Republic is the only country that declared between 100 and 200 new cases in 2014. Countries such as Angola, Burkina Faso, Cameroon, Chad, Congo, Côte d'Ivoire, Gabon, Guinea, Malawi, South Sudan, Uganda, United Republic of Tanzania, Zambia and Zimbabwe are reporting fewer than 100 new cases per year.

Countries like Benin, Botswana, Burundi, Equatorial Guinea, Ethiopia, Gambia, Ghana, Guinea Bissau, Kenya, Liberia, Mali, Mozambique, Namibia, Niger, Nigeria, Rwanda, Senegal, Sierra Leone, Swaziland and Togo have not reported any new cases for over a decade. Transmission of the disease seems to have stopped in some of these countries but there are still some areas where it is difficult to assess the exact situation because the unstable social circumstances and/or difficult accessibility hinder surveillance and diagnostic activities. Infection and symptoms The disease is mostly transmitted through the bite of an infected tsetse fly but there are other ways in which people are infected: Mother-to-child infection: the trypanosome can cross the placenta and infect the fetus. Mechanical transmission through other blood-sucking insects is possible, however, it is difficult to assess its epidemiological impact. Accidental infections have occurred in laboratories due to pricks with contaminated needles. Transmission of the parasite through sexual contact has been documented. In the first stage, the trypanosomes multiply in subcutaneous tissues, blood and lymph.

This is also called haemo-lymphatic stage, which entails bouts of fever, headaches, joint pains and itching In the second stage the parasites cross the blood-brain barrier to infect the central nervous system. This is known as the neurological or meningo-encephalic stage. In general this is when more obvious signs and symptoms of the disease appear: changes of behaviour, confusion, sensory disturbances and poor coordination. Disturbance of the sleep cycle, which gives the disease its name, is an important feature. Without treatment, sleeping sickness is considered fatal although cases of healthy carriers have been reported. Disease management: diagnosis Disease management is made in 3 steps: Screening for potential infection. This involves using serological tests (only available for T.b.gambiense) and checking for clinical signs - especially swollen cervical lymph nodes. Diagnosing by establishing whether the parasite is present in body fluids. Staging to determine the state of disease progression. This entails examining the cerebrospinal fluid obtained by lumbar puncture. Diagnosis must be made as early as possible to avoid progressing to the neurological stage in order to elude complicated and risky treatment procedures The long, relatively asymptomatic first stage of T. b.

gambiense sleeping sickness is one of the reasons why an exhaustive, active screening of the population at risk is recommended, in order to identify patients at an early stage and reduce transmission by removing their status of reservoir. Exhaustive screening requires a major investment in human and material resources. In Africa such resources are often scarce, particularly in remote areas where the disease is mostly found. As a result, some infected individuals may die before they can ever be diagnosed and treated. Treatment The type of treatment depends on the disease stage. The drugs used in the first stage are safer and easier to administer than those for second stage. Also, the earlier the disease is identified, the better the prospect of a cure. The assessment of treatment outcome requires follow up of the patient up to 24 months and entails laboratory exams of body fluids including cerebrospinal fluid obtained by lumbar puncture, as parasites may remain viable for long periods and reproduce the disease months after treatment. Treatment success in the second stage depends on drugs that cross the blood-brain barrier to reach the parasite. Such drugs are toxic and complicated to administer. In total five different drugs are used for the treatment of sleeping sickness. These drugs are donated to WHO by manufacturers and distributed free of charge to disease endemic countries.

Drugs used in first stage treatment: Pentamidine: discovered in 1940, used for the treatment of the first stage of T.b. gambiense sleeping sickness. Despite non-negligible undesirable effects, it is in general well tolerated by patients. Suramin:: discovered in 1920, used for the treatment of the first stage of T.b. rhodesiense. It provokes certain undesirable effects, including urinary tract and allergic reactions. Drugs used in second stage treatment: Melarsoprol: discovered in 1949, it is used for the treatment of both gambiense and rhodesiense infections. It is derived from arsenic and has many undesirable side effects, the most dramatic of which is reactive encephalopathy (encephalopathic syndrome) which can be fatal (3% to 10%). An increase in resistance to the drug has been observed in several foci, particularly in central Africa. It is currently recommended as first-line treatment for the rhodesiense form, and as second-line for the gambiense form. Eflornithine: this molecule, less toxic than melarsoprol, was registered in 1990.

It is only effective against T.b. gambiense. The regimen is complex and difficult to apply. Nifurtimox: A combination treatment of nifurtimox and eflornithine was introduced in 2009. It simplifies the use of eflornithine by reducing the duration of treatment and the number of IV perfusions, but unfortunately it has not been studied for T.b. rhodesiense. Nifurtimox is registered for the treatment of American trypanosomiasis but not for human African trypanosomiasis. Nevertheless, after safety and efficacy data provided by clinical trials, its use in combination with eflornithine has been included in the "WHO List of Essential Medicines" and is currently recommended as first-line treatment for the gambiense form. Both drugs are provided free of charge by WHO to endemic countries with a kit containing all the material needed for its administration.

Public private partnership In 2000 and 2001, WHO established public-private partnerships with Aventis Pharma (now Sanofi) and Bayer HealthCare which enabled the creation of a WHO-led control and surveillance programme, providing support to endemic countries in their control activities and the supply of medicines free of charge. The partnership was renewed in 2006, 2011 and 2016. The success in curbing the number of sleeping sickness cases has encouraged other private partners to sustain the WHO’s initiative towards eliminating the disease as a public health problem. WHO response WHO provides support and technical assistance to national control programmes. WHO provides the anti-trypanosome medicines free of charge to endemic countries through public-private partnerships with Sanofi (pentamidine, melarsoprol and eflornithine) and with Bayer HealthCare (suramin and nifurtimox). The conditioning and shipment of medicines is done in collaboration with MSF-Logistics. In 2009, WHO set up a biological specimens bank that is available to researchers to facilitate the development of new and affordable diagnostic tools.

The bank contains samples of blood, serum, cerebrospinal fluid, saliva and urine from patients infected with both forms of the disease as well as samples from uninfected people from areas where the disease is endemic. In 2014 a coordination network for human African trypanosomiasis was established under WHO leadership to ensure strengthened and sustained efforts to eliminate the disease. The stakeholders include national sleeping sickness control programmes, groups developing new tools to fight the disease, international and non-governmental organizations, and donors. The objectives of the WHO programme are to: strengthen and coordinate control measures and ensure field activities are sustained; strengthen surveillance systems; ensure accessibility to the diagnosis and the best treatment available; support the monitoring of treatment and drug resistance; develop an information database for epidemiological analysis, including the atlas of the human African trypanosomiasis, completed in collaboration with the Food and Agriculture Organization (FAO); ensure skilled staff by offering training activities; support operational research to improve diagnostic and treatment tools; promote collaboration with the FAO in charge of animal trypanosomiasis and the International Atomic Energy Agency (IAEA) dealing with vector control through male flies made sterile by radiation.

The 3 UN agencies along with the African Union have promoted the Programme Against African Trypanosomiasis (PAAT); synergize vector and disease control activities in collaboration with the Pan African Tsetste and Trypanosomosis Eradication Campaign (PATTEC) of the African Union. For more information contact:

Question: Which insect is the host of the parasitic organism that causes sleeping sickness?
Answer: TSETSE FLY