Facts On Infection & Risk Factors For African Trypanosomiasis

October 16, 2023

African trypanosomiasis is a disease caused by the parasitic invasion of various systems in the body. The disease is also called sleeping sickness because it causes disturbances to the sleep cycle. The bite of an infected tsetse fly is the primary cause of transmission. The tsetse fly, which is only found in sub-Saharan Africa, harbors Trypanosoma brucei parasites that spread through your blood after a bite.

There are two forms of the disease, Trypanosoma brucei gambiense (TbG) and Trypanosoma brucei rhodesiense (TbR). TbR is the more severe form, but it accounts for less than two percent of reported cases. Symptoms of TbR can appear one to three weeks after transmission, while patients with TbG can remain asymptomatic for months or years. Treating African trypanosomiasis in the early stages is imperative, as if it's left untreated, the infection can progress and spread to the central nervous system and cause extensive damage.

Locations Of Possible Infection

Locations of possible infections include the circulatory, lymphatic, and central nervous systems. The disease has two phases that occur in different parts of the body. The first phase occurs in the lymphatic and circulatory systems and is called the haemo-lymphatic stage. The parasites cause severe swelling of the lymph nodes, especially along the back of the neck. Other early symptoms include intermittent fevers, joint pain, skin irritation, headaches, and a red nodule at the site of the bite.

The second and more severe phase is called the neurological or meningo-encephalic stage. This stage starts when the parasites cross the blood-brain barrier and invade the central nervous system. Signs of this phase include changes in behavior, muscle weakness, and daytime sleepiness. Disruption of the sleep cycle is the main symptom of the second stage. The neurological damage caused during this stage is irreversible. Without treatment, the disease typically overcomes the body's defenses and causes mental deterioration and organ failure. African trypanosomiasis is typically fatal if left untreated.

Individuals At Highest Risk

African trypanosomiasis occurs in many regions of sub-Saharan Africa on a regular basis. There are over seventy million individuals living in thirty-seven countries at risk of contracting the disease. Approximately one-third of these individuals are at a moderate to high risk of infection. Risk factors include living in an area where the tsetse fly is found and being bitten by the flies. TbG is found in twenty-four countries in west and central Africa, while TbR is found in thirteen countries in eastern and southern Africa. Uganda is the only country with both forms of the disease.

Anyone traveling to these areas is at risk of contracting African trypanosomiasis. Individuals at highest risk for this condition are those who live in rural areas and work outdoors in occupations like fishing, hunting, farming, and breeding farm animals. These are areas where transmission occurs more frequently because of increased exposure to infected tsetse flies.

How Infection Is Transmitted

Individuals can become infected with African trypanosomiasis in a few ways, but it's mainly transmitted through the bite of an infected tsetse fly. The infection can be transmitted from mother to child while the baby is in utero. The trypanosome parasite can cross the placenta and infect the fetus. Accidental transmissions from handling contaminated blood in a laboratory have occurred but are uncommon. Transmission of the parasite is also possible through sexual contact or a blood transfusion. There is some evidence of other types of flies or other blood-sucking insects playing a role in transmission, but these modes are difficult to assess.

The communities that are most at risk usually have limited access to health care and education about how infection is transmitted. As a result, many cases go undiagnosed. African trypanosomiasis can develop in a single village or an entire region, with varying levels of intensity. War, poverty, and displacement of populations are other factors that facilitate transmission.

Extent Of Cases Of Infection

The extent of cases of infection stretches across thirty-seven countries in sub-Saharan Africa. It's estimated that hundreds of thousands of cases of African trypanosomiasis have gone undiagnosed and untreated since the start of data collection. The Democratic Republic of Congo has the highest number of cases of African trypanosomiasis in the world, which is about seventy-five percent of all TbG infections. Southeast Uganda and western Kenya lost over forty-eight thousand residents to the disease in 2008 and infections are still a regular occurrence in these areas. The number of infections dropped significantly by 2009 however, with less than ten thousand cases being reported.

The World Health Organization reported 3,797 cases of African trypanosomiasis in 2014 and 2,804 new cases in 2015. The estimated number of actual cases during this time was actually closer to twenty thousand. The disease caused about 3,500 deaths in 2015. African trypanosomiasis was one of the leading causes of death in parts of Angola, the Democratic Republic of the Congo, and South Sudan. The number of new cases of infection has declined drastically, and eradication of the disease is expected by the year 2020 according to the World Health Organization.


There have been several outbreaks of African trypanosomiasis over the last hundred years. The first occurred mainly in Uganda and the Congo Basin from 1896 to 1906. An outbreak took place in Uganda in 1901 and killed approximately two-thirds of the population in certain areas. The death toll was more than 250,000 individuals. Other estimates reported almost half the citizens in the region surrounding the banks of the lower river Congo died during this time as a result of the disease and smallpox.

Another epidemic took place in 1920 throughout several African countries. It was eventually brought under control by mobile teams who performed screenings of at-risk populations, which numbered in the millions. Less than five thousand cases were reported in the entire continent by the mid-1960s. The most recent outbreak happened in several regions of the continent. It began sometime in 1970 and lasted almost thirty years. The infection rate was ultimately brought under control by the World Health Organization and other organizations throughout the 1990s and early part of the twenty-first century.

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