African trypanosomiasis

African trypanosomiasis is a serious parasitic infection that affects humans and animals.

It is commonly known as sleeping sickness due to the way it disrupts sleep patterns. The disease is caused by microscopic organisms called Trypanosoma brucei. This infection is classified as a neglected tropical disease. It primarily occurs in rural areas of sub-Saharan Africa. People living or traveling in these regions face the highest risks. Occupations like farming, fishing, and hunting increase the chance of exposure.

The infection is spread through the bite of an infected tsetse fly. There are two specific species of the parasite that cause human disease. Trypanosoma brucei gambiense is responsible for over 92% of reported cases. This type is primarily transmitted between humans. The second type is Trypanosoma brucei rhodesiense. This version is zoonotic, meaning it lives in animals like cattle and wildlife.

When animals like cows are infected, the disease is called nagana. The transmission process depends on the presence of these flies in the environment.

Doctors divide the disease into two distinct clinical stages. The first is the hemolymphatic stage. During this phase, the parasites live in the blood and the lymphatic system. Patients may experience intermittent fevers, severe headaches, and joint pains. It can also cause lymphadenopathy, which is the swelling of lymph nodes. A specific sign called Winterbottom's sign involves swollen nodes at the base of the skull.

The second is the neurological stage, also called the meningoencephalitic phase. This begins when the parasites cross the blood-brain barrier. Once they invade the central nervous system, they affect the brain and spinal cord.

The transition between these stages varies by parasite type. For T. b. rhodesiense, the neurological stage may begin in 21 to 60 days. For T. b. gambiense, it can take 300 to 500 days. Because the stages often overlap, symptoms can be hard to distinguish. Doctors use a lumbar puncture to check cerebrospinal fluid for parasites. This test confirms if the central nervous system is involved. This distinction is vital because the treatment methods change significantly between stages.

Treatment success depends heavily on early detection. For the hemolymphatic stage, drugs like pentamidine or suramin are used. A newer option, fexinidazole, can be taken by mouth for either stage of gambiense infection. If the disease reaches the neurological stage, more intensive drugs are required. These include eflornithine or a combination of nifurtimox and eflornithine. Melarsoprol is used for rhodesiense, but it has serious side effects. Without medical intervention, the disease is invariably fatal. Untreated rhodesiense kills within months, while gambiense can take years.

One of the most fascinating aspects is how the parasite affects the circadian rhythm. This is the body's internal biological clock. The parasite alters the expression of clock genes in brain regions like the suprachiasmatic nucleus (SCN). It also triggers inflammation by increasing TNF-α levels. This disruption causes sleep inversion, where patients sleep during the day and stay awake at night. They may also experience sudden episodes of sleepiness. Interestingly, sleep patterns can return to normal after successful treatment.

History shows both the impact and the progress in fighting this disease. Major outbreaks occurred between 1896 and 1906 in Uganda and the Congo Basin. Other significant outbreaks happened in 1920 and 1970. In 1990, there were approximately 34,000 deaths. By 2015, annual deaths had dropped to about 3,500. Currently, about 70 million people in 36 countries are at risk. More than 80% of all cases occur in the Democratic Republic of the Congo.