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African trypanosomiasis
African trypanosomiasis is an insect-borne parasitic infection of humans and other animals.
Human African trypanosomiasis (HAT), also known as African sleeping sickness or simply sleeping sickness, is caused by the species Trypanosoma brucei. Humans are infected by two types, Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense. Trypanosoma brucei gambiense causes over 92% of reported cases. Both are usually transmitted by the bite of an infected tsetse fly and are most common in rural areas.
Initially, the first stage of the disease is characterized by fevers, headaches, itchiness, and joint pains, beginning one to three weeks after the bite. Weeks to months later, the second stage begins with confusion, poor coordination, numbness, and trouble sleeping. Diagnosis involves detecting the parasite in a blood smear or lymph node fluid. A lumbar puncture is often needed to tell the difference between first- and second-stage disease.
Prevention of severe disease involves screening the at-risk population with blood tests for Trypanosoma brucei gambiense. Treatment is easier when the disease is detected early and before neurological symptoms occur. The use of pentamidine or suramin treats the hemolymphatic stage of T. Brucei infection but if the disease progresses to the neurological stage dosages of eflornithine or a combination of nifurtimox and eflornithine can serve as a treatment for late-stage African Sleeping Disease. Fexinidazole is a more recent treatment that can be taken by mouth, for either stage of Trypanosoma brucei gambiense. While melarsoprol works for both types, it is typically used only for Trypanosoma brucei rhodesiense, due to its serious side effects. Without treatment, sleeping sickness typically results in death.
The disease occurs regularly in some regions of sub-Saharan Africa with the population at risk being about 70 million in 36 countries. An estimated 11,000 people are currently infected with 2,800 new infections in 2015. In 2018 there were 977 new cases. In 2015 it caused around 3,500 deaths, down from 34,000 in 1990. More than 80% of these cases are in the Democratic Republic of the Congo. Three major outbreaks have occurred in recent history: one from 1896 to 1906 primarily in Uganda and the Congo Basin, and two in 1920 and 1970, in several African countries. It is classified as a neglected tropical disease. Other animals, such as cows, may carry the disease and become infected in which case it is known as nagana or animal trypanosomiasis.
African trypanosomiasis symptoms occur in two stages: 1) the hemolymphatic stage and 2) the neurological stage. The hemolymphatic stage refers to the period when parasites are present in the blood and lymphatic system, prior to central nervous system involvement. The neurological stage, also called the meningoencephalitic phase, begins when Trypanosoma parasites cross the blood–brain barrier and invade the central nervous system. In addition to the hemolymphatic stage neurological symptoms can still present themselves, resulting in a difficulty in distinguishing the two stages based on clinical features alone.
The disease has been reported to present with atypical symptoms in infected individuals who originate from non-endemic areas (e.g., travelers). The reasons for this are unclear and may be genetic. Delayed or missed diagnosis in infected individuals who originate from non-endemic areas (travelers) has been reported symptoms including higher susceptibility and quicker progression of advanced stages of the disease. The reasons for this are unclear, but certain symptoms, such as high fever, could be due to genetic factors or a lack of previous exposure to non-human-pathogenic forms of trypanosomes. The low number of such cases may also have skewed findings. In such persons, the infection is said to present mainly as fever with gastrointestinal symptoms (e.g., diarrhea and jaundice) and with lymphadenopathy rarely developing.
Systemic disease is sometimes presaged by a trypanosomal ulcer developing at the site of the infectious fly bite within 2 days of infection. The ulcer is most commonly observed in T. b. rhodesiense infection and rarely in T. b. gambiense infection, where ulcers are more common in persons from non-endemic areas.
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African trypanosomiasis
African trypanosomiasis is an insect-borne parasitic infection of humans and other animals.
Human African trypanosomiasis (HAT), also known as African sleeping sickness or simply sleeping sickness, is caused by the species Trypanosoma brucei. Humans are infected by two types, Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense. Trypanosoma brucei gambiense causes over 92% of reported cases. Both are usually transmitted by the bite of an infected tsetse fly and are most common in rural areas.
Initially, the first stage of the disease is characterized by fevers, headaches, itchiness, and joint pains, beginning one to three weeks after the bite. Weeks to months later, the second stage begins with confusion, poor coordination, numbness, and trouble sleeping. Diagnosis involves detecting the parasite in a blood smear or lymph node fluid. A lumbar puncture is often needed to tell the difference between first- and second-stage disease.
Prevention of severe disease involves screening the at-risk population with blood tests for Trypanosoma brucei gambiense. Treatment is easier when the disease is detected early and before neurological symptoms occur. The use of pentamidine or suramin treats the hemolymphatic stage of T. Brucei infection but if the disease progresses to the neurological stage dosages of eflornithine or a combination of nifurtimox and eflornithine can serve as a treatment for late-stage African Sleeping Disease. Fexinidazole is a more recent treatment that can be taken by mouth, for either stage of Trypanosoma brucei gambiense. While melarsoprol works for both types, it is typically used only for Trypanosoma brucei rhodesiense, due to its serious side effects. Without treatment, sleeping sickness typically results in death.
The disease occurs regularly in some regions of sub-Saharan Africa with the population at risk being about 70 million in 36 countries. An estimated 11,000 people are currently infected with 2,800 new infections in 2015. In 2018 there were 977 new cases. In 2015 it caused around 3,500 deaths, down from 34,000 in 1990. More than 80% of these cases are in the Democratic Republic of the Congo. Three major outbreaks have occurred in recent history: one from 1896 to 1906 primarily in Uganda and the Congo Basin, and two in 1920 and 1970, in several African countries. It is classified as a neglected tropical disease. Other animals, such as cows, may carry the disease and become infected in which case it is known as nagana or animal trypanosomiasis.
African trypanosomiasis symptoms occur in two stages: 1) the hemolymphatic stage and 2) the neurological stage. The hemolymphatic stage refers to the period when parasites are present in the blood and lymphatic system, prior to central nervous system involvement. The neurological stage, also called the meningoencephalitic phase, begins when Trypanosoma parasites cross the blood–brain barrier and invade the central nervous system. In addition to the hemolymphatic stage neurological symptoms can still present themselves, resulting in a difficulty in distinguishing the two stages based on clinical features alone.
The disease has been reported to present with atypical symptoms in infected individuals who originate from non-endemic areas (e.g., travelers). The reasons for this are unclear and may be genetic. Delayed or missed diagnosis in infected individuals who originate from non-endemic areas (travelers) has been reported symptoms including higher susceptibility and quicker progression of advanced stages of the disease. The reasons for this are unclear, but certain symptoms, such as high fever, could be due to genetic factors or a lack of previous exposure to non-human-pathogenic forms of trypanosomes. The low number of such cases may also have skewed findings. In such persons, the infection is said to present mainly as fever with gastrointestinal symptoms (e.g., diarrhea and jaundice) and with lymphadenopathy rarely developing.
Systemic disease is sometimes presaged by a trypanosomal ulcer developing at the site of the infectious fly bite within 2 days of infection. The ulcer is most commonly observed in T. b. rhodesiense infection and rarely in T. b. gambiense infection, where ulcers are more common in persons from non-endemic areas.