Trypanosomiasis in Humans or African sleeping sickness is caused by Trypanosoma species parasites that are spread by Tsetse fly of the genus Glossina. Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense are two protozoans that serve as causative agents of sleeping sickness in Humans. Trypanosoma species are collectively called Trypanosomes.

What is sleeping sickness?

Trypanosomiasis is commonly called African sleeping sickness because of the distribution of the disease as well as the common and most remarkable symptom of somnolence (sleepiness). It is found in sub-Saharan African and the most remarkable symptom in the late stage of the disease is the frequent day-time drowsiness often experience by patients that does not resolve but rather progresses to coma when not treated. African Trypanosomiasis (Sleeping sickness) is different from American trypanosomiasis which is caused by Trypanosoma cruzi and does not present with drowsiness but rather heart failure.

African sleeping sickness Transmission

1. Tsetse fly bite
2. Blood transfusion

The distinguishing character of the vector that transmit sleeping sickness (Tsetse fly) with other vectors that transmit infections through sucking of blood is that both the male and female tsetse flies feed on blood meal and so both can transmit the infection; this is different from the usual transmission of blood infections such as Malaria, Leishmaniasis and Elephantiasis (Filariasis)

Trypanosomiasis Epidemiology

Sleeping sickness caused by Trypanosoma brucei gambiense is found in Central Africa (Uganda), West Africa (Senegal) and Southern Africa (Angola). In these regions of Africa, man is the main reservoir of the parasite and treating infected patients helps to control further infections. The specie of Tsetse fly responsible for transmitting sleeping sickness in these regions is Glossina palpalis.

Sleeping sickness caused by Trypanosoma brucei rhodesiense occurs in East and Central Africa from Ethiopia to Botswana. Wild and domestic animals serve as major reservoirs in these regions. Transmission occurs through bite of the Tsetse fly called Glossina morsitans (commonly called the Savannah fly).

Tsetse Fly – The Causative agent of Trypanosomiasis taking a blood meal; this is the mode of transmission of sleeping sickness

Trypanosomiasis Pathophysiology

The pathogenesis of African trypanosomiasis starts with a bite from an infected tsetse fly (whether male or female) which then transmit infection by depositing metacyclic trypomastigotes (which care the infective forms of trypanosomes) into the subcutaneous tissue. This bite causes local skin reaction (trypanosomal chancre) and local lymph node swelling that usually resolves after a week. About 2 to 3 weeks after bite by tsetse fly, the trypanosomes invade the bloodstream and are taken to other parts of the body including the brain where it causes progressive demyelinating encephalitis that manifest with the CNS symptoms including somnolence (sleepiness from where the disease got its name).

Types of Trypanosomiasis

1. African Trypanosomiasis (African sleeping sickness)
2. American Trypanosomiasis (Chagas disease) this is not related to African trypanosomiasis in anyway. American trypanosomiasis is different in the vector for transmission, different in symptoms and treatment.

Types of African Trypanosomiasis

1. West African Trypanosomiasis
2. East African Trypanosomiasis

West African sleeping sickness

West African sleeping sickness is caused by Trypanosoma brucei gambiense this type progresses slowly and symptoms include fever, weight loss, drowsiness and hepatosplenomegaly may occur. It may take years to cause death.

East African sleeping sickness

East African sleeping sickness is caused by Trypanosoma brucei rhodesiense it is more severe than the East African sleeping sickness and progresses rapidly with death occurring within few weeks to few months (sometimes death may occur before the onset of CNS symptoms). Symptoms are similar to that of East African sleeping sickness but with rapid progression from recurrent fever to development of drowsiness, coma and death;

African sleeping sickness Symptoms and Signs

The symptoms and signs of trypanosomiasis occur in accordance with the stage of the disease: there are early local signs, systemic symptoms and signs and late symptoms.

Early Local sign of African sleeping sickness

The first symptom of African trypanosomiasis is the appearance of a red skin ulcer (known as Trypanosomal chancre) that is hard and painful at the site of the bite by tsetse fly this ulcer usually heals within 2 weeks; systemic symptoms occur after the skin and are listed below.

Systemic symptoms of African sleeping sickness

1. Fever
2. Headache
3. Dizziness
4. Lymph node swelling (lymphadenopathy) – the posterior cervical lymph nodes are commonly affected (Winterbottom’s sign)

The systemic symptoms of trypanosomiasis may last for 1 week with resolution of fever. There will be alternating period of fever and fever-free period and this continues for few months before the disease gets to the late stage.

Late stage symptoms of Trypanosomiasis (African Sleeping Sickness CNS Symptoms)

1. Headache
2. Insomnia (sleeplessness) even though it is name as sleeping sickness, insomnia occurs before progression to somnolence (drowsiness)
3. Daytime drowsiness (sleeping almost always even during the day)
4. Convulsions
5. Changes in the behavior of the individual (mood changes)
6. Difficulty with walking as a result of muscle tremors
7. Slurred speech
8. Coma and death occurs when not treated as a result of pneumonia.

The late stage involves the central nervous system from where the disease got its name Sleeping Sickness. The late stage is usually progressive and the symptoms worsen from somnolence (drowsiness) to coma as demyelinating encephalitis develops.

Trypanosomes (Trypomastigotes seen in a blood smear) – this is a method of diagnosis of trypanosomiasis

Diagnosis of Trypanosomiasis

1. In the early phase of the disease (acute phase), it can be diagnosed by identifying trypomastigotes in blood smears, lymph node aspirate or cerebrospinal fluid when viewed under the microscope.
2. Serologic tests such as Enzyme-Linked Immunosorbent Assay ( ELISA), Immunofluorescence Antibody Test (IFAT) or Hemagglutination Assay (HA) help to identify IgM antibodies against Trypanosoma species in the late phase of the disease

African sleeping sickness treatment (Trypanosomiasis treatment Guideline)

1. Suramin is the drug of choice for trypanosomiasis and it is most effective in the early phase of the disease;
2. Pentamidine can be given if Suramin is not available
3. In the late phase when CNS symptoms have developed, Suramin cannot be used alone again as it does not penetrate the CNS (it does not cross the blood brain barrier). The drug used in the late phase is Melarsoprol (this drug is however very toxic as about 2 to 10% of patients treated with it will develop acute encephalopathy, peripheral neuropathy and hepatorenal toxicity and more than 50% may die from this adverse effect of Melarsoprol). First, Suramin is given to clear the parasites in the blood and then Melarsoprol is given. The use of 1mg/kg/day of Prednisolone decreases the mortality rate of Melarsoprol by 50% – but this has been found effective only in Trypanosoma brucei gambiense infection.
4. Eflornithine (difluoromethylornithine) is also effective and has fewer side effects than melarsoprol. It can clear parasites from blood and cerebrospinal fluid (CSF); it however has variable effect on Trypanosoma brucei rhodesiense infection.

African sleeping sickness Prevention

1. Use of insecticides to kill tsetse flies
2. Use of nettings on windows and for sleeping on beds
3. Use of protective clothing that cover the most parts of the body
4. Clearing of bushes and forests around villages and houses
5. Do not keep cattle or animals around the house
6. Prompt treatment of infected persons especially in areas where man is the major reservoir of parasite