Trypanosomiasis

Trypanosomiasis or trypanosomosis is the name of several diseases in vertebrates caused by parasitic protozoan trypanosomes of the genus Trypanosoma. In humans this includes African trypanosomiasis and Chagas disease (American trypanosomiasis). A number of other diseases occur in other animals. African trypanosomiasis in humans, which is caused by either Trypanosoma brucei gambiense or Trypanosoma brucei rhodesiense, is presently estimated to threaten over 40 million people in sub-Saharan Africa, especially in rural areas and populations affected by war or poverty. However, only 1.5 million people are estimated to live in areas at moderate or high risk, and for over 20 years the number of cases has been going down due to systematic surveillance and control efforts: in 1998 almost 40,000 cases were reported but almost 300,000 cases were suspected to have occurred; in 2009, the number dropped below 10,000; and in 2018 it dropped below 1000, and it has remained under that number ever since. Chagas disease causes 21,000 deaths per year mainly in Latin America.

Signs and symptoms The tsetse fly bite erupts into a red chancre sore and within a few weeks, the person can experience fever, swollen lymph glands, blood in urine, aching muscles and joints, headaches and irritability. In the first phase, the patient has only intermittent bouts of fever with lymphadenopathy together with other non-specific signs and symptoms. The second stage of the disease is marked by involvement of the central nervous system with extensive neurological effects like changes in personality, alteration of the biological clock (the circadian rhythm), confusion, slurred speech, seizures and difficulty in walking and talking. These problems can develop over many years and if not treated, the person dies. It is common in Subsaharan Africa.

Diagnosis Cattle may show enlarged lymph nodes and internal organs. Haemolytic anaemia is a characteristic sign. Systemic disease and reproductive wastage are common, and cattle appear to waste away. Horses with dourine show signs of ventral and genital edema and urticaria. Infected dogs and cats may show severe systemic signs. Diagnosis relies on recognition of the flagellate on a blood smear. Motile organisms may be visible in the buffy coat when a blood sample is spun down. Serological testing is also common. One common way in which trypanosomiasis can be diagnosed in humans is through the detection of antibodies against trypanosomes made by host organisms. One commonly used antibody test which operated based on this principle is the card agglutination test, C.A.T.T. for T. gambiense. In this test, reagent is mixed with blood and shaken. Within a matter of minutes, a researcher or public health professional can determine whether someone has made these antibodies and therefore is infected with trypanosomes. Regarding the accuracy of this test, it is reported to have an 87 to 98 percent sensitivity rating. Another way to diagnose trypanosomiasis in humans is to detect the trypanosome protozoans themselves. One way to do this would be to use lymph node aspirate. In this test, which has a sensitivity of between 40 and 80 percent, a healthcare worker will first find a cervical lymph node which is enlarged. Once the healthcare worker has punctured that lymph node, its aspirate is examined under a microscope for trypanosomes to confirm diagnosis.

Prevention The use of trypanotolerant breeds for livestock farming should be considered if the disease is widespread. Fly control is another option but is difficult to implement. The main approaches to controlling African trypanosomiasis are to reduce the reservoirs of infection and the presence of the tsetse fly. Screening of people at risk helps identify patients at an early stage. Diagnosis should be made as early as possible and before the advanced stage to avoid complicated, difficult and risky treatment procedures.

Treatment Stage I of the condition is usually treated with pentamidine or suramin through intramuscular injection or intravenous infusion if sufficient observation is possible. Stage II of the disease is typically treated with melarsoprol or eflornithine preferably introduced to the body intravenously. Both pentamidine and suramin have limited side effects. Melarsoprol is extremely effective but has many serious side effects which can cause neurological damage to a patient, however, the drug is often a patient's last hope in many late stage cases. Eflornithine is extremely expensive but has side effects that may be treated with ease. In regions of the world where the disease is common eflornithine is provided for free by the World Health Organization.

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