How can you diagnose the African sleeping sickness?

The definitive diagnosis of African sleeping sickness (also known as human African trypanosomiasis) caused by Trypanosoma brucei gambiense and T. brucei rhodesiense is made by microscopic examination of a blood or lymphatic fluid sample to identify the presence of trypanosomes. However, this method can be challenging, especially in low-parasitemia cases. Several diagnostic tests are used to detect the presence of the parasite or its components:

Microscopic Examination:

1. Thick Blood Smear: This involves making a thick film of blood on a slide, staining it, and examining it under a microscope for the presence of trypanosomes. It is a widely used method, especially in remote areas with limited resources.

2. Thin Blood Smear: A thin blood film is created to visualize individual trypanosomes and differentiate between different species. It is more sensitive than the thick blood smear but requires more expertise and can be time-consuming.

3. Lymph Node Aspirate: In the early stages of infection, when parasitemia is low, a lymph node aspirate may be examined for the presence of trypanosomes. This method is particularly useful in the diagnosis of T. b. gambiense infections.

Serological Tests:

1. Card Agglutination Test for Trypanosomiasis (CATT): This is a rapid, field-friendly serological test commonly used for T. b. gambiense infections. It involves mixing blood with antigens coated on cards and observing for agglutination, which indicates the presence of antibodies against trypanosomes.

2. Enzyme-Linked Immunosorbent Assay (ELISA): ELISA is a serological test that detects antibodies against trypanosomes in blood or cerebrospinal fluid (CSF). It is more sensitive than CATT and can be used for both T. b. gambiense and T. b. rhodesiense infections.

Polymerase Chain Reaction (PCR):

PCR is a molecular diagnostic technique that amplifies and detects the DNA of Trypanosoma brucei. It is highly sensitive and specific, allowing for the detection of the parasite even in low-parasitemia cases. PCR is particularly useful in areas where both T. b. gambiense and T. b. rhodesiense are present, as it can differentiate between the two species.

Animal Inoculation:

In some cases, animal inoculation (usually in mice) is performed to isolate and identify the trypanosomes from blood or CSF samples. The animals are monitored for signs of infection, and the parasites can be recovered and examined.

Depending on the diagnostic resources and expertise available, a combination of these tests may be used for accurate diagnosis of African sleeping sickness, considering the stage of infection and the specific region where the patient is located.