My Interesting Parasite

Trypanosoma brucei and Sleeping Sickness

As much as I enjoy sleeping and a good nap, I would never want to get sleeping sickness. Sleeping sickness, also known as African Trypanosomiasis is caused by Trypanosoma brucei. There are two types of African Trypanosomiasis, East African trypanosomiasis by the parasite Trypanosoma brucei rhodesiense and West African trypanosomiasis by Trypanosoma brucei gambiense. These microscopic parasites are transmitted by the tsetse fly and are only found in rural Africa. In 2009, the number of new cases reported dropped to 9,878 and below 10,000 for first time in 50 years. The estimated number of actual cases is currently 30,000.  Currently, there is no universal methodology to control human African trypanosomiasis. Since the disease requires medcial staff with experience, is located in difficult access areas, and not a pandemic, WHO established a control and surveillance program that focuses on wider accessibility of people at risk to diagnosis and treatment and strengthening control and surveillance guidelines and policies. 

Life Cycle

The cycle in the fly takes approximately 3 weeks. Humans are the main reservoir for Trypanosoma brucei gambiense, but this species can also be found in animals. Wild game animals are the main reservoir of T. b. rhodesiense.

1: The infected tsetse fly injects metacyclic trypomastigotes into skin tissue. The parasites enter the lymphatic system and passes into the bloodstream.

2-3:-Once inside the body the parasite transforms into bloodstream. Trypomastigotes. are carried to other sites throughout the body, reach other blood fluids and continue the replication by binary fission.

4-5: The entire life cycle of African Trypanosomes is represented by extracellular stages. The tsetse fly becomes infected with bloodstream trypomastigotes when taking a blood meal on an infected mammalian host

6-7: In the fly’s midgut or  the parasites transform into procyclic trypomastigotes, multiply by binary fission, leave the midgut, and transform into epimastigotes.

8:The epimastigotes reach the fly’s salivary glands and continue multiplication by binary fission.

Signs and Symptoms

Within 1-3 weeks, the infective bite develops into a red sore. Several weeks to months later, the infected person may have fever, rash, swelling of the face and hands, headaches, fatigue, aching muscles and joints, itching skin, and swollen lymph nodes. Additionally, weight loss, progressive confusion, personality changes, daytime sleepiness with nighttime sleep disturbances, and other neurologic problems occur after the infection has invaded the central nervous system.

Diagnosis

The diagnosis depends on finding the parasite in body fluid or tissue by microscopy. T. b. rhodesiense parasites can easily be found in blood. They can also be found in lymph node fluid. It is  difficult to detect T. b. gambiense in blood. Therefore, the classic method for diagnosing T. b. gambiense infection is by microscopic examination of lymph node aspirate, usually from a posterior cervical node.

Treatment and Prevention

The specific drug and treatment course will depend on the type of infection and the disease stage. Pentamidine is the recommended drug for first stage T. b. gambiense infection. The other drugs (suramin, melarsoprol, eflornithine, and nifurtimox) used to treat African trypanosomiasis are available in the U.S. only from the CDC. After treatment patients need to have serial examinations of their cerebrospinal fluid for 2 years, so that relapse can be detected if it occurs. If treated, sleeping sickness is curable, but is fatal if untreated over months to years.

There are no medications to prevent Sleeping Sickness, but there are other ways to prevent infection, such as:

1.      Wear protective clothing, including long-sleeved medium weight shirts and pants.

2.      Wear neutral-colored clothing.

3.      Inspect vehicles for tsetse flies before entering.

4.      Avoid bushes.

Helpful links:

http://www.who.int/trypanosomiasis_african/en/

http://www.who.int/trypanosomiasis_african/surveillance/en/

http://www.cdc.gov/parasites/sleepingsickness/