The Life Cycle of Trypanosomiasis
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This short presentation covers the Life Cycle of Trypanosomiasis and the prevention of the spread of its vector which is the Tsetse fly.
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The Life Cycle of Trypanosomiasis
- 1. The Life Cycle of Trypanosomiasis Report by: Veronica Baje
- 2. African Trypanosomes • “African trypanosomes” or “Old World trypanosomes” are protozoan hemoflagellates of the genus Trypanosoma, in the subgenus Trypanozoon. • Two subspecies that are morphologically indistinguishable cause distinct disease patterns in humans: T. b. gambiense, causing chronic African trypanosomiasis (“West African sleeping sickness”) and T. b. rhodesiense, causing acute African trypanosomiasis (“East African sleeping sickness”). • The third subspecies T. b. brucei is a parasite primarily of cattle and occasionally other animals, and under normal conditions does not infect humans.
- 4. Prevention and Control There is no vaccine or drug for prophylaxis against African trypanosomiasis. Preventive measures are aimed at minimizing contact with tsetse flies. Local residents are usually aware of the areas that are heavily infested and they can provide advice about places to avoid. • Wear long-sleeved shirts and pants of medium-weight material in neutral colors that blend with the background environment. Tsetse flies are attracted to bright or dark colors, and they can bite through lightweight clothing. • Inspect vehicles before entering. The flies are attracted to the motion and dust from moving vehicles. • Avoid bushes. The tsetse fly is less active during the hottest part of the day but will bite if disturbed. • Use insect repellent. Permethrin-impregnated clothing and insect repellent have not been proved to be particularly effective against tsetse flies, but they will prevent other insect bites that can cause illness.
- 5. • Control of African trypanosomiasis rests on two strategies: reducing the disease reservoir and controlling the tsetse fly vector. • Because humans are the significant disease reservoir for T. b. gambiense, the main control strategy for this subspecies is active case-finding through population screening, followed by treatment of the infected persons that are identified. • Tsetse fly traps are sometimes used as an adjunct. Reducing the reservoir of infection is more difficult for T. b. rhodesiense, since there are a variety of animal hosts. • Vector control is the primary strategy in use. This is usually done with traps or screens, in combination with insecticides and odors that attract the flies.
Editor's Notes
- During a blood meal on the mammalian host, an infected tsetse fly (genus Glossina) injects metacyclic trypomastigotes into skin tissue. The parasites enter the lymphatic system and pass into the bloodstream . Inside the host, they transform into bloodstream trypomastigotes , are carried to other sites throughout the body, reach other body fluids (e.g., lymph, spinal fluid), and continue the replication by binary fission . 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 , . In the fly’s midgut, the parasites transform into procyclic trypomastigotes, multiply by binary fission , leave the midgut, and transform into epimastigotes . The epimastigotes reach the fly’s salivary glands and continue multiplication by binary fission . The cycle in the fly takes approximately 3 weeks. Rarely, T. b. gambiense may be acquired congenitally if the mother is infected during pregnancy.