Subscribe here to get periodical Newsletter issues on Microorganisms and Environment Management at free of cost.
Protozoa
Trypanosoma bruce rhodesiense
Disease
African Trypanosomiasis "sleeping sickness"
Symptoms
African trypanosomiasis symptoms occur in two stages. The first stage, known as the haemolymphatic phase, is characterized by fever, headaches, joint pains, and itching. Fever is intermittent, with attacks lasting from a day to a week, separated by intervals of a few days to a month or longer. Invasion of the circulatory and lymphatic systems by the parasites is associated with severe swelling of lymph nodes, often to tremendous sizes. Winter bottom's sign, the tell-tale swollen lymph nodes along the back of the neck, may appear. Occasionally, a red sore called a chancre will develop at the location of the tsetse fly bite. If left untreated, the disease overcomes the host's defenses and can cause more extensive damage, broadening symptoms to include anemia, endocrine, cardiac, and kidney dysfunctions. The second, neurological phase, begins when the parasite invades the central nervous system by passing through the blood–brain barrier. Disruption of the sleep cycle is a leading symptom of this stage and is the one that gave the disease the name 'sleeping sickness.' Infected individuals experience a disorganized and fragmented 24-hour rhythm of the sleep-wake cycle, resulting in daytime sleep episodes and nighttime periods of wakefulness. Other neurological symptoms include confusion, tremor, general muscle weakness, hemiparesis and paralysis of a limb. Parkinson-like movements might arise due to non-specific movement disorders and speech disorders. Individuals may also exhibit psychiatric symptoms such as irritability, psychotic reactions, aggressive behaviour, or apathy which can sometimes dominate the clinical diagnosis. Without treatment, the disease is invariably fatal, with progressive mental deterioration leading to coma, systemic organ failure, and death. An untreated infection with T.b. rhodesiense will cause death within months, whereas an untreated infection with T.b. gambiense will cause death after several years. Damage caused in the neurological phase is irreversible.
Treatment
The specific drug and treatment course will depend on the type and stage of infection (i.e. whether the central nervous system has been invaded by the parasite). Pentamidine, which is the recommended drug for first stage T. b. gambiense infection. The other drugs, such as suramin, melarsoprol, eflornithine, and nifurtimox are also used to treat African trypanosomiasis (only in the U.S).

There is no test of cure for African trypanosomiasis. After treatment patients need to have serial examinations of their cerebrospinal fluid for 2 years, so that relapse can be detected if it occurs.
Preventive measures
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.

Other helpful measures include

  • 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.

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.

 
 
Copyright © 2005 ENVIS Centre ! All rights reserved This site is optimized for 1024 x 768 screen resolution Query Form | Feedback | Privacy