Trypanosomiasis


Trypanosomiasis

Description, Causes and Risk Factors:

Any disease caused by a Trypanosoma (A genus of asexual digenetic protozoan flagellates (family Trypanosomatidae) that have a spindle-shaped body with an undulating membrane on one side, a single anterior flagellum, and a kinetoplast; they are parasitic in the blood plasma of many vertebrates (only a few being pathogenic) and as a rule have an intermediate host, a bloodsucking invertebrate, such as a leech, tick, or insect; pathogenic species cause trypanosomiasis in humans and other diseases in domestic animals.

Trypanosomiasis is a widespread tropical disease that can be fatal if not treated. It is spread by the bite of an infected tsetse fly (Glossina Genus). The tsetse fly bite erupts into a red sore and within a few weeks the person can experience fever, swollen lymph glands, aching muscles and joints, headaches and irritability.

In advanced stages, the disease attacks the central nervous system (CNS), causing changes in personality, alteration of the biological clock (the circadian rhythm), confusion, slurred speech, seizures, and difficulty walking and talking. These problems can develop over many years in the Gambiense form and some months in the Rhodesiense form; if not treated, the person will die.

Control of sleeping sickness is based on reduction of the reservoirs of infection by early diagnosis and control of tsetse flies. The disease is mostly transmitted through the bite of an infected tsetse fly but there are other ways in which people are infected with sleeping sickness.

Mother-to-child infection: the trypanosome can cross the placenta and infect the fetus. Mechanical transmission through other blood sucking insects is possible. However, it is difficult to assess the epidemiological impact of transmission.

Accidental infections have occurred in laboratories due to pricks from contaminated needles.

In the first stage, the trypanosomes multiply in subcutaneous tissues, blood and lymph. This is known as a hemolymphatic phase, which entails bouts of fever, headaches, joint pains and itching.

In the second stage the parasites cross the blood-brain barrier to infect the central nervous system. This is known as the neurological phase. In general this is when more obvious signs and symptoms of the disease appear: changes of behavior, confusion, sensory disturbances and poor coordination. Disturbance of the sleep cycle, which gives the disease its name, is an important feature of the second stage of the disease. Without treatment, sleeping sickness is considered fatal.

Symptoms:

The symptoms of trypansomiasis depend on host and the sub-species of trypanosome. In T. Gambiense infections there is massive stimulation of immune system and complement-mediated lysis of host cells (gives characteristic anemia). Generalized pain, weakness, cramps and swelling of neck lymph nodes (Winterbottom's sign). Parasites invade all organs of the body including heart and CNS. The latter leads to apathy, mental dullness, tremors, convulsions and sleepiness, coma. There is rapid weight loss and death a few months later from malnutrition, heart failure, pneumonia or a parasitic infection. In the case of T. brucei rhodesiense infections, there is no coma or nervous system symptoms as probably patient dies before these can develop.

Recently on the increase, there are a minimum of 20,000 new cases a year; 50,000,000 people are at risk.

Diagnosis:

The diagnosis of Trypanosomiasis is made through laboratory methods, because the clinical features of infection are not sufficiently specific. The diagnosis rests on finding the parasite in body fluid or tissue by microscopy. The parasite load in T. b. rhodesiense infection is substantially higher than the level in T. b. gambiense infection.

T. b. rhodesiense parasites can easily be found in blood. They can also be found in lymph node fluid or in fluid or biopsy of a chancre. Serologic testing is not widely available and is not used in the diagnosis, since microscopic detection of the parasite is straightforward.

The classic method for diagnosing T. b. gambiense infection is by microscopic examination of lymph node aspirate, usually from a posterior cervical node. It is often difficult to detect T. b. gambiense in blood. Concentration techniques and serial examinations are frequently needed. Serologic testing is available outside the U.S. for T. b. gambiense; however, it normally is used for screening purposes only and the definitive diagnosis rests on microscopic observation of the parasite.

All patients diagnosed with African trypanosomiasis must have their cerebrospinal fluid examined to determine whether there is involvement of the central nervous system, since the choice of treatment drug(s) will depend on the disease stage. The World Health Organization criteria for central nervous system involvement include increased protein in cerebrospinal fluid and a white cell count of more than 5. Trypanosomes can often be observed in cerebrospinal fluid in persons with second stage infection.

Treatment:

All persons diagnosed with Trypanosomiasis should receive treatment. The specific drug and treatment course will depend on the type of infection (T. b. gambiense or T. b. rhodesiense) and the disease stage (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, is widely available in the U.S. Physicians can consult with CDC staff for advice on diagnosis and management and to obtain otherwise unavailable treatment drug.

After treatment patients need to have serial examinations of their cerebrospinal fluid for 2 years, so that relapse can be detected if it occurs.

NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.

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