Tropical Diseases - Trypanosomiasis
Trypanosomiasis is a group of diseases caused by similar kinds of parasitic protozoa. The diseases, which include two kinds of African sleeping sickness and Chagas disease of Central and South America, affect about 10 million people. The sleeping-sickness forms of trypanosomiasis are transmitted by species of the tsetse fly, while Chagas' disease is carried by insects known as assassin bugs or kissing bugs . Besides affecting humans, the trypanosomiasis organisms infect other animals, including cattle, horses, dogs, and donkeys, and have made an area of nearly four million square miles of Africa uninhabitable. According to the World Health Organization, the African land devastated by trypanosomiasis contains large fertile areas capable of supporting 125 million cattle, but domestic animals cannot survive the infestation of tsetse flies.
The two kinds of African sleeping sickness, Gambian and Rhodesian, are similar. Gambian, or mid-African, sleeping sickness is transmitted by a tsetse fly that lives near water; Rhodesian, or East African, sleeping sickness is carried by a woodland species of tsetse fly that uses antelopes as a reservoir of the infectious organism. The most likely victims of tsetse fly bites are young men, probably because they are more likely to be exposed to the insects.
The symptoms of trypanosomiasis infections from tsetse fly bites can vary considerably according to various factors, such as the general health of the victim. A small area of inflammation, called a chancre , appears at the site of the tsetse fly bite about two days after the incident; some patients complain of pain and irritation in the area around the bite for several weeks, but others have no symptoms. Then, for a period of perhaps several months, episodes of fever occur, with temperatures rising to 106° F. The bouts of fever may be accompanied by skin rashes, severe headaches, and heart palpitations. Loss of appetite and weight follow, with insomnia, an inability to concentrate, tremors, and difficulty in speaking and walking. There also may be signs of anemia and delayed reaction to a painful stimulus. Eventually, the protozoa can invade the central nervous system, producing convulsions, coma, and death.
Sleeping sickness, which may progress gradually, gets its name from the appearance of the patient, who develops a vacant expression and drooping eyelids, along with blurred speech, general lethargy, and occasional periods of paralysis.
Gambian and Rhodesian Varieties
A major difference between the Gambian and Rhodesian forms of African sleeping sickness is that the Rhodesian variety, which has similar symptoms, is more acute and progresses more rapidly than the Gambian. The fevers are higher, weight losses greater, the disease more resistant to treatment, and the span of time from first symptoms to death much shorter. Even with intensive treatment, Rhodesian sleeping sickness patients have only a 50-50 chance of survival, while 90 to 95 percent of the Gambian sleeping sickness patients recover when properly treated for the disease.
Several chemotherapeutic agents are available for treatment of Gambian and Rhodesian sleeping sickness; they include suramin, pentamidine, and tryparsamide given by injection. Good nutrition, good nursing care, and treatment of secondary infections are additional therapeutic measures.
Chagas' disease, or American trypanosomiasis, is a primary cause of heart disease from Mexico through much of South America. The protozoan infection is rare in the United States, but cases have been reported. The first symptoms may be edema of the face. The accumulation of fluid occuring in the area of the eyelids, conjunctivitis, hard reddish nodules on the skin, along with the fever and involvement of the heart, brain, and liver tissues. The assassin or kissing bugs by which the disease is spread tend to bite the face, especially around the lips or eyelids, accounting for the swelling of those facial areas. The bite may be painful, or if the victim is sleeping at the time, it may not be noticed at all.
The protozoa multiply rapidly at the site of the bug bite, frequently producing symptoms resembling those of leishmaniasis—intermittent fever, swollen spleen, and enlarged liver, after signs of an insect bite. After several days, the trypanosomiasis organisms spread from the site of infection into other tissues, especially the heart and brain, where they cause tissue destruction, inflammation, and often death.
There is no specific treatment for Chagas' disease, and, except for experimental drugs, most therapeutic measures are intended to treat the symptoms.
Like the African sleeping sickness forms of trypanosomiasis, the American type can involve reservoirs of wild and domestic animals; the disease has been found in cats and dogs as well as in opossums and armadillos. Persons traveling in endemic areas should use preventive measures that are appropriate, such as insect sprays and repellents. Efforts to eradicate large areas of insects carrying the trypanosomiasis organisms have been futile; in some instances it has been found to be more effective to move villages away from the insects than to try to remove the insects from the villages.