New Form Of Sleeping Sickness Discovered In India Stems From Deficiency In Natural Immunity Protein
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Posted on Feb 19, 2007, 7 a.m.
By Bill Freeman
Human trypanosomiases are commonly known as sleeping sickness in Africa and Chagas disease in South America. The first case of human trypanosomiasis has now been discovered in India. The specialist investigations conducted, at the request of WHO and the Maharashtra Public Health Department, India, by an IRD scientist (1), has led to the identification of the parasite and the treatment of the patient, a farmer from the State of Maharashtra. He proved to be infected by Trypanosoma evansi, a trypanosome which is usually a parasite of various animals, particularly cattle. The mode of infection has not yet been clearly determined, but the discovery of this first human case of T. evansi raises questions both as to the evolution and adaptation of the parasite and on the real size of the problem.
Human trypanosomiases are commonly known as sleeping sickness in Africa and Chagas disease in South America. The first case of human trypanosomiasis has now been discovered in India. The specialist investigations conducted, at the request of WHO and the Maharashtra Public Health Department, India, by an IRD scientist (1), has led to the identification of the parasite and the treatment of the patient, a farmer from the State of Maharashtra. He proved to be infected by Trypanosoma evansi, a trypanosome which is usually a parasite of various animals, particularly cattle. The mode of infection has not yet been clearly determined, but the discovery of this first human case of T. evansi raises questions both as to the evolution and adaptation of the parasite and on the real size of the problem.
A farmer in India, from the village of Shivani (district of Chandrapur) 140 km from Nagpur in the central State of Maharashtra, has recently been identified as the first confirmed case of human trypanosomiasis recorded in that country. Human trypanosomiases are endemic in Africa and South America : respectively sleeping sickness caused by the parasites Trypanosoma brucei gambiense or T. b. rhodiense, and Chagas disease induced by T. cruzi. In other regions of the world such as India, only animals were up to now known to be infected by certain trypanosomes, which are not pathogenic for humans.
In December 2004, a researcher form the IRD centre in Montpellier, a specialist in the African form of human trypanosomiasis (sleeping sickness), undertook the identification of the pathogenic agent, at the request of the Indian authorities and mandated by the WHO in collaboration with local medical services (1). Morphological examination of parasites contained in the patient’s blood revealed the presence of many trypanosomes belonging to the species T. evansi, which usually infects animals, particularly cattle.
The patient, who had been suffering for several months from recurring bouts of fever, had very high blood parasite count, equal or greater than 106 parasites/ml of blood. Parasitological, serological and molecular analyses confirmed this result. It is the world’s first formally identified case of human trypanosomiasis caused by T. evansi. This trypanosome, which was first identified in 1881 India, in the Punjab, in the horse and Bactrian camel, usually causes a disease called “surra “ in bovines and camel species. Although cases of human carriers of animal trypanosomiases were recorded during that century in India, Sri Lanka and Malaysia, these have either never been formally demonstrated or were only very short-lasting infections.
The patient showed no nervous system damage, indicating an early stage of the disease and the researchers could start treatment. Injections of sodium suramine, a medicine usually used in cases of African T. b. rhodesiense trypanosomiases at the same stage, steadily improved the patient’s health (2).
The patient, who works in permanent contact with animals, had a cut in his hand when he was admitted to the health care centre. Consequently, he was probably infected directly into the bloodstream from an animal infected with T. evansi. However, that does not exclude another indirect, mechanical infection pathway, by way of blood-sucking insect for example. An insect vector is involved in transmission of both sleeping sickness and Chagas disease (3).
Research continues aiming to unravel the transmission process and mechanisms by which the parasite adapts from animal hosts to humans. It should help determine whether or not this first recorded infection of T. evansi trypanosomiasis in humans is an isolated case. Only the recording and diagnosis of other human cases, by indications of the parasite in biological fluids (blood, lymph or cerebrospinal fluid), could signal the disease as an emerging problem. A survey was launched recently to investigate such a possibility. Commissioned by the DGHS (Directorate General of Health Services of Maharashtra), and supported by the WHO and the IRD, it is expected soon to bring data that might shed light on this question.
Notes:
(1) This specialist work was conducted by IRD research unit 177 (Montpellier, France), in collaboration with the WHO, the Health Services Directorate of Bombay (India) and the departments of medicine and microbiology of the Government Medical College of Nagpur (India).
(2) This man has now been cured, but he remains under medical supervision until February 2006, in case of a resurgence of the infection.
(3) The parasite is then transmitted by the tsetse fly in the case of sleeping sickness and by assassin bugs (of the insect sub-family Triatominae) in Chagas disease. Otherwise, the animals can be contaminated mechanically by T. evansi when infected blood passes through the buccal apparatus of blood-sucking insects, or by ingestion of infected raw meat.
