Leishmaniasis

Leishmaniases are parasitic diseases caused by protozoan flagellates of the genus Leishmania. These parasites infect numerous mammal species, including humans, and are transmitted through the infective bite of an insect vector, the phlebotomine sandfly.

The leishmaniases are threatening 350 million people in 88 countries of four continents. The annual incidence of new cases is estimated between 1,5 and 2 million.1 In numerous underdeveloped countries, they remain a major public health problem.

The genus Leishmania includes around 30 different taxa, the majority of which commonly infect humans, in whom they are responsible for various types of disease :
- visceral leishmaniasis,
- cutaneous leishmaniasis (of localized or diffuse type)
- mucocutaneous leishmaniasis.

This variability of the clinical features results from both the diversity of the Leishmania species and the immune response of the hosts.

Visceral leishmaniasis is widely distributed around the world, and is found in 47 countries. Its mean annual incidence is estimated around 500 000 new cases. The main historical foci of endemic VL are located, east to west, in China, India, Central Asia, East Africa, Mediterranean basin and Brazil. The anthroponotic species L. donovani is restricted to China, India and East Africa, while the zoonotic species L. infantum extends from China to Brazil.

VL is a disease of the mononuclear phagocytic system, commonly affecting the spleen, liver, lymph nodes and bone marrow. But other organs (intestine, lung) and tissues (skin) may also become involved, as they contain elements of the mononuclear phagocytic system.

In the well established VL, the patient presents a protuberant abdomen and muscle wasting of limbs. A general syndrome including fever, asthenia, weight loss, anaemia, splenomegaly, hepatomegaly and sometimes adenopathia, dominates the classical presentation.

The number of VL cases associated with immunosuppression, particularly HIV infection has increased regularly over the past 15 or so years. In Southern Europe, there were a total of 1 616 cases reported, for the period 1990-98.

Leishmaniasis in Europe
Leishmania infantum is the aetiological agent of both cutaneous and visceral forms of human and canine leishmaniasis in Southern Europe. European leishmaniasis is a vector-borne zoonosis, the visceral form of which (VL) can be life threatening and cause high morbidity and distress. Infants are historically mainly affected, but L. infantum has been shown to be an opportunistic parasite in HIV patients. With the increase of speed and volume of travel, some Europeans become infected with exotic species and correct choice of treatment can be difficult without rapid identification of the organism. Serology is the method of choice for diagnosis of leishmaniasis, and the leishmanin skin test in some cutaneous cases but these methods are not species or strain specific and often fail in immunocompromised patients. Typing methods should be integrated into diagnosis procedures for leishmaniasis. Current standard methodology for identification of Leishmania demands isolation of the organisms, mass culture and allozyme (or isoenzyme) analysis (IEA). We propose, to develop new alternative PCR-based typing methods, tested for correlation with reference IEA typing but that will show molecular diversity and be effective for low parasite loads and contamination with host DNA.