Leishmaniasis is one of the zoonoses, diseases affecting animals and then transmitted to humans. We should rather speak of leishmaniasis because this disease of parasitic origin groups together three very different families from the point of view of symptoms and their location. We distinguish :

• Cutaneous leishmaniasis, also known as “Oriental pimple”
• Visceral leishmaniasis, called “kala-azar”
• Mucosal leishmaniasis, where mucosal involvement appears in 1 to 3% of cases after several months of evolution of a poorly or untreated skin form.

Cause:

In the three cases, it is about a parasitosis, disease due to the contamination of the organism by a parasite, the “leishmania” of which there are several families which will determine the type of attack: Leishmania donovani et children for visceral form, Leishmania tropics especially for the cutaneous form, Leishmania braziliensis for the mucous form. The parasite takes up residence in certain white blood cells of their host, macrophages, cells responsible for cell destruction (phagocytosis).

Transmission mode :

This parasite is transmitted to humans by an insect, a kind of mosquito called a sand fly, or sand fly. Only the female feeds on blood (she is said to be hematophagous). It gorges itself on the blood of individuals it bites at dusk, and if it is infected, it also transmits the parasite to them which will invade their blood.

The natural reservoir of the Leishmania infantum parasite is the dog (as well as wild canines: foxes, jackals, etc.), and also cats and hares. In other words, the sandfly becomes infected by biting an infected animal and then transmits the disease to humans.

Affected bitches can transmit the parasite to their litters.

For Leishmania donovani and Leishmania tropica, the natural reservoir is man. An affected human, if bitten by a sandfly mosquito, can thus transmit the parasite to other people.

And since the immune deficiency of HIV / AIDS infection increases the risk of leishmaniasis by 100, people living with HIV / AIDS are important reservoirs of parasites.

Direct human transmission can occur only through blood, for example by needle exchange among drug addicts.

Sexual transmission is possible.

Incubation

Incubation, in other words the time between the first contact with the parasite and the appearance of the first signs of leishmaniasis, is very variable depending on the form:

• From several weeks to several months for the cutaneous form
• From 1 to 6 months at least for the visceral form
• From a few months to several years (up to 40 years!) For the mucous membrane

Diagnostic :

• Cutaneous form : easy to detect since it affects the skin, especially when it concerns the face, the cutaneous form does not go unnoticed. A sample from the skin lesion shows the presence of the parasite. It is also possible to detect the parasite indirectly by performing an intradermal reaction to leishmanin (IDR), (same type of examination as the intradermal reaction for the detection of tuberculosis). This consists of injecting a leishmania extract under the skin and then observing that there is a skin hypersensitivity reaction at the site of the injection.
• Visceral form : in addition to the signs of the pathology, the diagnosis can be made by a direct examination of the bone marrow (myelogram), a lymph node, blood or other fluids which finds the parasite, as well as serology, in other words the discovery in the blood of antibodies directed against the parasite. Be careful, the serology can be negative in case of immuno-depression, the patient no longer being able to produce antibodies. Finally, a blood test may show indirect signs of infection, with intense inflammatory syndrome (high sedimentation rate), low levels of red and white blood cells and platelets. Note also the existence of a rapid test for leishmaniasis using a test strip containing a leishmania antigen.
• Mucous form : Like the cutaneous form, it is possible to find the parasite in oral lesions.