3 main forms of leishmaniasis are distinguished: 

1. In cutaneous leishmaniasis, the most common form, an ulcer develops where the infected sand fly bites. Several ulcers may form at the same time, at the different stinging sites. The ulcers may disappear spontaneously over months or years but can leave severe scarring.
2. In mucocutaneous leishmaniasis, the ulcers form on the mucous membranes of the mouth or nose, for example, and can disfigure the entire face.
3. In visceral leishmaniasis, also known as kala-azar, the most severe form of the disease, internal organs are affected. Patients suffer from enlargement of the spleen and liver, fever, weight loss, and anaemia. The visceral form can be fatal without treatment, but can also be latent or cause only mild symptoms, depending on the host’s resistance. 

The incubation period can vary from 10 days to up to several years, but on average it takes 2 to 6 months from the bite of the sand fly to the onset of symptoms. 

Humans usually get infected through the bite of infected female sand flies, more specifically, the sand fly species of the genera Phlebotomus (Europe, Asia and Africa) and Lutzomyia (Americas). These sand flies themselves get infected through taking a blood meal from an infected animal or human.

At least 20 species of the Leishmania parasite are known to infect humans. Around 70 animal species have been found as natural reservoirs for the parasites.

Some species of the Leishmania parasite may also be spread through contaminated needles or blood transfusions. Congenital transmission (spread from a pregnant woman to her baby) has also been reported.

The diagnosis of leishmaniasis is mainly based on symptoms, the microscopic identification of the parasite in infected tissue, detection of the genetic material through PCR and serology, the latter is mainly of importance for visceral leishmaniasis.

Cases in Belgium are all travel-related. In Europe, only two transmission cycles are endemic: visceral and cutaneous human leishmaniasis caused by Leishmania infantum throughout the Mediterranean region, and cutaneous human leishmaniasis caused by Leishmania tropica, which sporadically occurs in Greece and probably in neighbouring countries. 

The disease is common in tropical regions, and is considered a neglected tropical disease. An estimated 1.3 million new cases occur annually worldwide, of which 20,000 to 30,000 die.

Leishmaniasis is a treatable disease, although it is possible that it recurs even if treatment has been effective. The treatment of leishmaniasis depends on form of the disease.

No vaccines or drugs to prevent infection are available. The best way to prevent infection when traveling to endemic regions is to protect you from sand fly bites. This is done by covering your skin, sleeping under a bed net and using insect repellent, especially from dusk to dawn, when sand flies generally are the most active, and in humid areas, where sand flies usually live.