Leishmaniasis

Leishmaniasis is an infectious disease caused by a parasite. This parasite is transmitted by a vector, namely sand flies. 

There are many types of Leishmania. Leishmania infantum is a species that grows around the Mediterranean Sea, where it is transferred from dogs or rats to humans by sand flies. Leishmaniasis is thus a zoonosis. Some Leishmania species are transferred from humans to humans by sand flies, for example in India. The parasites can also be transmitted through blood transfusions and, in dogs, through fighting wounds with blood-blood contact.

Fig 2. - Leishmania donovani. Motic B410E PlanApo 100X o.i. Moticam S12. 

Image credit: Willem Cramer

The symptoms in humans depend on the severity of the infection and the type of Leishmania. The syndromes that can occur are at the cutaneous (the skin), mucocutaneous (the skin and mucous membranes) or visceral (the intestines) level.

Fig 2. - Leishmania donovani. Motic B410E PlanApo 100X o.i. Moticam S12. 

Image credit: Willem Cramer

• With the cutaneous form, an ulcer develops where the infected sand fly stings. Several ulcers can develop at the same time, at the different stinging spots. The sores can disappear spontaneously over months or years, but can leave severe scars.

• With the mucocutaneous form, ulcers develop on the mucous membranes of the mouth or nose, for example, and can deform the entire face.

• In the visceral form, an enlargement of the spleen occurs first and later also of the liver. Anemia, a decrease in the number of white blood cells, bleeding in the mucous membranes and pigmentation of the skin can also occur. Patients suffer from weight loss, long-lasting fever with alternating fever peaks, general malaise, and sometimes diarrhea or cough. The visceral form can be lethal without treatment, but can also be latent or cause only mild phenomena, depending on the host's resistance. The incubation period can vary from 10 days to several years, on average it takes 2 to 6 months from the bite of the sand fly to the onset of symptoms. Often secondary infections occur.

There is no vaccine against Leishmaniasis, neither for animals nor for humans. That is why it is important to protect humans and animals against the sand flies that are mainly active around dusk. Protective clothing, insect repellent and mosquito nets can help keep the flies at bay. There are special collars with insecticides for dogs. The sand flies are less often present indoors and insecticides can also be used. Leishmaniasis is common in tropical regions, as well as in countries around the Mediterranean.

Fig 3. - Leishmania donovani. Motic B410E PlanApo 100X o.i. Moticam S12. 

Image credit: Willem Cramer

In the photos, amastigotes are indicated with an arrow. Amastigotes are the parasites forms that persist in the infected host; they infect cells recruited to lesions and disseminate the infection to secondary sites.

Sample: Leishmania donovani viewed through Motic B410E PlanApo 100X o.i. Recorded with Moticam S12.  With thanks to Cees Koopman veterinarian.

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