Parasites: Leishmania, a single-celled organism

The parasite Leishmania is a single-celled organism that can affect the skin, mucous membranes and internal organs. It is transmitted from an animal to a human by a fly. In some countries it is transmitted from person to person. The parasite sometimes occurs in dogs that have been on holiday to countries around the Mediterranean Sea. Ulcers can develop on the skin, sometimes years after the infection has occurred. Where can you become infected with Leishmaniasis and how should it be treated?

The parasite

The Leishmania is a protozoan (a single-celled organism) that is transmitted via a host to an animal or human. The infection is caused by a small sand fly that occurs in countries around the Mediterranean Sea, but also in other warm countries in Africa and Asia. These sand flies usually sting small mammals, which then get this parasite into the bloodstream. Sand fleas bite these animals and can then infect another animal or human. As a result of this infection, sores that look like leprosy can develop. Infection with this parasite is called leishmaniasis, sand mosquito disease or black fever


Leishmaniasis is an infection by the parasite of the skin, mucous membranes or internal organs. The parasite is found on a species of fly, also called a sand mosquito, which does not occur in the Netherlands. The parasite enters the bloodstream and is taken up by macrophages (large white blood cells). They multiply in the cell and can spread further through the bloodstream. Because more and more dogs go on holiday these days, infections in dogs are seen more often these days. Leishmaniasis is an imported disease. It is estimated that around 12 million people worldwide are infected with this parasite. More and more people are traveling to the tropics, which will increase the number of infections. Usually the parasite is transmitted from animals to humans, but in some countries such as India it can also be transmitted from human to human.

Symptoms of the disease

This condition is classified into the following types: cutaneous leishmaniasis , mucocutaneous leishmaniasis and visceral leishmaniasis :

Cutaneous leishmaniasis

This form of leishmaniasis is not fatal and usually a person will recover on their own. It can take anywhere from 1 month to more than a year for someone to be cured. Long-lasting ulcers and extensive scar tissue may develop. Depending on the type of parasite, the course and severity of the infection will differ. An ulcer may develop within a few weeks at the spot where the sand fly stings. The ulcer sometimes has a raised edge and is red in color. When it heals it leaves a scar. Multiple sores may develop and it may look like leprosy.

Mucocutaneous leishmaniasis

This form of infection causes ulcers to develop on the mucous membranes, for example in the mouth or nose. Ultimately, the parasites can penetrate to the upper respiratory tract and cause major damage. The damage caused can change the entire shape of the nose and sometimes even eat it away completely. This form of leishmaniasis can be fatal.

Visceral leishmaniasis

The parasites have invaded the internal organs, such as the liver or spleen. It can lead to weight loss, prolonged fever, anemia, diarrhea, coughing and a general feeling of being ill. The parasite may be present without complaints and complaints may only develop after years. This form of leishmaniasis can be fatal.


Cutaneous leishmaniasis usually clears up on its own, but can take a long time. Sometimes the ulcer can be treated locally with medication or heat therapy, for example. Mucocutaneous leishmaniasis and visceral leishmaniasis should always be treated as it can be life-threatening. A medication may be given for treatment, for example an antimony-containing preparation.


It is important to protect yourself from sand flies if you are in an area where the flies occur. The flies are mainly active after sunset. Therefore, wear protective clothing, sleep in a mosquito net and use an insect repellent such as DEET. If you bring a dog, there are special collars that protect the dog.