What is Leishmaniasis Disease?

Mary McMahon

Leishmaniasis is a parasitic infection which is endemic to many developing nations around the world. There are several forms of leishmaniasis disease, all of which require medical treatment with antiparasitic drugs. Travelers in developing nations are often encouraged to take steps to avoid leishmaniasis infections, especially since the parasitic protozoans which cause the infection are growing steadily more resistant to the antiparasitic drugs most commonly used to treat leishmaniasis.

Leishmania protozoa are capable of surviving and multiplying within the macrophages.
Leishmania protozoa are capable of surviving and multiplying within the macrophages.

Several different protozoans can cause leishmaniasis disease, but all of them are in the genus Leishmania. These very simple organisms generally live in animals, and they are picked up by sand flies when those flies feed on animal populations. When the sand flies bite humans, the humans in turn are infected with the protozoans. Most cases of leishmaniasis disease are zoonotic, transmitted from animals to people, although the disease can also be passed from person to person. The best way to avoid leishmaniasis disease is to avoid contact with sand flies, by using screens and insecticides and avoiding the outdoors when the flies are most active, at dawn and dusk.

Once the parasite enters the body, the immune system tries to fight it off, recognizing it as a foreign invader. Macrophages are sent to eat the parasite so that it cannot harm the body, but the leishmaniasis parasites instead turn the macrophages to their advantage, swelling the specialized immune system cells and causing them to burst, thereby spreading the infection further in the body. Without treatment, leishmaniasis disease will run rampant in the body, causing extreme pain and sometimes death.

There are two main forms of leishmaniasis. Cutaneous leishmaniasis causes lesions to appear on the skin, classically with raised edges and depressed craters. The lesions may or may not be painful, depending on the case, but they are typically red, scabby, and very distinctive. Visceral leishmaniasis disease attacks the internal organs of the body, and it is fatal without treatment.

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In developing nations, access to drugs and treatments for leishmaniasis is very limited, due to expensive. Visceral leishmaniasis is a major killer of people in many nations throughout Southeast Asia and Africa, because the drugs are expensive or unavailable. Some organizations have attempted to develop effective, low-cost leishmaniasis drugs, but many have been hampered by a lack of interest in developing such drugs on the part of drug companies, as the pharmaceutical industry would prefer to invest in research with a high profit margin.

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Discussion Comments


@fify-- Leishmaniasis is a difficult disease to treat. How the leishmaniasis parasites are able to use macrophages to spread further in the body shows just how difficult it is to take control of this parasite. That's why there really isn't a treatment for it. Yes, there are drugs but they're not 100% effective and tend to have a lot of side effects.

Human vaccines have been developed for it in the past but scientists did not get good enough results to be able to use it for the general public. There is still a lot of research being done on it, so who know, we might have a working vaccine for it in the future.


@fify-- I know that there is a vaccine for animals and pets because my dog was vaccinated with it, but as far as I know there isn't a leishmaniasis vaccine for humans yet.

Leishmanasis is a huge threat for animals as well. It does infect humans, but much less than it does animals. It's present even in animals in Western nations. I personally wasn't aware of this until I adopted a dog and came to know about the vaccine.

Of course it's a huge issue for people in developing countries but we need to be careful about this in the US too. We're lucky that most Western nations- US, Canada and Europe- doesn't have much sand flies and we're at reduced risk because of that. But the parasite could possibly pass on to us from animals and we need to make sure to vaccinate them for this reason.


This sounds like a very dangerous disease. I have been bit by sand flies before but thankfully I was not overseas and did not get sick. But leishmaniasis sounds worse than malaria disease which spreads through mosquitoes. At least there are mosquito nets which are cheap or sometimes freely available in developing countries that can protect people at night from mosquitoes. It must be much harder to avoid sand flies.

I understand that this disease is treatable with medications but what about vaccination? I know there is a vaccination available for malaria. Is there a vaccination for leishmaniasis disease as well? Or is it being developed currently?

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