Leishmaniasis

When a female sand fly infected with Leishmania bites people to suck up blood, promastigote of leishmania is transmitted to them. Aside from this kind of transmission (via sand fly), cases of infection via injection needles, blood transfusions, and mother-to-child infection have been reported. Infection is possible even in areas where there are no sand flies via people and goods moving from areas where leishmaniasis is epidemic.

U.S. Centers for Disease Control and Prevention,
"Parasites - Leishmaniasis." Accessed March 19, 2014,
http://www.cdc.gov/parasites/leishmaniasis/biology.html

There are varieties of the leishmaniases distinctive to each infected region. Symptoms of infection are categorized into three types according to the variety: cutaneous leishmaniasis, mucocutaneous leishmaniasis, and visceral leishmaniasis.

Among the above three types of the leishmaniases, the most common is cutaneous leishmaniasis. Symptoms vary widely from no serious symptoms to death.

This is the most common type of leishmaniasis by far. When the macrophage of a person’s skin is infected by Leishmania parasite, bumps or lumps develop in a few weeks to a few months, and they continue to grow until they become ulcers. Ulcers are accompanied by pain and, when the same areas are infected by other bacteria or when an ulcer is formed near joints, they are sometimes accompanied by acute pain. These symptoms usually disappear without any treatment, but it takes a few months to sometimes a few years for them to disappear, and it leaves scars on the skin.

For this form, which is caused by infection of visceral macrophage, it takes a few months to a few years before symptoms emerge, such as fever, weight loss, and lower blood cell counts.

This disease occurs when infected macrophage from cutaneous leishmaniasis (infected by a protozoa, mainly Leishmania belonging to subgenus Viannia) is transferred to the nose, mouth, or pharynx. When cutaneous leishmaniasis is untreated or poorly treated, it can develop into mucocutaneous leishmaniasis in a few years. The early symptoms include tenacious nasal congestion, nose bleeding, and discomfort in the mouth or pharynx, but it may lead to severe mucocutaneous damage, affecting patient’s appearance.

When leishmaniasis symptoms are spotted, diagnoses are made according to the symptoms, starting with a medical interview on whether the patient has been in areas where leishmaniasis is epidemic.

A skin sample is taken from the infected area to verify the presence of Leishmania, using stained specimens and other methods.

The presence of Leishmania is tested in bone marrow aspiration, the liver, or in their cultures.

Mucocutaneous leishmaniasis and visceral leishmaniasis must be treated effectively. While, in principle, cutaneous leishmaniasis also calls for treatment, administration of drugs may not be necessary in some cases. In addition, different treatment are required based on the condition of the patient (pregnant woman, breast-feeding mother, child, immune compromised, or those without complications, etc.), as well as the portion of the body that is affected and the type of vector insect.

Oral medicines for these infections include azole antifungal drugs and miltefosine, but their efficacy differs greatly according to the type of the Leishmania.

Mainly drugs such as pentavalent antimonials and amphotericin B are administered, generally via infusion (intravenous injection) or hypodermic injection.

For cutaneous leishmaniasis that does not have a risk of developing into mucocutaneous leishmaniasis, liquid nitrogen cryotherapy or radiofrequency hyperthermia can be used.

The types of medicines include miltefosine, pentavalent antimonials, liposome-encapsulated amphotericin B, amphotericin B deoxycholate, paromomycin sulfate, and pentamidine isethionate. Of these, the most highly recommended is the oral medicine miltefosine. It is commonly administered for 28 days. It should be noted, however, that miltefosine must not be administered to pregnant women.

Currently, no vaccine or drug has been developed to prevent infection, and the most basic preventive measure is to avoid being bitten by a phlebotomus, a type of sand fly. Phlebotomus are very difficult to spot because they are tiny, about one-third the size of a mosquito, and they do not make a buzzing noise. Therefore, it is necessary to use insecticides and mosquito nets impregnated with an insecticide. The Olyset® Net developed by Sumitomo Chemical Co., Ltd. is known as such an insecticide impregnated mosquito net which is safe and has long-lasting insecticidal efficacy.

According to data released in 2013 by the Centers for Disease Control and Prevention (CDC), this disease is widely epidemic in rural areas in more than 90 countries/regions in the tropical or subtropical and southern European regions. Specifically, there is a high risk of infection in the following countries in the eastern and western hemispheres:

Mexico, Latin America

It is estimated that about 12 million people worldwide are infected, while about 900,000 to 1.3 million are infected every year. It is also estimated that about 350 million people are susceptible to infection.

About 20,000 to 30,000 people die of leishmaniasis every year. Of the types of the leishmaniases, visceral leishmaniasis is believed to kill those infected within two years when left untreated.

References

WHO- Neglected Tropical Diseases, accessed April 2, 2015,
http://www.who.int/neglected_diseases/mediacentre/factsheet/en/

CDC- Neglected Tropical Diseases, accessed April 2, 2015,
http://www.cdc.gov/globalhealth/ntd/diseases/