Leishmaniasis is a disease caused by protozoa species, which is transmitted by the bite of a female sandfly. It is classified as cutaneous, mucocutaneous, and visceral leishmaniasis.
The typical lesions of cutaneous leishmaniasis were described as early as 900 BC and have been referred to as the "Balkan sore" in the Balkans, the "Delhi boil" in India, the "Baghdad boil" in Iraq, and "saldana" in Afghanistan.
These protoza spend part of their life cycle in the gut of the sandfly, during feeding it ingest about 1000 parasites per bite into the host skin at the site of bite, from where they pass into the blood and tissues. These promastigotes are phagocytosed by macrophages at the reticuloendothelial system, where they shed their flagella and become amastigotes and multiply by binary fission. Once the infected macrophages rupture, the infection spreads to other macrophages and other parts of the body. Temperature is an important factor that determine the localization of the lesions. Species causing visceral leishmaniasis are able to grow at core temperatures, while those responsible for cutaneous leishmaniasis grow best at lower temperatures.
In cutaneous leishmaniasis, the hallmark of the disease is skin lesions, which can spontaneously heal in 2-10 months. Untreated cutaneous leishmaniasis have tendency to progress to cause disseminated mucocutaneous leishmaniasis and can cause death.
In mucocutaneous leishmaniasis, mucosal ulcerations usually develop by metastasis from disseminated protozoa rather than by local spread. Secondary infection plays a prominent role in the persistence of ulcers. Ulcer progression is slow and steady.
Visceral leishmaniasis become clinically apparent after weeks to months of infection. The disease can be acute, subacute, or chronic. The disease manifest in patients who loses immunity after they have left the endemic regions. Visceral leishmaniasis is progressive and mortality rates in untreated cases range from 75-95% or as high as 100% within 2 years in the developing countries
It is estimated by Centers for Disease Control and Prevention (CDC) that approximately 1.5 million new cases of cutaneous leishmaniasis and 500,000 cases of visceral leishmaniasis occur worldwide every year. Mucocutaneous leishmaniasis is less common. Current prevalence of the disease is about 12 million worldwide. The incidence is highest in tropical and subtropical regions where conditions are favorable for sandflies. Most cases of cutaneous leishmaniasis are seen in Afghanistan, Brazil, Iran, Iraq, Peru, and Saudi Arabia, while visceral leishmaniasis is most common in Bangladesh, Brazil, India, Nepal, and Sudan. Males are more commonly infected than females, most likely because of their increased exposure to sandflies. Visceral leishmaniasis has been shown to be common in males than in females.