Cutaneous leishmaniasis is a type of leishmaniasis caused by different species of leishmania parasites depending on the geographical location of the species and it is transmitted by a sandfly. This infection affects the skin and forms nodules and ulcers.

Cutaneous Leishmaniasis Epidemiology

The old World cutaneous leishmaniasis (also called Oriental sore or Delhi boil) is caused by Leishmania tropica and it is endemic in the Middle East, Africa and India whereas the New World cutaneous leishmaniasis (also called American cutaneous leishmaniasis or the Chicle ulcer or Bay sore) is caused by Leishmania Mexicana and it is found in Central America and South America.

Cutaneous Leishmaniasis Etiology

Cutaneous leishmaniasis is caused commonly by Leishmania tropica (this parasite is found in the old world) and Leishmania mexicana (found in the Americas). There are many other species of leishmania parasites that can cause cutaneous leishmaniasis depending on the geographical distribution of the species of parasite.

Symptoms of Cutaneous Leishmaniasis

1. Formation skin nodules that can be diffuse
2. Formation of skin ulcers that may not heal for a long time

Species of Leishmania parasite causing Cutaneous Leishmaniasis

1. Leishmania tropica
2. Leishmania major
3. Leishmania aethiopica
4. Leishmania mexicana
5. Leishmania amazonensis
6. Leishmania garnhami
7. Leishmania pifanoi
8. Leishmania venezuelensis
9. Leishmania braziliensis
10. Leishmania guyanensis
11. Leishmania panamanensis
12. Leishmania peruviana

Leishmania major and Leishmania tropica are common in Russia, Eastern Europe, the Middle East, Central Asia, the Mediterranean littoral and sub-Saharan Africa. The Leishmania major reservoirs are desert rodents, while reservoirs for Leishmania tropica are dogs and humans. There is a rare chronic relapsing type caused by leishmania tropica called Leishmaniasis recidivans.

Leishmania aethiopica is found in the highlands of Ethiopia and Kenya and its reservoir is the hyrax. Healing of the skin lesions is spontaneous and it leaves a scar.

Pathogenesis of Cutaneous leishmaniasis and Life cycle of Parasite

1. Whenever a sandfly bites, it injects Leishmania parasite into the skin. The local response of the skin depends on the species of leishmania, the size of the inoculum and the degree of response by the host immune system.
2. Single or multiple painless nodules occur on exposed areas of the skin within 1 week to 3 months following the sandfly bite.
3. These nodules enlarge and form ulcers with a characteristic erythematous raised border with formation of overlying crust in some cases. This ulcer is called an Oriental sore. The ulcer usually heals within months or years and leaves a pale disfiguring scar on the skin which can be seen while performing a physical examination on the patient.
4. When the cell-mediated immunity of the body is good, the immune system attacks the organisms resulting in skin destruction which manifests as the skin ulcer with subsequent healing as the infection is cleared (this is the similar situation that happens in tuberculoid Leprosy)
5. In a poor immune system, the parasites then migrate to the reticuloendothelial cells which are fixed phagocytic cells in lymph nodes and the infection becomes diffused.

The skin lesions often become superinfected with bacteria; the lesions are not contagious but humans may serve as reservoirs for the parasites which can be transmitted to others when the sandfly bites an infected individual and transmits it to another, especially in endemic regions.

Types of Cutaneous Leishmaniasis

1. Simple Cutaneous Leishmaniasis
2. Diffuse Cutaneous Leishmaniasis

Simple Cutaneous Leishmaniasis

This occurs when the immune system is able to control the infection. The response of the immune system leads to formation of ulcers on the skin that eventually heals with time within months or few years and leaves a scar at the point of bite by the sandfly.

Diffuse Cutaneous Leishmaniasis

In patients with a poor immune system, the diffuse type of cutaneous leishmaniasis occurs where nodular skin lesions arise but does not form ulcers and the lesions spread across the body with time. The lesions are mostly concentrated near the nose. An untreated infection in a deficient immune system can last more than 20 years because the cell-mediated immunity is defective and the Leishmanin skin test will always be negative because the body cannot mount an immune response (this is similar to the case of lepromatous leprosy). This chronic form of cutaneous leishmaniasis occurs commonly in Venezuela and Ethiopia.

Cutaneous Leishmaniasis Risk Factors

1. Travelling to an endemic area
2. Living in an endemic area

Cutaneous Leishmaniasis Diagnosis

1. Diagnosis of Cutaneous Leishmaniasis is made microscopically by identifying the presence of amastigotes in a Giemsa stained smear taken from the skin lesion.
2. The leishmanin skin test is also used for diagnosis of both cutaneous and mucocutaneous leishmaniasis and usually becomes positive when the skin ulcer appears and can be used to diagnose cases outside the area of endemic infection.

Cutaneous Leishmaniasis Treatment

1. Large skin lesions of cutaneous leishmaniasis or those in cosmetically sensitive sites can sometimes be treated locally or by curettage, cryotherapy or by application of topical anti-parasitic agents
2. The best drug for treatment of cutaneous leishmaniasis is sodium stibogluconate as for visceral leishmaniasis but this drug treatment is less successful as antimonial salts are poorly concentrated in the skin thereby reducing their potency and Leishmania aethiopica is not sensitive to antimonial salts
3. Use of antibiotics to treat associated infections

Cutaneous Leishmaniasis Complications

1. Secondary wound infection
2. Cosmetic problems especially on the face and uncovered parts of the body as the scar disfigures the affected parts

Cutaneous Leishmaniasis Differential Diagnosis

1. Mucocutaneous Leishmaniasis
2. Tuberculosis of the skin
3. Leprosy

Prevention of Cutaneous Leishmaniasis

Prevention is by controlling the vector which can be done by using bed netting, window screens, wearing protective clothing and use of insect repellent cream