17th June 2024

Leishmaniasis

Leishmaniasis is a protozoal infection endemic within many tropical and subtropical countries, with an annual incidence of up to 1,000,000 cases worldwide. Transmitted by the phlebotomine sand-fly, various forms of the disease exist, including visceral (kala-azar), cutaneous, mucocutaneous, and post-kala-azar. Visceral leishmaniasis presents with symptoms that include fever, weight loss, lymphadenopathy, and hepatosplenomegaly. Thrombocytopenia, leukopenia, and anaemia are often found on a full blood count. The untreated mortality is close to 100%. There are a variety of ways to make the diagnosis, including antigen-based point of care tests, serology, polymerase chain reaction (PCR), and direct detection of amastigotes through splenic, lymph node, or bone marrow aspiration. It is important to test patients for HIV as this often co-exists with visceral leishmaniasis, with the latter occurring as an opportunistic infection. When HIV co-infection is present, leishmaniasis serology is less sensitive. Treatment of visceral leishmaniasis normally requires intensive parenteral therapy over several weeks. Agents of choice include sodium stibogluconate, amphotericin B, paromomycin and pentamidine. Miltefosine is the only oral agent currently in use. It is beneficial in that it can be administered in the community; however, this may lead to poor compliance, especially due to gastrointestinal side-effects. Teratogenicity is another potential issue with this medication. Post-kala-azar leishmaniasis presents with diffuse maculopapular or nodular lesions, which start at the mouth before potentially spreading to the rest of the body. Again, this is associated with HIV co-infection. Lesions can be biopsied for diagnosis. The natural history of post-kala-azar leishmaniasis varies between regions. It often resolves spontaneously in Sudan, whereas it normally requires treatment in India, using the same medications as for visceral leishmaniasis.

Cutaneous leishmaniasis presents with one or more skin lesions, which can vary in appearance. They are classically said to resemble volcanoes, with a raised outer edge and depressed ulcerated centre. Cutaneous leishmaniasis is generally self-limiting and resolves over several months. The lesions can be biopsied for diagnosis, with PCR used to identify the subgenus. This can be important as the subgenus Viannia can cause mucocutaneous leishmaniasis, which involves disfiguring spread of lesions to the mucosa of the mouth and nose, often months to years after apparent healing of the primary lesions. Whether to treat cutaneous leishmaniasis with anything more than topical therapy (or at all) generally depends on whether it is classified as simple or complex. Cutaneous leishmaniasis may be deemed complex if there are several lesions involved, if the lesions are large, if the lesions are having a significant cosmetic impact, or if they involve the lymphatics. Simple lesions can be left to heal over time or treated with topical or oral therapy. Complex lesions require parenteral treatment, such as intravenous or intramuscular sodium stibogluconate. If there is suspicion that the causative subgenus is Viannia, either by local endemicity or by formal PCR analysis, then parenteral therapy would be used to reduce the risk of subsequent mucosal spread.