Leishmaniasis Overview and Types

Leishmaniasis: A Detailed Overview

• Definition: Leishmaniasis is a vector-borne parasitic disease caused by Leishmania species (over 20). It is primarily zoonotic and different species cause various disease manifestations. Domestic dogs are important reservoir hosts.

Types of Leishmaniasis

• Cutaneous Leishmaniasis (CL): Characterized by skin ulcers and nodules; potentially disfiguring nasal lesions.
• Mucocutaneous Leishmaniasis: Affects mucous membranes, causing disfiguring lesions.
• Visceral Leishmaniasis (VL): Damages internal organs; a life-threatening condition, fatal if untreated in over 95% of cases.

Transmission

• Vector: Transmitted by the bite of infected female phlebotomine sandflies (over 90 species known).

Morphology

• Human hosts: Amastigote (Leishman body) form.
• Sandfly vectors: Promastigote (Leptomonad) form.

Risk Factors

• Socioeconomic: Poverty, poor housing, poor sanitation increase sandfly breeding and human exposure.
• Malnutrition: Deficiencies in protein-energy, iron, vitamin A, and zinc increase disease severity.
• Population Mobility: Movement of non-immune populations contributes to disease outbreaks.
• Environmental Change: Urbanization and human encroachment on forested areas impact disease incidence.
• Climate Change: Alterations in temperature, rainfall, and humidity impact vector and reservoir host distribution and survival.

Visceral Leishmaniasis (VL)

• Description: Chronic systemic disease—intracellular protozoa. Characterized by fever, hepatosplenomegaly, lymphadenopathy, anemia, leukopenia, thrombocytopenia, wasting, and weakness; also known as kala-azar.
• Severity: Fatal if untreated in over 95% of cases.
• Post-Kala-azar Dermal Leishmaniasis (PKDL): Skin rash (macular, papular, or nodular) usually affecting the face, upper arms, trunk, and other body parts, typically appearing months to years after apparent VL treatment, mainly in East Africa and the Indian subcontinent; 5-10% of VL patients.
• Infectious Agents: Primarily Leishmania donovani, L. infantum, and L. infantum/chagasi.
• Reservoir Hosts: Humans, wild canids (foxes, jackals), and domestic dogs.
• Incubation Period: Generally 2-6 months, with a range of 10 days to years.
• Communicability: Not usually transmitted person-to-person, infectious to sandflies, infectivity can persist after clinical recovery. Person-to-person transmission, rare, mainly among co-infected HIV-positive IV drug users.
• Susceptibility: General susceptibility but VL induces lasting homologous immunity.
• Transmission Mode: Bite of infected female phlebotomine sandflies. Person-to-person is rare, (HIV and IV drug use).

Cutaneous and Mucosal Leishmaniasis

• Synonyms: Baghdad boil, Delhi boil, oriental sore (other regions). Espundia, Uta-and Chiclero ulcer (Americas).
• Definition: Polymorphic protozoan disease of the skin and mucous membranes, caused by various Leishmania species; obligate intracellular parasites in humans and mammals.
• Symptoms: Progresses from maculae to papules, enlarging, and forming ulcers (absence of bacterial infection). Lesions can be single or multiple, occasionally non-ulcerative and diffuse. Heal spontaneously in weeks/months or persist for a year or more. Some strains (especially Western Hemisphere) can disseminate to mucous membranes even years after initial healing.
• Prevalence: Most common form; primarily in the Americas, Mediterranean basin, Middle East, and Central Asia. Over 95% of cases occur in the Americas.

Occurrence of Leishmaniasis

• VL: Primarily in Brazil, East Africa, and India. 50,000–90,000 new cases annually, reported to WHO by 25–45%. In 2019, over 90% of new cases in 10 countries.
• CL: Primarily in the Americas(95%), Mediterranean basin, Middle East, and Central Asia. 600,000–1,000,000 new cases annually in 2019, 87% in 10 countries.

Diagnosis

• VL: Microscopy (intracellular amastigotes). PCR. Serology (IFA, ELISA). Urine antigen test. Recombinant k39 immunochromatographic strip test.
• CL: Visual inspection. Microscopic confirmation of intracellular amastigotes.

Control and Treatment

• Prevention: No vaccine currently available, but candidate vaccines in development.
• Control measures: Vary based on reservoir and vector habits. Include:
  • Case management: Rapid diagnosis and treatment of all forms
  • Vector control: Periodic residual insecticide spraying (stone walls, animal houses, rubbish heaps); Insecticide-treated bed nets.
  • Environmental control: Eliminate breeding sites, reservoir control (dogs, gerbils).
  • Patient/Contact Management: Reporting to health authorities, isolation, concurrent disinfection, quarantine of contacts, contact/source investigation.
• Treatment: Pentavalent antimonials (first line); amphotericin B and liposomal amphotericin B for antimony-resistant cases.

Epidemic Measures

• Effective control—understanding local ecology, transmission, reduce mortality, stop transmission, prevent geographical expansion.
• Key measures: Case detection & treatment, Vector control (indoor residual spray, nets, reservoir control), Surveillance.

Explore the different forms of leishmaniasis, including cutaneous, mucocutaneous, and visceral types. Learn about the transmission, risk factors, and morphology of this parasitic disease caused by Leishmania species.