Leishmaniasis

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Leishmaniasis manifests typically as a skin sore erupting weeks to months after a sandfly bite. At its most severe in Kala azar(black fever) it is associated with fever and massive splenomegaly. In man at least 21 species of Leishmania protozoa can cause disease transmitted by the female Phlebotominae sandflies. It has been known since the 7th century BC and remains a significant disease challenge through out the topics and subtropics with perhaps Afghanistan having the highest prevalence.

  1. Cutaneous leishmaniasis
    • Classic skin ulcer
    • May spontaneously resolve (especially if adequate TH1-type T-cells) or evolve
    • Diffuse cutaneous leishmaniasis - difficult to treat
  2. Mucocutaneous leishmaniasis
    • Disfiguring
    • Challenging to cure
  3. Visceral leishmaniasis(Kala azar) - fatal if untreated
    • Post kala-azar dermal leishmaniasis (PKDL) a disfiguring skin rash/nodular form of relapse should be monitored for. It can occur after any form of the disease in fact, usually as hypo-pigmented macules, papules, nodules, or facial erythema. Nerve involvement like leprosy is possible with the African Leishmania spp.

Contents

Aetiology

Female sandflies inject on biting the infective stage, metacyclic promastigotes. These are ingested by macrophages and transform into amastigotes which further spread in the animal host with differing tissue specificities depending on species of protazoa. An amastigote ingested by another sandfly transorms into a promastigote in the sandfly's midgut, which then develop into metacyclic promastigotes and migrate to the proboscis. Commonest are:

  1. L. donovani complex - visceral leishmaniasis
    • Leishmania donovani - old world
    • Leishmania infantum - old world (including Southern Europe)
    • Leishmania chagasi - America's
  2. L. mexicana
    • Leishmania mexicana
    • Leishmania amazonensis
    • Leishmania venezuelensis
    • Leishmania tropica
  3. Leishmania major - rarely servire and the classic cause of cutaneous leishmaniasis
  4. Leishmania aethiopica - mucocutaneous leishmaniasis
  5. Subgenus Viannia
    • Leishmania (Viannia) braziliensis - mucocutaneous leishmaniasis
    • Leishmania (Viannia) guyanensis
    • Leishmania (Viannia) panamensis
    • Leishmania (Viannia) peruviana

Diagnosis

  • Blood film (ideally from buffy coat) or aspirate (spenic/marrow) showing Leishman-Donovan bodies - amastigotes in monocytes/neutrophils or macrophages.
  • Serology (not specific)
    • K39 dipstick test recommended at present
    • DAT anti-leishmania antigen test requires higher technology base
    • Latex agglutination test

Prevention

  • High standards of hygiene and sanitation (animal intermediate hosts)
  • Insect repellants (can be very effective)

Vaccination not presently possible, but developments are likely

Treatment

Visceral leishmaniasis

The standard treatment of amphotericin B 1mg/kg on alternate days for 30 days is inferior to shortened combination regimes in terms of adverse events. The respective cure rates are
PMID link to reference awaited
:

This article is a work in progress. Please feel free to contribute to it.

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