Leishmaniasis

Leishmaniasis refers to zoonoses caused by parasites of the genus Leishmania. There are three main forms of leishmaniasis:

• visceral (also known as kala-azar or dum-dum fever)
• cutaneous
• mucocutaneous leishmaniasis

Epidemiology

Leishmaniasis is a truly global disease with a higher burden in the tropical regions of Africa, Asia and Latin America. The disease was once thought to be non-existent in Australia, however cases have been reported ^1,2. Globally the incidence of new disease was recently reported as a million cases a year ³, however precise numbers are impossible to calculate as the disease tends to affect the penurious in resource-poor countries.

Clinical presentation

Clinical presentation depends upon the type of leishmaniasis, although there is overlap between the forms:

• visceral leishmaniasis
  • fever
  • hepatosplenomegaly
  • skin disease may be seen
• cutaneous leishmaniasis (includes mucocutaneous form)
  • ulcerating skin lesions
  • +/- visceral sequelae in immunocompromised hosts

Pathology

Tiny insects called phlebotomine sand flies act as vectors for the pathogenic Leishmaniasis spp. (genus of trypanosomes: unicellular flagellate protozoan parasite). The female flies require the blood of certain mammals, including humans, for their own ovulatory processes. Whilst the flies take the blood they become infected with the amastigote form of Leishmaniasis which multiplies and transforms inside the sand fly's gut to form the promastigote actively motile form ⁷.

The next time the fly bites an animal host the Leishmaniasis protozoa pass back to the human (or other mammal) to complete its life cycle ⁷. Potentially fatal species include L. donavi and L. infantum.

Radiographic features

Visceral leishmaniasis causes splenomegaly that is not always distinct from other forms of splenomegaly. Reported cases suggest that multiple nodular lesions in the spleen may occur ^4-6.