Leishmaniasis

Excerpt

Leishmaniasis is a disease caused by the protozoa Leishmania and is most commonly transmitted by infected sandflies. It has been historically widespread in tropical climates across multiple continents including Europe, Africa, Asia, and America. In humans, these parasites replicate intracellular and present classically with a visceral or cutaneous disease.

Leishmaniasis has tremendous historical relevance, with recorded disease thousands of years before common era (BCE). An examination of ancient Egyptian mummies dating back to 3500 to 2800 BCE yielded successful amplification of Leishmaniasis donovani DNA. During a time period referred to as the Middle Kingdom, Egyptian trade and military excursions involving Nubia (modern Sudan) are thought to be responsible for the introduction of leishmaniasis into Egypt, as DNA-positive samples were not seen prior to this time period. Furthermore, some sources suspect Sudan as the original foci of visceral leishmaniasis (VL). Additionally, medical manuscripts called Ebers Papyrus from 1500 BC described a cutaneous condition thought to be cutaneous leishmaniasis then termed “Nile Pimple.” With this ancient concept of disease in mind, an early form of vaccination was attempted in the Middle East and Central Asia. This was performed by taking exudates of active lesions and inoculating them into the buttocks of children.

Over the next thousand years cutaneous sores consistent with leishmaniasis were described, and in historical northern Afghanistan, a disease termed the "Balkh sore" is now thought to have been caused by L. tropica. In Asia and the Middle East, the disease continued to be documented, and conditions termed the "Aleppo boil," "Jericho boil," and the "Baghdad boil." Many of these names remain relevant in modern times.

Early recognition of the infectious nature of leishmaniasis was first encountered by a Scottish physician who noticed the parasites in a Delhi boil, but it wasn’t until similar findings were seen by Russian physician Piotr Fokich Borovsky that these bodies in Asian sores were actually suspected to be protozoa as published in 1898. In 1900, a British pathologist noted ovoid bodies and suggested these represented degenerated trypanosomes. He then termed this illness “dum-dum fever.” Around the same time, Irish doctor Charles Donovan published a paper on similar ovoid bodies from the spleen of native Asian Indians. An investigation into the Indian disease kala-azar and splenic ovoid bodies described by the pathologist Leishman and clinician Donavan suggested that these ovoid bodies did not degenerate trypanosomes but a new protozoan species later termed Leishmania donovani. Over the next decades, subspecies would be identified including L. tropica, L. aethiopica, and many more. Classification of the disease into a new world and old world leishmaniasis would then be based on these organisms and their geographic distribution.