Black fever, also known as Visceral leishmaniasis and kala-azar, is the second largest parasitic killer in the world with up to 400,000 infections each year worldwide.

Visceral leishmaniasis is both an anthroponotic and a zoonotic disease. VL is the most severe form of leishmaniasis, it came to the attention of doctors in 1824 in India, mistakenly thought to be a form of malaria, it was given the name kala-azar, Kala means black while Azar means fever in Hindustani.

Causal agent:

Leishmania donovani or Leishmania infantum are often present in amastigote (without a flagellum) form in the mononuclear phagocyte system (part of the immune system) of the infected individual, it can also be found in the promastigote form in the vector.

Disease reservoir:

The disease is mainly found in domestic dogs, it can also be another wild animal like foxes in France and jackals in the middle east...

The infected dog's symptoms may include weight loss, sores on the skin, peeling, bald patches, ulcers, conjunctivitis, muscular atrophy, nasal discharge and even blindness, mild heart attacks and organ failure.

The Vector:

The adult female Sandfly/Phlebotominae is a bloodsucker, when it bites an infected animal amastigotes (which are round, non-motile, and only 3–7 micrometers in diameter) are ingested along with the prey's blood. 

Those amastigotes inside its stomach, transform into promastigotes (with a flagellum) allowing mobility, those promastigotes migrate to the proximal end of the gut ready to be released inside the human host, where they transform back into amastigotes.

Those amastigotes multiply by simple division inside the phagolysosome until breaking it down by sheer pressure of mass or by triggering the exocytosis response of the macrophage, where they migrate to fresh cells through the bloodstream infecting the host completely.

The picture below summarise the process : 

Symptoms include:

-A specific skin lesion that represents the mosquito's bite:

-Mad fever, which can fluctuate a lot during the disease going from 40 to 38 and usually doesn't respond to treatments.Chills and sweating are also frequent but they are dangerous and it can misguide doctors to think of asepsis.

-Enlargement of the spleen called Splenomegaly, generally progressive and it can become so huge, down to the umbilicus.

-Pallor generally due to an anemia caused by the parasite and is the result of a reduced amount of oxyhemoglobin and is visible in the skin or mucous membrane.

The blackening of the skin that gave the disease its common name in India does not appear in most types of the disease.

Other signs include  Hepatomegaly, enlarged lymph nodes,diarrhea etc...

Without a treatment, the disease is generally deadly.the patient becomes dehydrated, malnourished and dies quickly in few months.This condition is called cachexia.

Various treatments are available, Chemotherapy remains the most important Antimony complex has been the first line treatment of VL during the last several decades. The second line of drugs consists of amphotericin B, paromomycin and recently developed miltefosine used to cure resistant types of the parasite.

Visceral leishmaniasis is a serious and deadly disease but a treatable one.if you intend to visit an endemic country like India or Africa make sure to cover yourself well and avoid mosquito's bites.

References : 

https://www.ncbi.nlm.nih.gov/pubmed/12150849

https://www.ncbi.nlm.nih.gov/pubmed/16778314

https://en.wikipedia.org/wiki/Visceral_leishmaniasis

https://www.ncbi.nlm.nih.gov/pubmed/11703838

https://www.dndi.org/diseases-projects/leishmaniasis/disease-background-vl/

Picture Credit:

Pixabay: 1 /3

Wiki: 2 /4 /5

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