Leishmaniasis

Leishmaniasis is a neglected tropical disease that affects mainly the poor and occurs in India, Peru, Nepal, Ethiopia, Sudan and Brazil.  There is increasing resistance against existing treatments and there are no new drugs at advanced stages of development.  No vaccine has ever been developed for Visceral Leishmaniasis

Cause

Leishmaniasis infection is caused by the leishmania protozoan parasites.  Transmission is by the bite of the female vector phlebotomine sandfly.  The female sandfly becomes infected by biting and sucking blood from a person or animal infected with the leishmania parasite. 

Consequences

Infection with leishmania manifests in various forms; visceral, cuteneous and mucocuteneous.  Visceral Leishmaniasis is the most severe form of the disease.

Cuteneous infection is the most common form with numerous ulcers developing on the exposed parts of the body (face, arms, and legs).  The healing of ulcers leaves permanent scars all over the affected areas of the body.  Mucocuteneous infection results in destruction of the mucous membranes of the nose, mouth and throat.  Symptoms of Visceral Leishmaniasis (Kalar-Azar) include irregular bouts of fever, enlargement of the liver and spleen, marked weight loss and if left untreated can lead to death.

In general, Leishmanisis infection is associated with pain, debilitating illnesses, permanent scarring, social rejection and death.

Global burden

Over 300 million people are at risk of the disease with 12 million people believed to be currently infected (WHO).  About 70,000 deaths in children and young adults occur annually.

About 95% of cases of human Visceral Leishmanisis occur in India, Bangladesh, Nepal, Sudan and Brazil (Trends Parasitol. 2006. 22552-557).  Amongst parasitic infections, Visceral Leishmanisis ranks second to malaria on mortality and is in the top ten infectious diseases globally by DALY’s lost (WHO World Health Report 2002)

Vaccines

There are currently no vaccines for the treatment or prevention of Leishmanisis.  With the development of a marked resistance to available drugs, the development of a vaccine needs to be accelerated.  Efforts at developing an effective vaccine have recently being given prominence by the WHO.  However, difficulties arise in the induction of an effective immune response following the administration of vaccines.  The induction of strong Th1-type cytokine immune responses is required as it is known that Th2-type responses are induced in chronic leishmaniasis.