Therapy Analysis - Leishmaniasis
Leishmaniasis: an old plague for a new world
An estimated 2 million people become infected with the Leishmania parasite every year.
The resulting disease lacks notoriety, particularly as it occurs most frequently in developing countries, but it is nevertheless well documented.
Texts dating back to the 15th and 16th century Incan period refer to the risk run by seasonal agricultural workers who were found to have skin ulcers when they returned from the Andes, which was attributed to 'valley sickness' or 'Andean sickness'. Over time, further terms were coined, including 'white leprosy' because of the strong resemblance of the characteristic lesions to leprosy, and 'Dum-Dum fever', which was named after a town considered to be particularly unhealthy.
One of the first clinical descriptions of leishmaniasis was made in 1756 by Alexander Russell. William Boog Leishman clinically identified the Leishmania organism - the protozoal flagellates of which there are 11 specific species - in 1901. Captain Donovan defined it as a 'new' organism soon after in 1903, and Major Ross made the final link and named it Leishmania donovani. Many other species of organism have since been separately identified, most of which are found in the systemic or visceral form of infection. It was revealed that the parasite is transmitted to humans and animal reservoirs from the bite of female sand flies.
The physiological hallmark of leishmaniasis is an extremely enlarged spleen and it is divided into 2 main kinds: cutaneous and visceral. Cutaneous infection manifests as skin ulcers, smaller satellite lesions and swelling of lymph nodes. Sadly, the permanent scars that remain after what is often a long healing process are not just physical; they often provoke social prejudice, which is not surprising given that 90% of all cutaneous infection occurs in countries where access to education is limited: Afghanistan, Brazil, Iran, Peru, Saudi Arabia and Syria. The infectious burden does not end there. Once the cutaneous infection is cleared, mucocutaneous infection (espundia) may occur as a secondary consequence. The lesions, which affect the mucus membranes of the mouth, nose and throat and surrounding tissues, result in severe facial disfigurement, and other inherent breathing and swallowing difficulties. Again, 90% of these infections occur in Bolivia, Brazil and Peru.
Visceral leishmaniasis, otherwise known as kala azar (Hindi for black fever), is the most severe form of the disease. It is estimated that 500,000 people are infected each year worldwide (except, interestingly, in Australia). In this manifestation, the parasites migrate to the bone marrow, lymph nodes and spleen, causing damage to the immune system by destroying blood cells and platelets, and giving rise to several unpleasant symptoms, including fever, fatigue, weight and appetite loss, weakness, dizziness and abdominal discomfort. Left untreated, infected people in developing countries die within 2 years from secondary infections such as tuberculosis and pneumonia, while those who survive can expect to encounter the cutaneous form up to 10 years after the first occurrence. Visceral leishmaniasis can even be passed from an asymptomatic mother to her unborn child, and co-infection with HIV is also increasing. In North-Western Ethiopia, 30% of patients treated by Médecins Sans Frontières for leishmaniasis were also infected with HIV. These patients are difficult to diagnose and over half experience relapses after treatment.
