The leishmaniases are a group of diseases caused by protozoan parasites from more than 20 Leishmania species. These parasites are transmitted to humans by the bite of an infected female phlebotomine sandfly, a tiny – 2–3 mm long – insect vector.
There are three main forms of the disease: cutaneous leishmaniasis (CL), visceral leishmaniasis (VL), also known as kala-azar, and mucocutaneous leishmaniasis (MCL). CL is the most common form, VL is the most severe form and MCL is the most disabling form of the disease.
Most people who become infected with the parasite do not develop any symptoms during their lifetime. Therefore, the term leishmaniasis refers to the condition of becoming sick due to a Leishmania infection, not to being infected with the parasite.
In 2018, 92 and 83 countries or territories were considered endemic for, or had previously reported cases of, CL and VL, respectively.
Today, more than 1 billion people live in areas endemic for leishmaniasis and are at risk of infection. An estimated 30 000 new cases of VL and more than 1 million new cases of CL occur annually.
CL usually produces ulcers on the exposed parts of the body, such as the face, arms and legs. There may be many lesions – sometimes up to 200 – which can cause serious disability. When the ulcers heal, they invariably leave permanent scars, which can lead to stigmatization, especially for women and girls.
VL is characterized by irregular bouts of fever, substantial weight loss, swelling of the spleen and liver and serious anaemia. If the disease is not treated, the fatality rate can be as high as 100% within 2 years.
MCL produces lesions that can partially or totally destroy the mucous membranes of the nose, mouth and throat cavities and surrounding tissues. This disabling form can also lead to social exclusion.
PKDL (post-kala-azar dermal leishmaniasis), a complication of VL, is mainly seen in East Africa and South-East Asia. It is characterized by a discoloured (hypopigmented) flat skin (macular) rash, combined with some slightly elevated (maculopapular) or elevated (nodular) rash, usually in patients who have recovered from VL. PKDL usually appears 6 months to 1 or more years after apparent cure of VL, but it may occur earlier or even concurrently with VL, especially in Sudan. PKDL heals spontaneously in most cases in Africa but rarely in patients in India.
Antileishmanial treatment depends on the causative species and the condition of the patient (e.g. pregnancy, immunosuppression).
Regardless of the causative Leishmania species, antileishmanial treatment cannot provide a sterile cure, and the parasite remains in the human body and can cause a relapse when there is immunosuppression.
Treatment is complex and should be administered by highly experienced health personnel. Most antileishmanial medicines are injectable.