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.
Causes
Leishmaniasis is due to protozoan parasites from the Leishmania species. You get leishmaniasis from being bitten by an infected sand fly.
Leishmaniasis is due to protozoan parasites from the Leishmania species. You get leishmaniasis from being bitten by an infected sand fly.
The parasite lives and multiplies inside the female sand fly. This insect is most active in humid environments during the warmer months and at night, from dusk to dawn. Domestic animals, such as dogs, can serve as reservoirs for the parasite. Transmission may occur from animal to sand fly to human.
Humans can also transmit the parasite between each other through a blood transfusion or shared needles. In some parts of the world, transmission may also occur from human to sand fly to human.
There are three main forms of the disease:
cutaneous leishmaniasis (CL),
visceral leishmaniasis (VL) also known as kala-azar,
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.
Symptoms:
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.
Diagnosis
It’s important to tell your doctor if you lived in or visited a place where leishmaniasis is common. That way your doctor will know to test you for the parasite.
If you have leishmaniasis, your doctor will use other tests to determine which species of Leishmania is the cause.
Diagnosing cutaneous leishmaniasis
Your doctor may take a small amount of skin for a biopsy by scraping one of the ulcers. They’ll often look for the DNA, or genetic material, of the parasite. They can use a variety of methods to identify the species of parasite causing the infection.
Diagnosing visceral leishmaniasis
Many times, people don’t remember a bite from a sand fly. This can make the condition hard to diagnose.
A history of living or traveling to an area of leishmaniasis is helpful. Your doctor may first perform a physical exam to look for an enlarged spleen or liver. They may then perform a bone marrow biopsy or take a blood sample for examination.
A variety of specialized tests aid with diagnosis. Special chemical stains of bone marrow can help identify immune cells infected with the parasite.
Treatment
Antiparasitic drugs, such as amphotericin B (Ambisome), treat this condition. Your doctor may recommend other treatments based on the type of leishmaniasis you have.
Cutaneous leishmaniasis
Cutaneous ulcers will often heal without treatment. However, treatment can speed healing, reduce scarring, and decrease risk of further disease. Any skin ulcers that cause disfigurement may require plastic surgery.
Mucocutaneous leishmaniasis
These lesions don’t heal naturally. They always require treatment. Liposomal amphotericin B and paromomycin can treat mucocutaneous leishmaniasis.
Visceral leishmaniasis
Visceral disease always requires treatment. Several medications are available. Commonly used medicines include sodium stibogluconate (Pentostam), amphotericin B, paromomycin, and miltefosine (Impavido).
Prevention
There’s no vaccine or prophylactic medication available. The only way to prevent leishmaniasis is to avoid getting bitten by a sand fly.
Follow these steps to help prevent being bitten by a sand fly:
- Wear clothing that covers as much skin as possible. Long pants, long-sleeved shirts tucked into pants, and high socks are recommended.
- Use insect repellent on any exposed skin and on the ends of your pants and sleeves. The most effective insect repellants contain DEET.
- Spray indoor sleeping areas with insecticide.
- Sleep on the higher floors of a building. The insects are poor fliers.
- Avoid the outdoors between dusk and dawn. This is when sand flies are most active.
- Use screens and air conditioning indoors when possible. Using fans might make it more difficult for the insects to fly.
- Use a bed net tucked into your mattress. Sand flies are much smaller than mosquitos, so you need a tightly woven net. Spray the net with insecticide containing pyrethroid if possible.
- Buy bed nets, insecticides, and repellents before traveling to high-risk areas.