What Is Leishmaniasis?

Overview

There are several types of diseases affecting humans worldwide. One such type are parasitic diseases (caused by parasites: organisms that require another living organism, called the host, to complete their life cycles, to derive nutrition or do both). Some of these parasites are microscopic and are usually transmitted by a vector. For example, malaria is caused by Plasmodium, which is spread to humans through mosquitoes. 

Leishmaniasis is one of the parasitic diseases affecting humans and is considered a  neglected tropical disease. It is transmitted primarily through a bite from an infected female sandfly, mainly of the genus Phlebotomus which spreads the disease in Africa, Asia, and Europe, and Lutzomyia which spreads the disease in the Americas. Sandfly is a blood-sucking insect, which acts as the vector and releases Leishmania, a single-celled protozoan parasite into the bloodstream of an individual (the host), causing an infection.¹

Types of leishmaniasis

There are three types of leishmaniasis based on clinical diagnosis: cutaneous, mucocutaneous, and visceral. 

1. Cutaneous: Cutaneous leishmaniasis (CL) is the most common among the three types. It occurs on body parts exposed to sandfly bites like the tips of ears, nose, cheeks, forearms, and legs. The distinguishing feature is the skin lesions that develop from slow-healing skin ulcers. In the beginning, there is an increase in temperature at the site of the bite due to inflammation, then the site slowly fills up with blood, forming a papule. After two days, it becomes a pustule and breaks open which triggers itching. This is how an early ulcer is formed. Sometimes, a relapse of a lesion back into an active one can also occur. A subtype of cutaneous leishmaniasis called diffused cutaneous leishmaniasis is difficult to cure.¹
2. Mucocutaneous: Mucocutaneous leishmaniasis (ML) affects the mucous membranes of the nose, mouth, and throat. This type can go undetected because of slow invasion which provides plenty of time for the gradual destruction of the mucosal membranes. The lesions begin from the nasal areas and travel down to the throat region.¹
3. Visceral: Visceral leishmaniasis (VL) is the lethal type if not treated in time. It is also known as Kala-Azar or black fever and is prevalent in Asian countries like China and India.¹ The name Kala-Azar comes from the characteristic grey-black skin discolouration due to an increased immune reaction. Visceral leishmaniasis is caused by Leishmania donovani in Asia and Leishmania infantum in South America and Mediterranean Europe.² Symptoms take up to 8 months to appear.¹ This type primarily affects the internal organs such as the liver and spleen.²

Causes of leishmaniasis

Leishmaniasis is a common disease in tropical regions like India, Africa, South America and in areas like North America, and Eastern and Mediterranean Europe. According to the World Health Organisation, data accumulated till 2010 reveals that 90% of visceral leishmaniasis (VL) cases came from South Asian, South American, and African countries such as Bangladesh, Brazil, Ethiopia, India, South Sudan, and Sudan.¹ The disease is prevalent in poverty-stricken areas where malnourishment, poor sanitation, improper waste disposal methods, and lack of public health awareness are common.

A major reason why this occurs is the presence of sandflies. These flies thrive in moist habitats like salt marshes and places containing decaying matter like burrows. Their larvae are found in the mud and near fresh water.³ Several chemicals are secreted by the Leishmania parasites that aid their development within the sandfly's internal environment. They anchor and multiply in their anterior midgut.⁴ A female sandfly sucks blood to develop her eggs and transmits the Leishmania parasite she carries. 

Signs and symptoms of leishmaniasis

Depending on the type of leishmaniasis involved, various symptoms are noticed. Some common symptoms are fever and weight loss.

Symptoms of cutaneous leishmaniasis (CL) include the presence of skin ulcers or lesions.¹ Symptoms of mucocutaneous leishmaniasis (ML) include ulcers in the mucosal membranes of the nose, mouth, and throat.Visceral leishmaniasis (VL) causes chills, fatigue, skin discolouration, inflamed lymph nodes, and abdominal swelling due to the enlargement of the liver and spleen.

Management and treatment for leishmaniasis

The vector of leishmaniasis is the sandfly and some preventive measures can be taken to limit its breeding. Sleeping outside or on the ground should be avoided to prevent being bitten as sandflies are nocturnal. Insecticides can be used to kill insects in homes. Screens with very small holes (such as mosquito nets) can be used to cover windows and air conditioning vents to prevent sandflies from entering houses at night. In malnourished locations, diets must be fortified with zinc, adequate protein, and vitamin A.

All types of leishmaniasis are treated with a group of compounds called pentavalent antimonials. One drug belonging to this class is a chemical known as sodium stibogluconate (SSG) which is administered intravenously to patients. Liposomal amphotericin B (another type of drug) is used to treat visceral leishmaniasis (VL).¹ In some cases some therapies that are lethal to the Leishmania parasite are also carried out to supplement the treatment of ulcers. Examples of such therapies include cryotherapy (where the ulcer and its surroundings are cooled down at regular intervals) thermo therapy (where heat is applied on and around the ulcer, and laser therapy.

Diagnosis

In order to diagnose leishmaniasis, a needle biopsy is  performed. A small part of tissue is excised from suspected areas such as an ulcer, bone marrow, or swollen lymph node. To confirm cases of cutaneous or mucocutaneous leishmaniasis, a skin biopsy is performed.

Complications

Some of the complications of leishmaniasis include sepsis, pneumonia, relapse of a skin ulcer from a skin lesion, bacterial infections resulting from open ulcers, severe bleeding in the case of visceral leishmaniasis, or a rash called post kala-azar dermal leishmaniasis (PKDL).

If visceral leishmaniasis is left untreated, it can be fatal to the infected person.

FAQs

How can I prevent leishmaniasis?

You should avoid sleeping outside or on the ground. Since sandflies are nocturnal creatures, it is best to stay in closed spaces at night. Use insecticides to kill insects inside your home. To prevent sandflies from entering your home and air conditioning system, you can cover the windows and air conditioning with screens that have very fine holes.

How common is leishmaniasis?

It is a very common neglected tropical disease. It is endemic in Asia, Africa, the Mediterranean and Eastern Europe, and the Americas. Each year there are about 1.5 to 2 million new cases worldwide.¹

Who is at risk of leishmaniasis?

People living in poverty-stricken areas, those who are malnourished,  those who live in locations with poor sanitation and waste disposal systems, and those who do not have proper homes with closed-off interiors are all at a higher risk of leishmaniasis. Immunocompromised people are also at a higher risk.

What can I expect if I have leishmaniasis?

Fever, weight loss, fatigue, the appearance of skin ulcers, and swollen lymph nodes are some signs and symptoms of leishmaniasis.

When should I see a doctor?

You must visit a health care professional when you notice a skin ulcer that is blood-filled and itchy. If your lymph nodes are swollen, that is another sign for you to immediately seek the help of a doctor.

Summary

Leishmaniasis is a parasitic disease and one of the top ten neglected tropical diseases in the world. It is transmitted primarily through a bite of an infected Phlebotomus female sandfly, a blood-sucking insect, which releases Leishmania, a single-celled parasite into the bloodstream of an individual, causing an infection. A female sandfly sucks blood to develop her eggs and transmits the Leishmania parasite she carries. These flies thrive in moist habitats like salt marshes and places containing decaying matter like burrows. Their larvae are found in the mud and near fresh water. The disease is prevalent in poverty-stricken areas where malnourishment, poor sanitation, improper waste disposal methods, and lack of public health awareness are present.

There are three types of leishmaniasis, namely cutaneous, mucocutaneous, and visceral. Cutaneous leishmaniasis (CL) occurs on parts exposed to sandfly bites like the tips of ears, nose, cheeks, forearms, and legs. The distinguishing feature is the skin lesions that develop from slow-healing skin ulcers. Mucocutaneous leishmaniasis (ML) affects the nose, mouth, and throat mucous membranes. Visceral leishmaniasis (VL) is also known as Kala-Azar or black fever, which is prevalent in South Asian countries like China and India. The name Kala-Azar comes from the characteristic grey-black skin discoloration due to an increased immune reaction. It  is lethal if not treated on time. 

To prevent this disease in malnourished locations, efforts must be made to enrich daily diets with zinc, adequate protein, and vitamin A. Other measures include prohibiting people from sleeping outside or on the ground.  At homes, insecticides should be used to kill insects.