Leishmaniasis

Leishmaniasis is a group of diseases caused by tiny parasites called Leishmania. These parasites are spread by the bite of small flying insects called sandflies. The disease is most common in warm parts of the world, including Africa, Asia, the Americas, and southern Europe.

There are three main types of leishmaniasis. The skin form causes sores on the body. The form that affects the nose and mouth causes sores there as well. The form that affects internal organs starts with skin sores and later causes fever, tiredness, and swelling.

People can help prevent leishmaniasis by using special nets to keep sandflies away and by treating the disease early. Doctors can diagnose the disease by looking at samples under a microscope or by doing blood tests. Treatment depends on the type of infection and where it was caught. Many millions of people live in areas where leishmaniasis is common, and the World Health Organization works to help provide treatment.

Signs and symptoms

Leishmaniasis can cause skin sores that appear weeks or months after a bite from an infected sandfly.

There are three main types: cutaneous leishmaniasis causes sores on the skin that heal but may leave scars; mucocutaneous leishmaniasis affects the skin and the inside of the nose and mouth; and visceral leishmaniasis is the most serious form. This form can be dangerous without treatment and may cause fever, problems with the spleen and liver, and anemia.

Cause

Leishmaniasis is spread by the bite of infected female phlebotomine sandflies. These sandflies can carry a tiny organism called protozoa Leishmania. When a sandfly bites, it can pass these organisms into the skin. The organisms then grow inside the body and cause health problems.

Sandflies can get infected when they bite animals or people who already have the disease. Inside the sandfly, the organisms change and get ready to spread to new hosts. Scientists study the genes of some Leishmania types to understand the disease better and find new ways to treat or prevent it.

Vector

In most places, the genus Phlebotomus is the main carrier of leishmaniasis, though in some areas, Lutzomyia also plays a role.

Possible non-human reservoirs

Some animals, like certain monkeys, can carry types of Leishmania that can infect people.

Organisms

The severe form of the disease is often caused by Leishmania donovani, L. infantum, or L. chagasi. The skin form can be caused by more than fifteen different Leishmania species.

Risk factors

Factors that increase the chance of getting leishmaniasis include poor nutrition, living in areas without good sanitation, having a weaker immune system, and changes in the environment that help sandflies thrive. Living in crowded or dirty conditions, not having enough healthy food, moving to new areas where the disease is common, and changes in climate or land use can all make people more likely to get sick from leishmaniasis.

Diagnosis

Leishmaniasis is diagnosed with special laboratory tests. Scientists look for tiny parts of the parasite called amastigotes in blood or tissue samples from the body. The samples are placed on a slide and stained to help see the amastigotes more clearly. They appear as small, round bodies with a nucleus inside.

Other tests, such as enzyme-linked immunosorbent assay and polymerase chain reaction (PCR), can also detect the parasite’s DNA. These tests are very sensitive and can find even very small amounts of the parasite. Special tests can identify different species of the parasite by looking at its DNA.

Prevention

Leishmaniasis can be prevented by using insect repellent on your skin and under your sleeves and pant legs, following the instructions on the label. Repellents that contain DEET work best.

To reduce sandfly bites, you can use nets treated with insecticide or insect repellent while sleeping. Fine mesh sizes of 0.6 mm or less are best, but a mosquito net with 1.2 mm mesh can also help. Many Phlebotomine sandfly bites happen around sunset, so putting nets over doors and windows or using insect repellents can be useful.

Spraying houses and animal shelters with insecticides, using insecticide-impregnated dog collars, and treating or managing infected dogs are also important steps in prevention.

Controlling leishmaniasis needs many different actions. Insecticide spraying, treated nets, and caring for sick people are common ways to help, and scientists are looking for new methods to control the disease in the long term.

One important method is Vector Control using an Integrated Vector Management (IVM) approach to reduce sand fly numbers. New ideas being studied include changing sand flies genetically so they can’t spread the parasites, using special baits that attract and kill sand flies, and creating barriers with spatial repellents and insecticidal paint.

For Reservoir Control, managing domestic dogs is important because they can carry the parasites. Special dog collars treated with deltamethrin are now used as a safer and better choice. Controlling wild animals that can carry the parasites, like rodents and marsupials, is harder because of worries about protecting nature.

Vaccination: Vaccines for dogs have been made and are used in some places to help stop the spread. Vaccines for humans are being tested and could provide long-term protection in the future.

Treatment

The way to treat leishmaniasis depends on where the disease was caught, the type of Leishmania, and what kind of infection it is. For a serious form of the disease found in India, South America, and the Mediterranean, a medicine called liposomal amphotericin B is usually used and works very well. In Africa, a mix of two medicines is used. There is also a pill called miltefosine that can help with different kinds of leishmaniasis and usually has fewer side effects.

Researchers are looking into new ways to treat leishmaniasis. For a skin form of the disease, doctors may use creams or pills to help. Some groups are working to find new medicines and make existing ones more affordable.

Epidemiology

Leishmaniasis affects many people in warm parts of the world, especially in Africa, Asia, the Americas, and southern Europe. It is spread by sandflies and can affect the skin, the mouth and nose, or deep inside the body.

The skin form is the most common. The deep form can be serious and is found in places like Bangladesh, Brazil, Ethiopia, India, and Sudan. Most cases happen in a few countries, such as Brazil, Ethiopia, India, Somalia, South Sudan, and Sudan. The disease is also found in parts of the Americas, from northern Argentina to South Texas.

History

Early writings and drawings show signs of a skin disease that might be leishmaniasis. Ancient tablets from King Ashurbanipal and old texts mention skin sores. Persian doctors, like Avicenna, described a condition called "balkh" sore. In 1756, a doctor named Alexander Russell described the disease after studying a patient from Turkey.

In India, the disease was known as "kala-azar", meaning "black fever". Evidence of the skin form of the disease has also been found in very old pottery from Ecuador and Peru. Some old writings from the time of the Incan people and Spanish explorers also mention sicknesses that sound like leishmaniasis.

The person who first discovered the tiny creature that causes the disease is not known for sure. In 1898, a doctor named Peter Borovsky described the parasite. In 1901, William Leishman found the organism in a patient who had died from an illness called "dum-dum fever". Soon after, Charles Donovan confirmed these findings in patients in Madras, India. Later, Ronald Ross named the parasite Leishmania donovani. During the Second World War, leishmaniasis was a problem for soldiers fighting in Sicily, and a treatment called pentostam was found to work well.

Society and culture

Leishmaniasis can cause visible scars and changes to the face, which may lead to social challenges. People with these signs might face difficulties in jobs, school, and social life because others may treat them differently. As more people learn about the disease, support for mental health and education in communities becomes important.

The disease can also bring financial hardship, especially in places where treatment is not free. People may lose income due to being sick, and animals used for work or farming can become sick too, making life harder for families. In some areas, beliefs about the disease being caused by spiritual reasons can affect when people seek medical help.

Research

As of 2017, there was no vaccine for humans to prevent leishmaniasis. Scientists are working to create one. Right now, there are effective vaccines for dogs. Another way to stop leishmaniasis is through good public health practices. Researchers are also studying special drugs to help treat the disease.