Leishmaniasis lesions are sometimes referred to as "1-year sores."
Image credit: CDC/Dr. D.S. Martin
In many parts of the world, leishmaniasis is frighteningly commonplace. For the populations of poorer, hotter countries, the disease is a specter that haunts their daily lives. It has the ability to kill, maim and ostracize.
According to the World Health Organization (WHO), an estimated 12 million people are infected with leishmaniasis across 98 countries.
As many as 20,000-30,000 die at the hands of the disease yearly; millions more are permanently scarred.
Roughly 90% of leishmaniasis cases are to be found in just five countries: India, Bangladesh, Nepal, Sudan and Brazil.
Often referred to as a "flesh-eating" condition, leishmaniasis is a parasitic disease that can be fatal if sufficient health care is not received. Despite its prevalence, the West appears to be relatively ignorant of its horrors.
In this article, we will take a brief look at what leishmaniasis is, how it spreads and what might be done to limit its reach.
What is leishmaniasis and who is at risk?
Leishmaniasis is a disease spread by a protozoan parasite from the innocent-looking sandfly. At least 90 species of sandfly and upward of 20 species of Leishmania parasite work in conjunction to spread the life-threatening disease.
The cycle of infection begins when the sandfly feasts on the blood of an infected mammal. It then returns the parasite to the warmth of a new host with its next feed. Once within the body, the parasite sets up shop inside the host's immune cells, specifically the macrophages.
Macrophages are designed to kill intruders and break them into their constituent parts, but the leishmaniasis parasite is well-designed to avoid their onslaught. The protozoa uses proton pumps to protect itself from the acidic environment within the macrophages and acid phosphatases to disarm the host's enzymes; in this way, the Leishmania parasite is able to survive in the most hostile of environments.
It seems that this pairing of Phlebotomus sandfly and Leishmania parasite has been working against humanity since time immemorial. Some believe the so-called plague of boils in the Bible might refer to leishmaniasis:
Exodus 9:9: the "breaking out in sores on man and beast throughout the land of Egypt."
The people most at risk of the disease are those who live in areas frequented by the sandfly species that carry the parasite. These species are suited to a number of very different environments; they can thrive in forests or deserts or anywhere warm in between. This makes the disease's epidemiology multifaceted and incredibly difficult to control.
In general, it is the poorer nations of the world who are at greatest risk. This is partly because leishmaniasis relies on a host's immune system to be weakened by disease or malnutrition before it can take hold of the victim. Additionally, the conditions of poverty, as we shall see later, make the perfect breeding ground for sandflies.
In the US, according to the CDC, leishmaniasis is incredibly rare. Other than a small number of cases in Oklahoma and Texas, individuals with the disease have always recently returned from countries where leishmaniasis is resident.
Types of leishmaniasis
Because of the large variety of Leishmania parasites, the disease itself has a range of possible characteristics. In general, there are three major types of leishmaniasis, defined as follows:
Fast facts about leishmaniasis
- Leishmaniasis is caused by a parasite transmitted by a sandfly bite
- At least 98 countries are infected by leishmaniasis
- The conditions created by a war zone favor leishmaniasis transmission.
- Cutaneous leishmaniasis (CL): CL is the most common form of the illness and is the origin of its "flesh-eating" moniker. Ulcers appear at the site of the sandfly's bite, they do not easily heal and leave permanent scars on the skin. The "diffuse" version of CL produces lesions across the entire body that resemble leprosy. Two thirds of new cases occur in Afghanistan, Algeria, Brazil, Colombia, Iran and Syria
Approximately 0.7 million-1.3 million new cases of CL are reported each year
- Visceral leishmaniasis (VL): also known as kala-azar (black fever), the symptoms include fever, weight loss, anemia and enlarged organs, particularly the spleen and liver. This variant is fatal if left untreated. The majority of cases are to be found in Bangladesh, Brazil, Ethiopia, India, South Sudan and Sudan
There are around 200,000-400,000 new cases of VL reported worldwide each year
- Mucocutaneous leishmaniasis (ML): ML is the rarest of the three types. If left unchecked, it can completely destroy the mucosal membranes of the nose, mouth and throat. Without treatment, ML is generally fatal. An estimated 90% of ML cases occur in Bolivia, Brazil and Peru
The number of ML cases that occur each year is unknown.
Worst affected by leishmaniasis are countries where the majority of the population live in poverty; along with Chagas disease, dengue and sleeping sickness, leishmaniasis is classed as a "neglected disease."
These neglected diseases receive little research funding. They are considered "diseases of poverty."
On the next page, we look at the social impact of leishmaniasis and the effects of war on its transmission.