Overview

Life in all forms exists around us, even if we cannot always see it.

Creatures so small, invisible to the human eye, can cause issues with a big impact. The sandfly can spread one of these creatures, the Leishmania parasites. A bite from an infected sandfly can cause Leishmaniasis, a disease most common in tropical and subtropical areas. 

Recently, Leishmaniasis cases have been recorded in more places, and climate change is playing a major role in this shift. 

That means Leishmaniasis is no longer to be considered a distant disease that occurs in remote regions, but one that might end up existing on every continent. 

What is leishmaniasis?

Leishmaniasis is a disease caused by microscopic, one-cell parasites transmitted through female sandflies that feed on blood. The sandflies contract the parasites after having fed on an infected human or animal, and then spread them through feeding off a human. There are over 20 Leishmania species, and over 90 species of sandflies that can transmit Leishmania parasites to humans and animals.¹

The disease appears in 3 ways:

1. Cutaneous Leishmaniasis (CL)

This is the most common form of Leishmaniasis. The disease manifests by causing a skin infection at the site of the bite, where bumps (nodules) appear. Over time, the nodules can become ulcers. CL symptoms can take a few weeks or months to appear after the sandfly bite, and they usually take a long time to heal. The site of infection may leave a scar after healing. 

2. Mucocutaneous Leishmaniasis (ML)

ML is usually a complication of CL, where ulcers also develop in mucous membranes (nose, mouth, throat). Symptoms include nosebleeds, dyspnoea (shortness of breath), and difficulty swallowing. Untreated cases can become severe and lead to facial disfigurement and death. Some ML cases are complex, and symptoms can appear after years of healing the skin ulcers.   

3. Visceral Leishmaniasis (VL)

VL is the most severe form of Leishmaniasis. It affects internal organs (spleen and liver). Symptoms include persistent fever, weight loss and fatigue, anaemia, and enlargement of the spleen and liver. VL compromises the immune system, making individuals more susceptible to other infections. More than 95% of cases are fatal if not treated.^1,2

Who does it affect?

According to the World Health Organisation (WHO), Leishmaniasis is among the 7 most prominent tropical diseases, with at least 12 million people having it and 350 million people being at risk. Every year, there are 2 million new cases, out of which 70,000 cases are fatal.^1,3

Individuals with HIV and other conditions that compromise the immune system are more susceptible to becoming infected, especially with VL.⁴

Where is leishmaniasis found?

As of 2021, Leishmaniasis has been recorded in 99 countries as an endemic condition. It is found on 5 continents, including:

1. Africa — In North and East Africa
2. Asia — In Central and Southwest Asia
3. Europe — In Southern France, Greece, Italy, Portugal, Spain, and in many Mediterranean islands
4. South America — In Mexico, except Chile and Uruguay
5. North America — In Texas, Arizona, Oklahoma, and Central America

There are approximately 50,000 to 90,000 cases of VL each year, and most occur in Brazil, East Africa and India. For CL, approximately 600,000 to 1 million cases occur worldwide annually, with emphasis in the Middle East, Central Asia, and the Americas. Lastly, more than 90% of ML cases occur in Bolivia, Brazil, Peru and Ethiopia.^1,2,3

With constantly rising temperatures, incidents are expected to appear in more countries. 

The role of climate in disease spread

Leishmaniasis cases are more prominent in countries with tropical and subtropical weather conditions, as the disease vectors, the sandflies, thrive in warm and humid environments.

Warm temperatures, rainfall, and high humidity affect sandfly life span and populations. Climate change is creating new appropriate environments for sandflies to inhabit and breed in, spreading the disease in countries and regions that were considered low-risk before.⁵

In parts of Europe and North America, the weather conditions were never favourable for sandflies to survive and populate, but now, a growing number of Leishmaniasis cases are being recorded in both continents. 

The human risk 

Even though Leishmaniasis affects approximately 2 million people each year, many people in low-risk areas are not aware of the disease. With the global temperatures constantly increasing, people living in newly endemic areas may not realise that Leishmaniasis cases have been reported in their region. Even if they do, they may not receive proper information about the disease and how to protect themselves. Additionally, there can be a lack of preparation on the part of the healthcare system in those regions, and healthcare providers may not be prepared to recognise or treat Leishmaniasis, especially if they have never encountered similar cases before.

What can be done?

1. Response measures from governments and healthcare systems

Decreasing the risk of infection in newly endemic areas needs to be a priority. Hospitals in such areas need to closely monitor any Leishmaniasis cases and study the frequency of the disease in their region. 

Governments should treat Leishmaniasis as a national public health issue and ensure the public is educated about Leishmaniasis and encouraged to seek medical help immediately if they notice any suspicious symptoms. Seeking help from a specialist early on can minimise the risk of a serious infection outbreak, and also help understand infection patterns, such as times in the day when sandflies are more active or specific locations where they are mostly found.

While there is currently no vaccine for Leishmaniasis, rising temperatures and increasing case numbers are helping scientists understand disease patterns, how it spreads, and how it affects the human body. With ongoing research, there is hope for new answers regarding Leishmaniasis prevention and treatment. Government funding for research centres and universities could be essential to accelerate the development of vaccines against Leishmaniasis. 

2. Personal precautions 

On a personal level, each individual should educate themselves about the disease and learn how to protect themselves, whether travelling to endemic areas or living in a newly affected area. Protective measures include:

• Covering exposed skin with clothing
• Insect-repellent sprays
• Using insecticides
• Using essential oils (citronella, linalool, and geraniol)⁶
• Mosquito nets for beds and/or windows

FAQs

Where is leishmaniasis found?

Leishmaniasis is present in 90 countries in Africa, Asia, Europe, North America, and South America. 

How are climate change and leishmaniasis associated?

Leishmaniasis is caused by getting bitten by an infected sandfly. Sandflies thrive in warm, humid environments, where weather conditions are favourable for them to complete their life cycle, including breeding. With climate change, there are new record warm temperatures recorded in many regions, which creates more favourable environments for sandflies to migrate to. 

How can I know if an insect bite is leishmaniasis?

The first step is to educate yourself about Leishmaniasis symptoms and monitor closely any suspicious bite, especially if you travel or live in endemic areas. A suspicious bite is one that turns into an ulcer, doesn’t heal, and is persistent for weeks or months. If you also start noticing symptoms such as fever, fatigue, and weight loss, you should consult a healthcare provider. 

Is leishmaniasis contagious?

The main route of Leishmaniasis transmission is through the bite of an infected sandfly. This is how most people get infected. It is not contagious from human to human, even if you touch someone’s infected skin. In rare cases, it is possible to get Leishmaniasis if the blood of an infected person comes into direct contact with someone’s bloodstream, such as when sharing needles or when conducting blood transfusions. 

Summary

Leishmaniasis is among the 7 most common tropical diseases, but with climate change, it is not so tropical anymore. As of 2021, 90 countries on 5 continents are endemic for Leishmaniasis. Sandflies are now able to migrate and survive in regions they could not before, putting more people in danger of contracting the disease. 

Governments need to take action to increase public awareness in newly endemic areas and encourage individuals to seek immediate care if they get suspicious insect bites. With a constantly increasing number of Leishmaniasis cases each year, governmental financial support to accelerate research and drug development may be important. 

Climate change does more than affect temperatures and rising sea levels; it is also changing disease patterns. With collective efforts and appropriate public education, it is possible to protect communities by minimising the spread of Leishmaniasis and treating cases before they become life-threatening.