This week on “Shedding light on NTDs”, we are taking a look at leishmaniasis. Leishmaniasis is a parasitic disease that spreads through the bite of phlebotomine sand flies . There are two main forms: visceral and cutaneous . Visceral leishmaniasis (VL) infection is characterized by fever, weight loss, anemia and enlargement of liver and spleen . VL accounts for approximately 50,000-90,000 cases worldwide per year and is often fatal. Cutaneous leishmaniasis (CL) infection is characterized by skin lesions and ulcers on exposed parts of body, leaving life-long scarring and potentially disability. The lesions typically start as bumps from the sand fly bite but can progress to open-wound ulcers that vary in size, anywhere from a centimeter to more than an inch in diameter. As the most common form of leishmaniasis, there are between 600,000 and one million new cases of CL a year worldwide. Around 70 species, including humans, are natural hosts for the parasite, which makes it very difficult to target the parasite for eradication .
More than one billion people residing in over 90 countries across Asia, East Africa, South America and the Mediterranean region are at risk of infection. Seven countries, including Brazil, Ethiopia, India, Kenya, Somalia, South Sudan and Sudan, account for 90% of the new VL cases annually [2, 3]. Most of the CL cases annually occur in six countries, including Afghanistan, Algeria, Brazil, Colombia, Iran and Syria .
Brazil is currently facing an outbreak of VL in Parauapebas, a state in the northwest region of the country. Two children, an 11-month-old and 2-year-old child, recently passed away from VL infections, in addition to 36 new cases in humans and over 300 confirmed cases in dogs living in the region . In April 2018, health officials in Pakistan’s Mohamed Agency reported732 cases of CL and initiated an emergency treatment campaign to administer medication to infected individuals, which mostly included children . Unfortunately, these two outbreaks are just the tip of the iceberg when it comes to grasping the full scope of leishmaniasis infection impact. Where there are reported cases, it can be assumed that in remote regions, there are many more additional cases of leishmaniasis going unreported and untreated.
In regions where there is poor infrastructure, such as lack of running water, poor waste management or open sewerage, sand flies find the perfect breeding ground, as well as ample access to blood meals. Close living conditions combined with an increase in infected flies contribute to those in poverty having an increased risk for leishmaniasis infection . Additionally, nutrient-poor diets, also associated with poverty, provide an environment for the infection to progress to the severe VL infection more readily . Furthermore, leishmaniasis is a treatable condition, but it requires early medical attention and effective treatment in order to prevent VL and cure the disease. Yet, in the regions where the impact of leishmaniasis is greatest, there is limited access to healthcare, in both cost to care and distance to treatment centers, furthering the disparities experienced by the poor.
Due to leishmaniasis’ association with poverty and prevalence in remote locations where surveillance is limited, it is difficult to estimate the true incidence and case-fatality rate of the infection. The World Health Organization (WHO) estimates that there are 700,000 to one million new cases of CL and VL combined every year and 20,000 to 30,000 deaths annually due to VL infection . Leishmaniasis poses a threat to anyone entering a region where it is present, meaning tourists, researchers, soldiers, missionaries or Peace Corps volunteers are all at risk of infection in addition to those living in the area . Yet, the infection disproportionately affects those living in poverty and continues to pose a deep burden for those without a strong voice, making it an important neglected tropical disease worth discussing. Parents are losing their children from a single bug bite because they do not have the tools to seek effective healthcare and they are constantly at risk because of their living conditions that cannot be changed or improved without the support of government resources. It will take extensive support from government agencies, the medical community, and committed individuals to decrease the impact of leishmaniasis. Global support is the only means to one day reduce the number of fatalities from leishmaniasis infection.