Visceral Leishmaniasis - Symptoms, Diagnosis, Treatment, and Prevention

What Is Visceral Leishmaniasis?

Visceral leishmaniasis is a type of leishmaniasis disease that is considered to be endemic in many countries. It is commonly known as black fever or kala-azar. Leishmaniasis is a serious and life-threatening infectious disease caused by the parasitic protozoan known as Leishmania donovani. Leishmania has more than 20 species that can cause this disease. The world health organization (WHO) lists three different types of leishmaniasis.

1. Visceral Leishmaniasis: The most severe type of leishmaniasis that damages numerous organs.

2. Cutaneous Leishmaniasis: The most prevalent type of leishmaniasis that results in skin lesions.

3. Mucocutaneous Leishmaniasis: The type of leishmaniasis that results in skin and mucous membrane lesions.

According to World Health Organization statistics, the following ten nations reported more than 90 percent of all new cases of visceral leishmaniasis in 2019: Brazil, Ethiopia, Eritrea, India, Iraq, Kenya, Nepal, Somalia, South Sudan, and Sudan (WHO 2021 report). This fatal disease is endemic in more than 70 countries on all continents except Antarctica and Australia, with an estimated 200 million individuals at risk.

Visceral Leishmaniasis: How Does It Spread?

As discussed earlier, visceral leishmaniasis is a parasitic infection caused by the parasite Leishmania donovani. This leishmania parasite normally lives in infected sand flies. Sandflies infected with leishmaniasis spread this disease. The bite of an infected sandfly causes leishmaniasis in humans, and they lay eggs by feeding on blood. There are around 70 animal species that are natural hosts of these parasites, including humans. Infected sand flies bite animals, too, such as dogs. Those who keep the dog as a pet can get this infection from an infected pet dog (bitten by sandflies). This is how these flies spread this disease from one individual to another.

Interesting Facts About Sandflies:

• Sandflies are different from houseflies. They are very small, approximately two to three millimeters in length, which is why they are not easily visible like houseflies.

• The bodies of sandflies are covered with hair. During the day, the sandfly appears brownish in color.

• The sandfly that spreads visceral leishmaniasis is a female phlebotomine sandfly carrying the parasites.

• They can not fly for more than 106.68 meters. They can not reach the higher walls of the house. Therefore, when spraying insect-repellent chemicals, the higher portions of the wall are not sprayed because these sandflies cannot reach that area.

• The sand fly is assumed to stay within 106.68 meters of its breeding place. They love moist and warm areas. Therefore, they are frequently observed near beaches, wetlands, creeks, and lake beds.

• They frequently take up shelter in bushes or the heavy layer of decomposing leaves that naturally covers the ground.

• They are nocturnal creatures, which means they are active during the night. Therefore after sunset, the risk of this infection increases. However, the majority of sandflies are active outdoors between dark and dawn; some can also bite indoors and throughout the day.

What Are the Signs and Symptoms of Visceral Leishmaniasis?

The symptoms of visceral leishmaniasis are listed below.

• Fever that persists for more than two weeks.

• The occurrence of black or gray pigmentation on the skin, for this reason, is called “kala-azar,” or black fever.

• Enlargement of the liver.

• Enlargement of the spleen.

• Weakness.

• Weight loss.

• Hair fall.

• Anemia (low red blood cell counts).

• The skin may become dry, flaky, and scaly in some areas.

• Loss of appetite.

• Vomiting.

• Diarrhea.

Less common signs and symptoms are

• Jaundice.

• Bleeding from the mouth or nose.

• Abdominal fluid accumulation.

• Swelling (starts from legs, may spread to overall body).

Who Is at Risk of Contracting Visceral Leishmaniasis?

The risk factors of visceral leishmaniasis are listed below:

• Poverty raises the chance of contracting leishmaniasis because of a lack of resources.

• People who have low immunity (immunocompromised people) are at the highest risk of getting this disease.

• Poor housing and hygienic conditions in the home may promote sandfly breeding and resting places, for example, a lack of waste management or exposed sewage. The sandfly resides in muddy home cracks and crevices, particularly in dark and humid areas.

• Malnutrition increases the likelihood that this infection will become a serious illness.

• Leishmaniasis incidence can be impacted by changes in urbanization and human intrusion into forested regions. People who live in tropical and subtropical areas are at a higher risk.

• Migration and the transfer of non-immune people into regions with active transmission cycles are frequently linked to outbreaks of both cutaneous and visceral leishmaniasis. In addition to widespread deforestation, occupational exposure continues to be a major risk factor for contracting this parasitic infection.

• Variations in temperature, rainfall, and humidity can significantly modify the distribution of these parasites and reservoir hosts, as well as their chances of surviving and growing their populations.

• Small temperature changes can significantly impact how leishmania promastigotes (infective stage) develop in sandflies, allowing the parasite to spread to regions that were not previously endemic for the disease.

• Drought, hunger, and flood can cause significant displacement and migration of people to locations where leishmania is transmitted. In addition, poor nutrition might decrease their immunity which increases the likelihood of this disease.

How Is Visceral Leishmaniasis Diagnosed?

Visceral leishmaniasis is diagnosed based on clinical signs and symptoms and results of laboratory examination. The first symptom that can give a hint for diagnosing this disease is prolonged fever in a person residing in an endemic area. For confirmation of this disease, laboratory tests are conducted, which include immunological and parasitological testing.

The rapid immunochromatographic test based on recombinant rK39 antigen is the only immunological test available now at the primary level. Other levels of care also use indirect immunofluorescence (IIF) and enzyme immunoassay (ELISA), which are serological tests for detecting antibodies in the provided sample.

The purpose of parasitological tests is to identify parasites in affected tissues, primarily in the bone marrow, by direct inspection or isolation in culture (in vitro). In addition, the PCR (polymerase chain reaction) method is used in molecular tests to detect leishmania DNA (deoxyribonucleic acid).

How Is Visceral Leishmaniasis Treated?

The medicine Amphotericin B, which includes conventional Amphotericin B and the newer introduced, more effective liposomal Amphotericin B, is considered the first-line treatment for visceral leishmaniasis. Other medicines that are used for this disease are

• Pentavalent antimonials drugs (Sodium stibogluconate and Meglumine antimoniate).

• Miltefosine.

• Paromomycin.

How Is Visceral Leishmaniasis Prevented?

As visceral leishmaniasis is endemic, the government conducts various preventive programs to control and eliminate this disease, like increasing awareness about this disease, frequent health checks in suspected areas, etc.; this is because, till now, no vaccine has been developed to prevent this disease. The preventive measures include:

• For the human population, recommended personal protection measures include avoiding outdoor activities from sunset to dawn, using mosquito nets, and using protective clothes and insect repellents. People who show clinical signs of the condition should be treated as soon as feasible.

• Preventive strategies for vector control are aimed toward integrated management efforts in environmental sanitation. As a control measure, the safe use of residual pesticide spraying is suggested.

• For the purpose of reducing urban reservoirs, personal protective collars for dogs that are insecticide-impregnated are advised, as well as the usage of mosquito-proof meshes (netting) in dog kennels to keep out sandflies. Dogs are the primary carrier of visceral leishmaniasis in the Americas and keep the disease alive in crowded urban areas. In places with the endemic transmission, serological surveys in dogs are suggested, and when a dog tests positive for the parasite, humane euthanasia is recommended.

Conclusion:

Visceral leishmaniasis or black fever can be potentially fatal if it is not identified and treated in its early stages. The governments of the endemic countries have aimed to eradicate the incidence of this disease and are acting on it by running a visceral leishmaniasis elimination program. Furthermore, active involvement in these programs and adopting all necessary measures to control the sandfly can help limit the number of cases in the future.