Visceral Leishmaniasis

Visceral leishmaniasis (VL) is a parasitic disease found in tropical and subtropical areas. It is a systemic disease that primarily affects vulnerable age groups such as children under age 5 and people over 50, as well as adults with comorbidities or immunosuppressive conditions such as HIV/AIDS. If not treated in a timely manner, it can result in death in more than 90% of cases. In the last five years, an average of some 2.850 cases of visceral leishmaniasis were recorded, with an average case fatality rate of 8.2%.

Visceral leishmaniasis has been recorded in 13 countries (Argentina, Bolivia, Brazil, Colombia, Costa Rica, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Paraguay, Uruguay, and Venezuela). It should be noted that Brazil accounts for 93% of cases. Despite the downward trend in cases of VL in the Region, the geographical distribution of the disease has expanded.

Some of the recommendations presented here may differ from the specific recommendations for other continents, given the Region's distinct epidemiological and biological characteristics, including the different circulating species of Leishmania, transmission cycles, and treatments. Treatment may be local or systemic, depending on the clinical form of the disease and the local use criteria. Recommendations are for pediatric and adult patients and, when available, based on the species of Leishmania presumptively involved.

Recommendations for the treatment of cutaneous and mucosal/mucocutaneous leishmaniasis, as well as therapeutic regimens, routes of administration, and dosages.

2.850 cases of visceral leishmaniasis were recorded, with an average case fatality rate of 8.2%. Visceral leishmaniasis has been recorded in 13 countries (Argentina, Bolivia, Brazil, Colombia, Costa Rica, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Paraguay, Uruguay, and Venezuela). It should be noted that Brazil accounts for 93% of cases. Despite the downward trend in cases of VL in the Region, the geographical distribution of the disease has expanded.

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VL is caused by intracellular protozoan parasites of the genus Leishmania. In the Americas, Leishmania infantum (also known as L. chagasi) is the species involved in VL.

The main sylvatic reservoirs identified are foxes (Cerdocyon thous and Lycalopex vetulus) and marsupials (Didelphis spp). In urban areas, dogs (Canis familiaris) are the main reservoir; however, sylvatic reservoirs can also be present in the transmission cycle.

In the Americas, the main VL vector is Lutzomyia longipalpis, but Lu. evansi is an important vector in some Central American countries, as well as in Colombia and Venezuela. The vector Lu. cruzi is also found in municipalities in the border areas between Bolivia (Plurinational State of) and Brazil and between Bolivia (Plurinational State of) and Argentina.

Congenital and parenteral transmission (through sharing of needles among people who use drugs) has been reported. There is no direct person-to-person transmission.

Though the incubation period can range from 10 to 24 days, it is usually between two weeks to two months. The infection exhibits a broad clinical spectrum, which can range from mild to more severe clinical manifestations.

The classic manifestations of VL are fever, either constant or sporadic; splenomegaly (enlargement of the spleen), which manifests in the vast majority of patients; hepatomegaly (enlargement of the liver), which may or may not be present; pallor caused by severe anemia; leukopenia; thrombocytopenia; and slow, progressive weight loss. Other secondary signs and symptoms include respiratory or gastrointestinal disorders, such as vomiting and diarrhea. In severe cases, malnutrition and edema of the lower limbs may occur, which can progress to anasarca. Other serious signs are bleeding, petechiae, jaundice, and ascites. In these patients, when death occurs, it is usually caused by bacterial infection or bleeding.

Clinical

Consideration should be given to people from endemic areas who have persistent illness, and persistent and unexplained fever, accompanied by suggestive signs and symptoms.

Laboratory

This involves immunological and parasitological tests. The immunological test currently available is the rapid immunochromatographic test, based on recombinant rK39 antigen, which can be performed at the primary care level. Indirect Immunofluorescence (IFA) and enzyme-linked immunoassay (ELISA) tests are also used in some countries, at other levels of care. Parasitological tests are performed by detecting parasites in infected tissues, primarily in the bone marrow, by direct examination or isolation in culture (in vitro). Molecular tests detect Leishmania DNA using the PCR method.

No vaccines or medications are available to prevent infection.

Humans

Recommendations for individual or collective protection measures are aimed at reducing contact with vectors, in particular: avoiding outdoor activities from dusk to dawn; use of mosquito nets; and use of protective clothing and insect repellents. People with clinical manifestations of the disease should be treated as early as possible.

Vector control

Preventive measures focus on integrated environmental management, through the cleaning of yards and grounds, in order to change the environmental conditions that provide breeding sites for immature forms of the vector. The use of residual chemical control is indicated as a control measure, based on the epidemiological situation and entomological surveillance indications.

Control of urban domestic reservoirs

Recommended preventive measures consist of the use of nets in kennels, and, for individual protection, insecticide-impregnated dog collars. In the Americas, dogs are the main reservoir of visceral leishmaniasis and play a major role in maintaining the parasite in urban environments.

In areas of transmission that are epidemiologically important, serological surveys in the canine population are recommended and, when positive, humane euthanasia is indicated.

In 2022, PAHO published new Guidelines for the Treatment of Leishmaniasis in the Region of the Americas, detailing treatment regimens and indication criteria for leishmaniasis for the Region, consistent with WHO standards for guideline development.

In order to treat visceral leishmaniasis in pediatric patients and in immunocompetent or immunocompromised adults, the use of amphotericin B liposomal is strongly recommended.

For the treatment of visceral leishmaniasis in pediatric patients and immunocompetent adults, the use of pentavalent antimonials or amphotericin B deoxycholate is recommended on a conditional basis.

In order to treat visceral leishmaniasis in immunocompromised patients, pentavalent antimonials are not recommended.

For the treatment of visceral leishmaniasis in pediatric and adult patients, miltefosine is not recommended.