Overview
Visceral leishmaniasis, widely known as kala-azar, is caused by parasites carried by tiny sandflies. The parasites move from the skin into the spleen, liver and bone marrow, causing long fever, a swollen abdomen, weight loss and severe anaemia.
WHO states it is fatal in over 95% of cases if left untreated, and that eastern Africa carries most of the global burden. It is also treatable and curable, which makes early diagnosis the whole battle.
Disease Summary
- Category
- Infectious Disease
- Cause
- Leishmania parasites
- Transmission
- Bite of an infected sandfly
- Body System
- Blood and Lymphatic System
- Preventable
- Yes
- Curable
- Yes
Symptoms
Common Symptoms
Symptoms usually develop within months of the sandfly bite, though it can take longer. They build slowly, which is why people often present late.
Irregular Bouts of Fever
WHO describes irregular bouts of fever as the hallmark. The fever comes and goes over weeks rather than settling.
Weight Loss
Progressive weight loss is one of the defining features, listed by both WHO and CDC.
A Swollen Abdomen
The spleen and liver both enlarge, which people usually notice as a swelling or heaviness in the upper abdomen.
Anaemia
The bone marrow is affected, so the blood count falls. This causes pallor, breathlessness and exhaustion.
Low White Cell and Platelet Counts
CDC describes low counts across all blood cell types, which increases the risk of infection and of bleeding.
Night Sweats and General Illness
Drenching night sweats and a general sense of being unwell are listed by CDC.
Weakness
Profound weakness develops as the anaemia and weight loss progress.
Darkening of the Skin
The name kala-azar means black fever, referring to the darkening of the skin that can occur in some people with the illness.
Danger Signs
Seek urgent medical attention immediately if any of the following symptoms develop.
Fever for More Than Two Weeks With an Enlarging Abdomen
This combination in an endemic area is the picture WHO describes, and needs urgent parasitological testing.
Bleeding
Bleeding from the gums or nose, or heavy bruising, reflects the very low platelet count and needs immediate care.
Severe Pallor or Collapse
Severe anaemia can cause collapse and may need transfusion.
Severe Wasting
Marked malnutrition worsens the outlook and needs treating alongside the infection.
Any of These in Someone Living With HIV
WHO states that people with both infections face elevated risk of developing disease, of relapse and of death.
Diagnosis
Clinical Picture Plus Exposure History
WHO states the diagnosis combines clinical signs with parasitological or serological tests. Fever, an enlarged spleen and weight loss in someone from an endemic area is the trigger.
Examination for an Enlarged Spleen and Liver
The enlarged spleen is often the finding that first suggests the diagnosis.
Rapid Diagnostic Test
WHO names rapid diagnostic tests explicitly. These detect antibodies and can be done at a clinic without a laboratory.
Finding the Parasite in a Tissue Sample
CDC states that diagnosis uses tissue samples, most commonly from the bone marrow. Seeing the parasite is definitive proof.
Blood Counts and Protein Tests
The characteristic pattern of low counts across all blood cell types with raised total protein supports the diagnosis.
Laboratory Tests
Antibody Rapid Diagnostic Test
A positive result in someone with the right symptoms supports the diagnosis. WHO names rapid diagnostic tests as an acceptable route to confirmation alongside clinical signs.
Microscopy of a Tissue Sample
Seeing the parasites under the microscope is definitive. Bone marrow is the sample used most often because it is safer than sampling the spleen.
Molecular Test
Confirms the infection and identifies which parasite species is responsible, which helps guide the choice of medicine.
Full Blood Count
Shows the low red cell, white cell and platelet counts that are typical of this illness and that determine how urgently supportive care is needed.
HIV Test
WHO reports high rates of combined infection in several endemic countries, and the combination substantially changes management.
Treatment
Liposomal Amphotericin B
CDC describes this as generally the treatment of choice. It kills the parasites inside the cells where they hide.
Miltefosine
An oral option, which matters greatly in settings where daily intravenous treatment is hard to deliver.
Pentavalent Antimonial Medicines
Still widely used in eastern Africa, where CDC states these remain effective. Treatment needs monitoring because side effects can be significant.
Supportive Care
CDC states treatment requires supportive care addressing malnutrition, anaemia, bleeding and other infections present at the same time. This is not optional extra care, it is part of the treatment.
Treatment Alongside HIV Care
People with both infections need HIV treatment as well, and may need longer courses and continued preventive treatment because relapse is common.
Prevention
Sleep under an insecticide-treated net
Sandflies bite mainly between dusk and dawn. CDC notes sandflies are much smaller than mosquitoes, so a fine-mesh or treated net matters.
Avoid outdoor exposure from dusk to dawn
CDC states sandflies bite primarily during these hours, so limiting outdoor activity then reduces exposure.
Wear covering clothing and use repellent
CDC advises protective clothing and insect repellent on exposed skin.
Vector control in the community
WHO lists control of the sandfly among the core strategies for controlling the disease.
Early diagnosis and prompt treatment
WHO lists this among the control strategies, because treating cases quickly reduces the reservoir of infection in the community.
Improving housing and sanitary conditions
WHO lists poor housing and sanitation as risk factors, because they create the breeding and resting places sandflies use.
Risk Factors
People Living in Poverty in Endemic Rural Areas
WHO names poverty directly as a factor increasing vulnerability.
- Communities in eastern Africa, which WHO reports carried 73% of global cases in 2022
- Households with poor housing and sanitary conditions, which favour sandflies
- Families without the resources to reach a diagnostic centre
- Communities affected by displacement and conflict
Children in Eastern Africa
WHO reports that half of eastern African cases in 2022 were in children under 15.
- Children under 15 years in endemic districts
- Malnourished children, in whom WHO states infection is more likely to progress to full illness
- Children whose prolonged fever is treated repeatedly as malaria
- WHO’s targets include eliminating deaths from this illness among children
People Living With HIV
WHO reports that combined infection has been documented in dozens of countries.
- People with untreated or advanced HIV
- WHO reports high rates of combined infection in several endemic countries
- This group faces higher risk of developing illness, of relapse and of death
- They may need continued preventive treatment after the main course
Displaced and Migrant Populations
WHO links epidemics to the movement of people without immunity into areas where the parasite circulates.
- People displaced by conflict into endemic areas
- Seasonal agricultural workers
- Communities with no previous exposure and therefore no immunity
- WHO notes the disease has outbreak potential
Complications
Death
WHO states the illness is fatal in over 95% of cases if left untreated.
Skin Changes After Apparent Cure
WHO reports that 5% to 10% of people in east Africa and the Indian subcontinent develop a skin condition six months to a year or more after apparently being cured.
Severe Anaemia and Bleeding
The low blood counts can require transfusion and are a frequent reason for admission.
Other Infections
The illness suppresses the immune system, so other infections are common and are often what causes death in untreated cases.
Relapse
WHO reports elevated relapse risk in people also living with HIV, who may need continued preventive treatment.
Late Reactivation
CDC notes that a hidden infection can become active years or decades later in someone whose immune system becomes weakened.
When to Seek Medical Care
Prolonged Irregular Fever After Being in an Endemic Area
Fever lasting more than two weeks that has not responded to malaria treatment needs further investigation.
Swelling or Heaviness in the Upper Left Abdomen
WHO lists enlargement of the spleen as a core sign of the illness.
Unexplained Weight Loss With Fever
The combination of the two is characteristic and should not be waited out.
Pallor, Breathlessness or Easy Bruising
These reflect the falling blood counts and need assessment.
Any of These in Someone Living With HIV
WHO states this group faces elevated risk of illness, relapse and death, so assessment should not be delayed.
Prognosis
Untreated, It Is Almost Always Fatal
WHO states the illness is fatal in over 95% of untreated cases.
Treated, It Is Curable
WHO states that leishmaniasis is a treatable and curable disease, though cure depends on the immune system working.
A Minority Develop Skin Changes After Cure
WHO reports this in 5% to 10% of people in east Africa and the Indian subcontinent, appearing six months to a year or more after apparent cure.
Speed of Treatment Is a Formal Target
WHO’s eastern Africa framework targets detection and treatment within 30 days of symptoms starting, and aims to end deaths among children.
Differential Diagnosis
Malaria
Also causes irregular fever, anaemia and an enlarged spleen. It is separated by a malaria test, and it is far more common, which is why this diagnosis is often delayed.
Typhoid Fever
Causes prolonged fever and an enlarged spleen, and is confirmed by blood culture.
Widespread Tuberculosis
Causes prolonged fever, wasting and night sweats, and is identified by specific testing and chest imaging.
Blood Cancers
Lymphoma and leukaemia also cause fever, weight loss, an enlarged spleen and low blood counts. The bone marrow sample distinguishes them.
Schistosomiasis Affecting the Liver and Spleen
Causes a large spleen and liver, but without the fever and the falling blood counts seen here.
References
World Health Organization: Leishmaniasis
WHO fact sheet on the forms of leishmaniasis, transmission, risk factors, diagnosis and control.
World Health Organization: New framework to eliminate visceral leishmaniasis in eastern Africa
Regional burden figures and the elimination targets for eastern Africa.
CDC: About Leishmaniasis
Overview of the forms of leishmaniasis, symptoms and how it is acquired.
CDC: Clinical Care of Leishmaniasis
Treatment options, routes, durations and the supportive care required.
Frequently Asked Questions
How is visceral leishmaniasis caught?
Through the bite of an infected female sandfly. WHO states that over 90 sandfly species transmit the parasites. CDC notes sandflies are about a quarter of the size of mosquitoes and bite mainly between dusk and dawn.
How dangerous is it?
Very, if untreated. WHO states it is fatal in over 95% of cases if left untreated. With treatment it is curable, which is why prolonged fever with an enlarged spleen in an endemic area should always be investigated.
Is there a vaccine?
No. CDC states there are no vaccines or medicines to prevent leishmaniasis. Prevention relies on avoiding sandfly bites, particularly between dusk and dawn, and on finding and treating cases early.
Can it come back after treatment?
It can. WHO reports that 5% to 10% of people in east Africa and the Indian subcontinent develop a related skin condition six months to a year or more after apparent cure, and that people also living with HIV face a higher risk of relapse.
Why does it keep being treated as malaria?
Because the early picture is very similar: irregular fever, anaemia and an enlarged spleen. Malaria is far more common, so it is treated first. Fever that continues after malaria has been excluded or treated needs a different explanation.