Visceral leishmaniasis (kala-azar): symptoms, causes, diagnosis and treatment

Leishmaniasis is caused by protozoan parasites of the genus Leishmania, with more than 20 species, spread by sandflies. WHO describes three main forms: visceral, the most serious; cutaneous, the most common, which causes skin ulcers; and mucocutaneous, which affects the mouth, nose and throat.

TravelHealthPro, the UK national travel health service, explains that visceral leishmaniasis, also known as kala-azar, occurs when the parasite infects several organs, commonly the liver, spleen and bone marrow. It can cause fever and weight loss, and people can be very unwell; without treatment it can be potentially fatal.

WHO says most cases of visceral leishmaniasis occur in Brazil, east Africa and India, with an estimated 50,000 to 90,000 new cases annually worldwide, only 25 to 45% of which are reported to WHO. It notes that in the WHO European region, cutaneous and visceral leishmaniasis are endemic and imported cases are common, mainly from Africa and the Americas.

The disease is linked to poverty, malnutrition, poor housing, population displacement and a weak immune system. For UK travellers, TravelHealthPro says those with conditions and medication that cause immunosuppression are at greater risk of developing visceral leishmaniasis, and that the infection is widely distributed in Central and South America, the Middle East, Africa and southern Europe.

WHO adds that people living with HIV who are infected with leishmaniasis have high chances of developing full-blown disease, with high relapse and mortality rates, although antiretroviral treatment reduces progression and delays relapses.

WHO characterises visceral leishmaniasis by irregular bouts of fever, weight loss, enlargement of the spleen and liver and anaemia. Only a small fraction of people infected with the parasites eventually develop the disease, and symptoms can appear long after exposure, which is why a travel history matters.

WHO describes a later complication, post-kala-azar dermal leishmaniasis, a macular, papular or nodular rash usually on the face, upper arms and trunk that appears months to years after apparent cure, mainly in east Africa and the Indian subcontinent.

WHO says people suspected of having visceral leishmaniasis should seek medical care immediately. Diagnosis combines clinical signs with parasitological or serological tests, such as rapid diagnostic tests. In practice, UK specialists in infectious or tropical diseases manage cases, and TravelHealthPro says treatment is usually advised by an infectious disease specialist and depends on many factors.

WHO says treatment depends on the type of disease, other pathologies, the parasite species and geographic location. It stresses that medicines require an immunocompetent system because they do not get rid of the parasite from the body, so relapse is a risk if immunosuppression occurs. There are highly effective and safe antileishmanial medicines for visceral leishmaniasis, although they can be difficult to use.

TravelHealthPro says travellers should be aware of the risk at their destination, and that the key to prevention is insect bite avoidance. Sandflies are very small and their bites can be painless. They are most active from dusk till dawn, are commonly found in rural areas but have adapted to urban environments, and are found closer to ground level, so those spending time near or on the ground are at increased risk.

WHO lists insecticide-treated nets and personal protection among vector control measures. If you develop fever, weight loss or an enlarged tummy after returning from an affected area, tell your GP about your travel history so the possibility is considered.