Kala Azar, also known as Visceral Leishmaniasis, is a serious parasitic disease caused by the protozoan Leishmania donovani. It primarily affects the liver, spleen, and bone marrow, leading to chronic fever, anemia, and significant weight loss. The name “Kala Azar” literally means “black fever” — derived from the Hindi words Kala (black) and Azar(fever), due to the darkening of the skin observed in some patients.
In India and other tropical countries, Kala Azar remains a major public health concern, particularly in Bihar, Jharkhand, West Bengal, and Uttar Pradesh. It is considered the second largest parasitic killer after malaria worldwide.
Causative Protozoan: Leishmania donovani
The disease Kala Azar is caused by a protozoan parasite, Leishmania donovani, transmitted through the bite of an infected female sandfly (Phlebotomus argentipes). The parasite lives and multiplies within human macrophages (white blood cells) and disrupts the immune response.
Scientific Classification Table
Kala Azar was first identified in India during the 19th century. British doctors initially mistook it for malaria due to similar symptoms such as fever and spleen enlargement. In 1903, William Leishman and Charles Donovan independently discovered the parasite, later named Leishmania donovani in their honor.
The Bengal Epidemic (1870–1920) marked a significant period when the disease caused thousands of deaths in eastern India, leading to the development of focused medical research and vector control programs.
Kala Azar is found mostly in tropical and subtropical regions. The disease is endemic in more than 60 countries, including:
In India, 90% of cases are reported from Bihar, followed by West Bengal and Uttar Pradesh. Poor sanitation, overcrowding, and the presence of sandfly breeding sites increase transmission risk.
Role of the Sandfly (Phlebotomus argentipes)
The female sandfly acts as the biological vector for transmitting Leishmania donovani. When it bites an infected person, it ingests parasites present in the blood. Later, when it bites another healthy person, it transfers the parasites through its saliva.
Life Cycle of Leishmania donovani
The parasite exhibits two main forms:
The life cycle continues as the sandfly transmits the promastigotes during its bite, which then invade human macrophages and transform into amastigotes.
Early Symptoms
Advanced Stage Symptoms
If left untreated, the disease can become fatal due to complications like secondary infections or organ failure.
Impact on Internal Organs
The parasites invade macrophages in the liver, spleen, and bone marrow, leading to organ enlargement and impaired function. The bone marrow suppression causes pancytopenia (deficiency of all blood cells), which increases infection risk.
Effect on the Immune System
Leishmania donovani suppresses the host immune response, making the body more susceptible to bacterial infections. Chronic infection can lead to immune exhaustion and malnutrition.
Laboratory and Microscopic Tests
Modern Diagnostic Methods
Recent developments include molecular diagnostic kits and serological assays, which are faster and safer alternatives to traditional invasive methods.
In detail, early diagnosis is critical for mortality reduction.
Antimonial Drugs and Alternatives
Recent Advances in Treatment
Vector Control Strategies
Public Health Programs in India
The National Kala Azar Elimination Programme (NKEP) was launched by the Government of India in collaboration with WHO. The goal is to eliminate Kala Azar as a public health problem through early detection, treatment, and vector control.
(Session 2026 - 27)