Summary about Disease
Kala-azar, also known as visceral leishmaniasis (VL), is a neglected tropical disease caused by protozoan parasites of the Leishmania donovani complex. It's transmitted to humans through the bite of infected female phlebotomine sandflies. VL is characterized by fever, weight loss, enlargement of the spleen and liver (hepatosplenomegaly), and anemia. If left untreated, it is almost always fatal.
Symptoms
Common symptoms include:
Prolonged fever (often irregular)
Weight loss
Fatigue and weakness
Enlargement of the spleen (splenomegaly)
Enlargement of the liver (hepatomegaly)
Anemia (low red blood cell count)
Darkening of the skin (particularly on the hands, feet, abdomen, and face - hence the name "Kala-azar," meaning "black fever" in Hindi)
Swollen lymph nodes (less common)
Bleeding (due to low platelet count in severe cases)
Causes
Kala-azar is caused by infection with Leishmania donovani or *Leishmania infantum* parasites (depending on the geographic region). These parasites are transmitted to humans through the bite of infected female phlebotomine sandflies. Sandflies become infected by feeding on infected animals (dogs, rodents, or humans acting as reservoirs). The parasite then multiplies in the sandfly and is transmitted to the next host when the sandfly takes another blood meal.
Medicine Used
Treatment for Kala-azar includes:
Liposomal Amphotericin B: A highly effective and often preferred treatment, especially for initial treatment and patients with underlying conditions.
Miltefosine: An oral medication, making it easier to administer in resource-limited settings.
Sodium Stibogluconate (SSG) or Meglumine Antimoniate: Older medications that are less preferred due to higher toxicity and lower efficacy compared to newer treatments, but may still be used in some regions where newer options are unavailable or unaffordable.
Combination therapy: Combining different medications can sometimes improve treatment outcomes. The specific medication and treatment duration will depend on the patient's overall health, the severity of the disease, and the region where the infection was acquired. Treatment should always be administered under the supervision of a qualified healthcare professional.
Is Communicable
Kala-azar is not directly communicable from person to person through direct contact. It is transmitted through the bite of infected sandflies. Therefore, it is not contagious in the traditional sense.
Precautions
Precautions to prevent Kala-azar include:
Sandfly Control:
Insecticide spraying (indoor residual spraying - IRS) in homes and surrounding areas
Use of insecticide-treated bed nets (ITNs)
Use of insect repellents on exposed skin
Wearing long-sleeved clothing and pants, especially during peak sandfly activity (dusk and dawn)
Environmental Management:
Clearing vegetation and debris around homes to reduce sandfly breeding sites
Improving sanitation and waste management
Animal Reservoir Control:
Controlling Leishmania infection in domestic animals (especially dogs) through treatment or culling, depending on local policies and resources.
Early Diagnosis and Treatment:
Prompt diagnosis and treatment of infected individuals to reduce the parasite reservoir.
Personal Protective Measures:
Using window screens and door screens to prevent sandflies from entering homes.
How long does an outbreak last?
The duration of a Kala-azar outbreak can vary considerably depending on several factors, including:
Control Measures: The effectiveness and speed of implementation of control measures (e.g., insecticide spraying, treatment of cases) significantly impact the outbreak's duration.
Environmental Factors: Climate conditions (temperature, humidity) affect sandfly populations and transmission rates.
Geographic Area: The size and population density of the affected area influence the spread of the disease.
Public Health Response: The capacity and resources of the public health system to diagnose, treat, and prevent the disease play a crucial role.
Reservoir Hosts: the number of reservoir hosts. Outbreaks can last from several months to years if not properly controlled. Intensive interventions can shorten the duration, while delays in implementing control measures can prolong the outbreak.
How is it diagnosed?
Kala-azar is diagnosed through a combination of clinical findings and laboratory tests:
Clinical Examination: Assessing the patient for typical symptoms like fever, weight loss, splenomegaly, hepatomegaly, and anemia.
Parasitological Tests:
Microscopic Examination: Direct visualization of Leishmania parasites in samples from bone marrow, spleen, or lymph node aspirates. This is highly specific but may have lower sensitivity.
Culture: Growing Leishmania parasites in culture from aspirate samples. This is more sensitive than microscopy but takes longer.
Serological Tests:
rK39 Immunochromatographic Test (Dipstick test): A rapid and relatively inexpensive test that detects antibodies against the rK39 antigen of Leishmania donovani. This test is widely used for screening in endemic areas due to its ease of use and rapid results.
Enzyme-Linked Immunosorbent Assay (ELISA): A more sensitive serological test that can detect antibodies against Leishmania.
Direct Agglutination Test (DAT): Another serological test used in some regions.
Molecular Tests:
Polymerase Chain Reaction (PCR): A highly sensitive and specific test that detects Leishmania DNA in samples. PCR is becoming increasingly important for diagnosis, especially in cases where parasitological tests are negative or in atypical presentations. Bone marrow aspiration is often considered the gold standard for diagnosis, but less invasive methods like the rK39 dipstick test are often used for initial screening.
Timeline of Symptoms
The timeline of Kala-azar symptoms can vary depending on individual factors and the severity of the infection:
Incubation Period: The time between the sandfly bite and the onset of symptoms can range from weeks to several months (typically 2-6 months).
Initial Stage:
Fever: Gradual or intermittent fever develops.
Weakness and Fatigue: Increasing fatigue and general malaise.
Progressive Stage:
Splenomegaly: The spleen gradually enlarges, causing abdominal discomfort.
Hepatomegaly: The liver may also enlarge.
Weight Loss: Significant weight loss occurs despite adequate food intake.
Anemia: Anemia develops, leading to further fatigue and weakness.
Skin Darkening: Darkening of the skin, particularly on the face, hands, and feet, may become noticeable (though not always present).
Late Stage (Without Treatment):
Severe Anemia: Profound anemia leads to severe weakness and pallor.
Bleeding Tendencies: Low platelet count can cause bleeding from the nose, gums, or skin.
Secondary Infections: Increased susceptibility to other infections due to weakened immune system.
Death: Without treatment, Kala-azar is almost invariably fatal, usually due to complications such as secondary infections, hemorrhage, or organ failure. The progression of symptoms can be more rapid in children and immunocompromised individuals. Early diagnosis and treatment are crucial to prevent severe complications and death.
Important Considerations
Co-infection with HIV: Individuals co-infected with HIV and Leishmania* have a higher risk of developing VL, relapse, and drug resistance. Management of co-infection requires a comprehensive approach.
Post-Kala-azar Dermal Leishmaniasis (PKDL): Some individuals who have been treated for VL may develop PKDL, a skin condition characterized by nodules or lesions. PKDL can occur months or years after successful treatment of VL and requires separate treatment.
Drug Resistance: Resistance to antileishmanial drugs is a growing concern in some regions. Monitoring for drug resistance and adapting treatment strategies is essential.
Public Health Importance: Kala-azar is a significant public health problem in endemic areas, particularly in resource-limited settings. Control programs require a multidisciplinary approach, including vector control, early diagnosis and treatment, and health education.
Surveillance: Continuous surveillance is needed to monitor disease trends, identify outbreaks, and evaluate the effectiveness of control measures.
Access to Treatment: Ensuring access to affordable and effective treatment is critical for reducing morbidity and mortality associated with Kala-azar.
Research: Continued research is needed to develop new diagnostic tools, treatments, and prevention strategies.