Summary about Disease
Black fever, also known as visceral leishmaniasis (VL) or kala-azar, is a parasitic disease caused by protozoa of the Leishmania genus. It's transmitted to humans through the bite of infected female sandflies. The parasites migrate to the internal organs, such as the spleen, liver, and bone marrow, causing a range of symptoms. If left untreated, it is almost always fatal.
Symptoms
Common symptoms of visceral leishmaniasis include:
Fever (often intermittent and prolonged)
Weight loss
Enlargement of the spleen (splenomegaly)
Enlargement of the liver (hepatomegaly)
Anemia (low red blood cell count)
Weakness and fatigue
Darkening of the skin (particularly in patients from the Indian subcontinent, hence the name "kala-azar," meaning "black fever" in Hindi)
Swollen lymph nodes (less common)
Bleeding
Causes
Visceral leishmaniasis is caused by infection with Leishmania parasites. The parasites are transmitted to humans through the bite of infected female phlebotomine sandflies. The sandflies become infected by feeding on infected animals (reservoirs), such as dogs, rodents, and other mammals. Humans are typically infected when they are bitten by sandflies that have previously fed on an infected animal.
Medicine Used
Treatment for visceral leishmaniasis involves antiparasitic medications. Common medications include:
Liposomal Amphotericin B: Often the preferred treatment, especially in resource-limited settings. Highly effective and administered intravenously.
Sodium Stibogluconate: An older medication, now less commonly used due to toxicity and increasing resistance in some areas.
Miltefosine: An oral medication that is effective but contraindicated in pregnant women.
Pentamidine: Another older medication, used less frequently due to its toxicity.
Paromomycin: Aminoglycoside antibiotic; used in combination with sodium stibogluconate in some regions. The specific treatment regimen depends on factors such as the geographical location, the species of Leishmania involved, the patient's overall health, and the availability of medications. Treatment duration and dosage will be determined by a healthcare professional.
Is Communicable
Visceral leishmaniasis is not directly communicable from person to person. It is transmitted only through the bite of infected sandflies. Direct contact with an infected person, such as through touching, kissing, or sharing utensils, will not spread the disease.
Precautions
Precautions to prevent visceral leishmaniasis focus on avoiding sandfly bites, especially in endemic areas. These include:
Using insect repellent: Apply insect repellent containing DEET or picaridin to exposed skin.
Wearing protective clothing: Wear long sleeves and pants, especially during dawn and dusk when sandflies are most active.
Sleeping under insecticide-treated bed nets: Use bed nets treated with insecticide to prevent sandfly bites while sleeping.
Spraying insecticides: Spray insecticides inside homes and in surrounding areas to kill sandflies.
Controlling sandfly breeding sites: Eliminate standing water and other breeding sites for sandflies.
Protecting animals: Use insecticide collars on domestic dogs and control rodents to reduce the reservoir of infection.
How long does an outbreak last?
The duration of a visceral leishmaniasis outbreak can vary greatly depending on several factors:
Effectiveness of control measures: Prompt and effective measures to control sandfly populations and treat infected individuals can shorten an outbreak.
Geographical area: Outbreaks in areas with poor sanitation and limited access to healthcare may last longer.
Environmental factors: Weather conditions and environmental changes that favor sandfly breeding can prolong an outbreak.
Availability of resources: Adequate resources for diagnosis, treatment, and vector control are essential for containing an outbreak. Outbreaks can last from several months to several years if control measures are inadequate.
How is it diagnosed?
Visceral leishmaniasis is diagnosed through a combination of clinical evaluation and laboratory tests. Common diagnostic methods include:
Physical examination: Evaluation of symptoms and physical signs, such as fever, splenomegaly, and hepatomegaly.
Microscopy: Examination of bone marrow, spleen, or lymph node aspirates under a microscope to identify Leishmania parasites.
Serological tests: Detection of antibodies against Leishmania parasites in the blood using tests such as the ELISA (enzyme-linked immunosorbent assay) or direct agglutination test (DAT).
Molecular tests (PCR): Polymerase chain reaction (PCR) to detect Leishmania DNA in blood or tissue samples. This is a highly sensitive and specific method.
rK39 rapid diagnostic test: A rapid immunochromatographic test that detects antibodies to the rK39 antigen of Leishmania. It's easy to use and provides results quickly.
Timeline of Symptoms
The timeline of symptoms in visceral leishmaniasis can vary, but generally follows this pattern:
Incubation period: The time between the sandfly bite and the onset of symptoms can range from a few weeks to several months (typically 2-6 months).
Initial symptoms: Early symptoms may include fever, fatigue, and weight loss. These symptoms may be mild and non-specific initially, making diagnosis challenging.
Progressive symptoms: Over time, the symptoms become more pronounced, including persistent fever, significant weight loss, enlargement of the spleen and liver, anemia, and darkening of the skin.
Advanced stages: If left untreated, the disease can progress to severe complications, such as bleeding, secondary infections, and ultimately, death.
Important Considerations
Early diagnosis and treatment: Early diagnosis and treatment are crucial to prevent severe complications and death.
Coinfection: Visceral leishmaniasis can occur as a coinfection with other diseases, such as HIV, which can complicate diagnosis and treatment.
Drug resistance: Resistance to antileishmanial drugs is an increasing concern in some regions, highlighting the need for drug resistance monitoring and the development of new treatments.
Post-kala-azar dermal leishmaniasis (PKDL): Some patients, particularly in the Indian subcontinent, may develop PKDL after successful treatment of visceral leishmaniasis. PKDL is a skin condition characterized by lesions that can occur months or years after treatment.
Public health measures: Effective public health measures, including vector control, reservoir control, and health education, are essential for preventing and controlling visceral leishmaniasis.