Table of Contents
- What is Kala azar?
- Kala azar Epidemiology
- Visceral leishmaniasis (Kala azar) mode of Transmission
- Causes of Kala azar (causative agent of kala azar)
- Kala azar (Visceral Leishmaniasis) Pathogenesis and Life cycle of parasite
- Visceral leishmaniasis (Kala azar) Symptoms
- Kala azar Diagnosis
- Visceral leishmaniasis Management (Kala azar Treatment)
- Kala azar Prevention
What is Kala azar?
Kala azar (also called Visceral Leishmaniasis or Black Sickness or Black Fever) is a disease caused by different species of Leishmania parasite named Leishmania donovani, Leishmania chagasi and Leishmania infantum; it is the most severe clinical form of Leishmaniasis. Kala azar is transmitted by the Female Phlobotine Sandfly.
Kala azar Epidemiology
Visceral leishmaniasis is endemic in some countries of Africa such as Ethiopia and Sudan; it occurs also in the Middle East, India and South America. Kala azar is becoming a common opportunistic infection in HIV/AIDS which means it tends to infect HIV/AIDS patients commonly because their immune system is down. Kala azar occurs in epidemics in some parts of India where man is the main host. Children and visitors to endemic regions are mainly at risk. The major animal reservoirs of Leishmania donovani in Europe and Asia are foxes and dogs while the reservoirs in Africa are rodents.
Visceral leishmaniasis (Kala azar) mode of Transmission
- The commonest mode of transmission of Kala azar is by inoculation of promastigotes to humans through the bite of female sand flies as they take a blood meal. The reservoir of the aflagellate forms (amastigotes) includes humans or mammals such as dogs
- Kala azar can be transmitted through blood transfusion and injections but this is rare
Causes of Kala azar (causative agent of kala azar)
The incubation period of Kala azar is usually 1 to 2 months, but may even take several years to manifest as the onset of symptoms occurs gradually, making the patient to feel quite well despite the fact that there are abnormal physical signs.
The Leishmania species causing visceral leishmaniasis includes Leishmania donovani, leishmania infantum and leishmania chagasi.
Kala azar (Visceral Leishmaniasis) Pathogenesis and Life cycle of parasite
Primary cutaneous lesions (or Primary Leishmanioma) forms on the skin at the sites of sandfly bites these lesions are tiny and may be unnoticed. This triggers an immune response with lymphocytes and plasma cells developing around amasitigote-containing histiocytes in the dermis; this sensitizes epithelioid cells and giant cells which then help to destroy the infection in competent immune system leading to healing. When the immune system cannot destroy the infection, then the amastigote parasites in the skin escape into the blood and spreads to cells of the reticuloendothelial system (spleen, liver, bone marrow and lymph nodes), where they keep multiplying and clinical features develop.
Visceral leishmaniasis (Kala azar) Symptoms
- It may be asymptomatic (no symptoms may be noticed even though an individual has the disease)
- Abdominal discomfort
- Abdominal distension (caused by hepatosplenomegaly)
- Low-grade fevers (that may also be high and intermittent)
- Loss of appetite (anorexia)
- Weight loss
- Hyperpigmentation of the skin (darkening of the skin)
- Rough skin
- Lymphadenopathy commonly occurs in African Kala azar
- Swelling of the legs (edema) may occur
- Dry and brittle hair
- Bleeding from the gums, skin and many other sites may occur this is an important cause of death in Kala azar
- Some patients develop post – Kala Azar derma leishmaniasis after months or years of treatment for visceral leishmaniasis
Kala azar Diagnosis
- Definitive diagnosis of Kala azar is done by demonstration of Leishmania parasite in a smear of peripheral blood with Giemsa stain and tissue touch preparation of organ aspirates, which are then examined using a light microscope
- Diagnosis could also be made by culture of tissue aspirates taken from the spleen, Bone Marrow, liver or lymph node. A parasite yield of 95% is diagnostic in spleen culture, 85% in Bone marrow, 75% in Liver culture and 60% in lymph node using different media such as Novy-MacNeal-Nicolle medium (NNN) or Schneider insect media
- Serologic tests such Enzyme-Linked Immunosorbent Assay (ELISA) or Direct Antiglobulin Test (DAT) help to diagnose the specific species of parasite involved and they are 100% sensitive
- Montenegro skin test (also called the Leishmanin skin test) shows negative in visceral leishmaniasis due to immune suppression making it impossible for the body to mount an immune response; this same test becomes positive after 6 to 8 weeks of recovery from Visceral leishmaniasis
- A full blood count will show decreased blood cells (Pancytopenia) leading to Leucopenia, anemia and thrombocytopenia
Visceral leishmaniasis Management (Kala azar Treatment)
- Definitive treatment includes use of Pentostam (Sodium Stibogluconate) given intravenously or intramuscular route, 20mg/kg per day for 28 days. If relapse occur or there is incomplete cure, the drug can be repeated for 40 to 60days
- If there is resistance to antimony salts, the best form of treatment is the use of Amphotericin B lipid formulation (given intravenously, 2- 5mg/kg per day for 5-25 weeks). This drug is however costly.
- Pentamidine is also effective and is given by intravenous route or intramuscular route, 4 mg/kg per day for 3-4 weeks
- Supportive treatment include giving of antibiotics to treat infections, correction of malnutrition and blood transfusion to correct pancytopenia
Without treatment, death occurs in Kala azar within a year due to bacterial infection and uncontrolled bleeding following pancytopenia (decrease in cell counts including platelets that help in blood clotting) this is the reason why patients with visceral leishmaniasis are transfused with blood when there is pancytopenia.
Kala azar Prevention
- Use of mosquito nets
- Use of insecticides
- Use of insect repellent cream
- Wearing of protective clothing
Prevention of Kala azar basically involves the control of the vector and treatment of people infected with visceral leishmaniasis