Kala-Azar is the second biggest parasitic killer in the world and infects around 3 lakh people annually. Along with Chagas disease and sleeping sickness, kala-azar is one of the most lethal and neglected tropical diseases (NTDs). Only malaria is more dangerous. Kala Azar is known to be endemic in 47 countries with approximately 200 million at risk. The parasite spreads to humans by the bite of infected female sand flies. It is known to attack the immune system and can be fatal if not treated. Between 2-400,000 cases, 90% of cases are found in India, Bangladesh, Nepal, Sudan, and Brazil.
Kala-Azar or Visceral Leishmaniasis is a slow progressing indigenous condition that is caused by a protozoan parasite. The disease-causing parasite belongs to the genus Leishmania. The parasite infects the reticuloendothelial system and may be found in abundance in bone marrow, spleen, and liver. In India, generally, the parasite that causes this disease is Leishmania donovani.
Post-Kala-Azar dermal leishmaniasis is a condition in which Leishmania donovani parasites invade the skin cells. The parasites stay, and develop in the skin cells and evolve as dermal lesions. In this section, we will learn more about the causes of kala-azar and kala-azar symptoms
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In India, there is only one sand fly vector of kala-azar- Phlebotomus argentipes which is the cause of kala-azar. Sandflies are tiny insects that are about ¼ the size of a mosquito. The length of a sand fly can range from 1.5 mm to 3.5 mm.
These sand flies breed in high relative humidity, warm temperatures, high subsoil water, and an abundance of vegetation. Micro-climatic conditions are the ideal breeding grounds for sandflies. The high organic matter available in such places serves as food for its larvae.
These sand flies are ecologically sensitive insects, fragile, and cannot bear desiccation or the removal of moisture.
The leading cause of kala-azar is a bite from female phlebotomine sand-flies which is the vector or transmitter of the Leishmania parasite. Listed below is how the infection occurs:
The sand flies feed on animals and humans for blood which they need to develop their eggs.
If blood having Leishmania parasite is drawn from an animal or human, the next person to receive a bite will become infected and develop Leishmaniasis.
After months of the initial infection, the disease can progress into a severe form called Visceral Leishmaniasis or Kala-Azar.
In the beginning, Leishmania parasites cause skin sores or ulcers at the site of the bite. As the disease advances, it attacks the immune system. Kala-azar presents itself in full form after two to eight months, with general signs and symptoms such as prolonged fever, and the following:
Recurring fever with a double rise in temperature.
Loss of appetite and weight loss.
Weakness and fatigue.
Dry, thin, scaly skin, and hair loss. Grayish discoloration of the skin of hands, feet, face, and abdomen in light-skinned people, hence the name kala-azar or black fever.
Rapid deficiency in red blood cells or hemoglobin.
Enlargement of the spleen.
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Kala-azar can be diagnosed based on symptoms such as a case of fever lasting more than two weeks. And no response to anti-malarial or antibiotics. Lab findings may include anemia and progressive leucopenia.
In the lab, the following test may diagnose kala-azar:
Serology test – this standard test for kala-azar is based on relative sensitivity; specificity and feasibility include Direct Agglutination test (DAT), rk39 dipstick, and ELISA. All these tests detect IgG antibodies that are long-lasting. The aldehyde test is a non-specific test.
Parasite detection in bone marrow/spleen/ lymph node aspiration or culture medium is the confirmatory diagnosis. Sensitivity varies with the organ selected for aspiration. Spleen aspiration has the highest sensitivity and specificity, with precaution, expertise, and better hospital facilities.
The treatment of kala-azar is about the killing of the parasite with effective drugs that are cheap and less toxic. Pentavalent antimonial is the first-line drug, and pentamidine and amphotericin B are the second-line drugs. These medicines can only be given through injection. They are toxic and have many side effects. The treatment extends to a period of 30 days.
This is all about Kala Azar, a tropical disease, its causes, symptoms, and treatment process. Focus on how this disease spreads and how the patients are treated.
1. How can kala-azar be managed?
Specific diagnosis and treatment of kala-azar are problematic for many reasons. Treatment is lengthy and costly. The diagnosis is invasive and obtained by organ needle aspiration for microscopic detection. Bone marrow, spleen, and lymph node tissues are sampled in case of suspected infection. The diagnostic sensitivity of spleen aspiration is higher- 95 % to 98 %. However, the procedure carries a lot of risk of bleeding. Bone marrow testing accuracy is considered lowest- 53% - 95%. Organ aspirations and examinations require technical skills that are not available in rural areas. Correct diagnosis methods are not undertaken outside of research laboratories.
2. How to prevent kala-azar?
Vaccines or preventive drugs for visceral Leishmania are not available. The most effective method is prevention. One has to protect the self from sandfly bites. The following precautions are suggested:
Outdoors- one can avoid outdoor activities from dusk to dawn when sand flies are most active. When outdoors, wear long pants, long-sleeved shirts, and socks. Tuck the shirt into the pants. Apply insect repellent to all skin that is uncovered or exposed under the ends of pants and sleeves.
Indoors- Live in well-screened or air-conditioned areas. Spray living/sleeping areas with insecticide to kill insects. The use of a bed net soaked with spray works to keep the flies away.
3. What are the major causes of Kala Azar?
In India, there is only one sand fly vector of kala-azar- Phlebotomus argentipes which is the cause of kala-azar.