HUMAN DISEASE: KALA-AZAR OR DUMDUM FEVER

· It is a serious oriental disease of man. It is called visceral leishmaniasis as parasites are migrated inside the internal organs such as the liver and spleen.
· The word kala-azar has been derived from two Indian words Kala and Azar, meaning “black sickness”, an illness in which the colour (pigmentation) of the skin turns black.

· The word Kala also means “deadly”, thereby signifying a fatal illness.

Occurrence:

· It occurs in Nepal, India, China, Mediterranean countries, parts of Africa and South America, Southern Europe, Russia.

· In Nepal, it is mostly reported from Saptary and Siraha districts.

Causative organism (Pathogen):
· Pathogenic, protozoan flagellate, endoparasite, Leishmania donovani which is transmitted by the bite of blood-sucking female Sandflies called Phlebotomus argentipes.
· Leishmania is an intracellular digenetic parasite of the reticuloendothelial system i.e. liver, spleen, bone marrow (WBCs) and lymph nodes.

· It is present in Leishmanial or Amastigote form (without flagella) in man and Leptomonad or promastigote form (with flagella) in Sandfly.
· The species Leishmania donovani was reported simultaneously by Leishman from London (May 1903 AD) and Donovan from Madras (July 1903 AD); hence the name Leishmania donovani.

Source of Infection:

· Blood and tissue fluids of the infected persons.

· Dogs, cats and jackals may serve as reservoir hosts for human infection.

Mode of Transmission
· The amastigote forms of the Leishmania donovani residing in the reticuloendothelial system of human beings multiplied by longitudinal binary fission, each measuring 2-4 µ in length.

· They get transferred into the gut of the sandfly when the sandfly bites the infected person.

· In the mid-gut of the sandfly, they divide by longitudinal binary fission and then reach the pharynx and buccal cavity of the sandfly.

· From these places, they again reach the healthy person after the bite of the infected sandfly.

Incubation period: From 3-6 months and symptoms may appear even after 2 years.

Hosts: Primary host (man), Secondary host (Sandfly), reservoir host (dog).

Symptoms:
A. Early symptoms
· Swelling, high fever, enlargement of the spleen (splenomegaly) and liver (hepatomegaly), enlargement of lymph nodes followed by general weakness, weight loss, sweating, gingival bleeding, thrombocytopenia (decrease in a number of platelets in the blood), emaciation, anaemia due to reduction in a number of blood cells and peculiar darkening of the skin. (Kala-black, Azar- sickness.).

B. Advanced symptoms
· Dry, rough and dark or pigmented skin, hair becomes brittle and falls out (Alopecia- baldness, loss of hair).
· Not treated on time, the patient dies within 2 years.

· Death is generally due to secondary infections by bacteria or viruses.

· In the long run, it may invite other diseases like pneumonia, disease of bone marrow, TB etc.

· Total leucocyte count reduces to less than 4,000/mm3.

Diagnosis
· Microscopical examination of blood, a biopsy was taken from spleen or bone marrow for the presence of Amastigote forms (round, non-motile, 3-7µ in diameter) of Leishmania donovani.
· In WBCs, there is a decrease in neutrophils but an increase in lymphocytes and monocytes.

· The number of RBCs is also decreased.

Treatment
· Pentavalent antimony compounds like Sodium-antimony tartrate and gluconate, Urea stibine, Aminostiburea, Neostibosan etc.
· Pentamidine isethionate is also used.

Prevention (Prophylaxis)
i. Eradication of vector (Sandfly)
· In endemic areas, low trees and bushes etc should be cleared out.
· Periodic fumigation and spray of insecticides of sleeping quarters should be done.

ii. Attack on the Parasite
· Those areas where dogs act as reservoir hosts, all street dogs should be isolated and treated.

iii. Personal defence
· Use mosquito nets or screens and avoid sleeping on ground floors (avoiding the bite of sand fly).

iv. Have houses well lit and ventilated.
(In short, Eradication of insect vector sandfly by insecticides, elimination of reservoir hosts and avoiding the bite of sand fly)

· Two main features of the sandfly are large dark eyes with feathery antennae.
· Other leishmanial diseases of man are:
1. Oriental sores (Skin lesions): Leishmania tropica
2. Mucocutaneous leishmaniasis: Leishmania brasiliensis
3. Oriental sores (Skin lesions): Leishmania chagasi

· Note: Amastigote stage was formerly called Leishmanial form and occurs in man and the Promastigote stage was formerly called Leptomonad form and occurs inside the gut of the sandfly.
· Kala-azar is the second parasitic killer after malaria.
· The Leishmania donovani is internalized by the dendritic cells and macrophages in the dermis where they turn into amastigotes by losing their flagella.
· Indian personnel Upendra Nath Brahmachari has developed a new medicine for kala-azar. He had also got Nobel Prize (1929AD) for this invention.

· The doses of the above-mentioned medicines are:
a. Ambisome: 21 mg/kg

b. Amphocil: 7.5 mg/kg.

· For this, a low dose (0.5mg-1mg/kg) is given to the patient on the first day, 1-2 mg/kg on the second day, 1.5 mg-3mg/kg on the third and subsequent days.

Also, Read our other Notes related to HUMAN DISEASES:

• Human Diseases: Introduction
• Typhoid: Enteric Fever
• Ascariasis: Common Roundworm
• AIDS
• Tuberculosis
• Cancer
• Kalazar
• Hepatitis
• Socially Significant Diseases