LEISHMANIA DONOVANI

      Leishmania donovani is one of the major protozoan flagellate parasites responsible for causing leishmaniasis. It is also commonly known as kala-azar or dum dum fever. It dwells in the reticulo-endothelisalLeishmania currently affects 12 million people in 88 countries per year. The core terai-region of Nepal is one of the infected places in a country

History

Leishman and Donovon reported this organism simultaneously. Leishman from London in 1903 and Donovan from Madras in the same year.

Distribution

This parasite is endemic in many countries like China, India, Africa, Europe and Russia. The tropical zones are the favorite places for this parasite. It has been also reported from many places of terai region of Nepal.

Morphology

This parasite exists in two stages namely promastigote and Amastigote stages

Amastigote Stage

—  Round or oval, measuring 2-4 micrometer

—  Outer covering is pellicle

—  Nucleas oval or round

—  Kinetoplast, DNA contaning and a mitrochondrial structures

—  Axoneme, the root of the flagellum lies near the kinetoplast.

—  Absence of free flagellum

Promastigote Stage

—  Short and oval but fully developed are slender spindle shaped bodies.]

—  Measures 5-10l*2-3w micrometer

—  Nucleus lies on the centre.

—  Kinetoplast lies near the anterior end

—  Consist of only one flagellum

Life Cycle

 The life cycle of leismania donovani completes in two host. Thus it shows digenetic life cycle. The hosts are

—  Primary Host- Man

—  Secondary or Intermediate host- Sand fly

—  Reservoir host- Man, Dogs

 Life Cycle In Man

When an infected sand fly sucks the blood of man along with its saliva a number of promastigote forms enter the blood stream of man. Here they become amastigote forms by losing their flagella. It attacks the macrophage cell of liver or spleen. It appears to be well adapted to a life inside these cells. They remain unaffected by the proteolytic enzymes of host within the macrophage the Leishmania divides by binary fission once in every 24 hours. These are liberated in blood after the rupture of macrophage.

Life cycle in sand fly

When the female sand fly sucks the blood of man along with blood and macrophages the Leishmania enter the alimentry canal. Within the gut they multiply by binary fission. Their number is increased during 4-5 days of blood meal. Soon the parasites migrate forward and the foregut is occupied by them. It gradually moves into the salivary glands by 7-8 days. Finally if these infected  sandfly bites a healthy person they transmits the parasites of promastigote’s stage to new host. In this way life cycle completes in a sandfly.

Method of Transmission- The transmission of leishmania donovani from one person to another is carried out by a sandfly. During their blood meal they transmit the parasite present in their salivary glands

Incubation Period- 3-6 months and sometimes sympotomps may appear even after a years.

Pathogenesis- It causes a disease known as visceral leishmaniasis or black fever. Its sypmotomps are Black Sickness (Hyperpigmented skin), Hepatosplenomegaly , High fever, Emaciation, Swollen gland, Fatigue, Anemia, Weight Loss etc.

Diagnosis- Through microscopically examination of blood and

Biopsy material taken from bone marrow or spleen of patient.

Treatment- The choice of drugs are antimony compounds and they are,

—  Stibamine

—  Aminostiburea

—  Neostibosan

—  Neostam

—  Sodium Antimony  gluconate

Preventive Measures

•      Control of sand fly populations

•      Providing barriers to protect humans from sand fly bites

•      Elimination of reservoir hosts

•      Treatment of infected individuals

•      Health education and awareness.