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.
