Tuesday, November 12, 2013

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
http://biology-today.com/wp-content/uploads/2010/09/leishmania-300x133.jpg
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.







No comments:

Post a Comment