Trypanosoma gambiense

                            Systematic position

Phylum- Protozoa

Subphylum-            Sarcomastigophora

Superclass- Mastigophora

Class- Zoomastigophora

Order- Kinetoplastida

Genus- Trypanosoma

Species- gambiense

                                          Habit & habitat

Ò  Discovered by Forde in 1901

Ò  Sir David Bruce discovered that sleeping sickness is caused by tse-tse fly

Ò  Confined mainly to the Central & West African regions

Ò  Causes  African Sleeping Sickness in man

Ò  Parasite lives in blood & lymph glands

1. In later cases invades CSF causing fever, anemia, lethargy & death
   
   2. Chief vector is the tse-tse fly, Glossina palpalis
    
   3. Domestic animals like dogs, pigs, buffaloes may act as temporary or reservoir hosts where the parasite doesn’t develops but waits for its introduction into human host
   
   4.Entry into humans is always through the bite of the tse-tse fly which feeds on blood of humans as well as reservoir hosts

Unicellular, leaf-like, elongate, tapering at both ends

Polymorphic occurs in two developmental forms- trypanosome & crithidial forms

Trypanosome form occurs in the blood of man

Crithidial form occurs in the salivary glands of tse-tse fly

1.The body is covered by thin, elastic & firm pellicle
2. Pellicle is supported by microtubules- maintains shape of body
3. Uniflagellate, flagellum arise from basal body present at the posterior end of body
4. Runs across the whole length of body, attached but free at the anterior end
5.T.S. shows usual 9+2 arrangement of fibrils
 6. During locomotion the attached end of flagellum is pulled up, this fold is called undulating membrane

7. Cytoplasm is enclosed within pellicle

8. Cytoplasm not divided into ectoplasm & endoplasm

9. All the cell organelles present

10. Food is stored in the form of glycogen & phosphates

11. Lysosomes secrete hydrolytic enzymes

12. Nucleus large, oval, double membrane bound, centrally placed

                               Reproduction

Ò  Sexual reproduction unknown

Ò  Asexual reproduction by longitudinal binary fission

Ò  Kinetoplast & blepharoplast divide first, become paired

Ò  Old flagellum remains attached & new one starts growing from blepharoplast

Ò  Nucleus divides mitotically into 2 daughter nuclei

Ò  Body splits mid-longitudinally into two daughter trypanosomes

                                       Life cycle

                                                     1.HOST

• Primary host- man

• Intermediate host- Glossina palpalis (tse-tse fly)

• Reservoir hosts- pigs, dogs, antelopes

                                     In man

Ò  Infection is always initiated by the bite of the fly

Ò  Fly harbours the metacyclic forms in its salivary glands

Ò  While feeding on human blood it transfers trypanosomes in human blood

Ò  Clotting of blood is prevented by an anticoagulant

1. All the stages of parasite are extracellular (present in the plasma only)
   2.  Metacyclic forms get transformed into long slender forms
   3. Swim freely by beating of flagellum & multiply by longitudinal binary fission
   4. Energy for division is obtained by anaerobic glycolysis
   5. when glucose deficiency prevails multiplication is hampered

6. Long, slender forms get converted into short, stumpy, flagella devoid forms

7. These forms stop feeding & wait for the tse-tse to suck them through blood

                                           In tse-tse fly

Ò  When tse-tse fly sucks blood of an infected person it takes the short, stumpy forms with the blood meal

Ò  Further development of parasite occurs in the peritrophic membrane of the midgut

Ò  Parasite transforms into long, slender form

1. Divides by longitudinal binary fission
   2. Energy is obtained by mitochondrial oxidation of pyruvic acid
   3. migrate to the salivary glands & transform to crithidial forms with shortened body, reduced free flagellum & kinetoplast in front
   4. Multiply in salivary glands into metacyclic forms & ready for infecting humans
   5. Transferred to human blood by bite of the fly

                              Sleeping Sickness

Ò  Also called as Trypanosomiasis

Ò  Bite of fly causes local irritation

Ò  Irregular, recurrent fever is the first symptom

Ò  Followed by weakness, loss of weight, anemia, increase in pulse rate & severe headache

Ò  In later cases, patient falls asleep & undergoes coma, finally death

Ò  Trypanosomes can be detected in stained blood

Ò  Parasites ma be obtained from the CSF

Ò  Suramin sodium, Bayer 205 are common drugs for treatment

Ò  Eradication of vector can control spread of disease

                           Polymorphic forms

                                     Four forms:

1. Leishmanial (Amastigote)
2. Leptomonad (Promastigote)
3. Crithidial (Epimastigote)
4. Trypanosomid (Trypomastigote)

                                  Trypanosoma

Leishmanial                       round, flagellum      reduced & fibril-like
  
 Leptomonad               Elongate, flagellum  short & unattached

 Crithidial                         Elongate, undulating
membrane inconspicuous
 
            Trypanosomid                     Elongate, undulating membrane conspicuous