In this article we will discuss about:- 1. Habitat and Morphology of Trypanosoma Gambiense 2. Nutrition Required 3. Reproduction 4. Life-Cycle.
Habitat and Morphology of Trypanosoma Gambiense:
Trypanosoma gambiense is a haemo-flagellate parasite. It resides in the blood plasma of man. Often they are found in the cerebro-spinal fluid, spleen and lymph nodes. In its vector host Tse-tse fly, Glossina palpalis it is found in the intestine. The disease caused by Try panosoma in man is known as Trypanosomiasis or Sleeping sickness. This fatal disease is most prevalent in West and Central Africa.
The Trypanosomes show polymorphism presenting different morphological forms under different conditions: In the blood plasma of man is found the Trypanosome form which looks like a thin, flattened and leaf-like body tapering at both ends. The pointed end is considered as anterior end and the blunt end is considered as posterior end. The length of the body is 15-32 micra and the breadth in the middle is about 2·5 micra.
The body is covered by a thin, elastic and firm pellicle. The pellicular part to which the flagellum is attached draws out as undulating membrane during flagellar movement (Fig. 50C). A whip-like long flagellum arise from a basal body (also called blepharoplast or centriole) located at the posterior end.
The flagellum skirts the whole body and projects out of the anterior end. Just posterior to the basal body there lies a small, spherical or disc-shaped Kinetoplast. The nucleus lies almost in the centre of the cell body as a large, oval, vesicular body. The nucleolus is large. Some vacuoles and volutine granules are present in the cytoplasm.
Nutrition Required by Trypanosoma Gambiense:
Nutrition is saprozoic. It feeds on the blood and tissue fluids of the host. It is believed that feeding occurs by pinocytosis.
Reproduction in Trypanosoma Gambiense:
Trypanosoma divides by longitudinal binary fission. The basal body takes the lead during division. It is followed by nuclear division. The cytoplasm divides longitudinally. The old flagellum is retained by one of the daughter cells and a fresh one is formed for the other individual. There is no record of sexual reproduction in Trypanosoma.
Life-Cycle of Trypanosoma Gambiense:
The life-cycle of Trypanosoma needs two hosts-man and Tset -tse fly for completion. Man is the primary host and the fly is intermediate host or vector. (Fig. 50D.)
Life-Cycle in Man:
When the vector bites a man it inoculates few parasites along with its salivary secretions. The entry of the parasites in the blood stream of man results Trypanosoma fever. Fever and headache reoccur at irregular intervals.
After their entry into the blood stream the parasites attain the characteristic long slender forms and undergo multiplication by longitudinal binary fission. After multiplying a number of times the parasites assume the characteristic short stumpy form and lose the free part of the flagellum during the process. The stumpy forms do not feed and it not sucked up by the fly, they die.
Some of the parasites shorten their body length and flagellum and become the characteristic intermediate form. The intermediate forms go to lymph gland or spleen and spend their period of incubation there. The period lasts for about three months and multiplication occurs during this period. Now they go to the cerebrospinal fluid.
Life-Cycle in Fly:
When the fly bites an infected man some stumpy forms are sucked up. The stumpy forms reach the midgut of the fly and undergo rapid multiplication. The resultant parasites assume the shape of slender forms. These forms reach the salivary glands of the fly via the proventriculus.
They get attached to the wall of the gland and undergo a phase of multiplication resulting crithidial stage. Crithidial forms are characterised by shorter flagellum and undulating membrane. The crithidia form undergo multiplication and produce the metacyclic trypanosomes which infect man along with the bite of the fly. The whole life-cycle (both in man and fly) takes 20-30 days for completion.