Blood and Tissue Protozoa
Blood and tissue protozoa are parasitic protozoa that primarily inhabit the blood, lymphatic system, or tissues of humans and animals. Most are transmitted by arthropod vectors and are responsible for serious systemic diseases. These organisms are medically important due to their ability to evade host immunity and cause chronic infections.
General Features
Blood and tissue protozoa are typically intracellular or extracellular parasites. Many exhibit complex life cycles involving both a vertebrate host and an invertebrate vector. They often show antigenic variation, enabling them to persist in the host for long periods.
Common characteristics include:
- Presence in blood cells, plasma, or tissues
- Vector-borne transmission in most species
- Alternation between asexual and sexual stages
- Ability to cause systemic and life-threatening diseases
A. Trypanosoma gambiense, T. rhodesiense, T. cruzi.
Trypanosoma is a genus kinetoplastids (class kinetoplastida) and they are heteroxenous (require more than one host to complete their life cycle). Trypanosomes possess different cell types during their life-cycle stages – Amastigote (am), Epimastigote (epi), Trypomastigote (tryp)
African Trypanosomiasis – T.b. gambiense and T.b. rhodesiense; American Trypanosomiasis - T. cruzi
Morphology: Trypanosomes are minute, actively motile, fusiform protozoa, flattened from side to side. The long, sinuous body has a tapering anterior and a blunt posterior end. Even in the same species the shape varies. A large oval nucleus, which has a central karysome, is situated toward the middle of the body. Reproduction takes place by binary longitudinal fission.