78. Protozoa. Phylum Sarcomastigophora. Subphylum Mastigophora (Flagellata). Trypanosoma brucei gambiense, Trypanosoma brucei rhodesiense. Trypanosoma cruzi.

protozoa overview

Protozoa are eukaryotic unicellular microorganisms that can have either a direct or complex life cycle:

• Direct Life Cycle: Involves a single host.

• Complex Life Cycle: Involves two or more hosts.

  • Definitive Host: The host in which the parasite undergoes sexual reproduction.

  • Intermediate Host: The host in which the parasite reproduces asexually.

Protozoa can exist as intracellular or extracellular parasites, and sometimes they exhibit a combination of both.

Types of Transmission:

1. Direct Contact Transmission: Spread through direct contact with an infected individual.

2. Vector-Borne Transmission: Spread by vectors such as insects.

3. Trophic Transmission: Spread through the food chain.

4. Fecal-Oral Transmission: Spread through ingestion of contaminated food or water.

Phylum Sarcomastigophora:

This phylum includes parasitic protozoans that move using flagella or pseudopodia. It is divided into the following subphyla:

1. Subphylum Mastigophora (Flagellates): Includes protozoans that are human parasites.

2. Subphylum Sarcodina (Amoebas): Protozoans that move by pseudopodia.

Other related phyla include:

• Phylum Apicomplexa (Sporozoa): Protozoans that are typically intracellular parasites.

• Phylum Ciliophora: Protozoans that move using cilia.

Genus Trypanosoma:

• Transmission: Typically transmitted by insect vectors, which act as intermediate hosts.

• Hosts: Vertebrates, including humans and animals.

• Life Cycle Forms:

  • Trypomastigote: The elongated, slender form with a flagellum.

  • Amastigote: The rounded form without a flagellum.

  • Epimastigote: Similar to the trypomastigote but with the kinetoplast located anterior to the nucleus.

Trypanosoma brucei:

• Trypanosoma brucei gambiense (causes chronic African trypanosomiasis or "sleeping sickness").

• Trypanosoma brucei rhodesiense (causes acute African trypanosomiasis).

• Disease: African trypanosomiasis (sleeping sickness).

• Transmission: By tsetse fly (Glossina species).

Trypanosoma cruzi:

• Disease: Chagas disease, which affects internal organs such as the heart and digestive system. It can lead to chronic conditions and sometimes death due to heart failure.

• Transmission: By Triatoma bed bugs

Life Cycle of Trypanosoma brucei:

• Tsetse fly (Glossina species) bites a human and injects metacyclic trypomastigotes into the skin tissue.

• The parasites enter the bloodstream and multiply by binary fission.

• The bloodstream trypomastigotes can transform into short and stumpy forms.

• When a tsetse fly takes another blood meal, it ingests the parasites.

• In the fly, the parasites develop from the amastigote stage to the trypomastigote stage.

• They then migrate to the salivary glands, revert to the epimastigote form, and develop into the infective metacyclic trypomastigotes.

Morphology of Trypanosoma:

• Possess a well-developed mitochondrion called a kinetoplast.

• Exhibit different forms during their life cycle, each adapted to their environment within the host or vector.