Protozoa Life Cycle

Balantidium trophozoite from a pig - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona

Protozoa multiply sexually, asexually and can also use a combination of both, as seen in the coccidia class. Replication can be by binary or multiple fission. Different protozoa use different forms of motility, including flagella, cilia, pseudopodia and gliding.

• Most protozoal reproduction is asexual via binary fission, schizogony and sporogony

• Some protozoa also use sexual reproduction called gametogony

• In some species, sexual and asexual reproduction occurs in the same host, whilst in others asexual reproduction occurs in the vertebrate host and sexual reproduction in the arthropod vector

• Homoxenous
  • Parasite uses a single host species during its life cycle (direct)
  • E.g. Eimeria

• Heteroxenous
  • Parasite uses more than one host during its life cycle (indirect)
  • E.g. Trypanosomes

• Facultatively heteroxenous
  • Parasite may use more than one host during its life cycle but this is not essential
  • E.g. Toxoplasma gondii

Example of a Protozoal Life Cycle

See Coccidia