Coccidia Life Cycle

Coccidia - Joel Mills

Coccidia belong to the phylum Apicomplexa and are protozoan parasites of mammals, birds and reptiles. Coccidia have three major stages to their life cycle: Sporogony, Schizogony, Gametogony. The first two stages are asexual, with sexual reproduction occurring in the third stage. The following is a general life cycle though there is some variation in the various suborders.

Sporogony

This is the fist stage of the coccidia life cycle and occurs exogenously in the environment. Sporozoites develop within the oocyst before it becomes infective. Once the sporozoites have been formed the oocyst is infective and on ingestion by the host will release sporozoites to invade intestinal epithelium.

Schizogony

Sporozoites grow within intestinal epithelial cells

• • Sporozoites feed and grow

• As the sporozoite grows the nucleus divides forming a schizont

• The schizont contains numerous elongated merozoites

• The formation of merozoites is the first asexual reproductive stage called schizogony

• The schizont ruptures releasing the merozoites which also invade the epithelial cells

• Another generation of schizonts form which is the beginning of the sexual phase of reproduction called gametogony

• The merozoites form male microgamonts or female macrogamonts
  • Collectively known as gamonts or gametocytes

• The microgamonts released from the microgametocyte penetrate and fertilise the macrogamont (which is contained within the macrogametocyte)

• Gametogony forms the zygote
  • Surrounded by a cyst wall
  • Forms the oocyst

• The oocyst is passed in the faeces and is unsporulated

• The oocyst becomes sporulated in the second asexual reproductive phase called sporogony

• Once the oocyst is sporulated it is infective