Eimeriidae

• EIMERIIDAE


  Family of intracellular parasites of the epithelial cells of the intestines
• EIMERIIDAE


  • They have a single host in which they undergo asexual (schizogony, merogony) and sexual (gametogony) multiplication
  • Sporogony - spores (sporocysts) containing 1 or more sporozoites occur outside the host
• Genera of importance in the EIMERIIDAE family


  • Eimeria - 4 sporocysts each containing 2 sporozoites
  • Isospora - 2 sporocysts each containing 4 sporozoites
  • Tyzzeria - no sporocysts, 8 sporozoites in the oocysts
  • Wenyonella - 4 sporocysts each containing 4 sporozoites
  • Cryptosporidium - 4 sporozoites not enclosed in a sporocyst
• Oocyst


  Contains a zygote, extruded from the host tissues and passed to the exterior in the feces, the resistant stage of the life cycle
• Oocyst wall


  • Composed of 2 layers
• Parasitic life cycle of the coccidian

  Initiated when the infective oocyst is ingested by the appropriate host
• Sporocysts in Eimeria spp.

  • More or less elongate ovoid form with one end more pointed (Stieda body) than the other
• Sporozoites


  • Bent and comma-shaped, contain a round homogenous vacuole at one end
• Excystation


  Release of contained sporozoites
• Stimuli necessary for excystation

  • CO2 - exposure to 15% CO2 in the gas phase
  • Trypsin and bile - bile facilitates the entry of trypsin through the altered micropyle, which then digest the sporocytic plug permitting the escape of motile sporozoites
• Schizogony (asexual)


  1. Initiated when sporozoites enter epithelial cells and becomes rounded up (trophozoite)

  2. Nucleus of the trophozoite becomes a schizont (1st generation schizont)
• Merozoite


  • Granular cytoplasm with a centrally-placed round nucleus
• Eimeria arloingi


  Most common coccidium of goats
• Coccidiosis in sheep and goats

  • Chiefly confined to young animals up to 4-6 months of age