Identifying Protozoal Species- Part 2 Eimeria Tenella

Eimeria & Isospora

Pathology is related to species and parasite intensity. Eimeria affect many species. 

Eimeria Tenella
Most important eimeria species. Affects chickens and parasitises the caeca. 

Schizonts 

• Schizogony terminates with gametocytes. Macrogametocytes are female and have a single large nucleus. Male microgametocytes are from large numbers of flagellated microgametes. 
• Life cycle consists of sporulated oocysts, release of the sporozoites which penetrate the epithelial cells, schizogony, and finally gametogony which leads to oocyst formation. 
• Eimeria Tenella oocysts are 25 micrometres and are one third the size of a typical trichostrongyle worm egg. When sporulated there are four sporocysts each of which contain two sporozoites.
• When sporozoites invade the epithelial cells of the caeca they become know as trophozoites which are the growing form of the parasite. 
• Second generation schizonts are subepithelial and leads to a breakdown of epithelial structure. 



Merozoite- banana shaped from schizonts 

• Merozoites are elongated banana shaped and nucleated organisms which are liberated when the schizont ruptures. 



Schizonts. 

Sporulated VS unsporulated oocyst.

Schizogony terminates when the merozoites give rise to female and male gametocytes.

Eimeria Nectarix and Eimeria Acervulina 

• Small intestine of chickens. 
• Slightly smaller oocysts than E.tenella. 

Eimeria Ovinoidalis and Emeria Crandallis 

• Lamb diarrhoea.
• Caecum & colon of sheep and goats.
• Oocysts have polar caps. 

Isospora Canis 

• Not very pathogenic.
• I.canis in dogs.
• I.felis in cats.
• Sporulated oocysts contain two sporocysts, not four as with eimeria, and each contains four sporozoites. (Eimeria is four sporocysts with two sporozoites).