Identifying Protozoal Species Part 3- Cryptosporidium & Sarcocystidae Family

Cryptosporidium 

Ziehl-Nielson Stain

• Diarrhoea in calves and lambs.
• Microvilli border of enterocytes in ileum of calves etc. 
• Oocysts only 5-6 micrometres and sporulate within the host unlike eimeria which sporulates outside the host. 



Safranin Stain


• Best seen in Ziehl-Nielson (red oocysts) or Safranin smears (orange oocysts).

Toxoplasmi Gondii 

• Definitive host= cat.
• Intermediate host= any mammal. Second most important cause of abortion in sheep. 
• Oocysts measure 12 micrometres. Sporulated oocysts contain two sporocysts. Each sporocyst contains four sporozoites. 
• Asexual reproduction occurs in the intermediate host and sexual reproduction in the definitive host.
• Form bradyzoite cysts in the brain of mice= infection route. 
• Banana shaped tachyzoites are the stage before bradyzoite cysts form. 



Brazyzoite cyst. 

• Latex agglutination or direct agglutination can be used to aid serology.

Tachyzoites. 

Neospora Caninum

• Major cause of abortion in cattle and hind leg paresis and other neurological signs in dogs.
• Definitive host= dog. Intermediate host= cattle.
• Oocysts are similar to toxoplasma oocysts.
• Tachyzoites are the invasive fast growing parasite stages.
• Brazyzoites can exist in the cerebrum of the dog.
• IFAT antibody test is used to detect antibodies in dogs and tachyzoites are fixed onto slides to serve as an antigen.
• ELISA is used to detect antibodies in cattle sera. 

Sarcocystis

Cyst in Muscle 

• Small intestine of dogs, cats, wild carnivores and humans.
• Intermediate host= parasite stages. 
• Schizonts in endothelial cells of blood vessels, marco and microcysts in skeletal muscle and heart muscle of ruminants, pigs and horses. 
• Septae divide the cyst.
• Oocysts contain two sporozoites.