Protozoa: Cryptosporidium parvum

Question 1

Describe the life cylce of C. parvum

Answer 1

1. Infected animals shed sporulated oocysts in faeces
2. Host ingests oocyst which travels to SI
3. Sporozoites hatch and burrow into gut epithelium
4. Become established in extracytoplasmic vacuole and become trophozoites
5. Trophozoites undergo schizogony
6. Infected vacuole will now contain 8 merozoites
7. Some merozoites go back and repeat 3-6. Some enter epithelial cells, undergo asexual reproduction again to form gametes
8. Gametes fuse to form zygote which lays down a cyst wall to become an oocyst
9. Thick walled sporulated oocysts excreted in faeces
10. Thin walled oocysts lyse in host and cause autoimmunity

Question 2

Give 2 features of sporulated oocysts

Answer 2

1. Very resistant

2. Can survive in the environment for months

Question 3

What is meant by ‘microgamete’ and ‘macrogamete’?

Answer 3

Microgamete = male gamete
Macrogamete = female gamete

Question 4

What are 2 clinical signs of C. parvum?

Answer 4

1. Diarrhoea

2. GI disease

Question 5

How is C. parvum diagnosed?

Answer 5

FEC

Question 6

Describe the epidemiology of C. parvum

Answer 6

• Oocysts autosporulate so infection can build up rapidly
• Once passed in faeces, oocysts immediately infective
• Adults can become immune, but will be carriers so will still shed oocysts

Question 7

How is C. parvum transmitted?

Answer 7

Faecal - oral route

Question 8

Describe treatment and control of C. parvum

Answer 8

Treatment - Halofuginone gives some efficacy, supportive therapy
Control - Clean and replace bedding regularly, remove calf from dam at birth