Cryptosporidia in Domestic Livestock

Question 1

C. Parvum

Distribution?
Zoonotic?
How many hosts are infected?
Transmission method?

Answer 1

Worldwide
It is zoonotic
over 150 hosts
faeco-oral route of transmission

Question 2

Describe the lifecycle

Answer 2

1. Ingestion of sporulated oocyst
2. Oocysts rupture, releasing the sporozoites that attach to and invade host intestinal epithelial cells and form trophozoites
3. Schizogony- production of merozoites
4. Merozoites invade intestinal cells and mature into male microgametes and female macrogametes
5. Microgametocytes rupture, releasing the microgametes which fertilise the macrogametocyte to form a zygote
6. Zygote matures into think walled sporulated oocysts which rupture and lead to self-infection OR
7. Zygote matures into thick walled sporulated oocysts- excreted in faeces

Question 3

Why is diagnosis difficult?

Answer 3

Clinical signs are not pathogen-specific

Oocysts are very small so difficult to detect in faeces, poor sensitivity and requires concentration of the sample

Question 4

Give three alternative diagnosis methods to FEC

Answer 4

Immunofluorescent antibody test (IFA)

ELISA can detect antigens but inconsistent results

PCR based assays- just for research but much more sensitive than other methods

Question 5

Coccidia and Cryptosporidium make up 31% of neonatal calf scour cases, what is the second most common?

Answer 5

Rotavirus- 29%

Question 6

Where do oocysts sporulate?

Answer 6

Inside the host, so there is a fast build up of infection. Oocysts are very resistant to disinfectants and environment.

Question 7

What is the main source of infection?

Answer 7

The dam, so remove dairy calves from their mothers at birth and avoid overcrowding during the calving season in beef cattle.

Question 8

What treatments are available?

Answer 8

No approved treatments but Halofuginone lactate has been successfully used for treatment

Question 9

In humans, there is a low infectious dose, 30 oocysts will infect 20% of people. How long following resolution of diarrhoea will they shed?

Answer 9

<50 days

Question 10

What is the main source of oocysts to humans?

Answer 10

Water sources- treatment with coagulation and filtration, then inactivation by UV treatment is required