Toxoplasma

Question 1

What are the different protozoa in cattle and sheep and what do they cause?

Answer 1

• Toxoplasma gondii - Major cause of abortion in sheep, Zoonotic
• Neospora caninum - Major cause of abortion in cattle
• Cryptosporidium spp. - Diarrhoea in young ruminants (0-2 week-old
  calves and lambs), Zoonotic
• Babesia spp. - Acute, potentially fatal tickborne disease of cattle
• Eimeria spp. - Diarrhoea in lambs and calves (1-3 months)
• Sarcocystis spp.

Question 2

What is the characteristics of phylum Apicomplexa?

Answer 2

• Large group of protozoa
• Mostly intracellular
• Locomotion by gliding
• Undergo sexual and asexual reproduction

Question 3

Who can toxoplasma gondii infect?

Answer 3

Any warm blooded animal

Question 4

What is the tachyzoite stage?

Answer 4

Fast growing tissue stage - intracellular, rapidly dividing, crescent shaped - 2 x 6um

Question 5

What is the bradyzoite stage?

Answer 5

slow growing phase within cyst in tissue of host - neural/muscle tissue

Question 6

What is an oocyst?

Answer 6

Resistant cyst stage formed from zygote - passed in faeces- 12um

Question 7

What is the life cycle of Toxoplasma gondii?

Answer 7

1. Cats infected by ingesting bradyzoite cyst in tissue of prey
2. Sexual cycle in small intestine - unsporulated oocysts shed in
   faeces (12μM in diameter)
3. Oocysts sporulate - contain two sporocysts each containing four sporozoites - contaminate environment, food and water
   
   • can be ingested by any warm-blooded animal
4. In intermediate host (rodents, birds)
   * sporozoites released, cross gut wall, develop into tachyzoites, which
   replicate rapidly, differentiate into bradyzoites that form cysts
5. back to cats ingesting bradyzoites

Question 8

Can vertical transmission occur?

Answer 8

yes - Vertical transmission can occur during pregnancy

Question 9

How do sheep become infected with toxo?

Answer 9

Transmission by ingestion of sporulated oocyst
-oocyst from cats contaminating pasture
-no direct sheep-sheep transmission

Question 10

Do cats have toxo?

Answer 10

• Enteric infection in cats – no clinical signs
• Output from cat >10 million oocysts

Question 11

How many oocyst cause abortion in sheep?

Answer 11

• 1000 oocysts cause abortion in a sheep
• 100 cats could produce enough oocysts to cause
  abortions in all UK sheep

Question 12

What are the clinical manifestations in sheep?

Answer 12

• Still births
• Abortions
• Mummifications
• White, discrete lesions on cotyledons
  -outcome dependent on stage of pregnancy during infection

Question 13

How is toxoplasmosis diagnosed?

Answer 13

• Serology – antibody detection in serum or foetal fluids
  * Dye test (humans – gold standard)
  * Immunofluorescence antibody test (IFAT)
  * Agglutination tests
• Histology
  * Cotyledons
  * Brain tissue
  * Non-suppurative inflammation