Parasitology: Neospora and Toxoplasma

Question 1

What cause toxoplasmosis?

Answer 1

Toxoplasma gondii

Taxonomy: Phylum Apicomplexa

Question 2

What are toxoplasma Tachyzoites?

Answer 2

proliferative form in blood or CSF

Question 3

What are toxoplasma bradyzoites?

Answer 3

lifelong “tissue cysts”.

Question 4

What are toxoplasma oocysts?

Answer 4

(with sporozoites) shed in faeces after completion of sexual phase in feline gut epithelium
– Infectious after 48 hours or more environmental incubation.
– Survive months to years despite freezing, heat, dehydration.

Question 5

How long do cats shed TP oocysts for?

Answer 5

– Oocysts are shed from cats for 1-2 weeks only.

Question 6

What are the PPP of TP life stages?

Answer 6

• Tissue cysts: 3-10 days
• Oocysts: ≥ 18 days
• Tachyzoites: ≥ 13 days

Question 7

What are the clinical signs of Toxoplasma Gondii?

Answer 7

anorexia, weight loss, lethargy, dyspnoea, ocular signs, myositis

Question 8

How do we diagnose T. Gondii?

Answer 8

Detection of oocysts
– Difficult and shedding occurred before clinical signs

Serology
–	IgG-class immunoglobulin
–	IgM-class immunoglobulin

Question 9

How do we treat T. Gondii?

Answer 9

Clindamycin

Reccomended: Clindamycin and pyrimethamine

Question 10

How can we prevent T.Gondii in cats?

Answer 10

• Do not allow cats to hunt rodents and birds (keep pets indoors)
• Feed cats only cooked meat or processed food from commercial sources
• At present there is no vaccine for toxoplasmosis in cats

Question 11

How can we avoid T. Gondii in humans?

Answer 11

• Pork is considered to be the most likely source of transmission from domestic food animals to humans
• T. gondii can survive in swine for over a year after being infected
• Lamb is the second most common source of infection, followed by beef and chicken

Question 12

Cat people be infected with T. Gondii from petting cats?

Answer 12

Oocysts sporulate in 48 hours at room temperature
Most cats do not leave faeces on their fur for two days, so it is unlikely that humans become infected from direct contact with cats themselves

Question 13

Who is at risk for severe toxoplasmosis?

Answer 13

• Infants born to mothers who became infected with Toxoplasma for the first time DURING or JUST BEFORE pregnancy.
• Persons with severely weakened immune systems, such as persons with AIDS or transplant recipients.

Question 14

Are we protecting our lamb from Toxoplasma gondii?

Answer 14

• Toxoplasmosis is the second most common cause of abortion in sheep in the UK, after Chlamydia
• There is a live vaccine, Toxovac

Question 15

What is neosporosis?

Answer 15

Neospora caninum is a protozoan parasite of animals
A major leading cause of abortion in cattle and neuromuscular disorders in companion animals
The parasite has not been detected in human tissues (zoonotic potential is uncertain)

Question 16

What are the factors related to increased infection risk of N. Caninum

Answer 16

• Age increases risk due to increased chance of horizontal transmission & recrudescence
• Farm dogs increase risk because they are the definitive host
• Other potential intermediate hosts such as poultry and horses increases risk as a source of infection for dogs and other canids
• Annual rate of cows returning to estrus post-pregnancy increases risk

Question 17

What are the factors related to decreased infection risk of N. Caninum

Answer 17

• Exposure to wild canids pose no risk because of negative interaction between the presence of farm dogs (which poses infection risk) and wild canids
• Cats have a decrease the risk due to absence of rats (I.H.)
• Use of beef bull semen to inseminate dairy cattle - crossbreed pregnancies decreases risk

Question 18

How can a farm improve its biosecurity to avoid N. Caninum?

Answer 18

– Quarantine and testing of replacement and purchased cattle
– Prevention of transmission from dogs and other potential definitive hosts
– Prevention of waterborne transmission
– Rodent control
– Prevention of putative factors for disease recrudescence in congenitally infected cattle