Infectious inflammatory - protozoal

Question 1

What are two protozoal causes of inflammatory neurological problems

Answer 1

• neospora
• toxoplasma

Question 2

What do both of these protozoa cause?

Answer 2

• focal inflammatory pathology within either the CNS (encephalomyelitis) or muscle (myositis)

Question 3

How do these present?

Answer 3

• pathology is likely to be progressive and in many cases may be multifocal

Question 4

Definitive host of Neospora caninum

Answer 4

• dogs
• wild canids

Question 5

Intermediate host of Neospora caninum

Answer 5

• cattle
• other ungulates

Question 6

Life cycle of Neospora caninum

Answer 6

• dog is infected by feco-oral route by infective oocysts or by ingesting tissues of an infected IH
  (- unborn puppies may be infected by the trans placental route)
• the motile and rapidly dividing tachyzoites are released from the oocyst or from tissues in the intestinal tract and they begin multiplying 1st asexually and then sexually in the dogs intestinal epithelium
• as the result of sexual gametogeny, oocysts are released in the environment in the faeces
• in a few days, the oocysts become infective through sporulation
• animals at pasture (typically cattle) serve as an IH
• the oocyst breaks down in the IH’s intestine and the released sporozoites disseminate throughout the body
• in response to the IH’s immune response, the sporozoites differentiate into bradyzoites, which form cysts in muscle and tissue
• tachyzoites are able to invade the foetus through the placenta
• bradyzoites multiple slowly and form tissue cysts

Question 7

Definitive host of Toxoplasma gondii

Answer 7

• cat

Question 8

Direct life cyst of Toxoplasma gondii

Answer 8

• sporozoites except then, in enterocytes, undergo merogony -> merozoites -> gametogeny -> gametes -> oocysts in faeces

Question 9

Life cycle of toxoplasma gondii

Answer 9

• eggs are passed in cat stool. many eggs are passed but usually for only 1-2w. after 1-5d in the environment, eggs become able to cause infection
• cats can become reinfected by consuming food or other materials contaminated with the eggs
• other animals (such as wild birds, rodents, deer, pigs, sheep) may consume the eggs in contaminated soil, water, plant material or cat litter
• shortly after the eggs are consumed, they release forms of the parasite that can move (called tachyzoites)
• tachyzoites spread throughout the animals body and form cysts in nerve and muscle tissue
• cats become infected after eating animals that contain these cysts
• people can become infected by eating undercooked meat containing cysts, they can also become infected if they eat food/water/soil contaminated with cat stool, or when they touch a pet cats litter and then touch their mouth
• rarely people are infected when they have a blood transfusion / organ transplant that contains the parasite
• rarely the infection is spread mother to foetus
• in people, parasites form cysts in tissues, usually in muscle and the heart, brain and eyes

Question 10

What is the clinical progression in adult onset cases a result of?

Answer 10

• the site of the pathology, therefore it doesn’t follow a predictable or pathognomonic course

Question 11

How can it present in puppies?

Answer 11

• a rare but classical form in puppies probably resultant from in utero transmission which presents with progressive hindlimb stiffness resultant from myositis affecting the quadriceps muscles