Parasitology 10: Protozoa

Question 1

If you house sheep in a space where you previously had, poultry, remained poultry coccidia can infect the sheep? t/f

Answer 1

False

coccidia is VERY specific

Question 2

Eimeria/Cystoisospora oocysts are infective immediately after shed in feces

Question 3

What is patent infection in Eimeria/Cystoisospora?

Answer 3

Is when the whole lifecycle is complete and the oocyst were developed

Question 4

What life cycle do Eimeria and Cystoisospora?

Answer 4

DIRECT

Question 5

What is Bradyzoite and Tachyzoite?

Answer 5

Bradyzoite : zoite of Apicomplexa with slow multiplication in cysts

**Tachyzoite* : zoite of Apicomplexa undergoing quick asexual multiplication in a host cell

Question 6

Toxoplasma gondii
important?
coccidian species with what as DH?
life cycles direct and indirect but what are the new 2?

Answer 6

IMPORTANT zoonotic parasite

coccidian species with CAT as DH

• Bradyzoite
• Tachyzoite

Question 7

Toxoplasma life cycle

Answer 7

Felids are only DH- sexual stages only in cats

3 infectious stages
Tachyzoites (groups or clones)
Bradyzoites (tissue cysts)
Sporozoites (sporulated oocysts)

IH= other warm blooded animals

When other warm blood animal eats sporulated oocysts:
- sporozites emerge
-penetrate intestine
-undergo rapid multiplication in cell: tachyzoites , which spread to all other tissues
-Eventually conversion occurs to cysts containing bradyzoites (infective stage as well)

Question 8

What is important to remember about Tachyzoite and Bradyzoite?

Answer 8

t= rapidly multiplying tissue stage, pathogenic stage

b= slowly dividing stage in cysts
-these stages are found in all animals infected with toxoplasma, including felids
-Only felids have the sexual stages in the intestine

Question 9

Can cats be IH when talking about toxoplasma gondii?

Answer 9

YES

Question 10

A cyst in toxoplasma gondii life cycle are?

Answer 10

ALL bradyzoites

Question 11

Which life cycle does toxoplasma gondii have?

Answer 11

Direct AND Indirect

prefers indirect

Question 12

Cat infections of toxoplasma gondii works how?

Answer 12

*Ingesting bradyzoites in cysts
* Most common and efficient route
* Get intestinal stages with multiplication and
gametogony
* Also leads to tachyzoites and bradyzoites (tissue cysts)

Ingesting sporulated oocysts or tachyzoites
* Less efficient, may not lead to patent infection
* Tissue multiplication with tachyzoites and bradyzoites
* Some may go back to GI and complete cycle

Question 13

Non-felid infections toxoplasma gondii works in what way?

Answer 13

Several ways
* Ingesting oocysts (sporozoites)
* Ingesting bradyzoites in cysts
* Congenitally
* Rare tachyzoite transmission

Result of all these routes: tachyzoite multipication and then bradyzoites in cysts

Question 14

Toxoplasma gondii in Cats
prevalence
most infections
disease

Answer 14

• High prevalence of antibodies in cats, 50% or more
• Most infections in cats probably occur in young
  cats
  -Immunity develops, prevents recurrence of oocyst
  shedding
• Only about 1% oocyst prevalence in feline fecal
  samples
  -Cats shed oocysts for just a few weeks, reshedding
  unlikely
• Disease in cats is rare
  -Disease caused by tissue tachyzoites

Question 15

Toxoplasma gondii in other animals
abortion and species

Answer 15

Common cause of abortion in small ruminants
* Occurs when first infection takes place during pregnancy
* Immunity develops and protects subsequent pregnancies

Cattle less susceptible to infection, abortion not seen

Sporadic disease in some circumstances
* Exotic animals in zoos, otters, marine mammals, birds, animals that are immunosuppressed

Question 16

What is the public health importance of toxoplasma gondii?

Answer 16

Humans can become infected by any of several routes
-undercooked meat (cyst)
-contaminated water and food
-transfusion
-transplacental

You can see the parasite systemically in humans

The biggest problem is ocular problems (blindness) irreversible

Question 17

Neospora canium is what?

Answer 17

Similar to toxoplasma but in dogs

Dogs and wild canids are the DH

Not zoonotic

Causes abortion in cattles

Question 18

What species is Neospora canium affect badly?

Answer 18

Cattle

can cause abortion, or lead to persistant infection than can infect subsequent pregnancies and may lead to abotion
-calves can be born and live with persistent infection and later abort

Persistently infected cows have a higher abortion rate than non-infected cows

Question 19

Sarcocystis spp
life cycle
species
cyst name in IH called

Answer 19

*Obligate indirect life cycle
*Many species, often host specific for
both intermediate and definitive host
*Cyst in intermediate host called a
sarcocyst

Question 20

Sarcocystis spp

Answer 20

Question 21

Sarcocystis neurona is important why?

Answer 21

Primary cause of Equine protzoal myeloencephalitis

horse is a dead-end host

Question 22

What is the life cycle of sarcocystis neurona?

Answer 22

Question 23

What are the clinical signs of Sarcocystis neurona?

Answer 23

-Many horses serologically positive
-Most infections asymptomatic

In some horses parasites in the CNS produce disease
* Lameness
* Stumbling
* Muscle atrophy
* Paresis

Definitive diagnosis and treatment are difficult

Neospora hughesi can also cause EPM, but S.
neurona more common

Question 24

Summary of species of parasite and its host?

Answer 24