6.4 Protists 1

Question 1

Protists are ________ celled, _____________ organisms

Answer 1

single; eukaryotic

Question 2

where do protists cause infections

Answer 2

virtually anywhere, intracellularly or extracellularly (often in moist spots)

Question 3

what are the strategies for protists to pass from host to host

Answer 3

• use a resistant stage
• intermediate host and/or paratenic host

Question 4

what is a paratenic host

Answer 4

where a parasite lives but does not replicate or further develop; serves to help the parasite transmit

Question 5

what are the major groups of parasitic protists (6)

Answer 5

• apicomplexa
• flagellates
• ciliates
• amoebae
• microsporidia
• myxosporidia

Question 6

what are 3 examples of apicomplexan protist parasites

Answer 6

coccidia, malaria, piroplasms

Question 7

what are 2 examples of flagellate protist parasites

Answer 7

kinetoplastids and trichomonads

Question 8

what is the general lifecycle of all Apicomplexa

Answer 8

unsporulated oocyst shed -> becomes a sporulated oocyst through the process of sporogony -> sporozoites generate a meront (shizont) through the process of merogony -> eventually meroozites undergo sexual development through the process of gametogony, producing microgametes and macrogametes that fuse to form an unsporulated oocyst

Question 9

what are the gut coccidia genera

Answer 9

eimeria, isospora, caryospora, cystoisospora

Question 10

what are the tissue coccidia

Answer 10

neospora, toxoplsama, sarcocystis

Question 11

what is the difference between monoxenous and heteroxenous life cycles

Answer 11

monoxenous: completes life cycle within a single host

heteroxenous: requires multiple hosts to complete life cycle

Question 12

Eimeriorina (Coccidia):
- obligate/facultative intracellular/extracellular

• monoxenous, heteroxenous or both
• where do they live in the definitive host? intermediate host?

Answer 12

• obligate intracellular
• both monoxenous (Eimeria, Cystoisospora) and heteroxenous (Toxoplasma, Sarcocystis)
• intermediate hosts in many tissues but in the GI tract of the definitive host

Question 13

T/F Apicomplexan parasites penetrate the host cells actively

Answer 13

T

Question 14

Describe the sporulated oocyst (at the end of sporogony) of eimeria

Answer 14

Contains 4 sporocysts each containing 2 sporozoites; the sporocysts have stieda bodies and the sporozoites have refractile bodies

Question 15

describe the Eimeria life cycle, starting with the sporozoites

Answer 15

sporozoites invade epithelial cells -> merogony (schizogony) gives rise to multinucleate meronts (aka schizonts) that eventually produce merozoites within host cells -> merozoites will reinvade new cells to start a second round of merogony -> eventually merozoites enter host cells and begin gametogony, giving rise to microgamonts containing male microgametes and macrogamonts containing female macrogametes -> sex produces a zygote aka unsporulated oocyst, which is passed in the feces -> in the environment the unsporuated oocyst undergoes sporogony, giving rise to a sporulated oocyst containing 4 sporocysts which each contain 2 sporozoites

Question 16

what conditions are necessary for sporogony to occur

Answer 16

warmth, oxygen and moisture

Question 17

what types of division (mitosis, meiosis, asexual division) gives rise to a sporulated oocyst

Answer 17

meiosis and asexual division

Question 18

what are clinical signs/lesions of Eimeria coccidiosis (5)

Answer 18

• enteritis (possibly bloody)
• mucosal inflammation with sloughing in serious cases
• villar atrophy
• malabsorptive diarrhea
• decreased production parameters

Question 19

what are the most pathogenic Eimeria species in cattle

Answer 19

E. bovis and E. zurnii

Question 20

what are the conditions for bovine coccidiosis in Canada

Answer 20

• environmental contamination with sporulated oocysts
• immunologically naive animals

Question 21

T/F infected animals become immune to Eimeria

Answer 21

T

Question 22

Describe the differences between Eastern and Western Canada in terms of bovine coccidiosis in Summer vs Winter

Answer 22

SUMMER
Eastern Canada: warm, lush pastures and naive calves on pasture in a high stocking density; ideal conditions for sporulation of oocysts, causing many cases of coccidiosis in naive calves

Western Canada: dry, hot pastures and susceptible calves on pasture in low stocking density; non-ideal conditions for sporulation of oocysts, causing low or no coccidiosis in naive calves

WINTER
Eastern Canada: susceptible calves now immune; good replication potential for coccidiosis but no susceptible hosts so low density of the parasites and no coccidiosis

Western Canada: susceptible calves still susceptible and now in high stocking density in an ideal environment for coccidiosis replication, causing cases of coccidiosis in naive calves

Question 23

What are the common Eimeria spp in domestic chickens and where are they in the GI tract

Answer 23

E. tenella (caudal) and E. acervulina (cranial)

Question 24

what are the critical determining factors of if Eimeria is going to cause coccidiosis in chicken

Answer 24

1) sufficient numbers of oocysts ingested by a susceptible host
2) immune status of the host with respect to that particular species of Eimeria

Question 25

what are some treatment methods for poultry coccidiosis

Answer 25

- prophylactic anticoccidial usage in feed - supplementing litter with anticoccidials - live vaccines for broilers/layers

Question 26

what are the different programs for anticoccidial usage in domestic poultry (specifiy which are between flocks and which are within a flock)

Answer 26

- continuous program (within a flock) - shuttle program (within a flock) - rotation program (between flocks)

Question 27

what species does Cystoisospora infect? Contrast this with Eimeria

Answer 27

Cystoisospora: carnivores/omnivores and birds of prey; we care mainly about young dogs, cats, and swine Eimeria: calves and domestic poultry

Question 28

T/F each Cystoisospora sp is host-specific

Answer 28

T

Question 29

How is the life cycle for Cystoisospora unique compared to Eimeria

Answer 29

the whole life cycle is the same EXCEPT that there is an addition path of infection wherein a paratenic host can ingest a sporulated oocyst, which will excyst in the extra-intestinal tissues and form a monozoic cyst which becomes ingested and digested when the paratenic host is eaten by the definitive host

Question 30

describe the sporulated oocysts of Cystoisospora

Answer 30

each sporulated oocyst contains 2 sporocysts each containing 4 sporozoites

Question 31

what are the clinical signs and lesions created by cystoisospora

Answer 31

- damage to epithelial cells - immune-mediated enteritis - malabsorptive diarrhea Like all coccidia, in young, naive animals

Question 32

What is the treatment for cystoisospora

Answer 32

- self-limiting if small number of oocysts - supportive care - anticoccidials if needed - control the environment

Question 33

what causes neonatal coccidiosis in swine and what is the usual age group

Answer 33

Cystoisospora suis; <4 weeks

Question 34

what is the PPP and sporulation time for cystoisospora in swine

Answer 34

PPP: 4-6d sporulation time: 3-5d

Question 35

what are the 4 main clinical signs for coccidiosis in neonatal swine

Answer 35

- pale yellow diarrhea - failure to gain weight - runting - death

Question 36

how is neonatal coccidiosis diagnosed and treated

Answer 36

- diagnosed by clinical signs, mucosal scraping on PM, or oocysts in feces - treat with prophylaxis once it has been established

Question 37

what is the principle way to prevent coccidiosis caused by Eimeria and Cystoisospora in animals?

Answer 37

control the environment, prevent accumulation of feces which contain unsporulated oocysts that become infective once sporulated; want to eliminate the contamination before they become infective