6.4 Protists 1 Flashcards
Protists are ________ celled, _____________ organisms
single; eukaryotic
where do protists cause infections
virtually anywhere, intracellularly or extracellularly (often in moist spots)
what are the strategies for protists to pass from host to host
- use a resistant stage
- intermediate host and/or paratenic host
what is a paratenic host
where a parasite lives but does not replicate or further develop; serves to help the parasite transmit
what are the major groups of parasitic protists (6)
- apicomplexa
- flagellates
- ciliates
- amoebae
- microsporidia
- myxosporidia
what are 3 examples of apicomplexan protist parasites
coccidia, malaria, piroplasms
what are 2 examples of flagellate protist parasites
kinetoplastids and trichomonads
what is the general lifecycle of all Apicomplexa
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
what are the gut coccidia genera
eimeria, isospora, caryospora, cystoisospora
what are the tissue coccidia
neospora, toxoplsama, sarcocystis
what is the difference between monoxenous and heteroxenous life cycles
monoxenous: completes life cycle within a single host
heteroxenous: requires multiple hosts to complete life cycle
Eimeriorina (Coccidia):
- obligate/facultative intracellular/extracellular
- monoxenous, heteroxenous or both
- where do they live in the definitive host? intermediate host?
- obligate intracellular
- both monoxenous (Eimeria, Cystoisospora) and heteroxenous (Toxoplasma, Sarcocystis)
- intermediate hosts in many tissues but in the GI tract of the definitive host
T/F Apicomplexan parasites penetrate the host cells actively
T
Describe the sporulated oocyst (at the end of sporogony) of eimeria
Contains 4 sporocysts each containing 2 sporozoites; the sporocysts have stieda bodies and the sporozoites have refractile bodies
describe the Eimeria life cycle, starting with the sporozoites
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
what conditions are necessary for sporogony to occur
warmth, oxygen and moisture
what types of division (mitosis, meiosis, asexual division) gives rise to a sporulated oocyst
meiosis and asexual division
what are clinical signs/lesions of Eimeria coccidiosis (5)
- enteritis (possibly bloody)
- mucosal inflammation with sloughing in serious cases
- villar atrophy
- malabsorptive diarrhea
- decreased production parameters
what are the most pathogenic Eimeria species in cattle
E. bovis and E. zurnii
what are the conditions for bovine coccidiosis in Canada
- environmental contamination with sporulated oocysts
- immunologically naive animals
T/F infected animals become immune to Eimeria
T
Describe the differences between Eastern and Western Canada in terms of bovine coccidiosis in Summer vs Winter
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
What are the common Eimeria spp in domestic chickens and where are they in the GI tract
E. tenella (caudal) and E. acervulina (cranial)
what are the critical determining factors of if Eimeria is going to cause coccidiosis in chicken
1) sufficient numbers of oocysts ingested by a susceptible host
2) immune status of the host with respect to that particular species of Eimeria
what are some treatment methods for poultry coccidiosis
- prophylactic anticoccidial usage in feed
- supplementing litter with anticoccidials
- live vaccines for broilers/layers
what are the different programs for anticoccidial usage in domestic poultry (specifiy which are between flocks and which are within a flock)
- continuous program (within a flock)
- shuttle program (within a flock)
- rotation program (between flocks)
what species does Cystoisospora infect? Contrast this with Eimeria
Cystoisospora: carnivores/omnivores and birds of prey; we care mainly about young dogs, cats, and swine
Eimeria: calves and domestic poultry
T/F each Cystoisospora sp is host-specific
T
How is the life cycle for Cystoisospora unique compared to Eimeria
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
describe the sporulated oocysts of Cystoisospora
each sporulated oocyst contains 2 sporocysts each containing 4 sporozoites
what are the clinical signs and lesions created by cystoisospora
- damage to epithelial cells
- immune-mediated enteritis
- malabsorptive diarrhea
Like all coccidia, in young, naive animals
What is the treatment for cystoisospora
- self-limiting if small number of oocysts
- supportive care
- anticoccidials if needed
- control the environment
what causes neonatal coccidiosis in swine and what is the usual age group
Cystoisospora suis; <4 weeks
what is the PPP and sporulation time for cystoisospora in swine
PPP: 4-6d
sporulation time: 3-5d
what are the 4 main clinical signs for coccidiosis in neonatal swine
- pale yellow diarrhea
- failure to gain weight
- runting
- death
how is neonatal coccidiosis diagnosed and treated
- diagnosed by clinical signs, mucosal scraping on PM, or oocysts in feces
- treat with prophylaxis once it has been established
what is the principle way to prevent coccidiosis caused by Eimeria and Cystoisospora in animals?
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
