Apicomplexa Flashcards
Apicomplexa - general characteristics
All have “apical complex” in infective stage (helps host cell invasion)
- widely diverse, infecting intestinal tissue and extraintestinal, blood, etc
- unicellular
- direct/indirect, asexual/sexual, predator/prey, or vector bone life cycle
Apicomplexa - intestinal stages
- Eimeria
- Isospora suis
- Cryptosporidium
- Toxoplasma gondii
Apicomplexa - extraintestinal stages
- Cytoisospora
- Sarcocystis cervi, neurona
- Toxoplasma gondii
- Hepatazoon americanum
Apicomplexa - blood stages
- Babesia
- Cytauxzoon felis
- Hepatozoon
- Plasmodium
- Haemoproteus
- Leucocytozoon
Sporogony
Asexual reproduction
- single zygote (in oocyst) produces infective sporozoites
- formation of infectious stages of parasite
Merogony (schizogony)
Asexual reproduction
- sporozoites undergo rapid division to become meront (schizont) stages containing invasive merozoites
- several generations possible, depending on species
Gametogony (gamogony)
Merozoites differentiate into gametes
- male microgametes and female macrogametes
Fertilization
Gametes fuse to produce zygote (oocyst)
Coccidian - generic life cycle
Zygote –> sporogony = sporozoites –> host cell invasion –> merozoites –> merogony/schizongony OR –> gamogon = gametes –> fertilization
Eimeria spp. - coccidia
- original description based on: host species, host location, oocyst morphology
- cosmopolitan distribution
- host and site specific (usually)
Which Eimeria species are pathogenic in cattle?
- E. bovis
- E. zuernii
Which Eimeria species are pathogenic in chickens?
- E. tenella
- E. maxima
Eimeria - oocysts
Unsporulated when released in feces
- sporogony occurs in environment
- sporulated oocyst = 4 sporocytes, each with 2 sporozoites (total of 8 infectious units per cyst)
Eimeria - sporulated oocyst
Ingested
- sporozoites infect target cells
- merogony (merozoites)
- gametogony (gametes)
- gametes fuse = oocyst production
Eimeria has a _____ life cycle
Direct
- host –> environment –> host
- completed in a single host!
Eimeria - pathology
- severe, watery diarrhea, dehydration
- bloody feces
- weight loss
- lethargy/depression
Pathogenesis of eimeria leaves a ______ number of oocysts in fecal floatations.
High!
- once oocysts are present, damage has been done
Eimeria - cattle
Pathogenic: E. bovis, E. zuernii
- PPP: 2-3 weeks
- clinical signs: severe, watery diarrhea, weight loss, lesions, submucosa destroyed
Nervous coccidiosis is associated with _____
Eimeria zuernii
Eimeria - small ruminants
Pathogenic (sheep): E. ahsata, E. ovina
- host specificity?
What species are not infected with Eimeria?
Dogs and cats
Which species are asymptomatic with Eimeria?
Horses
- E. leuckarti
Eimeria diagnosis
- clinical signs
- lesions: direct smear, lesion scoring, histology
- fecal exam: sugar float
When identifying the oocyst you do NOT want to _______
Refridgerate the sample
- will delay sporulation, which requires 48 hours
- use 2.5% potassium dichromate for storage
Anticoccidials
Prophylactic treatment
- wide range
- coccidiostat vs coccidiocidal
- rotation/shuttle programs
- stress in young animals
Are coccidia vaccines available?
Yes, live strains for poultry industry
- attenuated
- in ovo vaccination (live oocysts)
Other ways to control Eimeria
- environment: sanitation, litter management
- animal: monitoring, mixed ages, prophylactic treatment program
Cystoisospora can have extraintestinal stage in _______
Paratenic hosts
- monozoic tissue cyst
- commonly infect dog/cat
Isospora is strictly ______
Intestinal
Isospora/cystoisospora ______ life cycle
Direct
- unsporulated oocysts shed in environment –> sporogony –> sporulated oocysts
- DH ingests sporulated oocysts –> sporozoites release –> infect target cells
What differentiates isospora/cystoisospora from eimeria?
Isospora/cystoisospora have sporulated oocysts with:
- 2 sporocysts with 4 sporozoites each
Isospora/cystoisospora asexual stages
Sporozoites invade host intestinal cell undergo merogony –> merozoites form –> invade new host cell –> second generation of merozoites –> invade new cells
Isospora/cystoisospora sexual stages
Gametogony (gamogony)
- male/female gametes –> fertilization –> oocysts produced –> passed in feces unsporulated
Cystoisospora indirect life cycle
Unsporulated oocysts shed in environment –> sporogony –> sporulated oocysts (2 sporocysts w/ 4 sporozoites each)
- DH ingests sporulated oocysts OR paratenic host with monozoic cysts –> sporozoites released –> infect intestinal cells
Cystoisospora indirect asexual stages
Sporozoites invade host intestinal cell undergo merogony –> merozoites formed –> invade new host cell –> second generation of merozoites –> invade new cells
Cystoisospora indirect sexual stages
Gametogony (gamogony)
- male/female gametes –> fertilization –> oocysts produced –> passed in feces unsporulated
Cystoisospora - paratenic host
Ingests sporulated oocysts –> extraintestinal development of monozoic cysts
Isospora/cystoisospora PPP
At least 1 week for most species
- may be longer in monozoic cysts is infection route
Isospora suis
Neonatal porcine coccidiosis
- ubiquitous in closed confinement
- 15-20% of swine diarrhea
- sows do not have clinical disease, just neonates
Isospora suis - clinical signs
- diarrhea: pasty yellow, fluid after 2-3 days
- dehydration
- lethargy
- destruction of villous epithelium in SI: malabsorption
- recovery: resistance
I. suis PPP
5 days
- oocysts shed 1-3 weeks
I. suis diagnostics
Fecal oocysts
- fecal float
- 48 hr sporulation (required to differentiate from eimeria)
PM diagnosis
- intestinal scrapings of lesions, wet mount
I. suis control
- place sows on anticoccidial during 3rd trimester
- steam clean
- anticoccidials
- albon, baycox
Cystoisospora spp - dogs
Ubiquitous in young dogs
- host specific
- diarrhea, dehydration, anorexia
- asexual/sexual stages destroy intestinal cells
Isospora/cystoisospora - cats
More pathogenic in cats 4 weeks or younger
- diarrhea, dehydration, malnutrition, death
- moderate or subclinical in older cats
Isospora/cystoisospora oocyst rule outs
Cats: cryptosporidium, hammondia, t. gondii
Dogs: cryptosporidium, hammondia, neospora caninum, sarcocystis
Isospora/cystoisospora sporulation _____
16 hours
Isospora/cystoisospora - control
Dog/cats
- disingestion of paratenic hosts
- sanitation
- treat all animals
- anticoccidials
