systemic apicomplexans (part 2) - nc state university...morphology: neospora caninum oocyst small,...
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Systemic Apicomplexans
(part 2)Neospora and
Sarcocystis
Grouped by Infection Site and Morphology
systemic
intestines
blood/tissue
Flagellates(sg = Excavates)
HemoflagellatesTrypanosoma cruzi
Tritrichomonas foetus
Leishmania infantum
Giardia spp.
Mucoflagellates
Trypanosoma cruziLeishmania infantum
Intestinal apicomplexa
Blood apicomplexa (piroplasmidia)
Cryptosporidium parvum (gregarine)Eimeria spp. (coccidia)
Cystoisospora spp. (coccidia)
Cytauxzoon felisBabesia spp.
Toxoplasma gondiiNeospora caninumSarcocystis spp.
Systemic apicomplexa (coccidia)
Parasitic Protozoa Apicomplexa
(sg =Alveolates)
Neospora caninum• Canine coccidian
• Complex Life Cycles
• Bovine abortion
https://homesteadontherange.com
• Canine neurologic disease
Morphology: Neospora caninum Oocyst
Small, sub-spherical, smooth coat, no polar cap, single embryo when passed = unsporulated (sporulate after 1-3 days)
Sporulated oocyst contains 2 sporocysts with 4 sporozoites each = 8 sporozoites total
https://www.researchgate.net/figure/8663822_fig2_Fig-2-PCR-for-Neospora-caninum-and-Hammondia-heydorni-using-DNA-extracted-from-oocysts
Morphology:Neospora caninumBradyzoite cyst (cysts found in tissue); facilitate persistent infection
www.cmgm.stanford.edu
www.k-state.edu
Obligate Indirect Life Cycle
Definitive Host = canids
Trans-generational infection
Intermediate Host = herbivores (cattle)
Obligate Indirect Life Cycle: N. caninum
Canids
Obligate Indirect Life Cycle (heteroxenous) Definitive host – Canids only (Dog, Coyote, Wolf, etc.) Intermediate Host (IH) – Cattle and other animals
Transmission -- carnivorism, ingestion of tissue cysts from aborted cattle fetus
Invasion -- Zoites excyst from tissue cyst and invade enterocytes Asexual reproduction (enterocytes and other cells)
endodyogeny AND merogony
intermediate host definitive host
Sexual reproduction (only occurs in canids) in enterocytes Gametogony, Macrogamete, Microgamete, Exflagellation, Fertilization,
Zygote, Oocyst formation. Dissemination
Oocysts (unsporulated) exit the canid in the feces and contaminate the environment ~ 4 days post ingestion → sporulate after 1-3 days
Canids (definitive hosts) are the only hosts to pass oocysts Oocysts highly resistant and remain infectious for many months.
Obligate Indirect Life Cycle: N. caninumCanids
definitive host
Transmission / Invasion (details) After ingestion of cow tissue cyst
Intestinal Some zoites infect intestinal cells to complete sexual cycle oocyst
in the feces Systemic
Other zoites go to deeper tissue and go through asexual cycles → tachyzoites become tissue cysts with bradyzoites (predilection for neural tissue).
Congenital If dog is pregnant, zoites → transplacental to puppies.
definitive host Obligate Indirect Life Cycle: N. caninumCanids
Transmission - Cattle ingest sporulated oocysts from canid feces
intermediate hostdefinitive host
Obligate Indirect Life Cycle: N. caninum
Cattle
Invasion Intestinal – sporozoites penetrate intestinal lining
(no replication and invasion of enterocytes)
Systemic - zoites move to extra-intestinal cells → asexual replication tachyzoites (fast replication and transform into bradyzoites) bradyzoite (slow replication, form tissue cysts in neural, muscle, myocardial,
placenta, fetus)
Congenital Transmission - zoites → transplacental to infect calf
Complex Life Cycle: N. caninumCattle
Congenital Transmission (details)
Infected fetus aborts in 2nd or 3rd trimester, or born early, impaired
Infected fetus survives, passes infection on to offspring = Trans-generational infection Cows infected in utero will in-turn infect their calves, without reinfection
from sporocyst in dog feces These calves are usually seropositive and less likely to have abortions
OR
intermediate host intermediate host
intermediate host
“re-activated” bradyzoites invade the placenta and fetus
Ingest sporulated oocyst from dog
intermediate host
Complex Life Cycle: N. caninumcow-to-cow (Congenital Neosporosis)
(bradyzoites)
Dog-to-dog via sporulated oocysts -has not been reported Sporulated oocyst ingestion does not result in oocyst production FYI: If ingested, the parasite may go systemic & transplacental (not
Intestinal) –like intermediate host
Dog-to-dog via transplacental (bitch to puppies)
Complex Life Cycle: N. caninumDog-to-Dog
Intestinal phase = no pathology(only in canids)
Extra-intestinal phase = systemic disease (occurs in canids or intermediate hosts)
Explosive multiplication of tachyzoites massive direct destruction of host cells acute immune response
Tissue cysts w/ bradyzoites may cause tissue damage; low inflammation; latent “Re-activation” source for transplacental transmission
Pathogenesis: N. caninum
More commonly a neuromuscular disease of puppies after transplacental infection (congenital neospora)
Adults usually subclinical but may develop dz Neuromuscular dz = muscle atrophy, rigid
hyperextension, paralysis, head tilt, gait abnormality, dysphagia, seizure
Other non-specific clinical signs: nodular dermatitis, pneumonia, urine incontinence, fecal incontinence, nephritis, myocarditis, polymyositis
Clinical Disease: N. caninumDogs
rigid hyperextensionhttp://www.vin.com/apputil/content/defaultadv1.aspx?meta=Generic&pId=11157&id=3857014
Congenital Neosporosis Litter-mates dying with signs of
polyradiculitis (inflammation of the nerve roots, especially of the hind limbs)
Puppy with signs of paralysis of the rear limbs at 3-8 weeks of age (ascending paralysis)
Puppy with flaccid hind limb paresis
Clinical Disease: N. caninumPuppies
Abortions (10-20% of abortions caused by N. caninum)
Abortions usually occur with 1st post-infection pregnancy; autolysis of fetus
Later pregnancies usually go to term, but calves are infected (maintenance of dz in herds)
Trans-generational infections Seropositive calves give birth to seropositive
calves – without reinfection via sporocyst ingestion ↓ milk production and ↓ weight gain
https://www.cityu.edu.hk/ph/en/Research/VDP.html
Clinical Disease: N. caninumCattle
http://genex.crinet.com/page4393/AbortionInDairyCattleGeneralConcepts
Cattle Abortions
Diagnosis: N. caninum Dogs
Puppy – classic flaccid hind limb Serology, molecular tests-PCR Organism on biopsy, necropsy of litter
mates
Cattle Diagnostic arrays for multiple abortion
infectious agents Serology and molecular tests-PCR Antibody tests for whole milk
https://www.koofers.com/flashcards/cpb-exam-2-egglist-add-ons/review
cyst filled with bradyzoites
Dogs No drugs available to kill tissue forms
Cattle No drug therapy available
Treatment: N. caninum
Epidemiology, Control & ZoonosisN. caninum
Epidemiology -worldwide Risk factors = presence of dogs on farms and
dairy production (dairy cattle) Control
Limit cattle exposure to wild and domestic canid populations
Cull seropositive cows? Cull cows with midterm abortions?
Don’t let dogs have access to raw meat, offal or dead animals
Not Zoonotic
Sarcocystis cruzi
• Complex Life Cycle
• Canine coccidian
• Causes disease in cattle
Morphology: Sarcocystis cruzi Sporocyst (identified in feces, not oocyst)
Thin-walled oocyst sporulates and ruptures before exiting in the feces, thus sporocysts are seen in the feces
small, oval, smooth coat, no polar cap; 4 sporozoites
Morphology: Sarcocystis cruzi Sarcocysts (bradyzoites in muscles cysts)
zoites find their way to muscle tissue, where they go through schizogony and form sarcocysts.
Infective to the definitive, carnivorous host Facilitate persistent infection (immune system doesn’t clear)
The Korean Journal of Parasitology 2018; 56(2): 121-127.
Obligate Indirect Life Cycle Definitive Host =
canids, other carnivores
Intermediate Host = cattle
Obligate Indirect Life Cycle (heteroxenous) Definitive host – Canids (Dog, Coyote, Wolf, etc.), raccoons Intermediate Host – Cattle
Transmission carnivorism, ingestion of sarcocysts (bradyzoites inside a
muscle cysts) in cattle Invasion
Bradyzoites invades intestinal cells → gamatogony begins NO ASEXUAL reproduction occurs in the dog
Indirect Life Cycle: Sarcocystis cruziCanids
Sexual reproduction only occurs in dogs Gametogony, Macrogamete, Microgamete, Exflagellation, Fertilization,
Zygote, Oocyst Formation The oocyst sporulates within the gut lumen, then ruptures, releasing its 2
sporocysts into the gut lumen
Indirect Life Cycle: Sarcocystis cruziCanids
Dissemination Sporocysts exit the host in the feces and contaminate the environment Dogs are the only hosts to pass sporocysts. Sporocysts are infectious when shed, are very resistant and remain
infectious for several months if kept cool and moist.
Asexual reproduction – occurs in vascular endothelial cells and muscle cells Merozoites → merogony (schizogony), then disperse throughout to muscle cells Bradyzoites replicate form sarcocysts (slow process, over months) Sarcocysts (muscle cysts), full of bradyzoites develop within muscle cells and remain
viable for the life of the intermediate host.
Indirect Life Cycle: Sarcocystis cruziCattle
Transmission ingestion of a sporocyst from canid feces
Invasion Sporozoites cross intestines and enter vascular endothelial cells
Pathogenesis: S. cruzi Intestinal Phase in Canids – no pathology.
Systemic Disease in Cattle Direct destruction vascular endothelial cells and muscle
cells Acute immune response Multi-system DZ due to zoites throughout the vascular
endothelium and muscles, w/ immune reaction and inflammation that follows
Systemic Sarcocystosis -- cattle only Protracted fever, lymphadenopathy,
anorexia, cachexia, muscle spasms, myositis, hyper-excitability, diarrhea, hyper-salivation, weakness, hair loss around eyes, neck and tail switch (“rat-tail”), prostration, death
Sporadic abortions, still births
Pathology in cattle begins about 4-6 weeks post-ingestion of sporocysts
Immune status of the host and the dose of sporocysts determine clinical disease.
Clinical Disease: S. cruzihttp://old.iss.it/binary/crlp/cont/Fayer_Sarcocystis.pdf
Dogs – sporocysts on a routine fecal exam
Cattle – serology, necropsy
Diagnosis: S. cruzi
https://capcvet.org/guidelines/coccidia/
Cystoisospora spp.
Cystoisospora spp.
Neospora andToxoplasma
Sarcocystis
Cryptosporidium
Sarcocystis sporocystin dog feces
Sarcocyst in Muscle (histology/gross)
http://praca-w-niemczech.info/imalsdrm-sarcocystis.html
https://www.merckvetmanual.com/musculoskeletal-system/sarcocystosis/overview-of-sarcocystosis
Sarcocystis aucheniae in Llama
Treatment: S. cruzi Dogs
None – not necessary
Cattle Amprolium may provide some prophylactic
protection Treatment against sarcocysts is ineffective
Epidemiology, Control & ZoonosisS. cruzi
Epidemiology: distributed worldwide in cattle
Control: wild and domestic canid populations
Don’t let dogs have access to raw meat, offal or dead animals
Not Zoonotic
Sarcocystis neurona
• Sylvatic Life Cycle
• Opossum coccidan
• Causes Equine Protozoal Myeloencephalitis (EPM)
© Gregorita Ko
http://www.baltimorepestanimal.com/opossumdisease.html
DO
I: http://dx.doi.org/10.1645/GE-230R
Morphology: Sarcocystis neurona Sporocyst (not Oocyst)
Thin-walled oocyst sporulates and ruptures before exiting in the feces, thus sporocysts are seen in opossum feces
small, oval, smooth coat, no polar cap; 4 sporozoites
DOI: http://dx.doi.org/10.1645/GE-230R
Intact oocyst sporocyst
Sarcocystis neurona
https://veteriankey.com/common-equine-diseases/
Mature sarcocysts are essential for the completion of the life cycle.
Sarcocysts do not develop in the horse.
Obligate Indirect Life Cycle: S. neurona
Sylvatic (wild animals)
Life Cycle: S. neuronaSylvatic (wild animals)
Obligate Indirect Life Cycle (heteroxenous) Definitive host (DH) – Opossum (North and South American) Intermediate Host (IH) – other small mammals and birds
Transmission Opossum (DH) ingests sarcocyst in muscle of IH IH ingests sporocysts from opossum feces
Accidental host – horse ingest sporocyst from opossum feces Asexual stages in tissue, disseminates throughout body,
especially neural tissue (merozoites and schizonts detected) Systemic disease
Pathogenesis: S. neurona Intestinal Phase in Opossum – no pathology.
Systemic Disease in Horses a predilection for neural tissue (neurons and leukocytes
of the brain and spinal cord) Zoites cause destruction of host cells, and acute immune
response / inflammation (meronts and merozoites seen in neurons)
FYI: other protozoa (T. gondii, N. caninum, others may cause EPM-like symptoms in horses)
Clinical Disease: S. neurona Equine Protozoal Myeloencephalitis (EPM)
Spinal Cord involvement Gait abnormalities, unilateral muscle
atrophy (gluteal), myopathy, asymmetric weakness, and ataxia
Demarcated spontaneous sweating, loss of reflexes, cutaneous hyper-sensation.
Cranial nerve involvement Seizures, visual deficits, behavioral
abnormalities Brain involvement
Depression, head tilt, facial paralysis, muscle atrophy (masseter), dysphagia
Without treatment, may progress to recumbencyand death
http://www.sciencedirect.com/science/article/pii/S0304401700003848#FIG2
Sarcocystis neuronaAtaxia
http://www.sciencedirect.com/science/article/pii/S0304401715000448
Sarcocystis neuronaMuscle atrophy
Diagnosis: S. neuronaHorses
Observation of Clinical Signs Mostly neurologic and muscle atrophy. There is a broad spectrum of disease agents that induce
similar clinical signs Serology (CSF and serum)
Serology Antibody IgG against S. neurona indicates exposure; may also give a
false-positive (cross-reactivity to another non-pathogenic Sarcocystis species)
Seropositive + neurological clinical signs strongly supportive of EPM Paired serology testing using CSF and serum more predicative of active
disease Western Blotting and ELISAs use S. neurona specific antigens → less cross
reactivity
Diagnosis: S. neuronaHorses
PCR detects S. neurona DNA = current infection
Post-mortem demonstration of organism in CNS lesions.
Sarcocystis neuronaNecropsy / Histology
http://www.sciencedirect.com/science/article/pii/S0304401715000448
http://www.sciencedirect.com/science/article/pii/S0304401700003848#FIG2
https://tvmdl.tamu.edu/2018/03/16/equine-protozoal-myeloencephalitis-epm-diagnosed-horse/
EPM Treatment Ponazuril, diclazuril, pyrimethamine, sulfadiazine.
Long treatment period (6-8 wks). Be vigilant of side-effects.
Anti-inflammatories; supportive care
Improvement in 60-70%, complete recovery in up to 20%, relapse in 20% (not likely to clear organism)
Epidemiology, Control & Zoonosis: S. neurona
Epi: confined to the Americas (opossum Didelphis virginianaand D. albiventris distribution) estimated ~50% of all horses in US have been exposed to S. neurona <1% develop disease
Control: prevent access of opossums to horse-feeding / watering areas
Fallen fruit should be removed from horse pastures. Why?
Zoonosis: no reports of human infections Infection in dogs, cats and sea mammals (otters) reported
See Review Table: Systemic ProtozoaPosted on-line at Parasitology Website:
https://parasitology.cvm.ncsu.edu/vmp930/lecture.html
The information in the review tables is basic information that you should know. You should also be able to use that information via critical thinking to answer more complex case-based questions.
What you’re expected to know