6.5 Protists 2 Flashcards

1
Q

what is the smallest parasite commonly diagnosed? Is it a zoonotic threat?

A

Cryptosporidium; yes

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2
Q

when we think of Cryptosporidium what age group are we commonly thinking about

A

young and immunosuppressed; typically neonatal cattle

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3
Q

why is hygeine not an effective control measure against Cryptosporidium

A

the oocysts come into the environment sporulated; thin walled-cysts created in the host give rise to autoinfection

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4
Q

what is unique about the LOCATION of Cryptosporidium replication

A

epicellular (wraps the cell around it like a blanket, so cozy)

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5
Q

what is Cryptosporidium life cycle and what are the modifications

A

typical Apicomplexan (coccidian) life cycle - sporogony, merogony, gametogony

differences:
- sporogony occurs inside the host before the sporulated oocyst is shed into the environment, making it immediately infectious
- both thin walled and thick walled oocysts are formed; thin-walled will initiate the cycle within the host again (autoinfectious)

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6
Q

what are the clinical signs of Cryptosporidium

A
  • SI villous atrophy
  • enteritis
  • malabsorptive diarrhea (non-bloody, watery)
  • dehydration (biggest threat to neonates)
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7
Q

how long does the diarrhea induced by Cryptosporidium last

A

1-3 weeks in healthy animals, longer if immunocompromised

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8
Q

what is the appearance of Cryptosporidium oocysts in feces that helps us diagnose

A

refractile and small

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9
Q

how can we diagnose Cryptosporidium

A
  • fecal float
  • acid-fast staining of feces
  • IFA of fecal smears
  • puddle technique
  • fecal antigen tests available
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10
Q

how do we treat Cryptosporidium

A
  • no effective drugs (in contrast to Eimeria and Cystoisospora)
  • fluid replacement
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11
Q

what are some characteristics of heteroxenous coccidia

A
  • infects animals in a predator-prey relationship
  • extra-intestinal in the intermediate host (prey) and intestinal in the definitive host (predator)
  • dogs and cats are usually the definitive hosts, therefore have the intestinal phase
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12
Q

T/F the heteroxeous coccidia are also the tissue coccidia and the monoxenous coccidida are also the intestinal coccidia

A

T, with one exception…

Intestinal coccidia/monoxenous coccidia: Eimeria, (Cystoisospora), Cryptosporidium

Tissue coccidia/heteroxenous coccidia: Neospora, Sarcocystis, Toxoplasma, (Cystoisospora)

Cystoisospora has the paratenic host route whereby ingestion of sporulated oocysts causes an extra-intestinal cyst production that gets ingested by the definitive host…

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13
Q

Describe the intermediate and definitive hosts of the following heteroxenous coccidia:

  • Sarcocystis
  • Toxoplasma
  • Neospora
A

Sarcocystis: One intermediate host, one definitive host

Toxoplasma: Many intermediate hosts, cats are definitive hosts

Neospora: Many intermediate hosts, definitive hosts unknown

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14
Q

How is the apicomplexan life cycle broken down into the intermediate hosts, definitive hosts, and environment for heteroxenous coccidia (ex. Sarcocystis, Toxoplasma, Neospora)

A

Merogony occurs in extra-intestinal tissue in the intermediate host, gametogony and sporogony occur in the intestinal tissue of the definitive host, and the environment will contain the sporocysts

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15
Q

What are the definitive and intermediate hosts (specific) of SARCOCYSTIS

A

Intermediate hosts are herbivorous or omnivorous tetrapods

Definitive hosts are predatory reptiles, mammals and birds of prey

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16
Q

Where does Sarcocystic form sarcocysts in the intermediate hosts (the herbivorous and omnivorous tetrapods)

A

in the endothelium and muscles

17
Q

Sarcocystis is usually non-pathogenic in what host and pathogenic in what host

A

non-pathogenic in the definitive host; pathogenic in the intermediate host (makes predation easier and assists with transmission of the pathogen)

18
Q

Describe the life cycle of Sarcocystis

A

Intermediate host ingests sporulated oocysts or sporocysts from the environment -> 2 cycles of merogony occur in the vascular endothelium -> merozoites enter muscle or nerve cells and form a cyst containing bradyzoites -> intermediate host eaten by definitive host -> bradyzoites penetrate the intestinal epithelium and undergo gametogony -> zygote/oocyst formation -> sporulation occurs within the host

19
Q

Why might you see sporulated oocysts or sporocysts within the feces of a definitive host infected with Sarcocystis

A

The sporulated oocysts often break in the host, releasing the sporocysts

20
Q

What stage of Sarcocystis life cycle causes disease

A

the vascular phase (merogony - replication in the endothelium) in the intermediate host

21
Q

how is Sarcocystis commonly diagnosed in the definitive host and in the intermediate host

A

in the definitive host by finding oocysts or sporocysts in a fecal floatation

in the intermediate host infrequently diagnosed unless EQUINE PROTOZOAL ENCEPHALITIS

22
Q

What causes equine protozoal encephalitis? Describe why the disease has the clinical signs of ataxia, muscle atrophy

A

Caused by accidental ingestion of sarcocystis sporocysts by horses; the 2 cycles of merogony occur in the vascular endothelium but eventually escape to the muscles and brain; the key factor is NO sarcocyst formation so tachyzoites undergo extended replication in the brain in spinal cord causing tissue damage and the clinical signs

23
Q

how do you treat equine protozoal encephalitis

A

pyrimethamine/sulfas - long term therapy

24
Q

how is Toxoplasma different from Sarcocystis

A
  • range of intermediate hosts (vs Sarcocystis which only intermediate hosts are omnivorous/herbivorous tetrapods or horses accidentally)
  • Toxoplasma can move asexually between intermediate hosts
25
Q

what is the only definitive host of Toxoplasma

26
Q

Where are the extra-intestinal phases of Toxoplasma in kittens

A

lungs (primarily), also liver, muscle, heart, pancreas

27
Q

what are the clinical signs of Toxoplasma in cats

A

pneumonia, depression, anorexia

rapid death in severe cases

28
Q

what are signs of Toxoplasma in humans

A

lymphadenopathy, encephalitis, myocarditis, pneumonia

fatal in immunocompromised

29
Q

what is the most serious form of toxoplasmosis

A

congenital - abortion and neonatal death

30
Q

what are the lesions of congenital toxoplasma

A

inflammation and necrosis of fetal cotyledons; lesions in the liver and brain of the liver; abortion and neonatal death

31
Q

how is toxoplasma usually diagnosed and how do we interpret active/recent infection vs past infection

A

Serology

Active/Recent: elevated IgM in the absence of IgG

Past: low IgM and high IgG (IgGONE)

32
Q

T/F Congenital toxoplasmosis is treatable

33
Q

What is the definitive host of Neospora caninum

34
Q

Neospora caninum is ______tropic

A

neurotropic

35
Q

Neospora caninum is most important in dogs for causing ______________ and cattle for causing ______________

A

ascending paralysis; abortions

36
Q

what is the main difference between toxoplasma and neospora in terms of infection potential

A

neospora can cause congenital infection in an animal that was already exposed once, whereas toxoplasma will only cause congenital infection in an animal that was exposed for the first time during pregnancy

37
Q

how do we diagnose neospora caninum

A
  • clinical signs (ascending rigid paralysis in puppies)
  • organisms in CSF or brain of puppies
  • parasite-specific ELISA in cattle
38
Q

how do we treat neospora caninum

A
  • drugs undergoing testing but currently no treatment for calves
39
Q

how do we prevent neospora caninum

A

block transmission: prevent exposure to dogs, cull endogenously infected cows,