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TNG Exam 2 > Parasitology > Flashcards

Parasitology Flashcards

1
Q

what species is the definitive host for toxoplasma gondii, ie the only host in which this protozoa sexually reproduces.

A

feline

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2
Q

What is the mode of transmission for toxoplasma gondii?

A

ingestion of oocyst or tissue cyst with bradyzooites

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3
Q

Once ingested by non-felid, toxoplasma becomes ___________, then each of those enters a cell, forms a cyst containing bradyzoites (slow multiplication).

A

tachyzoites

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4
Q

T/F: Tachyzoites can infect placenta, fetus, and be secreted in milk.

A

true

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5
Q

What species is the definitive host for neospora caninum?

A

canine

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6
Q

Tachyzoites of neospora caninum infect the placenta and fetus and the effects are seen during which time period?

A

after birth

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7
Q

Trypanosoma cruzi causes chagas disease in dogs. This diseases causes what type of symptoms in puppies and what lesions?

A

weakness, progressive weight loss, chronic diarrhea after weaning
lesion = cardiac chronic inflammatory process

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8
Q

What are the parasites that cause repro and neonatal disease in horses?

A

none!

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9
Q

what is the most common parasite causing repro and neonatal disease in small ruminants?

A

toxoplasma gondii

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10
Q

what is the most common parasite causing repro and neonatal disease in cattle?

A

neospora caninum and tritrichomonas foetus

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11
Q

what is the most common parasite causing repro and neonatal disease in pigs?

A

toxoplasma gondii

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12
Q

T/F: infection in adult small ruminants by toxoplasma gondii rarely causes disease because these animals have immunity.

A

true

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13
Q

Infection with toxoplasma gondii in small ruminants during what repro stage actually affects reproduction (abortion)?

A

FIRST pregnancy

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14
Q

if the small ruminant is infected with toxoplasma gondii during early pregnancy (before 80th day), what occurs?

A

early embryonic death followed by resorption or mummification (so it rarely goes noticed)

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15
Q

if the small ruminant is infected with toxoplasma gondii later in pregnancy (up to 115th day), what is the outcome?

A

abortion, stillbirth, perinatal death

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16
Q

if the small ruminant is infected with toxoplasma gondii later in pregnancy (after 115th day), what is the outcome?

A

congenitally infected lambs/kids born

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17
Q

How can you diagnose toxoplasma gondii in small ruminants?

A
  1. history – few animals infected OR abortion storm if naive herd and widespread contamination of feed/water
  2. morphologic – placental lesion with multifocal white necrotic lesions in cotyledons
  3. immunohistochemistry – brain, muscle, placenta
  4. serology – antibodies to toxoplasma in fetal fluids, presence of IgG paired titers (2-4 weeks apart) showing 4x increase in dam.
  5. PCR
  6. check cats on farm
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18
Q

what is the best way to control toxoplasma gondii in small ruminants?

A

initial infection of ewe will provide immunity and prevent further infection
you can feed decoquinate or monensin
vaccines in other countries
impossible to eliminate environmental contamination
maintain population of ADULT cats
protect feed from cat fecal contamination
dispose aborted fetuses and placenta properly

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19
Q

T/F: people can be infected with toxoplasma gondii by handling placenta and fetuses.

A

true

20
Q

Toxoplasma gondii in pigs occurs when oocysts or cysts are ingested. primary infection produces what outcomes?

A

abortion
stillbirth
weakness

21
Q

Neospora caninum is a major cause of abortion in what species?

A

cattle

22
Q

Name the 3 methods of transmission of neospora infection to cattle

A
  1. cow ingests oocysts from dog feces (horizontal transmission) and tachyzoites develop into cysts with bradyzoites
  2. naive cow is pregnant, tachyzoites cross placenta to fetus (exogenous transplacental transmission)
  3. PI cow reactivates when it becomes pregnant, tachyzoites infect fetus (endogenous transplacental transmission)
23
Q

What causes reactivation of neospora tachyzoites in persistently infected cattle when they become pregnant?

A

decline in immunity and hormonal imbalance

24
Q

Name this Neospora caninum infection pattern:
High proportion of pregnant cows are affected in a short period of time. They recently acquired the infection by horizontal transmission (food/water contamination) and exogenous transmission (pass through placenta to fetus)

A

epidemic pattern

25
Q

Describe the Endemic pattern of infection by neospora caninum in cattle

A

Endemic pattern is related to endogenous transmission (PI animal gets pregnant, reactivates, tachyzoites infect fetus), but horizontal transmission can occur too.
infected cows give birth to one or more infected calves
if the heifer aborts during her first pregnany, there is high risk of further abortions. if no abortion in 1st preg, risk goes down.

26
Q

What test can we use to determine which animals to cull in regard to neospora caninum infection in cattle?

A

serology –
seropositive cows 3.5x more likely to abort than seronegative
we want to cull seropositive cows, esp if they abort on their 1st pregnancy.

27
Q

at what timeframe does abortion occur as a result of neospora caninum in cattle?

A

5-7 months

28
Q

Infection of a cow with neospora caninum during which period of pregnancy makes its LESS likely to produce transplacental transmission, but effects are more severe (abortion)

A

EARLY gestation

29
Q

infection with neospora caninum in cattle during late gestation makes it more likely that transplacental transmission will occur. This results in what outcome for the calves?

A

clinically normal calves

30
Q

How do we diagnose neospora caninum in cattle?

A
  1. submit fresh fetus and placenta for exam – histology, PCR
  2. dam – serology (EFA/IFA)
31
Q

Diagnosis of neospora caninum can look very similar to which other parasite? We must stain during immunohistochemistry to see the antibodies bind to the neospora cyst and change color

A

toxoplasma

32
Q

what is the treatment for neospora caninum infection in cattle?

A

none
and there is NO vaccine

33
Q

how do we control neospora caninum infections in cattle in a management sense?

A
  1. management of feed/water to prevent contamination
  2. limit # puppies and litters on the property
  3. promptly dispose of aborted fetuses and placentas
34
Q

How can we reduce levels of infection with neospora caninum within a herd?

A
  1. serologically test ALL cows and cull the positive ones (remember that some are infected in-utero and will not develop antibodies, thus are not detectable with serology)
  2. test replacement heifers and only keep seronegative ones
  3. use embryo transfer for valuable blood lines
  4. purchase sero neg replacement stock
35
Q

T/F: tritrichomonas foetus is a flagellate protozoa that exists as tachyzoite and bradyzoite.

A

False – it exists only in trophozoite stage, meaning that is requires living INSIDE of the animal and cannot survive outside of the animal

36
Q

This parasite is found extracellular on mucosal surfaces of the reproductive tract of cattle.

A

tritrichomonas foetus

37
Q

How is tritrichomonas foetus transmitted?

A

venereally
bull –> cow* most common
cow –>bull (also possible)
AI (survives in semen frozen, or on equipment)

38
Q

Preputial discharge in bulls right after infection may be a sign of this parasite, however, more commonly there are no clinical signs. Bulls are asymptomatic carriers for life and this parasite does NOT impact semen quality.

A

tritrichomonas foetus

39
Q

cows infected with tritrichomonas foetus can develop these 3 infections, leading to mucopurulent vaginal discharge or no detectable signs. conception is ok, but fetal death can occur at 2 months.

A

vaginitis
cervicitis
endometritis

40
Q

cows infected with ____________ are observed having longer open periods and decreased fertility. Many will clear the infection after a few months and develop short term immunity.

A

tritrichomonas foetus

41
Q

how do we diagnose tritrichomonas foetus in cattle?

A

Preputial scraping in bulls – culture (in-pouch system), PCR**, microscopic examination
+/- test repro secretions in cows if you suspect infection

42
Q

how do we treat tritrichomonas foetus infections in cattle?

A

we dont!
a killed vaccine exists but it does NOT prevent infection in cows, it has only shown to reduce duration and severity of disease, but has NO benefits in bulls.

43
Q

T/F: tritrichomonas foetus is more of an importance causing abortion in western US than eastern

A

T

44
Q

What are the recommendations if a herd has tritrichomonas foetus present?

A
  1. test and remove all infected bulls
  2. reduce length of breeding season to 120 days, preg check at 45-60d
  3. remove or separate open cows, sex rest for 90d
  4. test and cull cows with discharge or aborting
45
Q

how do you control/prevent tritrichomonas foetus infections in cattle?

A
  1. prevent contact with other herds
  2. avoid communal grazing
  3. use virgin bulls and heifers
  4. test all new bulls more than once
  5. use younger bulls
  6. dont intro cows of unknown status during breeding season
  7. increase AI use
  8. breeding season < 120d to detect fertility loss earlier

TNG Exam 2 (8 decks)

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