Parasitology

Question 1

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

Answer 1

feline

Question 2

What is the mode of transmission for toxoplasma gondii?

Answer 2

ingestion of oocyst or tissue cyst with bradyzooites

Question 3

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

Answer 3

tachyzoites

Question 4

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

Answer 4

true

Question 5

What species is the definitive host for neospora caninum?

Answer 5

canine

Question 6

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

Answer 6

after birth

Question 7

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

Answer 7

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

Question 8

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

Answer 8

none!

Question 9

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

Answer 9

toxoplasma gondii

Question 10

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

Answer 10

neospora caninum and tritrichomonas foetus

Question 11

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

Answer 11

toxoplasma gondii

Question 12

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

Answer 12

true

Question 13

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

Answer 13

FIRST pregnancy

Question 14

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

Answer 14

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

Question 15

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

Answer 15

abortion, stillbirth, perinatal death

Question 16

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

Answer 16

congenitally infected lambs/kids born

Question 17

How can you diagnose toxoplasma gondii in small ruminants?

Answer 17

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

Question 18

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

Answer 18

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

Question 19

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

Answer 19

true

Question 20

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

Answer 20

abortion
stillbirth
weakness

Question 21

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

Answer 21

cattle

Question 22

Name the 3 methods of transmission of neospora infection to cattle

Answer 22

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)

Question 23

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

Answer 23

decline in immunity and hormonal imbalance

Question 24

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)

Answer 24

epidemic pattern

Question 25

Describe the Endemic pattern of infection by neospora caninum in cattle

Answer 25

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.

Question 26

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

Answer 26

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.

Question 27

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

Answer 27

5-7 months

Question 28

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)

Answer 28

EARLY gestation

Question 29

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?

Answer 29

clinically normal calves

Question 30

How do we diagnose neospora caninum in cattle?

Answer 30

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

Question 31

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

Answer 31

toxoplasma

Question 32

what is the treatment for neospora caninum infection in cattle?

Answer 32

none and there is NO vaccine

Question 33

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

Answer 33

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

Question 34

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

Answer 34

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

Question 35

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

Answer 35

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

Question 36

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

Answer 36

tritrichomonas foetus

Question 37

How is tritrichomonas foetus transmitted?

Answer 37

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

Question 38

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.

Answer 38

tritrichomonas foetus

Question 39

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.

Answer 39

vaginitis cervicitis endometritis

Question 40

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.

Answer 40

tritrichomonas foetus

Question 41

how do we diagnose tritrichomonas foetus in cattle?

Answer 41

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

Question 42

how do we treat tritrichomonas foetus infections in cattle?

Answer 42

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.

Question 43

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

Answer 43

T

Question 44

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

Answer 44

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

Question 45

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

Answer 45

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