Causes of bovine abortion (Yr 4)

Question 1

what is abortion defined as in cattle?

Answer 1

calving that occurs at less than 270 days gestation

Question 2

what effect does abortion have on the cow?

Answer 2

reduced reproductive performance (retained membrane, conception…)
reduced milk production

Question 3

what is the reason abortions are notifiable?

Answer 3

Brucellosis

Question 4

what percentage pregnancy loss is acceptable in a healthy herd?

Answer 4

<5% (early and late losses)

Question 5

what are the two general categories of abortion causes?

Answer 5

infectious
non-infectious

Question 6

what are some possible non-infectious causes of abortion?

Answer 6

nutritional (energy, deficiencies)
developmental (hormones, congenital abnormalities)
toxins (aflatoxins, nitrite)
trauma, twins, hyperthermia…

Question 7

what is a primary abortive agent?

Answer 7

anything that destroys integrity of feto-maternal unit which then allows opportunistic pathogens to invade (doesn’t have to cause abortion itself)
can be infectious or non-infectious

Question 8

what are some primary infectious abortive agents?

Answer 8

Brucella abortus
BVD
Leptospirosis
neospora
BHV-1
parainfluenza-3
Bacillus licheniformis
fungi

Question 9

what are the main two opportunistic abortive agents?

Answer 9

Listeria monocytogenes
Salmonella dublin
Leptospira
E. coli

Question 10

what are the three infection routes of abortive agents?

Answer 10

resident flora of reproductive tract
transplacental
haematogenous

Question 11

what are pathogens could cause abortion at any stage of gestation?

Answer 11

BVD, salmonella, Trueperella pyogenes, M. tuberculosis

Question 12

when does the foetuses immune system develop?

Answer 12

90-120 days

Question 13

what is bovine herpesvirus 1 also known as?

Answer 13

infectious bovine rhinotracheitis

Question 14

what is a significant feature of BHV-1?

Answer 14

it lies latent in the trigeminal ganglion and will recrudesce in times of stress

Question 15

what are the clinical signs of BHV-1 causing abortion in cattle?

Answer 15

infectious pustular vulvovaginitis - pustule inside vulva (same on bulls penis)
abortions
milk drop (herd level)

Question 16

can you vaccinate for BHV-1?

Answer 16

yes (protect in the face of an outbreak)

Question 17

what is the most commonly diagnosed cause of abortion?

Answer 17

neospora

Question 18

what cattle are the most at risk of neospora abortions?

Answer 18

congenitally infected heifers in first gestation (usually only abort once)

Question 19

what are the ways a cow can become infected with neospora?

Answer 19

exogenous - by oocyst ingestion
endogensous - transplacental

Question 20

what is the best time for testing for neospora?

Answer 20

at drying off (antibody levels fluctuate throughout pregnancy)

Question 21

can you test the calf for neospora?

Answer 21

yes, but has to be done before they are given colostrum as material antibodies could pass to the calf

Question 22

what can be samples of a aborted foetus to test for neospora?

Answer 22

brain histopathology

Question 23

how can neospora be controlled?

Answer 23

keep dogs away from cattle feed/water and don’t allow them to eat placenta
culling seropositive cows/offspring
breed infected cattle to beef

Question 24

what are the two biotypes of BVD?

Answer 24

cytopathic
non-cytopathic

Question 25

what does the outcome of BVD infection depend on?

Answer 25

when the cow becomes infected during pregnancy

Question 26

what are the different stages of pregnancy a cow can become infected with BVD and what are the outcomes?

Answer 26

0-100 days - abortion or resorption
100-120 days - immunotolerance (PI status)
120+ days - seropositive calves (abort, weak, normal)

Question 27

what are the classic congenital issues of BVD seropositive calves?

Answer 27

cerebellar hypoplasia
cataracts

Question 28

what are the two major consequences of BVD?

Answer 28

lowered pregnancy rate
abortions

Question 29

how does BVD cause lower pregnancy rates?

Answer 29

epithelial lining of reproductive tract and follicle are infected (only during viraemic disease stage)