Causes of bovine abortion (Yr 4) Flashcards
what is abortion defined as in cattle?
calving that occurs at less than 270 days gestation
what effect does abortion have on the cow?
reduced reproductive performance (retained membrane, conception…)
reduced milk production
what is the reason abortions are notifiable?
Brucellosis
what percentage pregnancy loss is acceptable in a healthy herd?
<5% (early and late losses)
what are the two general categories of abortion causes?
infectious
non-infectious
what are some possible non-infectious causes of abortion?
nutritional (energy, deficiencies)
developmental (hormones, congenital abnormalities)
toxins (aflatoxins, nitrite)
trauma, twins, hyperthermia…
what is a primary abortive agent?
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
what are some primary infectious abortive agents?
Brucella abortus
BVD
Leptospirosis
neospora
BHV-1
parainfluenza-3
Bacillus licheniformis
fungi
what are the main two opportunistic abortive agents?
Listeria monocytogenes
Salmonella dublin
Leptospira
E. coli
what are the three infection routes of abortive agents?
resident flora of reproductive tract
transplacental
haematogenous
what are pathogens could cause abortion at any stage of gestation?
BVD, salmonella, Trueperella pyogenes, M. tuberculosis
when does the foetuses immune system develop?
90-120 days
what is bovine herpesvirus 1 also known as?
infectious bovine rhinotracheitis
what is a significant feature of BHV-1?
it lies latent in the trigeminal ganglion and will recrudesce in times of stress
what are the clinical signs of BHV-1 causing abortion in cattle?
infectious pustular vulvovaginitis - pustule inside vulva (same on bulls penis)
abortions
milk drop (herd level)
can you vaccinate for BHV-1?
yes (protect in the face of an outbreak)
what is the most commonly diagnosed cause of abortion?
neospora
what cattle are the most at risk of neospora abortions?
congenitally infected heifers in first gestation (usually only abort once)
what are the ways a cow can become infected with neospora?
exogenous - by oocyst ingestion
endogensous - transplacental
what is the best time for testing for neospora?
at drying off (antibody levels fluctuate throughout pregnancy)
can you test the calf for neospora?
yes, but has to be done before they are given colostrum as material antibodies could pass to the calf
what can be samples of a aborted foetus to test for neospora?
brain histopathology
how can neospora be controlled?
keep dogs away from cattle feed/water and don’t allow them to eat placenta
culling seropositive cows/offspring
breed infected cattle to beef
what are the two biotypes of BVD?
cytopathic
non-cytopathic
what does the outcome of BVD infection depend on?
when the cow becomes infected during pregnancy
what are the different stages of pregnancy a cow can become infected with BVD and what are the outcomes?
0-100 days - abortion or resorption
100-120 days - immunotolerance (PI status)
120+ days - seropositive calves (abort, weak, normal)
what are the classic congenital issues of BVD seropositive calves?
cerebellar hypoplasia
cataracts
what are the two major consequences of BVD?
lowered pregnancy rate
abortions
how does BVD cause lower pregnancy rates?
epithelial lining of reproductive tract and follicle are infected (only during viraemic disease stage)
