Pregnancy Failure Flashcards
When does pregnancy failure occur?
Early embryonic death (pre-implantation), late embryonic death (peri-implantation), abortion (post-implantation)
When is the period of maximal embryonic wastage?
Most wastage occurs very early in gestation, in cows 75% of waste occurs before day 21
What are the common causes of reproductive wastage?
Fertilisation failure, embryo mortality (early & late) & abortion
How might pregnancy loss result in pseudopregnancy?
Pregnancy loss after MRP, failure of CL regression, progesterone secretion, pseudopregnancy – can occur in the mare, goat, sow and queen
What are the two types of pseudopregnancy in the mare following pregnancy loss?
Type I – early embryonic death after MRP, persistent CL and prolonged luteal phase, treat with prostaglandin
Type II – fetal death after endometrial cup formation at day 36, lasts until demise of endometrial cups
By what two routes can chromosome abnormalities arise?
Inherited & de novo during gametogenesis, fertilisation and early embryo cleavage
What are the main causes of embryonic and fetal loss?
Nutrition, environmental, physiological, infectious agents
What developmental stages can be affected?
Early embryo mortality, maternal recognition, gamete transport, fertilisation, late embryo mortality
What events prior to fertilisation may result in embryo mortality?
Environmental influences may affect folliculogenesis, folliculogenesis may influence the embryo derived from the oocyte
How common are infectious causes of abortion?
In the minority – approximately 15%
What are the possible routes of infection?
Cervix, systemic infection, pathogens may affect the CL rather than conceptus
What are some of the common infectious agents causing abortion?
Cattle – Campylobacter fetus var. venerealis, Tritrichomonas fetus, Neospora caninum (most common), Bovine viral diarrhoea virus
Horses – Taylorella equigenitalis, Escherichia coli, Aspergillus, Equine herpesvirus-1
Sows – Porcine parvovirus
Ewes – Toxoplasmosis gondii, Border disease virus
What determines whether the aborted fetus is in a state of autolysis or fresh?
In species with CL dependent pregnancy there is a delay between time of death and lysis of the CL resulting in autolysis
In species which are CL independent for the most part of gestation fetal placenta leads to cessation of fetal contribution, thus placental progesterone declines and the fetus is expelled in a fresh state
What does the outcome of infection depend on?
The age of the fetus at the time of infection
What are the signs of porcine parvovirus or PRRS virus?
Stillbirths, mummifications, embryonic death, infertility
How does bovine BVD affect calves according to their age?
Early gestation, <100 days – virus +ve
Mid gestation, 90-125 days – virus +ve, antibody –ve
Mid to late gestation, >150 days – virus –ve, antibody +ve (normal development)
What are the common infectious causes of ovine abortion?
Schmallenberg virus, Chlamydophila abortus (main cause in the UK), Toxoplasma gondii, Campylobacter species, Salmonella species, Listeria species
What are the possible outcomes of Toxoplasma gondii infection?
Resorption, barrenness, mummification, stillbirth, abortion, live lambs
Why do Chlamydia and Campylobacter spread rapidly?
Organisms present in large numbers in aborted products
How does the incubation period for enzootic abortion differ in goats compared to sheep?
Shorter – infection and abortion can occur in the same year
What are the common causes of non-infectious pregnancy loss in the common species?
Cow – nutrition, stress, timing of insemination, conception too soon after calving
Sow – failure to establish pregnancy (pre-attachment before days 13-14), nutrition, stress, litter size, age of sow, weight of sow
Ewes – considered to be low – diet, multiple conceptus
Goats – high in Angora goats as increased metabolic demand for fibre production
What is the link between pregnancy loss and ovulation rate in the sow?
Negative correlation – as ovulation rate increases, embryo survival decreases
Is abortion a problem in the bitch and queen?
Limited evidence to suggest abortion is a clinical problem in bitch and queen
What are the various types of equine pregnancy failure?
Early embryonic death – before MRP Embryonic death – before 40 days Early fetal death – 60-100 days Late fetal death – after 150 days Abortion – before 300 days Stillbirth – after 300 days
