Reproductive Problems and Pregnancy Loss in the Mare Flashcards
What categories can mares be in when they arrive at stud?
- maiden
- foal heat
- barren
What are the signs of foal heat?
- 5 – 10 days post partum
- Foal develops diarrhoea
- Oestrus may be silent
What are the pros and cons of breeding at foal heat?
Pros
- Easy to identify and useful in mares that foal late
- Do if: post-partum events normal, mare foaled late in year
Cons
- No endometrial sloughing after parturition
- Lower conception rate and increased pregnancy loss
- Don’t if: poor involution of fluid present
Molly Malone ovulated 10 days ago on her right ovary and has a non-palpalable CL.
She has a 35mm follicle on her left ovary.
* Which structure is ‘dominant’?
* Why does she have this follicle?
* Might it ovulate?
* What will happen if it ovulates in a few days time?
Dominant structure - 10 days after ovulation, CL is dominant
She has this follicle because of follicular wave but isn’t likely to ovulate because she has high progesterone
- waves of follicular development and regression if environment isn’t suitable
If progesterone decreases, she may ovulate in the luteal phase
What causes prolonged dioestrus? What clinical signs are associated? How can it be treated?
- Caused by persistence of secondary CL in absence of pregnancy
- Up to 24% of cycles (i.e. it is common)
- Occurs as a result of a dioestrus ovulation
- Ovulation occurs in the luteal phase (the mare does not show oestrous behaviour)
- The mare produces PG at the normal time which lyses the primary CL but not the new CL (because it is too young and doesn’t respond to PG)
- The new CL can persist for up to 3 months (there is no further release of PG to lyse it)
- Uterus and cervix are typical of luteal phase
- Ovaries may be large as follicle growth continues; this may confuse the inexperienced
- Clinical signs are a failure to return to oestrus
- Treatment is single dose of PG to lyse this persistent secondary CL
It is 28th February. Dimple is a 6 year old TB mare that has been under lights since 1st December. She was teased 10 days ago and showed good oestrous behaviour and so was covered. She has been bred every other day since then.
Ultrasound imaging of the ovary and uterus, and speculum examination of the cervix are shown
- Describe the features
- What is going on?
- What do you need to do?
- Left and right ovaries - has medium sized follicles on both - moreso than she should at this time of year
- Ovaries will be size of fist
- Uterus has oedema within it
Transitional phase - high oestrogen concentration
Still in oestrus - follicle hasn’t reached ovulatory size
Treatment
- give oral progesterone (regumate for 10 days
- negative feedback effect - stop progesterone and will increase release GnRH
- Follicle will grow and ovulate which will kickstart breeding season
- exogenous GnRH or HCG to prompt follicle to ovulate
It is March 25th. Glossy Girl foaled in February and the foal heat was observed 7 days ago
Ultrasound imaging of the ovary and uterus, and speculum examination of the cervix are shown
- Describe the features in the images
- What is going on?
- What are you going to do?
On ovary image can see follicles and CL (dominant structure)
On uterus image - there is no oedema - not under influence of oestrogen
Under infleunce of progesterone from CL
Would give prostaglandin to lyse CL so one follicle will grow and ovulate
How can we shorten the luteal phase in the mare? Why would we want to?
- Most common method of manipulating the cycle is administration of prostaglandin
- Remember that this causes lysis of CL and a return to oestrus: the speed of response depends upon the stage of follicle growth at the time you administer the PG
- Single dose of PG between day 5 and 12 causes return to oestrus in 4 to 6 days(but ovulation may take up to 10 days early in the breeding season)
Jacinda is an 7 year old Irish Draft mare. She was inseminated with chilled semen shipped from Ireland yesterday.
Ultrasound imaging of the ovary (top) and uterus (bottom) are shown
- Describe the features
- What is going on?
- What are you going to do in this case?
- What actions do you need to take with respect to the ovary and why?
- What actions do you need to take with respect to the uterus and why?
On image of ovary - there is a follicle that is no longer round which indicates ovulation fossa (close to ovulation but hasn’t ovulation)
On image of uterus - fluid in uterus and oedema pattern in the wall
Mare is still in oestrus - but shouldn’t have fluid in her uterus 24 hours following breeding (should disappear after 4-6 hours following breeding)
Sign of breeding induced endometritis
Take sample from uterine fluid - expect to see >5 neutrophils per medium power field
Treat endometritis
How can you prompt ovulation in the mare?
GnRH Agonists (Ovuplant) or hCG (Chorulon)
* Place GnRH implant or inject hCG when follicle 3.5 cm in diameter
* Ovulation should occur within next 48 hours
* Therefore plan breeding 24 hours after injection
Hetty is 8 years old and presents in February for a BSE
Her vulva slopes slightly cranially but is not far from normal
Ultrasound of the uterus is shown
Describe the features you can see on the ultrasound image
What is going on?
What do you need to do?
On uterus image - bright echogenic structures in the lumen (sign of gas in uterus) because of slopey vulva
Indicates she is predisposed to developing endometritis
Surgical correction
What factors contribute to endometritis?
- Poor body condition (anus sinks cranially and vulval conformation changes)
- Urovagina
- Cervicitis
- Cervical trauma
- Uterine sacculation
- Uterine adhesions
- Uterine foreign body
What mares are most likely to have granulosa cell tumours? How do they present? What reproductive clinical signs are associated? How is it treated?
Most commonly recognised in young mares
Presentation depends on who you are!
* Medics see them as having colic
* Theriogenologists seen them as having abnormal cyclicity
* Practitioners see them as incidental findings
Reproductive clinical signs
* If produce oestrogen = persistent oestrus
* If produce progesterone = persistent anoestrus
* If produce androgens = virilisation
* Plasma inhibin concentrations may be elevated
* They don’t produce nymphomania rather persistent oestrus
Usually there is negative feedback so one ovary is very large whilst the other is very small
Treatment
- Unilateral ovariectomy
- Often cyclical activity in contra-lateral ovary does not recover until the next season
When does pseudopregnancy type 1 occur?
Pregnancy failure between day 15 and day 36
- mare has recognised that she is pregnant
- there is no return to oestrus
- primary CL will persist for its normal lifespan (about 40 days)
- CL can be lysed by the administration of prostaglandin
When does pseudopregnancy type 2 occur?
Pregnancy failure between day 36 and day 140
- endometrial cups will have formed
- there is no return to oestrus
- the secondary CLs will persist for their normal lifespan (about 150 days)
- secondary CLs cannot be lysed by the administration of prostaglandin and there is no mechanism to remove the endometrial cups
What occurs if pregnancy fails between day 1 and 5?
- pregnancy fails whilst in the oviduct
- mare has normal oestrus cycle as if never pregnant
What occurs if pregnancy fails between day 5 and day 15?
Mare has normal oestrus cycle as if never pregnant unless the pregnancy loss is associated with uterine inflammation - in which case there may be a short cycle
When does resorption, mummification and expulsion occur?
- Resorption if death of embryo
- Mummification if death of fetus whilst endometrial cups present (secreting eCG)
- Expulsion if fetal death after endometrial cups regress
When does abortion not occur following foetal loss?
when there are twins and one foal dies between day 80 – 150 whilst the other remains alive
How can chronic endometrial disease cause embryonic death?
- If the uterus is abnormal (eg has fibrosis, glandular abnormalities) it may be difficult to form a normal placenta and resorption may occur
- Sometimes called ‘Endometrosis’
- Detected on endometrial biopsy
What are infectious abortion causes? How are these investigated?
- Equine Herpes Virus
- Equine Viral Arteritis
- Placentitis (ascending commensals)
- Systemic infections
- Equine Infectious Anaemia
- Appropriate samples (fresh whole fetus, membranes and mare’s serum) should be sent to appropriate pathologist unless you are certain it is non-infectious
- If considered infectious plans must be implemented to isolate the infected mare and to prevent movement onto and off the stud
What are non-infectious causes of foetal abortion?
- Multiple conceptuses
- Umbilical cord abnormalities
- Uterine torsion
- [low progesterone]
- [stress]
- [severe malnutrition]
What is the prevalence of multiple ovulations?
- Incidence of multiple ovulations is 20%
- Prevalence of twins at 14 days is 10% of pregnancies (less in some breeds)
When do multiples conceptuses cause foetal abortion?
Incorrect diagnosis at 14 days caused by:
* Incomplete examination of the uterus (conceptuses are mobile)
* Failure to recognise twins
* Confusion of endometrial cysts
* Not counting the number of CLs
* Outcome is rarely successful as a result of competition for placental attachment area
How is equine herpes virus spread? When does it cause abortion?
EHV1 (rarely EHV4)
* Not a venereal pathogen: spread by the respiratory route
* Most abortions within 60 days of infection but most are seen after 8 months
* Common presentation: mare has respiratory disease and is then well until an unexpected abortion. Fetus normally delivered within the membranes and mare remains well
* In herds tend to get spread of abortions rather than a ‘storm’
* Some mares remain latent carriers with recrudescence when stressed (pregnant) so in a herd are a risk to other mares (there is no test for carriers)
How is equine herpes virus controlled?
- Aborting mare should be isolated from others as the aborted material is infectious
- Often isolation of the mare at the time of abortion does not reduce a herd outbreak as most mares were infected at the same time (some time earlier)
- Advise that mares are kept in groups according to stage of pregnancy
- Foals born alive may also shed virus for 1 week
- Isolate new arrivals before introducing to pregnant herd
- Control is normal via vaccination of pregnant mares at 5, 7 and 9 months of pregnancy (Equip EHV 1,4)
- Vaccination works but failures are not uncommon
How is equine viral arteritis transmitted? How does it present? How can it be prevented?
- Transmitted both via respiratory tract route and also venereally (including chilled semen)
- Classic disease is flu-like but with significant conjunctivitis, (pink eye) focal dermatitis, limb and ventral oedema
- Organism excreted at this time and in the stallion may infect the accessory glands and result in a persistent infection (mares clear infection within 1 month and develop immunity)
- Pregnant mares that get infected may abort (abortion may relate to degree of immunity or pathogenicity of virus strain)
- Aborted fetuses appear partially autolysed (unlike fresh foetuses seen with EHV) however still need appropriate pathological examination
Prevention
* Killed vaccine available in the UK (Equip Artervac)
* Administration to stallions must be accompanied by blood sampling to show sero-negative status prior to vaccination and sero-positive status post vaccination since vaccine response and infection response cannot be differentiated and without documenting vaccine response importation of stallion or his semen will be prevented
* Required every 6 months
* Although could be widely given to mares the most common procedure on a stud is demonstration of negative serology in mare prior to accepting on stud
What predisposes mares to bacterial/fungal placentitis? What do they cause? How does it present? How is it diagnosed? How is it treated?
- Ascending infection possibly associated with poor perineal conformation
- Reduces placental efficiency producing growth retardation of fetus
- Can spread to fetus producing septicaemia
- Usually vulval discharge, mammary changes and then abortion
- Placentitis can be detected by vaginal palpation and scooping, ultrasound examination
-
Treatment is culture/sensitivity but usually systemic potentiated sulphonamide and consideration of progesterone supplementation
- Local antibiotic pessary?
- NSAIDs
- Pentoxyfylline 8.5 mg/kg, orally, twice daily improves uterine perfusion
- Consider Caslick at next pregnancy
What 3 pathogens cause endometritis but not abortions?
- Taylorella equigenitalia
- Klebsiella pneumoniae
- Pseudomonas aeruginosa
What are 3 causes of stillbirths?
- Prolonged parturition
- Umbilical cord obstruction during parturition
- Premature placental separation
Sophie is 12 year old primigravida at 290 days of pregnancy. She has poor vulval conformation managed when 21 d pregnant with a Caslick procedure
Currently she has a purulent vulval discharge. Trans-abdominal ultrasound shows the combined thickness of the uterus and placenta to be 18 mm
- What is likely going on?
- What treatment are appropriate?
- Are there any risks with the treatments you propose?
- At what gestational age would the foal likely survive?
Ascending placentitis as thickness should be <8mm at this stage in pregnancy
Use systemic antibiotics and topical through cervix
Steroids
Improve perfusion
Risks
- topical could damage palcenta and initiate parturition
Foal is 40 days early at this point in time
- even at 20 days early it’s hit or miss
- cost is so high
