Equine Pregnancy Problems

Question 1

What hormones are involved in pregnancy

Answer 1

• Progesterone
• Estrogens
• eCG
• Relaxin

Question 2

Where does progesterone come from during pregnancy? How do these sources maintain pregnancy?

Answer 2

• Ovarian source is essential for maintenance of pregnancy until ~day 100
  
  • >1 ng/ml indicates presence of luteal tissue
  • ≥ 4 ng/ml consistent with pregnancy
  • <4 ng/ml if pregnant supplementation for pregnancy maintenance
  • Primary CL formed from the follicle that ovulated the oocyte
    
    • Progesterone levels peak around day 20 then decline until approximately days 40-45
  • Secondary follicles and CL
    
    • Development of endometrial cups occurs approximately days 35-38
    • Functional until approximately day 120
    • Production of equine chorionic gonadotropin (pregnant mare serum gonadotropin)
      
      • expresses both TSH and LH-like activities resulting in secondary CL
• Feto-placental progestogen production begins ~ day 70-80
  
  • Generally sufficient to maintain pregnancy after day 100
  • Low measurable maternal progesterone during this time
  • Maternal progesterone may drop <4 ng/ml after sloughing of endometrial cups
  • Progesterone peak just before foaling

Question 3

What hormones are responsible for pregnancy and fetal viability?

Answer 3

• Progestogens
• Estrogen - Estrone Sulfate

Question 4

What do the different changes in progestogen levels mean?

Answer 4

• Progestogens
  
  • Assays for progestogens produced by fetoplacental unit are not readily available
  • Some commercial P4 assays will cross-react
  • Rapid Decline (acute cases)
    
    • frequently seen in acute conditions where fetal death has occurred or expulsion is imminent
  • Precocious Rise (Chronic cases)
    
    • associated with fetal stress or placental pathology
    • Elevations for 2-3wks prior to day 310-320 are more likely to deliver live foals
    • Linked to accelerated adrenal gland maturation thus increasing production of fetal progestins leading to increased peripheral progestins in circulation

Question 5

Where is estrogen sourced from during pregnancy? what do the levels mean?

Answer 5

• After day 55 - source form fetal-placental unit
• After 3rd month of pregnancy good marker of fetal viability
• Fetal death leads to rapid decline in estrogen levels within a few days

Question 6

What is placentitis?

Answer 6

• leading cause of:
  
  • abortion
  • premature birth
  • still birth
  • hypoxic or septicemic foals
• Infection of the placenta
  
  • ascending infection of bacteria
    
    • transcervical
  • Diffuse
    
    • hematogenous

Question 7

What is the clinical presentation of placentitis?

Answer 7

• Premature udder development
• Premature lactation
• +/- vaginal discharge
• Spontaneous abortion
• Birth of septic/hypoxic

Question 8

What causes Ascending placentitis?

Answer 8

• Associated with poor anatomical barriers
  
  • Poor perineal confirmation
  • Poor cervical function/tone
• Bacteria
  
  • S. zooepidemicus
  • E. coli
  • K. pneumoniae
  • P. aeruginosa
• Fungal
  
  • Aspergillus sp.

Question 9

What is Ascending placentitis? what symptoms?

Answer 9

• Organisms originate form the vagina, skin, feces, or environment
• Ascends through the cervix to the cervical star
• Depleted area of villi
• Thickened
• Discolored
• Fibronecrotic exudate

Question 10

How can placentitis be diagnosed pre-partum?

Answer 10

• External clinical signs
  
  • premature udder development
  • premature lactation
  • vaginal discharge
• Culture and sensitivity of vaginal discharge of from external cervical os
• Combined utero-placental thickness
• endocrine testing
  
  • Blood progesterone
  • estrogens

Question 11

How is combined utero-placental thickness measured?

Answer 11

• Performed at the caudal allantochorion
  
  • Cranial of the cervical-placental junction
• landmark
  
  • middle branch of the uterine artery along the ventral aspect of the uterine body
• Measure:
  
  • caudal, ventral edge of the uterus between the middle branch of the uterine artery and the allantoic fluid

Question 12

How is fetal stress assessed using transabdominal US?

Answer 12

• Assess fetal well-being
  
  • normal HR during late gestation ~80 bpm (60-110)
  • Consistently low or high are associated with fetal stress
• Evaluate for areas of placental separation
• Echogenicity of fetal fluids
• Fetal activity

Question 13

What are the treatments for placentitis?

Answer 13

• Prolong gestation as long as possible: ≥ 320 days
  
  • Chronic in-utero stress leads to accelerated fetal maturation
• Broad spectrum antibiotics
  
  • Trimethoprim-sulfonamide 30 mg/kg PO BID
  • Penicillin and gentamicin
• Anti-inflammatory
  
  • Flunixin meglumine 1.1 mg/kg IV or PO for 7 days
• Promote uterine quiescence
  
  • altrenogest 0.044 PO BID or 0.088 mg/kg PO SID
• Anti-endotoxic and rheologic
  
  • pentoxifylline 8.4 mg/kg PO TID-QID
• Anti-oxidant
  
  • Vitamin E

Question 14

What causes hematogenous placentitis?

Answer 14

• Leptospira interogans spp (multiple serovars)
• Nocardioform actinomycete
  
  • Crossiella equi or Amycolatopis spp

Question 15

What happens in hematogenous placentitis caused by leptospira interrogans spp.?

Answer 15

• subspecies pomona - most abortions
• Mare is typically systemically ill
• Infects the fetus hematogenously
  
  • results in abortion, stillbirth, premature live birth
• Dx: Placenta - spirochetes on silver stain

Question 16

What happens in hematogenous placentitis caused by nocardia actinomycete

Answer 16

• Crossiella equi or Amycolatopis spp
• Characteristic placentitis
  
  • Thick, brown mucoid exudate at the jungiton between the gravid horn and the body
• Dx: confirm with culture

Question 17

What are the different events that result in mares being pregnant with twins? why?

Answer 17

• Two eggs, Two ovulations: dizygotic twins
  
  • Different genomes
  • synchronous and asynchronous ovulations
  • higher incidence in TB, draft and warmblood mares
  • Higher incidence with ovulatory drugs
• One egg, one ovulation: monozygotic twins
  
  • splitting of a single fertilized ovum
  • Identical genomes
• Two eggs, one ovulation: dizygotic twins
  
  • different genomes

Question 18

What are the possible outcomes of twin pregnancies in mares?

Answer 18

• Mare reduction of twins to single pregnancy
  
  • Unilateral fixation: 70-89% reductions
  • Bilateral fixation: 4-30% reduction
• Late Term abortion: 64.5%
  
  • placenta contact with the uterus becomes insufficient to maintain fetal life
• Premature udder development/lactation
• Dystocia/neonatal death
• Birth of small, growth retardd foals

Question 19

How are twin pregnancies diagnosed?

Answer 19

• Transrectal US: ideally 14 days post-ovulation
  
  • Prior to fixation
• Cysts or twins?
  
  • Embryo changes location
  • Embryo grows 3 -4 mm/day
• Transabdominal US: >80-90 days post-ovulation
  
  • different location, orientation, HR, size

Question 20

How can twin pregnancies be reduced by vets?

Answer 20

• Pinching
• US-guided allantocentesis
• US-guided fetal cardiac puncture
• Cranio-cervical dislocation

Question 21

What is the success of medically reducing twins in mares (besides pinching)

Answer 21

50% of mares maintain the remaining fetus

Question 22

What is the process of “Pinching”

Answer 22

• 90-95% success rate of mares carrying the remaining fetus to term
• Bilateral horns or manual separation prior to fixation
• Pre-treat mare with NSAIDs & for 3-4 days
• Pre-treat and maintain on progesterone for 10-14 days
• Re-evaluate remaining vesicle 2-3 days post pinching
• Monitor progesterone levels

Question 23

What is Equine Herpesvirus Abortion? How can this be prevented?

Answer 23

• EHV-1 & EHV-4
  
  • EHV-1 most common infectious cause of abortion
  • Highly contagious, transmission usually through respiratoy
  • Latency
  • Usually later term abortion (7mo - term)) may occur 2 wks to months post-infection
    
    • Mares abort suddenly w/out signs
    • Aborted fets normally fresh
    • Submit paired serum samples form mare and fetus plus fetal membranes
  • Foals may be born stillborn or weak or appear normal thn become clinical w/in 1-3 days
  • Mares recover with short-lived immunity, but future fertility is not compromised
• Prevention
  
  • management
  • Vaccinate mares at (3), 5, 7, & ( months of gestation with modified live or killed EHV-1
    
    • pneumabort-K or Prodigy

Question 24

What is Equine Viral Arteritis? How does it cause abortion?

Answer 24

• Abortion typically occurs 7-10 days following maternal illness
  
  • leukopenia, serous nasal discharge, ocular discharge, conjunctivitis, edema of limbs and ventral abdomen, petechiation, and fever
  • +/- respiratory signs
• Aborted fetus is often autolytic but may be fresh
  
  • most occur between 5-10mo gestation
• Transmission:
  
  • Aerosolized
  • Venereal: Mare ⇠⇢ stallion, semen, aborted tissues, placenta and fetus
    
    • Stallions may become long-term carriers
    • Infected/shedding stallions may be bred to seropositive or vaccinated mares
      
      • strict isolation for 3 wks following breeding to prevent shedding to naïve horses
• Vaccination: modified live
  
  • serotest stallions prior to initial vaccination and vaccinate annually

Question 25

What is Mare Reproductive Loss Syndrome?

Answer 25

• Pathogenesis: Unknown
  
  • Ingestion of Eastern Tent Caterpillar
  • Barbed setae on cuticle that may contain bacteria penetrate the intestine and distribute hematogenously throughout the mare
• Foals: early fetal loss, late fetal loss, pericarditis, pneumonia, umbilical cord inflammation, neurological disease, asphyxia
• Adults: placental separation (red bag), pericarditis and uveitis

Question 26

What is fescue toxicity? How does it affect pregnancy? how can it be prevented/treated?

Answer 26

• Acremonium contaminated fescue
  
  • ergot alkaloids act as dopamine receptor agonists (low circulating prolactin)
  • agalactia and FPT
• Pregnancy affects:
  
  • Thickened placenta
  • Prolonged gestation
  • Decreased relaxin
  • Large dysmature foals
  • Dystocia
  • Abortion or neonatal death
  • Retained placenta
• Tx:
  
  • Dopamine antagonists
    
    • domperidone, sulpiride
    • Starting 1mo prior to foaling
• Prevention:
  
  • Pasture management to control infestation
  • Supplemental feeding of non-fescue hay
  • Endophyte free fescue
  • Remove from pasture 90 days prior to foaling

Question 27

What are causes of abdominal enlargement during pregnancy (not the baby!)

Answer 27

• Ventral edema
• Prepubic tendon rupture
• Hydrops allantois
• Hydrops amnion

Question 28

Why does Prepubic tenon rupture occur? what happens after?

Answer 28

• Occurs:
  
  • late gestation
  • predisposed mares - hydrops, twins, lack of muscle tone
• Post rupture:
  
  • Present with abdominal pain and reluctance to walk
  • Abdomen is dependent ventrolateral and has thick plaque of edema
  • Udder loses support, blood vessels in the mammary gland can rupture resulting in blood in the milk
• Treatment:
  
  • abdominal support
  • induced assisted foaling
  • C-section
• Poor Prognosis
• Mares should not carry future pregnancies

Question 29

What is Hydroallantois?

Answer 29

• Thought to develop as a result of placental dysfunction
  
  • increase production of transudateDisruption of transplacental fluid absorption
• Excess allantoic fluid (100-200 liters)
• Fast distension over 10-14 days
• Typically present after 7th month of gestation
• Dx:
  
  • excessive abdominal enlargement
  • large fluid filled uterus
  • reluctance to walk, dyspnea, altered gait

Question 30

What are the possible sequelae of hydroallantois

Answer 30

• uterine rupture
• abdominal muscle rupture
• inguinal herniation
• abortion, stillbirth
• uterine inertia
• hypovolemic shock
• retained placenta

Question 31

What is the treatment for Hydroallantois

Answer 31

• Induce abortion
  
  • pre-treat with IV fluids
  • Manual cervical dilation
  • Puncture membranes
  • slow fluid drainage
  • Manual extraction of the fetus
  • hypovolemic shock

Question 32

What is the affect of hydroallantois on future fertility?

Answer 32

• Good prognosis