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REPRO > Pregnancy failure > Flashcards

Pregnancy failure Flashcards

1
Q

What is meant by early embryonic death?

A
  • Pre-implantation phase
  • Before foetal-maternal recognition of pregnancy
  • Does not involve elongation of life of CL (PgF2a released by endometrium)
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2
Q

What is meant by late embryonic death?

A
  • Peri-implantation phase
  • Occurs after life of CL has been extended
  • Luteotrophic factor (MRP) has been released
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3
Q

What is meant by abortion?

A
  • Post-implantation phase
  • After organogenesis (organs formed, ossification)
  • Material to to be born
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4
Q

When does maximal embryonic wastage occur in cows?

A
  • Days 8-18 after insemination

- Late mebryo mortality occurs days 21-42

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5
Q

What occurs in the first 21 days post-insemination in the cow?

A
  • Fertilisatoin
  • Early embryogenesis
  • Maternal recognition of pregnancy
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6
Q

What occurs at around day 21 in the cow in terms of pregnancy?

A
  • Placentomes visible, contact between endometrium adn allantochorion
  • Prior to this placenta is diffuse
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7
Q

What is the main form of embryo wastage in the cow?

A

Early embryonic death (before day 21)

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8
Q

What is meant by embryonic death in the horse compared to foetal death?

A
  • Embryonic: before 40d gestation

- Foetal: after 60d gestation

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9
Q

In the mare, what percentage of embryo loss occurs

a. before maternal recognition (early)
b. before 40d gestation
c. later than 60 days

A

a. 5-24%
b. 8-17%
c. 10%

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10
Q

What are the two types of foetal death in the mare?

A
  • Early (before d150)

- Late (after d150)

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11
Q

What are the two types of early foetal death?

A
  • Type 1

- Type 2

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12
Q

Describe type 1 embryonic death in the mare

A
  • Early embryonic death after maternal recognition
  • 15 days
  • Persistence of CL and prlonged luteal phase
  • Treat with prostaglandin
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13
Q

Describe type 2 embryonic death in the mare

A
  • Foetal death after endometrial cup formation at 36 days
  • Lasts until demise of endometrial cups (90-150 days)
  • Endometrial cups secrete eCG which is luteotrophic
  • Maintian primary CL and form and maintain accessory CLs
  • No treatment, wait for cups to complete cycle
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14
Q

List some causes of embryonic/foetal loss

A
  • Chromosomal abnormalities
  • Nutrition
  • Environmental
  • Physiological
  • Infectious agents
  • Insemination
  • Trauma
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15
Q

Describe chromosomal abnormalities as a cuase of embryonic/foetal loss

A
  • Inevitable
  • In monotocous species causes early embryonic loss with return to service
  • In polytocous, loss of chromosomally abnormal butkeep normal ones
  • May be inhereted or arise de novo through gametogenesis, fertilisation and early embryo cleavage
  • Abnormal meiosis, polyspermy, failure to extrude polar bodies
  • Less likely in animals than humans as select for high fertility and ability to carry to term
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16
Q

What is meant by fertility?

A

The ability to conceive and become pregnant, not ability to maintain pregnancy

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17
Q

Give an example of a nutritional deficiency that may lead to embryonic/foetal loss

A

Vitamin A and E deficiency in cows and pigs especially

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18
Q

Give examples of environmental factors that may lead to embryonic/foetal loss

A
  • Climate
  • Stress
  • Teratogens
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19
Q

What are teratogens?

A

Environmental factors that induce foetal abnormalities during developmental process, early embryo very susceptible, become sensitive again during CNS and CRS development

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20
Q

Give examples of physiological factors that may lead to embryonic/foetal loss

A
  • Ovulation rate
  • Uterine environment - asynchrony of uterus, ovary and embryo
  • Immunological (recognition of embryo as foreign body)
  • Endocrine
  • Failure of maternal recognition of pregancy (lack of preogesterone, esp cows)
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21
Q

Outline how insemination may lead to embryonic/foetal loss

A
  • Semen quality - may affect fertilisation/embryo quality

- Given in error during early pregnancy, may cause embryo loss

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22
Q

Outline how trauma may lead to embryonic/foetal loss

A
  • PD by rectal palpation after 42 days

- Palpation of uterus can cause substantial embryo mortality if performed in early pregnancy

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23
Q

How may things prior to fertilisation result in embryo mortality?

A
  • Environmental influences affecting folliculogenesis

- May influence quality of embryo derived from that oocyte

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24
Q

Give the proportion of causes of equine abortion (non-infectious, infectious, unknown)

A
  • Non-infectious 70%
  • Infectious 15%
  • Unknown 15%
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25
Q

How may pregnancy loss result in pseudopregnancy?

A
  • Maternal recognition of pregnancy
  • Failure of CL regression
  • Progesterone secretion continues
  • Pseudopregnancy maintained
  • Usually longer than normal pregnancy, as no parturient signal for luteolysis
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26
Q

What causes hydrometra in goats?

A
  • Fertilisation followed by embryonic death
  • CL persists
  • Accumulation of sterile secretions
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27
Q

Explain how pathogens may enter the pregnant uterus

A
  • Cervix - ascending infections, can occur with cervical incompetence or competent cervix (commensal or venereal)
  • Systemic infection
  • Pathogens affecting CL e.g. Infectious Bovine Rhinotracheitis (IBR)
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28
Q

What is the main bacterial cause of early embryonic death in cattle?

A

Campylobacter foetus var. venerealis

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29
Q

What is the main protozoan cause of early embryonic death in cattle?

A

Tritrichomonas foetus

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30
Q

What is the main bacterial cause of early embryonic death in horses?

A

Taylorella equigenitalis (CEM)

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31
Q

How are agents causing infection and early embryonic death introduced into the reproductive tract?

A

Via spem i.e. are venereal

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32
Q

What are common infectious agents causing abortion

A
  • Bacterial
  • Parasitic
  • Fungal
  • Viral
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33
Q

Outline the clinical signs of early embryonic death

A
  • Tissues resorbed

- Animal returns to oestrus

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34
Q

Outline the clnical signs of death followig infection

A
  • Pyometra may follow

- Cattle: CL persists, closed cervix and pus accumulation

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35
Q

Outline the clinical signs abortion

A
  • Expulsion of abortus tissue
  • Lysis of CL
  • May be in state of autoysis or fresh depending on speed with which agent dispatches foetus and means by which pregnancy is maintined
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36
Q

Outline the appearance of papyraceous mummification

A
  • Foetal fluids resorbed
  • Foetal membranes shrivelled
  • Uterus contracts
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37
Q

Describe foetal mummification in polytocous species

A
  • Mummified foetus expelled at parturition with no harm to live foetuses
  • Develops in multiparous bitch, queen and sow
38
Q

Outline abortion in species what CL dependent pregnancy

A
  • Pigs, goats, cows up to 200 days
  • Delay between time of death adn lysis of CL
  • Autolysis likely to occur (e.g. bovine herpesvirus 1)
  • Mummified calves have unusual appearance
39
Q

Describe the appearance of mummified calves

A
  • Fluid resorbed
  • Foetus and membranes covered in viscous chocolate coloured material
  • Haemorrhage of caruncles is a consequence of abortion
40
Q

Describe abortion in CL independent pregnancy

A
  • Ewes, mares
  • Foetal death leads to cessation of foetal contribution
  • Placental progesterone declines
  • Foetus expelled in fresh state immediately following death
41
Q

Describe foetal death in twin pregnancy in teh mare

A
  • One foetus grows more slowly than the other, smaller
  • Smaller dies and if other survives then dead will mummify
  • Will be delivered at term with llife foal
42
Q

Outline the treatment of prolonged gestation in cattle

A
  • Treat with PG to stimulate expulsion
  • Must be sure foetus is expelled to prevent foetal maceration
  • Bacteria enter uterus, digest soft tissues leaving bones
  • Bones embedded in uterine wall = endometritis and endometrial damage (slaughter)
43
Q

Give a key example of a pathogen of sows causing abortion

A

Porcine parvovirus

44
Q

Give key examples of pathogens causing abortion in cows

A
  • Neospora caninum

- Bovine viral diarrhoea virus (BVDV)

45
Q

Give a key examples of pathogens in ewes causing abortion

A
  • Chalmydial enzootic abortion
  • Toxoplasma gondii
  • Border disease virus
46
Q

What is SMEDI?

A

Stillbirths, mummification, embryonic death, infertility in teh sow
- Characterises a number of viral infections in the sow

47
Q

Describe the classical signs of SMEDI infection

A
  • Full term litter with small mummified foetuses (closer to uterine body) and full-grown stillborn or live weakly piglets (at ends of horn)
  • Progressive infection in utero along horn
  • Abortion rarely occurs
48
Q

What are common causes of SMEDI in sows?

A
  • Porcine parvovirus
  • PRRS
  • Less frequently by enteroviruses
49
Q

Give common bacterial agents of abortion in the mare

A
  • Streptococcus zooepidemicus
  • E. coli
  • Staphylococci
  • Mostly opportunistic
50
Q

Give a common fungal agent of abortion in the mare

A

Aspergillus

51
Q

Give common viral agents of abortion in the mare

A
  • Equine herpesvirus-1 (EHV-1)

- Equine arteritis virus (EAV)

52
Q

Describe the mechanisms of pregnancy failure in a mare with multiple conceptuses

A
  • Placenta is epitheliochorial
  • Conceptuses reliant on nutrition from entire surface
  • 2 embryos, not enough nutrients for each
53
Q

Describe the manifestations pregnancy loss in twin pregnancies in the mare

A
  • One foetus resorbed at an early stage
  • One foetus mummified at an early stage
  • Both twins aborted, usually mid to late gestation
54
Q

List common infectious causes of ovine abortion

A
  • Chlamydophila abortus
  • Toxoplasma gondii
  • Campylobacter species
  • Salmonella species
  • Listeria species
  • Schmallenberg virus
55
Q

Describe Schmallenberg virus

A
  • Late abortion or birth defects in newborn sheep, cattle and goats
  • Milk disease in adults (milk drop, pyrexia, diarrhoea)
  • Transmitted by insect vectors
  • No evidence of zoonosis
  • Foetal deformities vary depending on when infection occured during pregnancy
56
Q

List signs of Schmallenberg virus in newborn sheep

A
  • Hydrancephaly - often seen as deformed head but may appear nromal but unable to stand/suckle
  • Born with flexed forelimbs, overlong fixed hindlimbs, twisted spine, abnormally flexed deformed legs (arthrogryposis)
  • Bracynathia inferior (undershot jaws, parrot jaw)
  • Prevents priming of muscles so unable to stand
57
Q

During which period are sheep and cattle most sensitive to Schmallenberg virus?

A
  • When the CNS is developing
  • Cattle: 3-5 months
  • Sheep: 2-3 months
58
Q

Discuss vaccination against Schmallenberg virus

A
  • 3 vaccines: Bovilis SBV, SBVvox, Sulvac SBV
  • All inactivated virus vaccines
  • Uptake by farmer low
  • None currently available
59
Q

Describe Chlamydial abortion in sheep

A
  • Main cause of ovine abortion in UK
  • Last 3 weeks of pregnancy
  • Placental damage from day 90 colonised by bacteria, inflammation
  • Causes abortion storms (over 30% of ewes)
  • Housed, intensive flocks
  • Immune mechanism protecting mother does not control once in placenta
  • Nutrition limited during gestation
  • High levels of organisms present in abortio products, contamination of envronmetn and other ewes
60
Q

Describe the signs of Chlamydial abortion in sheep

A
  • Lambs weak, susceptible to other infections, low survival

- Placenta has thickened areas between cotyledons and brownish exudate over surface

61
Q

Give important features of Chlamydial abortion control

A
  • Isolate aborted ewes and aborted material
  • No cross fostering of lambs as will pass infection from ewe to new lamb
  • Vaccines available
62
Q

Describe Toxoplasma gondii

A
  • Intracellular protozoan
  • Sheep intermediate hosts
  • Infection by ingestion of oocysts in food, water etc
  • Time of infection and infective dose detemines impact on foetus
63
Q

What is the effect of Toxoplasma gondii in early, mid and late gestation

A
  • Early: large damage
  • Mid: medium damage
  • Late: low damage
64
Q

Describe the features of abortion due to toxoplasma gondii

A
  • Lesions in brain, liver and kidney of aborted foetus
  • Resorption, barrenness, mummification, stillbirth, abortion, live lambs all possible outcomes
  • Dark red placental cotyledons with white speckles of necrosis
  • Gritty texture of cotyledons
65
Q

Describe Campylobacter as a cause of abortion in sheep

A
  • Abortion in last 6 weeks of gestation
  • Birth of live weak lambs
  • Spreads rapidly due to organisms in aborted material
  • No lesions present in placenta
  • Areas of necrosis in foetal liver (white rings)
66
Q

Describe non-infectious pregnancy loss in ewes

A
  • Low incidence
  • Not usually detected until day 90
  • Associated with multple rather than single conceptions
  • Incidence of early embryonic death 20-33%
  • May be due to ingestion of phytoeostrogens
  • Structure defects of genital organs (limited cause)
67
Q

List common agents causing abortion in goats

A
  • Most agents causing abortion in sheep will also cause abortion in goats
  • Toxoplasma
  • Chlamydophila species
  • Listeria species
  • Coxiella species
68
Q

Compare enzootic abortion in sheep and goats

A
  • In goats infection and abortion can occur in the same year

- In sheep, abortion will occur the year after infection

69
Q

Outline non-infectious pregnancy loss in goats

A
  • Habitual abortion in most breeds, aborters usually culled
  • Angora goats have high abortion rates due to high metabolic demand for fibre production, causing nutritional stress and hypoglycaemia (abortion 90-120 days of gestation)
70
Q

Describe habitual abortion in goats

A
  • Genetically determined hyperactivity of maternal adrenal cortex
  • Initiates parturition
  • Foetuses dead and oedematous
71
Q

What is the most common cause of abortion in cows?

A

Neospora caninum

72
Q

List important causes of abortion in cows

A
  • Neospora spcecies
  • Bacillus lichenformis
  • Arachnobacter pyrogenes
  • Salmonella dublin
  • BVD
  • Other (nutrition, stress, timing of insemination/conception)
73
Q

Describe the effects of gestation age at time of infection with bovine BVD

A
  • Early: <100 days, abortion, mummification, or in few cases stillborn or alive, virus +ve
  • Mid: 90-125+ days, abortion, mummification, cerebellar hypoplasia, ocular/retinal lesions, epidermal lesions, other defects, virus +ve, Ab -ve
  • Late: >150 days, term calf, normal development, virus -ve, Ab +ve, persistently infected, can become cytopathic
74
Q

List major causes of non-infectious pregnancy loss in the cow

A
  • Nutrition
  • Stress
  • Timing of insemination
  • Conception toosoon after calving
75
Q

Describe nutrition as a cause of non-infectious pregnancy loss in the cow

A
  • Vitamin deficiencies in vit A, sleenium, phosphorous, copper
  • Negative energy balance
  • High intakes of rumen-degradable protein (high urea or ammonia in blood)
  • INgestion of dietyar phytooestrogens
76
Q

Give examples of stress that may cause abortion in cows

A
  • High temp and humidity - fertilisation filaure and early embryo mortality
  • Environment, psychological, milk milk yield in early lactation
77
Q

How does timing of insemination affect abortion in cows?

A

Too late in oestrus period leads to ovum ageing and embryonic death

78
Q

How does conception too soon after calving lead to abortion?

A

High embryo loss likely to due poor uterine environment

79
Q

In the sow, what groups can pregnancy failure be divided into?

A
  • Failure to establish

- Failure to maintain an established pregnancy

80
Q

Describe failure to establish pregnancy in sows

A
  • Unattached conceptuses susceptible to damage
  • High incidence of late returns ot oestrus
  • Can be due to lack of maternal recognition, stress e.g. gilt aggression, infection
  • Infection most likely cause
81
Q

What are the sensitive periods during which a pig conceptus is more likely to react to an adverse agent?

A
  • Pre-attachment: before days 13-14
  • Embryonic: days 14-35
  • Foetal: after day 35
82
Q

How does ovulation rate correlate to emrbyo survival in the sow?

A
  • Negative correlation
  • Increased ovulation rate leads to decreased embryo survival
  • Increased competition for uterine space
83
Q

Outline how nutrition affects embryo survival in the sow

A

High energy levels post service reduce embryo survival

84
Q

Outline the effect of stress on embryo survival in the sow

A
  • Increased stess reduces survival
  • Temperature, management etc
  • Avoid moving sows
85
Q

Give examples of intrapartum factors that affect embryo survival in the sow

A
  • > 20 mins between births
  • Litter size: most deaths in last 3rd of litter due to secondary uterine inertia
  • Older sows with more than 5 litters have increased intra-partum death
  • Weight of sow
  • Environmental stress - Temperaure, small farrowing crates
86
Q

Give examples of post-partum factors that lead to neonatal death

A
  • Mostly overlaying or chilling

- Lactation shorter than 3 weeks markedly increases piglet mortality

87
Q

Give the main causes of pregnancy wastage in the bitch

A
  • Abnormal uterine environment e.g. cystic endometrial hyperplasia
  • Foetal defects
  • Progesterone deficiency
  • Infectious agents
88
Q

What is the main cause of pregnancy wastage in the queen?

A

Progesterone deficiency

- Little evidence of abortion being a clinical problem in queen

89
Q

Describe how sheep become infected with Chlamydia

A
  • Ingestion/inhalation of infectious material

- Tonsil lymphoid tissue is primary site of infection, spreads via blood to caruncles then to placenta

90
Q

What diagnostic tests can be used for Chlamydia

A
  • Serological testing
  • Aborted material
  • post-mortem of lambs
  • Bacterial cultre from swab
  • Examination of fresh placenta
  • Ziehl-Neelson staining of placenta

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