Pregnancy complications and failure 1+2

what are the 3 times pregnancy failure occurs?

• early embryonic death

• late embryonic death

• abortion

what is meant by early embryonic death?

• pre-implantation, before maternal-foetal recognition

• doesn’t involve the elongation of the CL life

what is late embryonic death?

• peri-implantation

• occurs after CL life has been extended

what is classed as an abortion

post-implantation after organogenesis

what is fertility related to?

• ability to conceive and become pregnant - not pregnancy loss

when does pregnancy loss occur most commonly in:

Mares

• 10-14D post service

when does pregnancy loss occur most commonly in: beef cattle

• before 15d after service

when does pregnancy loss occur most commonly in: dariy heifers

• up to day 19

when does pregnancy loss occur most commonly in:ewes

• day 15-18 post service

when does pregnancy loss occur most commonly in: sows

• day 9 - blastocyst expansion

• day 13 - implantation

when do most losses of cow pregnancies occur?

• before day 21 gestation

in which 4 species does pseudopregnancy following pregnancy loss occur?

• mare

• goat

• sow

• queen

what are the 4 steps of pseudopregnancy after pregnancy loss

1. pregnancy lost after maternal recognition

2. failure of CL regression

3. progesterone secretion

4. pseudopregnancy

how many types of pseudopregnancy are there in the mare?

• 2

what is type one pseudopregnancy in the mare

• early embryonic death after maternal recognition

  • persistence of CL → prolonged luteal phase

is type 1 pseudopregnancy in the mare treatable, if so how do we treat it?

• yes

• use prostaglandin

what is type 2 pseudopregnancy in the mare

• foetal death after endometrial cup formation - at around 36 days

how long does type 2 pseudopregnancy last for?

• until the endometrial cups disintegrate - 90-150 days

how does pseudopregnancy arise in the goat?

• embryonic death after fertilisation

  • CL persists → closed cervix

  • sterile secretions accumulate in the uterus

  • hydrometra forms

what is hydrometra

• build up of fluid in the uterus - happens in goats during pseudopregnancy

can pseudopregnancy occur in goats without pregnancy loss?

• yes, cyclic, non-mated goats can experience pseudopregnancy → CL persists

• mechanism is unknown

what may chromosome abnormalities cause?

• embryo loss

how will embryo loss as a result of chromosome abnormalities affect:

1. monotocous species

2. polytocous species

1. early embryo loss with return to cyclicity

2. reduced litter size

what are 4 occasions that may cause genetic abnormalities to occur

1. inherited

2. de novo - gametogenesis

3. fertilisation

4. early embryo cleavage

what are 5 causes of genetic abnormalities?

1. abnormal meiosis

2. failure of meiosis

3. polyspermy

4. failure of polar body extrusion

5. fertilisation of oocyte and polar body at first cleavage

state 6 categories of what can cause embryonic and foetal loss

1. uterine environment

2. environment

3. infectious agents

4. husbandry/clinical

5. physiological

6. nutrition

state 3 things in the uterine environment that may affect embryonic survival

• immunological

• endocrine

• asynchrony

what are 4 environmental factors contributing to embryo loss

• climate

• stress

• teratogens

• pollutants

what are 2 husbandry/clinical things that may lead to embryonic loss

1. insemination - semen quality

2. trauma during rectal/uterus palpation

is only 1 stage of development affected that causes foetus/embryo loss?

• no it can be multiple

how do early events impact foetal survival?

• they may impact later stages → affecting survival

what may happen prior to fertilisation that affects foetal survival

• environment affecting folliculogenesis

what may happen prior to maternal recognition to cause foetal loss

• exposure of pre-implantation embryo to an abnormal environment e.g. in a lab -

what syndrome can arise in calves due to IVF?

• large calf syndrome

what are the majority of causes of abortion in bovine and ovine species?

• infectious

what are 3 routes of infection into the uterus

1. cervix

2. blood

3. CL affecting pathogens

state an infection that affects the CL

• infectious bovine rhinotracheitis

what are 2 example venereal pathogens in cattle and the type of organism each one is

1. campylobacter foetus - bacteria

2. tritrichomonas foetus - protozoa

what causes CEM in horses

• taylorella equigenitalis

what are 4 common infectious agents of abortion

1. bacterial

2. parasitic

3. fungal

4. viral

what are 4 manifestations of pregnancy loss

1. early embryonic death

2. death after infection

3. abortus tissue expulsion

4. foetal mummification

what may happen to the foetus after an early embryonic death

• tissues resorbed and animal returns to oestrus

what may follow after foetus loss due to infection

• pyometra

what may cause the expulsion of an abortus foetsu?

• during the first half of pregnancy the CL may lyse → expulsion

how does a foetus become mummified?

• foetal fluid is resorbed, membranes shrivel and uterus contracts

what happens to the mummified foetus in polytocous species?

• mummified feotus is expelled at parturition without affecting live foetuses

in which type of species is foetal mummification more common?

• multiparous species

what determins an autolytic or fresh aborted foetus?

• speed with which agent dispatches foetus and means of pregnancy being maintained: species CL dependent or independent

what is likely to occur to an aborted foetus in species with Cl dependent pregnancy?

• delay b/w time of death and lysis of CL

• autolysis likely to occur

what is likely to happen to an aborted foetus in CL independent species?

• foetal death → cessation of foetal contribution to pregnancy → placental P4 declines → foetus expelled freshly

outline the prevalence (+ cause, if any) of mummification of foetus in the pig

• very common

• due to viruses or overcrowing

outline the prevalence (+ cause, if any) of mummification of foetus in the cat

• common in large litters

outline the prevalence (+ cause, if any) of mummification of foetus in the dog

• caused by canine herpes virus

outline the prevalence (+ cause, if any) of mummification of foetus in the ewe

• seen with twins or triplets

outline the prevalence (+ cause, if any) of mummification of foetus in the mare

• rare as twin pregnancies are avoided

outline the prevalence (+ cause, if any) of mummification of foetus in cattle

• rare

• can see haematic mummification

what is an example pathogen in the sow whose impact is dependent on foetal age

• porcine parvovirus

what is an example pathogen in the cow whose impact is dependent on foetal age

• neospora caninum

• BVDV

what is an example pathogen in the ewe whose impact is dependent on foetal age

• Toxoplasma gondii

• border disease virus

what is the acronym for abortion in the sow

SMEDI

what does SMEDI stand for?

• stillbirthds

• mummification

• embryonic death

• infertility

why do we use SMEDI?

• characterises the various viral infections that affect sows and the different stages of development at time of infection

what is the classical sign of a SMEDI infection?

• full-term litter that has a few small, mummified foetuses from full-grown stillborn or live, weakly piglets

why do we see the range of different stages of mummification in sows affected with SMEDI?

• the infection has to work its way along teh horns of the uterus, therefore reaching each piglet at a different stage of development

what are the 2 classes of embryonic death in the mare and the days when they occur?

• early - <d11

• embryonic death = d14-40

what are the 2 types of foetal death in the mare and when they occur?

• early - before d150

• late - after d150

what is classed as an abortion in a mare

• expulsion of foetus and placental membranes before d300

what is classed as a stillbirth in a mare?

• expulsion of foetal and placental membranes after d300

what is the most common category of cause for eequine abortion?

• non-infectious e.g. cord abnormalities or twinning

what are 3 common bacterial infections that lead to abortion in the mare

1. streptococcus zooepidemicus

2. escherichia coli

3. staphylococci

what is a common fungal disease that causes abortion in the mare?

• aspergillus

what are 2 viral infections that cause abortion in the mare?

• equine herpes-virus 1

• equine arteritis virus - EAV

why are twins not desired in the mare?

• reduced surface area for nutrient exchange - the two placentas abut each other and each foal can’t receive sufficient nutrients

why are twins not desired in cows

1. reduces foetal growth and calf birth weight

2. freemartinism can occur

why do we not want twins/triplets/quads in a ewe?

• relative placental insufficiency and low birth weights

why do we not want enormous litters in sows?

• runts and placental insufficiency

what may occur in twin pregnancies if one foetus is lost?

• may be at an early stage

• may be mummified

• both twins may abort at mid-late gestation

what are the 3 anastamoses through which circulation b/w male and female calf may be shared, leading to free-martinism

• arterio-venous

• arterio-arterial

• veno-venous

what is IGUR?

• impaired growth and development

state 8 factors that contribute to IUGR

1. maternal nutrition

2. envrionmental contaminants

3. toxic substances

4. poor management

5. maternal intestinal malabsorption

6. insufficiency of uterus endometrium or placenta

7. temperature and stress

8. maternal/foetal metabolic and homeostatic mechanisms

what are 3 factors affecting placental efficiency

1. size/weight

2. uteroplacental blood flow

3. surface area

how may gyneacological immaturity affect the foetus?

• in adolescent ewes, if we breed at an immature body weight, the foetus and mother may compete for nutrients

how does the plane of nutrition and the age of the ewe affect foetus development

• adolescent ewes fed a moderate intake give birth to healthy lambs, higher placental and lamb weight

• the opposite for adolescent ewes fed a high nutrient intake

state the 5 most common infectious agents of ewes

1. toxoplasmosis

2. campylobacter

3. chlamydiosis

4. salmonellosis

5. listeria

what effect does shmallenberg have?

• late abortion or birth defects - malformed limbs

• affects sheep, cattle and goats

how may schmallenberg affect adult cattle

• milk drop, pyrexia, diarrhoea

what transmits schmallenberg and bluetongue virus

• culicoides species

when are we most likely to see severe consequences of schmallenberg in:

1. cattle

2. sheep

1. 3-5months

2. 2-3 months

what does schmallenberg target?

• CNS development

what 2 conditions does schmallenberg lead to?

• hydraencephaly

• arthrogryposis

why do we get arthrogryposis in schmallenberg affected animals?

• they don’t move very much therefore get lack of muscle development and fused joints

what may happen to foetuses that are infected in early gestation with schmallenberg?

• abortion

what is the issue with the prevalence of schmallenberg?

• it has a cyclicity of every 3-5 years, doesn’t circulate every year

What are 2 non-UK based viruses that express enzootic stability

• akabane virus

• epizootic-haemorrhagic disease

when does chlamydia affect ewes?

• last 3 weeks of pregnancy → abortion

How does chlamydia affect the placenta?

• causes inflammation

what are pathological features of the placenta infected by chlamydia

• thickened areas b/w cotyledons and brownish exurdate over the surface

What species of Toxoplasma affects the ewe?

• gondii

how is the effect of toxoplasma gondii in the ewe determined?

• depending on when during gestation it infects the ewe - the earlier in the pregnancy, the greater the effect

where do we find the lesions in the foetus do we see after toxoplasma gondii infection?

• brain

• liver

• kidney