Pathology of the genital tract in the pregnant animal Flashcards
Maintenance of pregnancy
Immunological tolerance/ suppression to maintain
allogeneic foetus
Hormonal influences e.g. maintenance of serum +
uterus progesterone concentration by corpus luteum + placenta
CL dependent – all of pregnancy in cattle, goats, pigs, dogs; – early pregnancy horse, sheep, cat
Luteolysis: stressors/ systemic cytokines
parturition + abortion
Parturition initiated by foetus itself
foetal stress (incl foetal/ maternal illness, hyperthermia)→ foetal ACTH → foetal glucocorticoid → placental oestrogens ↑ → myometrial oxytocin receptors ↑ + endometrial PGF2α → myometrial contraction, luteolysis,
progesterone ↓ → relaxin secretion → placental
separation from endometrium → fresh non-autolysed foetus
• Rapid foetal death → loss of pregnancy by other
mechanisms → autolysed foetus
mechanisms of embryonic/foetal loss
Failure of zygote to attach to endometrium Early embryonic losses chromosomal abnormalities inherited disorders uterine environmental factors Late embryonic loss: after dam recognised pregnancy stage (similar causes) Foetal Losses – non-viable Placentitis → foetal ischaemia Foetal death from various causes Stillbirth – potentially viable
embryonic death
Zygotes and early embryos
15-30% loss can be considered normal in most
species
Expulsion or reabsorption
Can return to oestrus at normal interval or delayed return to service (esp cow)
Often no diagnostic material available
Chromosomal abnormalities important cause
Infections rarer including Ureaplasma spp,
Tritrichomonas foetus, Campylobacter spp
foetal death
Foetus may be aborted, stillborn
Foetus may be retained - Mummification, maceration, (Emphysema)
foetal death - uniparous
Early gestation → may lead to mummification
(or resorption or abortion)
Late gestation → usually abortion
foetal death - multiparous
If most foetuses die → generally abortion
If one or only a few die → retention; at parturition
foetuses of differing sizes and degree of
mummification (SMEDI)
outcome of foetal death
Mummification - death (sterile) → resorption of fluids, retention or abortion
Maceration - death (infected) → decomposition, foetid, foetal bones present
Emphysema - death (infected) → decomposition, v.foetid!, gas liquefaction, hazardous
mummification
Mostly in multiparous animals and most commonly in sows
No bacterial infection
Foetal skin is developed enough to withstand autolysis
Absorption of placental and foetal fluids
No odour
Closed cervix
Time point of expulsion varies
Causes include genetic, viral, protozoan infections and placental insufficiencies; no putrefacting bacteria!
Diagnosis on mummified foetus usually not possible
Usually no effect on subsequent breeding
maceration
Foetus becomes liquified
Presence of bacterial uterine infection required
Reabsorption (in early cases) or expulsion with
purulent exudate
If foetal bones developed only incomplete maceration
Foetid odour
Common with venereal infections by Campylobacter
foetus venerealis and Tritrichomonas foetus or
nonspecific endometrial infections
Consequence often pyometra or endometritis
Perforation of uterine wall by foetal bones possible
foetal emphysema
Putrefactive organisms ascending from the vagina
(gas producing organisms, e.g. clostridial organisms)
Patent cervix
Mostly associated with dystocia at or near term and
incomplete abortion
Putrefaction of foetus, which distends with foul gas
and crepitates
Advanced uterine lesions
Often fatal to dam due to toxaemia
non-infectious abortion
Estimated percentage of non-infectious causes for abortion in the UK: – Cattle: ~ 50% non-infectious – Sheep: ~ 40% non-infectious – Pigs: ~ 60-70% non infectious – Horses: ~ 60-70% non-infectious
infectious abortion
in most species haematogenous infection of placenta and foetus; some pathogens with affinity for reproductive tract e.g. Brucella spp, Chlamydophila spp, Coxiella spp
Bacterial and fungal abortions in mares mostly ascending!
Venereal infections (e.g. Tritrichomonas foetus, Campylobacter foetus venerealis)
viral + protozoal
abortion investigations
Mostly detecting infectious causes for abortions
Diagnostic success rates for abortions vary between 8 and 50% depending on species and location in the world; better success if investigating outbreaks
Conditions in the dam can cause abortion
Cooperation between owner, clinician, pathologist and laboratory essential!
Dam, placenta and foetus should be examined and sampled!
Beware of zoonotic potential of many abortion pathogens!
abortions in livestock
Sheep – 59% diagnosis rate in 2011 (high infectious rate)
70% of these are diagnosed from placental examination alone (v.important to submit placenta even if contaminated or incomplete)
Investigate if >1-2% of ewes aborting
Cattle – 16% diagnosis rate in 2011 (less infectious reasons/unknown infections?)
Uncommon but very helpful if placenta is submitted for examination.
Investigate when abortion in > 3-5% of cows or cluster of abortions
Pigs –17.5% diagnosis rate in 2011 (total of 108 submissions) - only investigate outbreaks, otherwise diagnosis is unlikely
porcine foetopathy 2011
Submission number: 108 • Diagnostic rate ~ 17.5% • Diagnosed causes included: • PRRS (4) • Parvovirus (4) • Streptococcus spp (3) • Leptospira (1) • Pasteurella (1) • Other (6)
abortion investigations
High economic impact
Zoonotic risk (always transport in leak-proof sealed bags)
Low diagnostic success
Maternal + foetal + placental factors
Look for foetal distress → meconium staining, meconium in trachea/ lung and/ or oesophagus/ stomach
Look for degree of autolysis (autolysed foetus mostly died too quickly to initiate its own parturition)
Look if foetus and placenta are appropriate size (e.g.CRL), weight and stage of development
Choose your submission wisely
Remember: abortions may involve multiple pathogens/ factors
Diagnostic sampling for abortion investigations
good detailed history
Submit placenta(e), “fresh” foetus(es) (53 x more likely to reach a diagnosis) and maternal serum
> 4 times more likely to reach a diagnosis when submitting entire foetus, placenta and serum rather than pieces of foetus!
Interpret the results you receive from the laboratory in context with the specific premise/ farm situation
Seek advice if unsure – AHVLA, SAC, AHT
non-infectious
Dystocia Twinning in mares and cows Umbilical cord anomalies Placental insufficiencies esp mare Congenital/ Genetic Aplasia/ hypoplasia adrenal gland, anomalies anterior pituitary Husbandry Seasonal infertility esp sows Toxins Nutritional Stress Induced Spontaneous (no apparent cause)
diagnosis of bacterial + fungal diseases
amniotic fluid
Predominately by culture of foetal stomach contents (lung/liver)
Selective bacterial cultures for Campylobacter spp, Listeria monocytogenes, Brucella spp, fungi
Culture not possible for some bacteria e.g. Leptospira spp: PCR of kidney tissue, Chlamydophila abortus: impression smears of placenta stained with mZN; (PCR, IHC)
Macroscopical and histopathological examination of foetal tissues and placenta
Serology – Maternal, Foetal
fungal wet preparations of foetal stomach contents (placenta)
mycotic abortions
Mainly Aspergillus fumigatus
In cattle mainly haematogenous
In horses mainly ascending infection
Mostly sporadic but outbreaks associated with poor
quality feed
Thickened leathery placenta covered with exudate
Elevated greyish plaques on foetal skin and eyelid
Diagnosis: fungal culture/ fungal wet preparation of
foetal stomach contents
diagnosis of viral abortions
PCR e.g. PRRS, EHV-1, BVD, Schmallenberg-virus, EVA, FeLV,
(Virus isolation)
Histopathology +/- IHC or IF
Serology - Maternal, Foetal (free foetal fluids)
neospora caninum
protazoa
Persistent infection in cattle
Repeat abortions rare but occur
Dog responsible for horizontal transmission
Vertical transmission most common!
Diagnosis: foetal/ maternal serology for indication
Histopathology of heart and brain/ IHC for confirmation
tritrichomonas foetus
protazoa In cattle Transmitted at coitus (lives in prepuce of male) Foetal maceration common Endometritis/ pyometra Time of abortion: 2-4 months
toxoplasma gondii
protazoa In sheep (goats) Timing of infection important Transmission by cat faeces BEWARE ZOONOSIS!
toxoplasmosis
strawberry pip appearance of cotyledons : multifocal necrosis
mummification not uncommon
Diagnosis: foetal serology (IFAT) on free foetal fluids; Histopathology+ IHC
chlamydophila abortus
enzoonotic
thick oedematous intercotyledonary tissue of placenta covered with exudate
Diagnosis: impression smears mZN stain positive
differential diagnoses include brucellosis, Q fever, (fungal)
SMEDI
pigs
piglets carried to full term
underdeveloped + still born at birth
