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
