Pathogens involved in reproductive failure and disease 1 Flashcards
When does ovulation occur in the dog? Is this the most fertile time?
- 2 days after the LH surge
- Ovulation occurs 2 days after the LH surge; the oocytes then require an additional 2 3 days to mature, and will live for about 48 72 hours. Thus the fertile period of the bitch falls between days 4 7 after the LH surge with the most fertile days being on days 5 and 6 post LH surge
How might you differentiate pregnancy from a uterine infection (pyometra) in a dog?
- Abdo radiographs +/- ultrasound (rads will deect distended uterus and ultrasound will help to differentiate a pus filled uterus from a pregnant uterus
- uterine fluid analysis - will see heavy growth of E. coli
What are the clinical signs associated with pyometra?
- Lethargy
- PU/PD
- In open pyo - will see pus around
- tachycardic
- dehydration
- abdo mass
Is open or closed pyometra more common?
Closed pyo is more common
What host defences normally prevent bacteria from creating disease in the uterus?
- Normal flora of vulva/vagina up to cervix
- Hormones oestrogen - Increases uterine motility, mechanical expulsion of bacteria, increases blood supply to vagina and uterus, Increases neutrophil number and activity in cervix and uterus
- Mucosal immunity: Lymphoid follicles, Antibodies (IgA, IgG and IgM)
Why is dioestrus the danger time for pyometra?
- Progesterone is the dominant hormone in this stage: Stimulates secretory activity of endometrial glands, causes fluid accumulation in uterine lumen , predisposes bacteria being able to set up and colonise, Causes decreased myometrial activity -> decreased drainage, some dogs develop abnormal response to all this progesterone ‘cystic endometrial hyperplasia’, changes in the walls of the uterus, cysts develop and get increased fluid production
- E. coli is the most common pathogen and is the first on the scene: Lives nearby (transiently in vagina), normal part of vaginal flora (opportunistic pathogen) -> Progesterone facilitates E. coli binding to endometrium
What is the most common cause of pyometra?
- Although bacteria do not initiate this disease, the secondary infection accounts for most of the mortality.
- E. coli is almost always the first bacteria to invade, but it requires a compromised uterus
- Other bacteria (also normal flora) are also commonly involved
Why might a dog with pyometra be PU/PD?
- Gram negative bacteria have a substance in cell wall called endotoxin (AKA lipopolysaccharide)
- E. coli endotoxin = interferes with the action of vasopressin or antidiuretic hormone (ADH) causing relative diuresis
- Also get immune-complex deposition in glomerulus = glomerulonephritis
- All of these changes are usually reversible and should resolve once the primary problem is addressed (the pyometra)
- Don’t assume Lexie has ongoing renal disease or damage -> changes will be resolved following treatment
Is pyometra communicable?
No
Are dogs that have an ovarioectomy (comparred to an ovariohysterectomy) at increased risk of pyometra?
- No, as progesterone plays a role -> ovaries produce progesterone
- There’s no reason why a dog that has had an ovariectomy will be more at risk of pyometra compared to a dog that had an ovariohysterectomy
What are the causes of endmetritis in non-PP mares? Which specifically causes contagious equine metritis (CEM)?
- Streptococcus equi ssp. zooepidemicus (most common)
- Staphylococcus sp.
- E. coli
- Klebsiella pneumoniae
- Pseudomonas aeruginosa
- Taylorella equigenitalis -> causes CEM (venereally contagious)
Can endometritis be opportunistic in addition to a contagious infection?
Yes, it can be opportunistic (mostly endogenous/ascending infection)
What are some predisposing factors for opportunistic infections in mares?
- Post mating: inflammatory response common after mating -> 15% mares go on to develop infectious metritis
- Genetics
- Parity -> Multiparous mares overrepresented
- Perineal conformation vagina slopes ventrally
How is endometritis diagnosed?
- Culture -> can be difficult to grow
- this would be done by rectal palpation to guide biopsy forceps into the vagina
How is CEM transmitted?
- Obligate parasite of the equine genital tract
- Lives on mucosa of equine genital tract in carriers
- Venereal transmission: Usually from a carrier stallion at coitus, Possibly a carrier mare OR possibly infected semen or fomites (e.g. instruments, attendants)
