compared to 40-50 min), their use post-ovulation is not recommended because it
may compromise subsequent corpus luteum function.
Recalcitrant or recurrent infections
The most challenging cases are those in which infection fails to respond to
appropriate treatment. Fungal infections are, in this respect, a special case in that
they are often very difficult to resolve, presumably in part because establishment of
infection with these opportunistic pathogens requires underlying predispositions that
compromise innate resistance; the predispositions almost certainly need to be dealt
with to allow a reasonable chance of clearing the infection. Where a bacterial
infection is not cleared by appropriate treatment or returns soon after, further
investigation for additional predispositions is also warranted. This can be as simple
as checking the competence of the vulval seal but should also include vaginal
examination to establish that the vestibulo-vaginal sphincter is functional and the
cervix is competent (i.e. neither torn and unable to close properly, nor fibrosed and
unable to relax adequately). Hysteroscopy may also be indicated, since it can reveal
the presence of unexpected abnormalities such as adhesions or foreign bodies that
can act as a source of, or nidus for, infection. In the absence of a suitable
endoscope, ultrasonographic examination of a fluid-filled uterus can help identify
adhesions, as strands spanning the lumen or failure of a horn to fill normally.
If and when underlying abnormalities have been addressed, mares with recurrent
problems will require frequent monitoring and early and aggressive treatment
(ecbolics, uterine lavage) of any problems surfacing in the period around
insemination. There is also increasing evidence that strategic use of
immunomodulators, in particular corticosteroids, may normalize the disturbed uterine
inflammatory response thought to underlie heightened susceptibility to PMIE.
Conclusions
While identifying and treating pre-existing microbial endometritis remains an
important element of mare fertility management, intensive monitoring of mares
thought to be susceptible to post-breeding endometritis is essential to allow early
identification of delayed uterine clearance so that early and aggressive therapy can
be initiated to prevent the establishment of PBE. Persistent or recurrent uterine
infections are a relatively uncommon problem but, when they do occur, present a
considerable diagnostic and therapeutic challenge. There is increasing speculation
that endometrial swabbing may fail to identify some organisms because they are
somehow either localized or sequestered within the uterus (e.g. deep in the
endometrium, dormant, in biofilms, partially walled off). Small volume lavage may
improve sensitivity of detection by sampling from the entire uterus, while a biopsy
allows examination of the deeper layers of the endometrium and may give useful
additional information about degenerative changes. Initial manipulations can also
trigger a response that facilitates successful detection of an infection 1-2 days later.
In recalcitrant cases, however, a more thorough examination of the entire genital
tract, and for coincidental endocrinological abnormalities (e.g. PPID), is warranted to
uncover and allow correction of any predisposing factors.
Proceedings
of
the
South
African
Equine
Veterinary
Association
Congress
2016
14