some cases, the manipulation involved in recovering a swab or inseminating the
mare can reactivate such a ‘latent’ infection, and this is essentially the rationale
underlying the use of Tris-EDTA (to disrupt biofilms), N-acetyl cysteine (to remove
excess endometrial surface mucus) or Bactivate® (to activate ‘dormant’ streptococci)
to uncover a latent infection. How often such treatments are really helpful is, at
present, unclear although they are only likely to be of any relevance to the 10-15% of
mares that fall into the category ‘susceptible’ to persistent mating-induced
endometritis (PMIE).
Therapy
In terms of the therapeutic approach, endometritis can usefully be divided into two
major categories, pre-existing microbial endometritis, and inflammation triggered by
the introduction of semen into the uterus. Until relatively recently, the focus was on
the diagnosis and treatment of existing (i.e. prior to a proposed breeding) uterine
infections with bacteria or, occasionally, fungi or yeasts. When an active endometritis
is detected, treatment consists of uterine lavage to debulk bacteria and inflammatory
fluid, combined with uterotonics to assist uterine evacuation and (intrauterine)
administration of a course (usually 3- 5 days) of appropriate antimicrobials,
preferably during oestrus when uterine resistance to infection is maximal. In the case
of the venereally transmitted bacteria (Taylorella equigenitalis, Pseudomonas
aeroginosa and Klebsiella pneumoniae capsule types I, II and V), contemporaneous
antimicrobial treatment of the vagina and clitoris is recommended to ensure removal
of potential reservoirs for re-infection.
Fungal endometritis is an uncommon condition in mares, accounting for less than 5%
of diagnosed endometritides. It is generally accepted that fungal infection is
opportunistic and will only establish in a chronically disturbed uterine or vaginal
environment; pneumovagina, persistent endometritis and repeated intrauterine
antibiotic therapy are commonly cited as predisposing factors. Since the exact
conditions that allow fungal colonization of the uterus are obscure, there are currently
no treatments proven to offer a high likelihood of resolution, and recidivism is
common. Uterine infection with fungal organisms is therefore a considerable
therapeutic challenge with a poor prognosis both in terms of speed of recovery and
in terms of future breeding potential, since the organisms invade deep into the
endometrium where they instigate fibrotic degeneration. While both the identity of the
causal organism and the duration of infection may affect the response to treatment, it
is advisable to simultaneously correct any (suspected) predispositions (e.g.
pneumovagina) and to treat against a potential reservoir of infection in the caudal
reproductive tract (vagina and clitoral fossa). In the author’s experience, intrauterine
infusion with non-specific chemicals such as 2% acetic acid or hydrogen peroxide for
1-3 days or with anti-fungals such as clotrimazole (500mg) or nystatin (1.2 million
units) daily for 5-7 days yields a resolution rate of 20-30% per treatment cycle.
Recently, a combination of a single treatment with 2% acetic acid followed by six
consecutive days of intrauterine and intravaginal clotrimazole has yielded better
results. Resolution of fungal infection is often followed by a streptococcal
endometritis that also requires treatment. If initial treatment is unsuccessful, a period
of rest to allow spontaneous re-establishment of a normal uterine environment can
be surprisingly effective.
Proceedings
of
the
South
African
Equine
Veterinary
Association
Congress
2016
12