Practical Management of the Susceptible Mare
Introduction A more extensive account of the aetiology, pathogenesis and treatment of endometritis
in the mare can be found at the end of this lecture; diagnostic aspects have been covered
in the first lecture. The presentation here will focus on a personal approach to the
practical problem of management of the susceptible mare which the author has found to work
well in practice. It is important to remember that the underlying aetiology of the specific cause of
endometritis determines the type of treatment to be used. Recently, the following categorisation of endometritis has been introduced: The objective of the veterinary surgeon and stud farm owner/ manager should be to
produce the maximum number of live, healthy foals from mares mated during the previous
season. We could add 'as early as possible' to this in many breeding programmes. One of the main obstacles to this goal is the mare which is susceptible to recurrent
acute endometritis following mating. Mares with Acute Endometritis All the above are used to identify mares with acute endometritis, but in certain
circumstances detection of the susceptible mare can be difficult. Detection of the Susceptible Mare: Problems In the mare with subclinical endometritis there may only be subtle changes in the
uterine environment, not readily detected by current diagnostic procedures. Many mares show no signs of inflammation before mating, but will fail to resolve the
inevitable endometritis which follows mating. How can these mares be detected and subsequently managed to maximise their reproductive
potential? Management of the Susceptible Mare: Detection In many cases, the uterine luminal fluid which accumulates before mating is sterile and
contains no neutrophils (Pycock and Newcombe 1996a). The importance of these sterile fluid
accumulations is that, although initially sterile, the fluid may act as a culture medium
for bacteria which gain entry to the uterus at mating and may be spermicidal (McKinnon et
al 1993). Comparison with traditional methods for diagnosing endometritis (vaginascopic
examination; bacterial culture; cytology; rectal palpation and biopsy) supports the
statement that ultrasonographic detection of uterine fluid accumulation is faster than
conventional techniques and avoids the problems of inadvertently contaminating the uterus.
It can still be difficult to interpret the results as although in almost all cases if no
fluid is detected than no neutrophils were found on a smear (Pycock and Newcombe 1996a),
rarely this was not the case with neutrophils being found in the absence of detectable
fluid. Uterine Defence Mechanisms With the recognition that physical clearance of uterine fluid was the critical factor
in the defence against persistent uterine infection, it was a logical conclusion that any
impairment of this function rendered a mare susceptible to persistent endometritis
(Troedsson and Liu 1991). I do not believe that impaired mechanical clearance is an immunological problem and for
this reason I think the term "susceptible" mare rather than "immune
incompetent" mare may be more appropriate for these mares with a clearance problem.
The concept of susceptibility to endometritis was initially introduced by Farrelly and
Mullaney (1964) and Hughes et al (1966). Subsequently, the idea was developed further by
Hughes and Loy (1969) and Peterson, McFeely and David (1969) and formed the basis of the
present-day concept of the "susceptible" mare. Of course, not all mares have a
clearance problem and, in those mares, some immune defect is likely to be involved and
here "immune-incompetent" is an appropriate term. Management of the Susceptible Mare Ultrasound evaluation of the uterus for the detection of intraluminal uterine fluid Pre-Mating Intraluminal Fluid: Significance ? Mares with uterine fluid detected during a pre-breeding examination have a reduced
pregnancy rate (Pycock and Newcombe 1996a) The amount of fluid which should be considered significant is not clear and it may be
that quantity is more important than nature. This is particularly true of fluid appearing
during oestrus. The significance depends to some extent on when during oestrus the fluid
is observed: fluid detected early in oestrus may have disappeared when the mare is further
advanced in oestrus and the cervix relaxes more. Generally if there is more than one
centimetre of fluid during oestrus some attempt shopuld be made to remove this prior to
breeding using oxytocin. If the volume is above two centimetres, the fluid may need to be
drained and investigated for the presence of inflammatory cells and bacteria. The mare may
then need to have a large- volume uterine lavage. Fluid in diestrus is more serious and
any detectable volume nearly always indicates a problem. Uterine Fluid It has been suggested that fluid be graded from 1 to 3 according to the degree of
echogenicity. The more echoic the fluid, the more likely the fluid is contaminated with
debris including white blood cells. However, cellular fluid can appear relatively anechoic
so care is needed in interpretation. Inspissated pus can be so echoic that it is
overlooked. It may be that the actual appearance of the fluid and the ultrasonographic
appearance are not as closely linked as once thought. Ultrasonographic appearance may
relate to particle sizeand this is why the urine in the bladder can appear relatively
echoic, despite being a watery liquid. Cellular content AND particle size effect echogenicity of image Some lucent (black) fluids have high PMN counts SO do NOT place too much emphasis on grading fluid Recognition of the importance of the mechanical evacuation of uterine contents
accounted for the relatively recent introduction of large-volume uterine lavage as a
treatment for inflammatory disorders of the mare's uterus (Asbury 1990). I have found this
to be a useful therapeutic protocol in many cases. The technique involves the mechanical suction or siphonage of 2 to 3 litres of
previously warmed saline infused into the uterus via a catheter that has been retained
within the cervix via a cuff. The most convenient is a large-bore (30 French) (80 cm)
equine embryo flushing catheter (EUF-80; Bivona, USA). The rationale for such an approach are: The washings can also be inspected to provide immediate information concerning the
nature of the uterine contents. Undoubtedly large volume lavage is beneficial in many cases, particularly the mare with
a relatively large (above 2 cm depth) accumulation of fluid after breeding. Few controlled
studies on pregnancy rates have been conducted. In addition, the process is time-consuming
and there is the possibility of further contamination of the uterus by passage of a
drainage tube. For optimal practical management, the ideal method of treatment will involve the use of
a non-invasive technique with early and complete elimination of any intrauterine fluid.
This can be performed more realistically in practice when it may be difficult to justify
the time needed to large-volume lavage the uterus. Oxytocin, because of its ecbolic effect, was first suggested as a possible treatment
for mares susceptible to persistent acute endometritis by Allen (1991). It is interesting
to speculate why it was only relatively recently that a such a familiar drug as oxytocin
was suggested as a treatment for endometritis: Of course, the importance of fluid accumulation in the aetiology of persistent acute
endometritis had to be recognised. Even when this was established, many people believed
oxytocin would only induce uterine contractions after foaling. Other people believed it
would cause severe colic when given as an intravenous bolus. A third concern was that
there would be an adverse effect on gamete transport. The initial work of Allen (1991) and
subsequent clinical experience (Pycock 1994a; Pycock and Newcombe 1996b) have allayed all
these fears. The latter authors recently reported the following management protocol as useful in the
highly susceptible mare (i.e. a mare which from past experience/history is known to
produce a large amount (several centimetres depth) of luminal fluid after mating). It
should be remembered that this approach is being suggested as part of the management of
the susceptible mare and is not suggested as a routine for all mares. The protocol is as
follows: * A single breeding must be arranged 1,2 or even 3 days before the anticipated time of
ovulation. It is my experience that most stallion spermatozoa are viable at least 48-72
hours after mating and this is also supported by Umphenour, Sprinkle and Murphy (1993). In
any case records based on previous early pregnancy examinations will soon indicate if the
semen from a particular stallion is not viable after 48 hours. This early mating allows
more time for drainage of fluid via an open oestrous cervix and also utilises the natural
resistance of the tract to inflammation during oestrus. In the author's opinion, treatment
for endometritis is ideally performed on the day before, or the day of, ovulation.
Progesterone concentrations rise rapid ly in the mare and any post-ovulation treatment has
an increased risk of uterine contamination. In addition, uterine fluid is less likely to
drain if the cervix is beginning to close. * Ultrasound examination of the uterus 3-12 hours after mating is performed to assess
the amount and echogenicity of any intrauterine fluid. This examination and treatment of
mares very soon after mating before the bacteria have been long in a logarithmic growth
phase is important for the susceptible mare. Treatment has been successful as early as 2
hours after mating. * Intravenous administration of 25 i.u. oxytocin and, with scrupulous attention to
cleanliness, digital dilation of the cervix in mares that exhibit uterine fluid; oxytocin
is less effective at causing fluid drainage once the mare has ovulated. This is another
reason for ideally treating the susceptible mare before ovulation. * After 20 minutes the mare should be re-examined and any fluid pooling in the vagina
removed; * Infusion of a low volume of water-soluble broad-spectrum antibiotics (neomycin (1g),
polymixin B (40,000 i.u.), furaltadone (600mg) and 3g crystalline benzylpenicillin (Utrin
Wash, Univet Ltd., Wedgwood Road, Bicester) dissolved in 20ml of sterile water) into the
uterus via a sterile irrigation catheter. I use a low volume of antibiotic solution as, if
these mares have a drainage problem, it seems logical to use the minimum effective volume.
It is my experience that with larger volumes (above 100 ml) some of the solution is lost
via cervical reflux. * The mare is re-examined the following day and oxytocin treatment repeated if fluid is
still present. Only rarely will a second infusion of antibiotics or lavage procedure be
performed due to the risk of uterine contamination. Obviously it was impossible to be certain of the importance of each component of the
management protocol, but the results did indicate the benefit of this management regime in
mares in which subfertility is associated with intraluminal fluid. In some mares the
incorporation of large-volume lavage will be beneficial. These protocols are difficult to
apply in practice where stud farms are not being visited every day and is, therefore, best
reserved for the highly susceptible mare. Susceptibility to endometritis is not an
absolute state: failure of the defence mechanisms only needs to be of the degree necessary
to slow the process of clearance past a critical point. As many stud farms are visited on
an every other day basis for routine reproductive work, treatment schedules should be
based round these visits. Therefore, the need is for a single effective post-mating treatment for endometritis. Preliminary results from the use of oxytocin to assist uterine clearance appeared to
represent an advancement in the management of susceptible mares. In addition current
research (LeBlanc et al 1994) concluded that oxytocin enhances uterine clearance of
radiocolloid and may be useful for treating mares exhibiting impaired uterine clearance. As a further evaluation, a large controlled study was designed to critically evaluate
the efficacy of intrauterine antibiotics or intravenous oxytocin treatments, alone or in
combination, for the management of subfertility caused by persistent endometritis (Pycock
1994b). By using a large number of mares in normal clinical practice, the use of an
endometritis model was avoided. The following specific hypothesis was tested: When administered after mating,
intrauterine antibiotics and intravenous oxytocin, either alone or in combination, could
improve the pregnancy rate of mares. Materials and Methods: Summary of Results: In group 1 (non-treated) mares, more fluid accumulated in the uterine lumen after
mating, which was the most likely reason for the reduced pregnancy rates in this group.
The pregnancy rates were highest in mares which recei ved the combination of antibiotics
and oxytocin. Discussion and Conclusion: Treatments which either cause the elimination of, or reduce
the production, of intrauterine fluid, are useful in the management of post- mating
endometritis in the mare. As pregnancy rates were highest in mares given the combined
treatment, this suggested two different modes of action, namely antibacterial activity and
fluid drainage, which were additively helpful. Intrauterine antibiotic therapy has been the traditional approach to treating
endometritis and, therefore, it was considered important to include in the clinical study.
I have not seen a resistance or superinfection problem with this particular combination
reported here. Antibacterial activity may possibly be linked to reduction of intraluminal fluid since,
in those mares that were treated with oxytocin alone, some bacteria remained within the
uterine lumen and presumably the inflammatory efects of these bacteria caused further
fluid production and accumulation. The obvious conclusion from the study is that the use of oxytocin and antibiotic
intrauterine infusions is effective in increasing pregnancy rates and subsequent foaling
rates in mares. This conclusion was supported by the results of a second trial involving a
further 900 mares (Pycock and newcombe 1996b). From this it is necessary to ask the question "is it desirable to treat every mare
routinely after mating regardless of the clinical history?" The answer must be no, since treatment should be restricted to those mares which would
benefit. It may be useful to use ultrasonographic examination of the uterus to identify those
mares with uterine fluid after mating and only treat these mares. Another approach that appeared useful was to "target" categories of mares
which benefitted most from treatment in terms of pregnancy rate.This study indicated two
such categories: A) Old mares (over the age of 12); B) Mares mated at the first oestrus post-partum. Other compounds were, and still are, infused into the uterus of mares, based on the
research findings of the seventies and eighties which emphasised the immunological aspects
of the uterine defence mechanisms against acute endometritis. Early suspicions that
susceptible mares were deficient in uterine immunoglobulins led to the therapeutic use of
colostrum, an abundant source of immunoglobulins, infused into the uterus (Dewes 1980).
However, later work (Asbury et al 1980; Mitchell et al 1982) reported that concentrations
of immunoglo bulins were greater in susceptible mares. A reported deficiency of opsonin (Asbury 1984) led to the use of intrauterine plasma as
a source of opsonins. Studies following its use have indicated an improvement of fertility
(Asbury 1984; Pascoe 1994). Both authors suggested that the plasma had an enhancing efect
on phagocytosis by uterine neutrophils. Adams and Ginther (1989), in a study which
included control groups of mares, found that intrauterine plasma was not efficacious in
treating endometritis since there was no improvement in pregnancy rates. Troedsson et al
(1992) suggested that plasma treatment might only benefit certain susceptible mares. This
latter point was also alluded to recently by Pascoe (1994) who, whilst remaining
enthusiastic about the use of plasma in the management of immune-incompetent mares,
conceded that this may only apply to mares without a mechanical clearance problem.
Consequently I use plasma only in mares which repeatedly fail to become pregnant, but have
no history of fluid accumulation. Ideally, one should make an accurate diagnosis that a mare has a clearance problem as
oxytocin therapy is only likely to be beneficial in such mares. Detection of intraluminal
fluid is the best practical method. Scintigraphic and other methods based on charcoal
clearance are difficult to apply in the majority of practice-type situations. SUMMARY: PRACTICAL MANAGEMENT OF THE SUSCEPTIBLE MARE Use ultrasound evaluation of the uterus for detection of intraluminal uterine fluid, in
addition to conventional techniques of endometrial cytology and bacteriology, before
mating. Recent work has shown that, although initially sterile and free of neutrophils, mares
with uterine fluid accumulation before mating have a reduced pregnancy rate when no
treatment is performed (Pycock and Newcombe 1996a). If more than 2cm fluid are detected,
administer 3 ml oxytocin as an intravenous bolus. Confirm that the fluid has gone at the
next ultrasound examination. If intraluminal fluid is still visible, repeat the dose of
oxytocin and, possibly, digitally dilate the cervix also. Ensure good management techniques at all times. Particular regard should be paid to: A) Attention to Hygiene: i) at mating ii) at foaling: examine all mares post partum for the presence of
trauma which might compromise the physical barriers to uterine contamination; iii) at gynaecological examinations: examinations per vagina should
be performed as aseptically as possible. B) Correct timing of mating: This should ensure the minimal number of matings. C) Correction of any conformational defects. Adoption of a routine post-mating treatment policy i) Unable to detect the mare which needs post-mating treatment ii) History important iii) The most successful cycle on which to breed old barren mares is the first (NOT the
first cycle of the breeding season which is best avoided in older mares, but the first
cycle on which the mare is bred In any case evaluation of the uterus post-breeding is a crucial time to assess the
uterus of all mares and too many clincialns fail to evaluate the uterus post-breeding. I have not adopted a routine post-mating treatment policy. However, in my daily
routine, I assume that most multiparous mares are at risk for either clinical or
subclinical endometritis following insemination, be it natural or artificial. This view is
also held by Australian colleagues who claim increased pregnancy rates and subsequent
foaling rates through adoption of a routine post-mating treatment (Pascoe, personal
communication; Pascoe 1994). At a recent conference on equine endometritis, Zent (1993)
recently reported that, of 4000 brood mares under the care of members of his Kentucky
veterinary practice, all except maiden mares were routinely given at least one post-mating
intrauterine antibiotic infusion. He believed this treatment had improved pregnancy rates,
without the development of a resistance problem or an increased incidence of fungal
endometritis. Other large veterinary practices involved in stud medicine do not use
post-mating treatment to anything like this extent. This could be for two reasons: A) If a large percentage of the mares at the stud farm are young mares or mares with no
history of breeding problems, then the pregnancy rate without any treatment is likely to
be high, as few of the mares will be susceptible mares. Consequently, post-mating
treatment would have little observable benefit. B) If mares are never mated under any circumstances until endometrial swab and smear
results are negative and no uterine luminal fluid is present on ultrasound examination,
then this will also select for a high pregnancy rate in the absence of post-mating
treatment. However, if old mares, barren mares or mares with a history of being difficult to get
in foal make up a large percentage of the brood mare population at a particular stud farm,
then adoption of a routine post-mating treatment regime will probably increase pregnancy
rates. I base my decision on which treatment to adopt on history and clinical findings
including ultrasonographic evaluation of the uterus after mating. This ultrasound
examination of the uterus is very important and it is imperative it is performed in every
brood mare after mating. If the history suggests that the mare is highly susceptible to
persistent endometritis i.e. will develop significant amounts of intrauterine luminal
fluid after mating, then I consider adopting the protocol of early mating, intrauterine
antibiotics and oxytocin outlined earlier. Additionally uterine lavage may be used on one
or, rarely, two occasions. If there is no indication of susceptibility to endometritis, my treatment depends on
the ultrasonographic findings. If no uterine fluid is present, intrauterine antibiotics
alone are infused if the mare is believed to be at risk for subclinical endometritis. If
any uterine fluid is present, the mare is given 25 i.u. of oxytocin as an intravenous
bolus and re-examined 30 minutes later when intrauterine antibiotics are infused. I leave
2 x 3ml of oxytocin to be given by the stud farm personnel that evening and again in the
morning. This is by the intramuscular route. In some mares, the slower release of prostaglandin (cloprostenol 500mcg IM) may be
useful also. The mare is re-examined usually 2 days later and the uterus re-examined for fluid.
Further oxytocin treatment is given as required. Only in mares with a very poor history
and/or where significant fluid remains in the uterus is a second infusion of intrauterine
antibiotics given. I am not enthusiastic about repeated intrauterine antibiotic infusions
due to the possibility of uterine contamination. Recent work from our clinic has indicated
the usefulness of intramuscular administration of a third-generation cephalosporin for the
treatment of pyometra. This product may also be useful as a follow-up intramuscular
treatment after the initial intrauterine treatment, but this remains to be evaluated. An important concept that would appear important is to treat in relation to breeding
and not wait for ovulation My final decision to adopt a routine post-mating treatment of mares believed to be at
risk of persistent acute endometritis is dependent on balancing cost and time against
benefits to the breeder. The results of published clinical studies (Pascoe 1994; Pycock
1994b) and many breeding seasons field experience with large numbers of mares have
demonstrated the effectiveness of a single post-mating treatment to combat endometritis.
This has certainly been the case in the mares with which I have been involved. Against this demonstrable improvement in pregnancy rate, it must be examined if there
is any reason, apart from the economic reason, not to routinely treat all mares after
mating: Certainly management standards must not fall. Post-mating treatment should not be seen
as a means of getting away with poor management. No bacterial resistance problems or increase in fungal endometritis must be apparent
with the intrauterine antibiotics used. Some questions remain unanswered and a source of debate amongst clinicians. For example, Hearn (1993) recently voiced the concern that the early embryonic/foetal
loss rate of susceptible mares with endometritis who receive aggressive post-mating
therapy will be much higher despite the temporary improvement in uterine environment. This
was not supported by the clinical study reported here, perhaps because only a single
post-mating treat ment was performed. Undoubtedly the live foal-rate of mares which are
extensively treated post-breeding is less than in young, genitally-healthy mares.,
However, often susceptible mares are old and frequently when uterine biopsy results are
available, these often confim degenerative changes within the endometrium. Consequently
one's live-foal rate expectations are lower in these mares in any case. This is not a
reason to not treat mares post-mating in my opinion. Of course one should optimise the
chances for conception by the methods discussed above and in other papers, but even when
all these techniques of management, pre-mating examination etc. are applied, the
susceptible mare should still be treated post- mating. One question in particular remains less easy to address: At what point should the susceptible mare be mated and when should she be treated and
either short cycled or mated at the next natural oestrus? This must be a matter of clinical experience based on history, findings of clinical and
laboratory examinations and past results. Some clinicans remain cautious whereas others
will adopt a "mate at all costs" policy with aggressive post-mating treatment.
Hopefully this paper will allow a rational approach to the management of the susceptible
mare. REFERENCES Allen, W.E. (1991) Investigations into the use of oxytocin for
promoting uterine drainage in mares susceptible to endometritis. Vet. Rec. 127, 593-594. Cause and Pathogenesis Reduced fertility associated with endometritis, both acute and chronic, has been recognized for many years in broodmares. The term `endometritis' refers to the acute or chronic inflammatory changes involving the endometrium. These changes frequently occur as a result of microbial infection, but they can also be due to non-infectious causes. Recently, the following classification system has been introduced and is useful when considering endometritis as it occurs in the horse:
It is generally assumed that the uterine lumen of the normal fertile mare is bacteriologically sterile or may have a temporary, non-resident microflora, although bacteria have been seen in healthy uteri by scanning electron microscopy. Ricketts and Mackintosh (1987) suggested that the equine uterus may harbour obligate anaerobes as surface commensals. The environment of the uterine lumen must be compatible with embryonic and fetal life. This presents a particular problem for the mare as a transient endometritis is an inevitable sequel to coitus. Ejaculation occurs through the dilated cervix, contaminating the uterine lumen with microorganisms and debris. Parturition and a defective perineal conformation can also result in contamination. In the normal healthy mare, the induced postcoital endometritis resolves within 24--72 hours. Microorganisms and inflammatory by-prodÂucts disappear from the uterus to leave the endometrium in a satisfactory state to receive the fertilized ovum. Timing is critical, as the embryo descends from the uterine tube into the uterine lumen about 5.5 days after ovulation. In addition to being incompatible with embryonic survival, endometritis persisting after day 4 of dioestrus also causes lysis of the corpus luteum due to premature endogenous prostaglandin release so that the mare has a shortened luteal phase. In some mares the inflammation persists; these are referred to as susceptible individuals. The concept of susceptibility to endometritis was first suggested by Farrely and Mullaney (1964), who stated that infective endometritis is essentially the failure of as individual mare to limit the uterine and cervical microflora to a non-resident type. Hughes and Loy (1969) developed this concept and confirmed that resistant mares could eliminate induced infection without treatment; susceptible mares could not. In general, reduced resistance to endometritis is associated with advancing age and multiparity. Susceptibility to endometritis is not, however, an absolute state since failure of uterine defence mechanisms need only slow the process of eliminating infection. Studies on immunoglobulins, opsonins and the functional ability of neutrophils in the uterus of susceptible mares have not confirmed the presence of an impaired immune response (see the review by Allen and Pycock, 1989). Evans et al. (1986) first suggested that reduced physical drainage may contribute to an increased susceptibility to uterine infection. The physical ability of the uterus to eliminate bacteria, inflammatory debris and fluid is now known to be a critical factor in uterine defence. Since the first description of the identification of the collection of small volumes of intra-uterine fluid using ultrasound, which could not be palpated per rectum (Ginther and Pierson, 1984), general awareness of the frequency of this abnormality has increased. The detection of uterine fluid during both oestrus and dioestrus has been reported (Allen and Pycock, 1988). Endometrial secretions and the formation of the small volume of free fluid may be associated with the same mechanism which causes normal oestral oedema. Small volumes of intrauterine fluid during oestrus do not affect pregnancy rates (Pycock and Newcombe, 1996a), but in mares that are susceptible to endometritis there is an accumulation of more fluid than in resistant mares. Intrauterine fluid during dioestrus is indicative of inflammation, and associated with subfertility, due to early embryonic death and a shortened luteal phase. Initially, although a sterile transudate, fluid may act as a medium for bacteria which gain entry to the uterus at mating to multiply; it may also be spermicidal. The bacterial species which cause bacterial endometritis are numerous, and can be classified as follows:
Normally, the vestibular and clitoral area has a harmless and constantly fluctuating bacterial population. In association with benign saprophytic organisms, opportunistic organisms such as Streptococcus zooepidemicus, E. coli and Staphyloccocus spp. can be found. The stallion's penis is colonized by similar organisms. S. zooepidemicus is the most commonly isolated bacterial species from acute endometritis, particularly in the initial stages. E. coli is the next most common isolate. In addition to these opportunist pathogens, there are three bacteria which are venereally transmitted: Taylorella equigenitalis (contagious equine metritis organism, CEMO), Klebsiella pneumoniae (capsular types 1, 2 and 5) and Pseudomonas aeruginosa (some strains). Symptomless carriers of both sexes allow persistence within the horse population. Carrier mares, which may or may not have shown signs of previous endometritis, harbour the organisms in the vestibular area, particularly the clitoral fossa and sinuses. Mating or gynaecological examination may result in their transfer into the uterus. Stallions may harbour the organisms over the entire surface of the penis and in the distal urethra. Anaerobic bacteria have been isolated from the mare's uterus, with Bacteroides fragilis the most frequent. Further work is needed to assess the importance of anaerobes in endometritis.
Treatment of endometritis Antibiotic Therapy Since within 2 hours of breeding the spermatozoa necessary for fertilization are present within the uterine tube, and since the embryo does not descend into the uterus for about 5.5 days, mares may be treated safely from 12 hours after mating until 3 days from ovulation, providing non-irritant therapy is used. However, progesterone concentrations rise rapidly following ovulation in the mare and it is preferable to avoid treatment involving uterine interference beyond 2 days after ovulation. Both coitus and artificial insemination can be a source of uterine contamination; therefore, the successful management of susceptible mares should logically require some form of postmating therapy such as intrauterine antibiotic infusion and intravenous oxytocin. Uterine Lavage The rationale for such an approach are:
The washings can also be inspected to provide immediate information concerning the nature of the uterine contents. Oxytocin The author has found the following regimen to be an effective treatment in the mare highly susceptible to endometritis, i.e. the mare that will pool much uterine fluid after mating: (1) a single mating must be arranged 2--3 days before the anticipated time of ovulation; (2) ultrasound examination of the uterus 3--12 hours after mating is used to assess the amount and echogenicity of any intrauterine fluid; (3) intravenous administration of 25 IU of oxytocin and manual dilation of the cervix in mares that exhibit intrauterine fluid; (4) infusion of a low volume of water-soluble broad-spectrum antibiotics into the uterus. Asbury (1992) stated that there has been no corresponding improvement in the efficacy of the treatment of bacterial endometritis, despite the advances in the number and type of pharmacological agents available. Large field studies including proper controls are needed to critically evaluate therapy for endometritis. A recent clinical trial in over 1400 mares has shown that treatments with broad-spectrum antibiotic intrauterine infusions and intravenous oxytocin injection were effective in the treatment of endometritis and in the improvement of pregnancy rates (Pycock and Newcombe, 1996b). Intrauterine Plasma and Colostrum Infusions Colostrum is a rich source of immunoglobulins, and has been used by intrauterine infusion as a treatment. Since mares that are susceptible to endometritis do not possess a quantitative deficiency of immunoglobulins, it is questionable if such treatment should be used. In addition, transfer of infectious agents is also possible. Curettage Hormonal Therapy Prevention Treatment of venereal infections Fungal infections Diagnosis Successful culture of endometrial smears for fungi can be difficult because the organisms may be present in low numbers, and furthermore they require a long incubation period. For example, studies in Florida, USA, where C. albicans infection is very common, have shown that despite the identification of yeast buds in stained smears in the presence of neutrophils, the organism was frequently not detected following culture. Treatment Prognosis Metritis Systemic signs such as pulse rate and mucous membrane colour are used to monitor the response to therapy in conjunction with examination of the uterine fluid. Despite all efforts, some mares die due to toxaemia or irreversible changes in the foot following laminitis such as pedal-bone rotation.
References: Adams, G. P. and Ginther, O. J. (1989) J. Amer. Vet. Med. Assn, 194,
372. |
