Endometritis - Horse

Introduction

Endometritis is the infection of the uterine endometrium

Endometritis,Copyright RVC 2008

Equine Endometritis

Endometritis is a common cause of low fertility in the mare. It occurs following uterine contamination during covering, artificial insemination, reproductive examination, parturition and as a result of poor conformation.

Types of Endometritis

(1) Venereal Infectious Endometritis

(2) Non-venereal Infectious Endometritis

(3) Persistent Post-mating Endometritis

(4) Chronic Degenerative Endometritis

(5) Chronic Infectious Endometritis

Venereal Infectious Endometritis

Three major pathogens cause venereal endometritis in the mare:

• Taylorella equigenitalis - causing the notifiable Contagious Equine Metritis (CEM)
• Klebsiella pneumoniae - tests can be performed to identify capsule types 1, 2 and 5 which are sexually transmitted
• Pseudomonas aeruginosa - there is no available test to differentiate strains so all must be treated as pathogenic

The mare may present with vaginal discharge (ranging from scant to copious) in an acute infection. However she may also present in a carrier state, in which case there may be no outward clinical signs. Stallions are usually sub-clinical carriers of disease. All three bacteria prevent conception.

Equine Viral Arteritis (EAV) and Equine Herpes Virus 3 (EHV-3) are also classified as venereal infections however they do not cause endometritis or prevent conception.

Detailed guidelines on the diagnosis, treatment and prevention of all these infections can be found in the Codes of Practise which are followed by Thoroughbred breeders in the UK.

Non-venereal Infectious Endometritis

This occurs following infection during covering, reproductive examination or foaling. The mare will normally present with a history of infertility or early embryonic death and short cycles. There may also be evidence of vaginal discharge. Infection may be caused by:

• Bacterial Infection - Streptococcus zooepidemicus, Escherichia coli or Staphylococcus aureus
• Fungal Infection

Persistent Post-mating Endometritis

This is more common in older and multiparous mares. A transient inflammatory response is normal in the mare post-cover, however a normal immunological response is mounted and the infection cleared before the embryo exits the fallopian tube. In the cases of persistent post-mating endometritis the inflammation persists longer than 12-24 hours so that when the embryo enters the uterus the environment is still unsuitable for embryonic development, resulting in early embryonic death.

Chronic Degenerative Endometritis

Chronic degenerative endometritis aka endometriosis is degenerative change that occurs in older mares or following repeated inflammation of the uterus. If the condition is severe it may result in delayed clearance of the uterus post-cover. Definitive diagnosis can only be achieved by biopsy, which will show degenerative change of the uterus histologically.

Chronic Infectious Endometritis

Normally an underlying conformational condition such as pneumovagina predisposes the mare to chronic infectious endometritis. Infection Diagnosis is again by biopsy which should show infiltration of the endometrium with lymphocytes and plasma cells. Infection may be:

• Bacterial - Streptococcus zooepidemicus, Escherichia coli
• Fungal - more common if there is a history of multiply intra-uterine antibiotic treaments

Prognosis is guarded due to the chronic nature of the infection and the anatomical faults predisposing to infection. Surgical correction of the conformational abnormalities may be attempted.

Diagnosis

• Clinical examination may reveal vulval discharge or matted tail hairs.
• Vaginal examination should identify any discharge and increased vascularity of the tissue. Conformational abnormalities such as pneumovagina and urovagina may be evident.
• Ultrasound examination of the uterus - more than 2 cm of fluid with abnormal character suggests endometritis.
• Clitoral and endometrial swabs should be taken for culture and sensitivity. Clitoral swabs should be taken if a chronic venereal infection is suspected. Endometrial swabs should be taken during oestrus to identify either acute venereal infection or the causative organism of other endometrial infections.
• Uterine flush - the uterus should be flushed with 100mls of fluid which can then be examined cytologically.
• Uterine biopsy - this should be performed after all other tests have failed to reach a diagnosis or to definitively diagnose endometriosis.

Treatment

• Uterine lavage with copious amounts of fluid. This is beneficial because it:

- removes contaminants such as bacteria and purulent material

- stimulates uterine contractions to aid clearance

- causes mechanical irritation to the endometrium aiding healthy neutrophil recruitment

2-3 litres of saline or lactated ringers solution should be administered using a uterine flushing catheter and then drained back into the bag and inspected. Dilute Povidone iodine can also be used as a cheap alternative.

• Antibiotics (intrauterine or systemic) - antibiotic type should be guided by culture and sensitivity and activity of the drug in the uterus where possible. The length of the treatment should be proportional to the severity of infection.
• Administration of ecbolics to stimulate uterine contractility and clearance of infection - oxytocin and prostaglandin analogues
• Hormonal therapy - Oestradiol Benzoate and PG can be used to aid the clearance of infection. They are more effective during oestrus.

In the cases of venereal infections additional treatment may be required:

Acute infections: Repeated antibiotic clitoral irrigation and reintroduction of normal flora. A clitorectomy may be considered. Chronic/carrier infections: Repeated clorhexidine clitoral irrigation and reintroduction of normal flora.

Management of Susceptible Mares

(1) Identify problem mare

(2) Plan a single insemination using a stallion with high fertility rates approximately 1-2 days prior to ovulation. Semen extender may be delivered intra-uterine before cover.

(3) Ultrasound the uterus in the first 12 hours post-cover. The character and volume of fluid present should be assessed.

(4) Remove uterine contaminants via lavage and antibiotic infusion. Administer oxytocin 8 hours after treatment.

(5) Repeat ultrasound examination after 24 hours.

Treatments should not be repeated if possible as this may introduce infection.

Prevention

• Employment of strict hygiene measures during breeding, reproductive examinations and parturition
• Adherence to the Codes of Practise
• Surgical correction of any existing conformational abnormalities

Prognosis

The prognosis of this condition vary according to the type, severity and chronicity of the infection and the age of the mare.

Cattle Endometritis

Cattle endometritis is a common condition that is known by the layman as 'whites'. It occurs three weeks or more after calving and should not be confused with the more severe condition of metritis which occurs immediately post-partum. The main consequence of endometritis is poor fertility and it therefore has a major economic impact by increasing calving interval, services per conception and cull rates and by decreasing milk yield. It is reported to have an incidence of between ten and fifteen percent in dairy herds (however it is very variable from herd to herd), with the total cost of £160 per case.

Aetiology

The normally sterile uterus is contaminated by environmental microorganisms during parturition or immediately postpartum. The main bacteria involved in endometritis is Actinobaccillus pyogenes however numerous gram-negative anaerobes may also be involved. The presence of this opportunist bacteria can delay return to service and cyclical activity, prevent fertilisation and cause early embryonic death be producing a hostile uterine environment. It is also reported that it increases incidence of ovarian cysts.

Signalment

Endometritis can occur in any cow post-partum however incidence is increased by the following predisposing factors:

• Retained foetal membranes
• Dystocia
• Caesarian section or assisted calving
• Induced parturition
• Still Birth
• Twins
• Unhygienic calving environment - includes seasonal effect as indoor calving has higher endometritis rates
• Ovarian inactivity
• Parity
• Concurrent disease and nutrition - fatty liver disease and hypocalcaemia are reported to increase endometritis rates

Multiple defense mechanisms exist to prevent opportunistic infection of the uterus. The vulva and cervix provide a physical barrier to opportunist bacteria; resident bacteria in the vagina prevents the colonisation of harmful bacteria; involution and caruncle sloughing expel contaminants and tissue debris; a higher pH during oestrus prevent bacterial growth and various immunological mechanisms also act to prevent infection of the uterus. Following parturition endometritis may still occur, especially is one or more of the mentioned predisposing factors is present.

Clinical Signs

Mucopurulent vaginal discharge should be evident on vaginal exam 21 days or more post-calving. Discharge is relatively odourless (dependant on severity) and white in colour, hence the name 'whites'. The discharge should not be confused with lochial discharge or vaginitis. Rectal palpation should reveal a poorly-involuted, oedematous uterus. On a individual or herd level there may be a history of subfertility.

Diagnosis

Diagnosis should be based on the calving history and clinical signs following vaginal and rectal exam. Vets may use a scoring system to categorise the colour and odour of the vaginal discharge which indicates how severe the infection is and whether treatment is necessary. Measurements of the uterine and cervical diameter may be included in the scoring system. Definitive diagnosis can only be achieved by endometrial biopsy, however this is rarely indicated.

Treatment

Greater success is achieved with milder cases of endometritis. Treatments available include antibiotics, hormones and intrauterine antiseptics.

(1) Antibiotics

Various factors should be considered when selecting an antibiotic for the treatment of endometritis.

Criteria for antibiotic:

• appropriate efficacy in infected uterine environment
• appropriate efficacy against the causal bacteria
• no inhibition of natural uterine defense mechanisms
• appropriate concentration and duration of action in the infected uterine lumen
• little or no milk withdrawl period
• cost effective
• no detrimental effect on fertility

Generally a broad spectrum antibiotic, active against Actinobaccillus pyogenes and gram-negative anaerobes should be used. Ideal antibiotics are cephalosporins and oxytetracycline as they match the majority of criteria listed above. Some resistance to oxytetracyclines is reported and additonally some formulations cause irritation to the endometrium, therefore intrauterine cephalosporin should be considered the most effective antibiotic treatment.

Sulphonamides, aminoglycosides, nitrofurazones and penecillins have decreased activity as a result of the uterine environment and bacteria present. Metranidazole and chloramphenicol should not be used as they are banned from use in food-producing animals.

Some antibiotics are rapidly absorbed and distributed throughout the body, and in these cases it may be of more use to administer them parenterally.

(2) Hormones

Oestrogens: controversial treatment bases on the knowledge that the uterus is more resistant to infection during oestrus. It is not licensed in the EU for use in cattle.

Prostaglandins: PGF2a or analogues can be administered parenterally. They should be considered the treatment of choice if a corpus luteum is present. The administration of prostaglandins removes the inhibitory effect of progesterone on the uterus and induces oestrus, which both of these actions improve the uterine defense mechanisms. They may have an additional beneficial ecbolic effect, aiding clearance of the lumenal contents. There is no milk withdrawl period for prostaglandins, making them ideal for use in dairy cattle.

These are mainly used in chronic cases.

(3) Antiseptics

Chlorhexidine and metakresol sulphonic acid (Lotagen) antiseptic administered intrauterine are reported to be a effective alternative to antibiotic treatment, however few studies have been carried out to confirm this and detrimental effects on fertility are reported.

Prognosis

Prognosis is dependant on the severity of infection and the effectiveness of treatment. Greater success is seen with mild cases of endometritis

References

RVC staff (2009) Urogenital system RVC Intergrated BVetMed Course, Royal Veterinary College

Pycock, JF (1997) Self-Assessment Colour Review Equine Reproduction and Stud Medicine Manson

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