Endometritis - Cattle

Introduction

Endometritis is an infection of the uterine endometrium

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. Therefore it 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 by 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 an 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 withdrawal 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 additionally 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 withdrawal 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

Andrews, Blowey, Boyd & Eddy (2004) Bovine Medecine - Disease and Husbandry of Cattle (2nd edition) Blackwell