Puerperal metritis

What it is

After calving, the uterus of almost every cow becomes contaminated with bacteria, and in most cows the contamination is cleared during uterine involution. When defences fail or the bacterial load is high, bacteria persist and cause disease. The main organisms are Escherichia coli in the first days and, later, Trueperella pyogenes and anaerobes such as Fusobacterium necrophorum.

Postpartum uterine diseases are defined as follows:

• Puerperal metritis: within 21 days after calving, an abnormally enlarged uterus with a watery, red-brown, fetid discharge, with signs of systemic illness (reduced milk yield, dullness or other signs of toxaemia) and fever above 39.5 °C.
• Clinical metritis: an enlarged uterus with a purulent discharge in the same period, without systemic illness.
• Clinical endometritis: purulent discharge in the vagina from day 21 after calving, or mucopurulent discharge from day 26, without systemic signs.
• Subclinical (cytological) endometritis: a raised proportion of neutrophils on endometrial cytology without visible discharge.
• Pyometra: accumulation of pus in the uterus with a persistent corpus luteum and a closed cervix.

Retained fetal membranes (placenta not expelled within 24 hours after calving) are one of the main risk factors for metritis.

Who it affects

Mainly dairy cows in the first 10 days after calving. Risk is increased by dystocia, twin births, stillbirth, retained fetal membranes, hypocalcaemia, marked negative energy balance with fat mobilisation before calving and poor hygiene at calving or during calving assistance.

Anatomy involved

• Uterus: after calving it is a large, thin-walled organ filled with lochia that shrinks over several weeks. In metritis involution is delayed: on rectal palpation the uterus is enlarged, flaccid and fluid-filled.
• Placentomes and fetal membranes: the bovine placenta is cotyledonary; the villi of the chorionic cotyledons interlock with the crypts of the uterine caruncles. If they fail to separate after calving, the membranes are retained, hang from the vulva, decompose inside the uterus and favour infection.
• Endometrium: its persistent inflammation (endometritis) impairs fertility even when the cow looks healthy.
• Cervix: a large cervix and discharge passing through it point to endometritis; in pyometra it is closed.
• Severe forms can extend to the serosa (perimetritis) and cause adhesions or peritonitis.

Clinical signs

• Puerperal metritis: a fetid, watery, red-brown uterine discharge, fever, depression, loss of appetite, a drop in milk yield, ruminal stasis and dehydration, usually in the first 10 days after calving. Severe cases can be fatal.
• Retained fetal membranes: membranes protruding from the vulva; many cows show no other signs until metritis develops.
• Clinical endometritis: purulent or mucopurulent discharge in the vagina or on the tail, without systemic signs; it shows up as more days to pregnancy and more cows culled for reproductive failure.

Diagnosis

• Examination of fresh cows: rectal temperature, general condition, appetite and milk yield in the first days after calving. Fever alone is not enough for the diagnosis.
• Examination of vaginal discharge: with a gloved hand, a vaginoscope or a collection device. It is needed for clinical endometritis, because rectal palpation misses many cases.
• Rectal palpation and transrectal ultrasound: uterine size, fluid content, cervical diameter and ovarian structures (for example, the persistent corpus luteum of pyometra).
• Endometrial cytology: for subclinical endometritis.

Treatment and prevention

• Puerperal metritis: systemic antimicrobials, with supportive treatment (anti-inflammatories, fluid therapy and correction of hypocalcaemia if present).
• Retained fetal membranes: forced manual removal is not recommended, because it can damage the endometrium; the hanging part, or membranes that come away with gentle traction, can be removed. Cows that develop metritis are treated with antimicrobials.
• Clinical endometritis: the treatments used (prostaglandin F2α, intrauterine antimicrobials) have limited support; many cows recover on their own.
• Prevention: good management of the dry and transition periods (body condition, intake, prevention of hypocalcaemia), clean calving pens, hygienic calving assistance given only when needed, and daily monitoring of fresh cows.

Drug use in food-producing animals is subject to each country's regulations and to withdrawal periods for milk and meat.

Key studies

• Sheldon et al. (2006): proposed clinical definitions of postpartum uterine diseases, later adopted by most studies. It defines puerperal metritis (enlarged uterus, fetid watery red-brown discharge, systemic illness and fever above 39.5 °C within 21 days after calving), clinical endometritis (more than 50% pus from day 21, or mucopurulent discharge after day 26), subclinical endometritis (more than 18% neutrophils at 21 to 33 days or more than 10% at 34 to 47 days) and pyometra. It is an expert consensus document, not a clinical study.
• LeBlanc et al. (2002), cohort of 1865 cows from 27 herds examined between days 20 and 33 of lactation. Clinical endometritis was defined by purulent discharge or a cervical diameter above 7.5 cm after day 20, or mucopurulent discharge after day 26. Its prevalence was 16.9%, and 44% of cases were detected only by vaginoscopy; palpation of the uterus had no predictive value. Affected cows took 27% longer to become pregnant and were 1.7 times more likely to be culled for reproductive failure.
• Dubuc et al. (2010), observational study of 1363 Holstein cows from 3 herds. Risk factors for metritis were prepartum NEFA of 0.6 mmol/L or more, dystocia, retained placenta and haptoglobin of 0.8 g/L or more in the first week. Purulent vaginal discharge and cytological endometritis had partly different risk factors, which supports that they are distinct manifestations of uterine disease.
• Haimerl et al. (2017), systematic review and meta-analysis based on 23 trials on the treatment of metritis. There were enough studies to analyse only ceftiofur: 828 treated cows had less metritis at re-examination than 804 untreated cows. It was not possible to compare antibiotics with each other or with non-antibiotic treatments, and the authors point to the lack of high-quality studies.
• Dubuc et al. (2011), randomised trial in 2178 Holstein cows from 6 herds. In 1017 high-risk cows (twins, dystocia or retained placenta), ceftiofur given 24 hours after calving did not reduce metritis overall, although it did in some subgroups, and it reduced purulent vaginal discharge at the first examination. Prostaglandin F2α at 5 and 7 weeks after calving did not improve the cure of cytological endometritis or purulent discharge, nor fertility; 66% and 63% of those cases cured on their own. This contradicts the common use of prostaglandin to treat endometritis.