ISSN 2398-2977      

Cervix: fibrosis

pequis

Synonym(s): Failure of cervical dilation


Introduction

  • Cervical fibrosis refers to mares in which the cervix fails to dilate during estrus. 
  • Failure of dilation predisposes the mare to post-breeding endometritis. 
  • In fact there is no evidence that the cervix is fibrotic - research into the problem is in the early stages, and may show that the dysfunction is at the level of hormone receptors in the cervix rather than anatomical.
  • Cause: not yet understood.
  • Signs: failure of cervix to dilate during estrus.
  • Diagnosis: digital palpation, speculum examination.
  • Treatment: many treatments reported anecdotally.
  • Prognosis: guarded for pregnancy due to predisposition to and inability to resolve post-breeding endometritis.

Pathogenesis

Etiology

  • Not yet fully understood. 
  • ? breakdown in the normal hormonal mechanisms which drive cervical relaxation during estrus.
  • ? failure at the level of hormone receptors in the cervix.
  • Recent research suggests that in normal mares there is a correlation between abundance of estrogen receptor 1 and collagen remodeling (relaxation) in the cervix. This raises the possibility that the estrogen receptor 1 is a candidate for involvement in cervical dilation and that this mechanism is disrupted in mares with failure of cervical dilation.
  • However, signaling through hormone receptors is likely to b3e only part of the control of cervical dilation in the mare, which may also involve inflammatory or autonomic system pathways and/or metalloproteinase enzymes. Further research is required.

Predisposing factors

General

  • Late retirement to stud (often due to successful competitive career).

Pathophysiology

  • Cervix fails to dilate in estrus.
  • This may predispose the mare to accumulation of fluid in the uterus prior to breeding (pre-breeding endometritis) Uterus: endometritis - bacterial.
  • However, more commonly the problem becomes obvious at the time of insemination/breeding. The fluid that occurs as the result of the normal acute inflammatory reaction post-insemination (in response to the presence of semen in the uterus) is unable to escape through the cervix.
  • If untreated, secondary post-breeding endometritis results in failure of the embryo when it descends into the uterus c day 6 post-ovulation.

Timecourse

  • Chronic condition in older, maiden mares.
  • Anecdotally, once the mare has had one foal the condition tends to be less severe in subsequent years (? may suggest there is some anatomical element to the pathogenesis).

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Campbell M L H, Peachey L, Callan L, Wathes D C & de Mestre A M (2109) Cyclical cervical function in the mare involved remodelling of callgen content, which is correlated with modification of oestrogen receptor 1 abundance. Anim Repro Sci 210 (2019) 106192 SciDirect.
  • Campbell M L H & Bliss A J (2010) Use of a Novel, Objective Ultrasound Method for Measuring Cervical Relaxation at Different Stages of the Oestrus Cycle in Mares. Anim Repro Sci 121 (1-2), 84-85 SciDirect.
  • Bucca S, Carli T, Buckley G & Dolci U (2008) The use of dexamethasone administered to mares at breeding time in the modulation of persistent mating induced endometritis. Theriogenology 70 (7), 1093-1100 PubMed.
  • Troeddson M H T (2006) Breeding-induced endometritis in mares. Vet Clin North Am Equine Pract 22 (3), 705-712 PubMed.
  • Pycock J (2004) Pre-breeding checks for mares. In Pract 26, 78-85 InPractice.
  • Pycock J F & Newcombe J R (1996) The relationship between intraluminal uterine fluid, endometritis and pregnancy rate in the mare. Equine Pract 18, 19-22 VetMedResource.
  • Pycock J F (1993) Cervical function and uterine fluid accumulation in mares. Equine Vet J 25, 191.

Other sources of information

  • Smith J D (2007) Drugs in Equine Reproduction: What you Need to Know and More. In: Proc NAVC. Internet Publisher: International Veterinary Information Service, Ithaca NY. Website: www.ivis.org.
  • LeBlanc M M (2006) Reproduction Cases. In: Proc 52nd AAEP Convention. pp 531.
  • Pycock J F (2006) How to Maximize the Chances of Breeding Successfully From the Older Maiden Mare. In: Proc 52nd AAEP Convention. AAEP, San Antonio, TX, USA. pp 534.
  • LeBlanc M M (2005) Infertility in Mares that Cycle, Conceive and Lose their Pregnancy After 35 Days. In: Proc NAVC. pp 220-221.

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