Infertility in an American Quarter Horse mare with cervical duplication.

Research Overview

• This study reports a case of infertility in a 13-year-old American Quarter Horse mare caused by cervical duplication, a rare developmental disorder where the cervix fails to form properly.
• The mare was found to have a normal female karyotype, indicating that the infertility was due to anatomical abnormalities rather than chromosomal defects.

Introduction to Cervical Duplication

• Cervical duplication is classified as a disorder of sexual development (DSD).
• It arises from the incomplete fusion of the Müllerian ducts during fetal development.
• This leads to persistent median walls throughout the cervix, creating an abnormal, duplicated cervical structure.
• The condition is rare in mares and is an uncommon cause of infertility.

Case Presentation

• The subject was a 13-year-old American Quarter Horse mare experiencing infertility despite multiple breeding attempts.
• The mare was referred for a breeding soundness evaluation to diagnose the cause of failure to conceive.
• Upon physical examination, an abnormal cervical shape was palpated, indicating a possible structural anomaly.

Diagnostic Workup

• Further investigation involved cytogenetic analysis to evaluate the chromosome set of the mare.
• Polymerase chain reaction (PCR) assays were performed targeting genes indicative of sex chromosomes: the Y-linked SRY gene and the X-linked androgen receptor gene.
• Results showed a normal female karyotype (64,XX) with no presence of the SRY gene, ruling out chromosomal abnormalities or sex reversal syndromes.

Link Between Cervical Abnormality and Infertility

• The duplicated cervix disrupted normal uterine clearance mechanisms.
• This impairment was linked to the accumulation of fluid within the uterus, as detected through ultrasound imaging.
• Fluid retention and poor clearance create an unfavorable uterine environment, reducing the chances of successful pregnancy.
• Therefore, the infertility observed in this mare was directly associated with the abnormal cervical structure rather than genetic or hormonal causes.

Conclusion and Implications

• In mares with unexplained infertility, structural anomalies such as cervical duplication should be considered.
• Comprehensive diagnostics including physical examination, imaging, and cytogenetics are essential to differentiate between genetic and anatomical causes of infertility.
• This case contributes to veterinary understanding by highlighting cervical duplication as a potential yet rare cause of infertility in horses.