Contagious equine metritis: effect of intrauterine inoculation of contagious equine metritis agent in pony mares.

This research paper investigates the effect of an intrauterine injection of the contagious equine metritis (CEM) bacteria on pony mares. The results suggest that the bacteria cause cervicitis and vaginitis, which appear 1 to 3 days after the injection and last for 7 to 23 days. It also appears that the presence of CEM bacteria can increase during estrus, while the presence of local antibodies can enhance resistance to CEM bacteria.

Research Background and Methodology

• The research focused on contagious equine metritis (CEM) which is a sexually transmitted bacterial infection in horses. The objective was to understand the effects of an intrauterine inoculation of the CEM bacteria in pony mares.
• Pony mares were inoculated intrauterine with the CEM bacteria, that is the bacteria was injected directly into the uterus.

Findings: Acute Phase of Infection

• A direct correlation was observed between the onset and duration of cervicitis and vaginitis (inflammation of the cervix and vagina, respectively) and the presence of vaginal exudate.
• Visible clinical signs developed within 1-3 days of inoculation and persisted for about 7 to 23 days.
• During this acute phase of infection, the CEM bacteria could be detected in all collected uterine and cervical samples.

Findings: Asymptomatic Stage of Infection

• CEM bacteria were no longer found in uterine and cervical samples during the asymptomatic (non-symptom showing) phase of infection.
• However, in a proportion of the pony mares, the CEM bacteria remained present in the clitoral fossa, clitoral sinus, and urethral vestibule.
• Sampling during early estrus (female reproductive cycle) elevated the bacterial isolation rate in previously negative mares, suggesting a flare-up of bacterial presence during estrus.

Findings: Repeated Exposure Experiments

• Repeated experiments demonstrated the existence of local antibodies, as no CEM bacteria could be found at 2, 7, and 15 days after re-injection with a small number of bacterial cells.
• Mares that were re-injected with a large number of bacterial cells exhibited presence of CEM bacteria two days post-inoculation, however, all of the mares tested negative 15 days after re-exposure, suggesting an increased resistance to the CEM bacteria.