Leptospira's Role in ERU in U.K. Horses

<em>Leptospira</em>'s Role in ERU in U.K. Horses

Researchers found that Leptospira didn't appear to be a common factor in ERU cases in U.K. horses.

Photo: Kevin Thompson/The Horse

The exact causes of equine recurrent uveitis (ERU) confounded veterinarians and researchers alike for many years. While they’ve made great strides in determining what’s behind this painful, blindness-causing condition, some questions still exist. For instance, does the bacteria known to play a role in ERU development in U.S. horses—Leptospira spp—impact horses in other countries, as well? As it turns out, not necessarily.

A group of researchers in the United Kingdom recently evaluated Leptospira’s role in ERU in their region. They had four main goals:

  • Establish Leptospira prevalence in ERU horses;
  • Identify which strains of the bacteria are most commonly involved;
  • Compare blood serum and aqueous humor (the fluid that fills the eye) antibody levels; and
  • Evaluate the efficacy of serology alone as a confirmatory test.

“We had a feeling that Leptospira-associated uveitis is less prevalent here than in other parts of the world, particularly when you compare the situation here with what is published in the United States and Continental Europe, where the prevalence of uveitis in general is much higher,” said Fernando Malalana, DVM, Dipl. ECEIM, FHEA, MRCVS, RCVS, European Specialist in Equine Internal Medicine, from the University of Liverpool Equine Hospital.

Over a three-year period, the team collected surgically removed eyes as well as blood samples from horses diagnosed with ERU. They also collected eyes, blood, and aqueous humor samples from control horses euthanized for reasons unrelated to the study.

Study results confirmed the researchers’ suspicions: Leptospira didn't appear to be a common factor in ERU cases in the U.K.

Study findings included:

  • Thirty-seven of 72 study horses tested positive to one or more strains of Leptospira; of these,19 were in the ERU group and 18 were in the control group;
  • Six aqueous humor samples (all belonging to the ERU group) had detectable antibodies against Leptospira spp; and
  • No significant difference in blood serum samples between Leptospira-associated ERU and those not associated with the bacteria.

The researchers concluded that “serology alone may not help differentiate between Leptospira-associated and non-Leptospira-associated ERU cases, and aqueocentesis (taking an aqueous humor sample from inside the eye) is probably necessary to confirm the diagnosis of Letospira-associated ERU in the U.K.”

The study, “The Role of Leptspira spp. in horses affected with recurrent uveitis in the UK,” was published in the Equine Veterinary Journal

About the Author

Casie Bazay, NBCAAM

Casie Bazay holds a bachelor of science degree in education from Oklahoma State University. She taught middle school for ten years, but now is a nationally certified equine acupressure practitioner and freelance writer. She has owned Quarter Horses nearly her entire life and has participated in a variety of horse events including Western and English pleasure, trail riding, and speed events. She was a competitive barrel racer for many years and hopes to pursue the sport again soon.

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