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A new DNA test developed at Rutgers New Jersey Medical School helped confirm a diagnosis of Lyme disease in a horse. A report is published in the Journal of Veterinary Diagnostic Investigation.
Lyme disease (LD) is caused by the corkscrew-shaped bacterium (spirochete) Borrelia burgdorferi. The organism infects white blood cells and cells lining synovial cells, resulting in an inflammatory response.
It is transmitted by ixodes ticks – (typically I ricinus in UK, I scapularis (deer tick) in the north eastern US and Atlantic coast, and I pacificus on the US west coast.)
Many horses in areas where the infection is present carry antibodies without showing signs of disease. Conversely, infected animals may take a long time to produce a detectable antibody response.
Signs are generally non-specific. Swollen joints and uveitis (inflammation within the eye) have been reported. Other possible signs include stiffness, lameness, lethargy and behaviour change.
Rare cases may develop neuroborreliosis, in which the bacteria reach the central nervous system, resulting in neurological signs, fever, muscle wasting and difficulty eating.
Clinicians at the Cornell University School of Veterinary Medicine were struggling to diagnose a neurologic case of LD in a sick Swedish Warmblood mare. Although they suspected Lyme disease, standard PCR and antibody tests did not detect the organism.
The new “genomic hybrid capture assay,” a highly sensitive test developed by Steven Schutzer and the team at Rutgers New Jersey Medical School, identified the pathogen in a sample of the horse’s spinal fluid, allowing it to be diagnosed and successfully treated.
The test works by first selectively isolating DNA from the microorganism causing the disease.
“The method is like having a special, specific ‘fishhook’ that only grabs Borrelia DNA and not the DNA of other microbes, nor the DNA of the host (animal or human),” Schutzer said. “Detecting DNA of the disease is a direct test, meaning we know you have active disease if it’s circulating in the blood or spinal fluid.”
“The diagnosis of Lyme neuroborreliosis (neurologic Lyme disease) in horses is rarely confirmed antemortem and has frustrated veterinarians for years,” said Thomas Divers, the veterinarian who led the equine team on the paper and who is a professor of medicine and co-chief of the Section of Large Animal Medicine at Cornell University’s College of Veterinary Medicine in New York. “This is a very promising technique. Focused treatment against B. burgdorferi administered in this case resulted in the horse’s complete athletic recovery.”
For more details, see:
Genomic hybrid capture assay to detect Borrelia burgdorferi: an application to diagnose neuroborreliosis in horses
Thomas J. Divers, Emmanuel F. Mongodin, Christopher B. Miller,
Rodney L. Belgrave, Rachel B. Gardner, Claire M. Fraser, Steven E. Schutzer
Journal of Veterinary Diagnostic Investigation (2022).
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