When to stop Lyme disease treatment?

Don't expect Borrelia antibodies to disappear rapidly following treatment in horses naturally infected with Lyme disease.

Lyme disease (LD) is caused by systemic infection with the spirochaete Borrelia burgdorferi. The most common signs in affected animals are lameness, often affecting more than one limb, and reluctance to work. Diagnosis of the disease is complicated by the many other possible causes of lameness and the high incidence of sub-clinical infection in areas in which the infection occurs. Many clinically normal animals have antibodies to Borrelia burgdorferi in their blood.

How do you decide on the length of treatment course necessary in cases of Lyme disease in horses?
Changes in the antibody levels are often used to assess when treatment has been successful. In experimental infections, infected animals show marked reduction in antibody levels after antibiotic treatment.

Does the same apply to naturally infected cases? Research in New York State suggests that ELISA serology is less helpful in those cases for determining when treatment is complete.

The study saw Dr Thomas J Divers and colleagues at Cornell Veterinary School  collaborating with Dr Amy L Grice of the Rhinebeck Equine practice in New York State.

Thomas J Divers and colleagues at Cornell Veterinary School and Dr Amy L Grice of the Rhinebeck Equine practice compared Borrelia ELISA antibody concentrations in naturally exposed horses before and after antibiotic treatment for Lyme disease. The study included 68 horses treated with doxycycline or oxytetracycline and 183 horses that received no treatment.

They found that antibiotic treated horses had a decline in ELISA values in comparison to control horses. The scale of the decline in ELISA units following treatment was small compared to that previously reported in experimentally infected and treated ponies.

They conclude: “Persistently high ELISA titres following appropriate treatments for Lyme disease may not, without appropriate clinical signs, be a reason for more prolonged treatment.”

 Read more at equinescienceupdate.com