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When to stop Lyme disease treatment?

Report by Mark Andrews. Published online 27.05.13

New research suggests that persistently high antibody levels following appropriate treatment for Lyme disease may not, without appropriate clinical signs, be a reason for more prolonged treatment.


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 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.


They 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.

 

The research team 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.


Untreated horses were twice as likely to have their ELISA values increase compared to treated horses.


They conclude that field-exposed horses with high Borrelia burgdorferi ELISA values who are treated with either oxytetracycline or doxycycline can be expected to have only a small decline in ELISA values following treatment.


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


For more details see:

Changes in Borrelia burgdorferi ELISA antibody over time in both antibiotic treated and untreated horses.

Divers TJ, Grice AL, Mohammed HO, Glaser AL, Wagner B.

Acta Vet Hung. 2012 Dec;60(4):421-9.


doi: 10.1556/AVet.2012.036.