Objective—To determine whether systemic immunologic
hyperreactivity exists in horses with chronic laminitis,
compared with responses for nonlaminitic horses.
Animals—7 nonlaminitic horses and 7 CL horses.
Procedure—In experiment 1, intradermal testing
(IDT) was performed on 7 nonlaminitic and 7 CL horses
to evaluate the response to a combination of 70
allergens at 15 and 30 minutes and 4 and 24 hours
after injection. Three nonlaminitic and 3 CL horses
used in experiment 1 were used in experiment 2 to
determine whether histologic differences existed
between the 2 groups. The H&E-stained tissue sections
were evaluated on the basis of 3 criteria. For all
analyses, 2-sample t-tests were used to determine
significant differences between the groups.
Results—In experiment 1, CL horses had significantly
higher total responses to IDT than nonlaminitic
horses at the first 3 time periods. Also, CL horses had
significantly fewer total scores of 0 than nonlaminitic
horses at all time periods, except at 24 hours. In
experiment 2, we did not detect significant differences
between groups for any criterion.
Conclusions and Clinical Relevance—Results support
the hypothesis that CL horses develop hyperreactivity
to various antigenic stimuli, compared with
responses for nonlaminitic horses. Therefore, the possibility
that antigenic challenge may result in exacerbation
of clinical signs of laminitis should be discussed
with horse owners. Chronic laminitis should
also be a consideration when a horse becomes lame
following antigenic challenges. (Am J Vet Res 2003;64:279–283)