Objective—To determine the effects of treatment
with and without adjuvant radiation therapy on recurrence
of ocular and adnexal squamous cell carcinoma
(SCC) at specific anatomic locations in horses.
Procedures—Medical records of horses with histologically
confirmed ocular and adnexal SCC evaluated
from 1985 to 2002 were reviewed. Sex, breed, age,
type of treatment, location, and recurrence of SCC
were recorded. Two treatment groups determined by
recurrence of SCCs treated with and without adjuvant
radiation therapy were established.
Results—The anatomic site with the highest recurrence
rate was the limbus (junction of the cornea and
sclera) or bulbar conjunctiva (47.7%), independent of
treatment group. There was a significant difference in
recurrence rates of ocular and adnexal SCCs between
the 2 treatment groups, independent of anatomic location.
Recurrence rates of SCCs treated with and without
adjuvant radiation therapy were 11.9% and 44.1%,
respectively. Recurrence rates for SCCs of the eyelid,
limbus or bulbar conjunctiva, and cornea treated with
adjuvant radiation therapy were significantly different
from those for SCCs treated without adjuvant radiation
therapy. The most frequently represented anatomic
site for ocular and adnexal SCCs was the eyelid
(28.7%). Coat color, breed, and the interaction of age
and breed had a significant effect on tumor recurrence
regardless of treatment type and anatomic location.
Conclusions and Clinical Relevance—Results indicated
that ocular and adnexal SCCs treated with adjuvant
radiation therapy had a significantly lower recurrence
rate, compared with SCCs treated without adjuvant
radiation therapy, independent of anatomic location.
(J Am Vet Med Assoc 2004;225:1733–1738)
Objective—To determine prevalence of anthelmintic
resistance in cyathostome nematodes of horses in
the southern United States.
Animals—786 horses on 44 farms and stables in
Georgia, South Carolina, Florida, Kentucky, and
Procedure—Fecal egg count (FEC) reduction tests
were performed on 44 large farms and stables. Horses
on each farm were treated with an oral paste formulation
of fenbendazole, oxibendazole, pyrantel pamoate,
or ivermectin at recommended label dosages. A mixed
linear model was fitted to the percentage reduction in
FEC, accounting for differences among farms, states,
ages, treatments, and treatment by state interactions.
Results—By use of a conservative measure of resistance
(< 80% reduction), the percentage of farms with
anthelmintic-resistant cyathostomes was 97.7%, 0%,
53.5%, and 40.5% for fenbendazole, ivermectin, oxibendazole,
and pyrantel pamoate, respectively. Mean percentage
reductions in FEC for all farms were 24.8%,
99.9%, 73.8%, and 78.6% for fenbendazole, ivermectin,
oxibendazole, and pyrantel pamoate, respectively.
Pairwise contrasts between states for each treatment
revealed that in almost all instances, there were no significant
differences in results between states.
Conclusions and Clinical Relevance—The prevalence
of resistance found in this study was higher than that
reported previously, suggesting that anthelmintic resistance
in equine cyathostomes is becoming a major problem.
Furthermore, data from these 5 southern states,
which are geographically and physiographically distinct,
were remarkably similar. This suggests that drug resistance
in cyathostomes is highly prevalent throughout
the entire southern United States and probably nationwide.
(J Am Vet Med Assoc 2004;225:903–910)