Objective—To identify factors associated with development of vesicular stomatitis (VS).
Sample Population—138 livestock premises and 118 horses suspected of having VS in Texas, New Mexico, and Colorado.
Procedures—Premises with ≥ 1 animal with clinical signs and laboratory confirmation of infection were classified as case premises. Premises where laboratory confirmation results were negative were control premises. Among equine premises, case and control horses were selected on the basis of premises status. A survey was conducted to identify factors associated with VS for premises and specific horses.
Results—Control of insect populations in the 2 weeks before the VS investigation decreased the odds of disease for premises where vegetation coverage was grassland or pasture (odds ratio [OR], 0.08; 95% confidence interval [CI], 0.01 to 0.7). Odds of VS for premises covered with grassland or pasture increased when measures to control insect populations were not used (OR, 11; 95% CI, 0.8 to 156.3) and for premises that had a body of water (OR, 2.3; 95% CI, 1.0 to 5.6). Use of measures to prevent insect bites or harassment by insects (OR, 0.2; 95% CI, 0.1 to 0.8) and spending time in shelters (OR, 0.4; 95% CI, 0.2 to 1.1) in the 2 weeks prior to investigation decreased the odds of being a case horse.
Conclusions and Clinical Relevance—Insect control and spending time in shelters decreased the odds for infection with VS. Premises covered with grassland or pasture or that had a body of water were at a higher risk.
Objective—To estimate risk of exposure and age at
first exposure to Sarcocystis neurona and Neospora
hughesi and time to maternal antibody decay in foals.
Animals—484 Thoroughbred and Warmblood foals
from 4 farms in California.
Procedure—Serum was collected before and after
colostrum ingestion and at 3-month intervals thereafter.
Samples were tested by use of the indirect fluorescent
antibody test; cutoff titers were ≥ 40 and
≥ 160 for S neurona and N hughesi, respectively.
Results—Risk of exposure to S neurona and N hughesi
during the study were 8.2% and 3.1%, respectively.
Annual rate of exposure was 3.1% for S neurona and
1.7% for N hughesi. There was a significant
difference in the risk of exposure to S neurona among
farms but not in the risk of exposure to N hughesi.
Median age at first exposure was 1.2 years for S neurona and
0.8 years for N hughesi. Highest prevalence
of antibodies against S neurona and N hughesi was
6% and 2.1%, respectively, at a mean age of 1.7 and
1.4 years, respectively. Median time to maternal antibody
decay was 96 days for S neurona and 91 days for
N hughesi. There were no clinical cases of equine protozoal
Conclusions and Clinical Relevance—Exposure to
S neurona and N hughesi was low in foals between birth
and 2.5 years of age. Maternally acquired antibodies
may cause false-positive results for 3 or 4 months after
birth, and EPM was a rare clinical disease in horses ≤ 2.5
years of age. (Am J Vet Res 2004;65:1047–1052)
Objective—To assess the use of CSF testing with an indirect fluorescent antibody test (IFAT) for diagnosis of equine protozoal myeloencephalitis (EPM) caused by Sarcocystis neurona.
Sample Population—Test results of 428 serum and 355 CSF samples from 182 naturally exposed, experimentally infected, or vaccinated horses.
Procedure—EPM was diagnosed on the basis of histologic examination of the CNS. Probability distributions were fitted to serum IFAT results in the EPM+ and EPM-horses, and correlation between serum and CSF results was modeled. Pairs of serum-CSF titers were generated by simulation, and titer-specific likelihood ratios and post-test probabilities of EPM at various pretest probability values were estimated. Post-test probabilities were compared for use of a serum-CSF test combination, a serum test only, and a CSF test only.
Results—Post-test probabilities of EPM increased as IFAT serum and CSF titers increased. Post-test probability differences for use of a serum-CSF combination and a serum test only were ≤ 19% in 95% of simulations. The largest increases occurred when serum titers were from 40 to 160 and pre-test probabilities were from 5% to 60%. In all simulations, the difference between pre- and post-test probabilities was greater for a CSF test only, compared with a serum test only.
Conclusions and Clinical Relevance—CSF testing after a serum test has limited usefulness in the diagnosis of EPM. A CSF test alone might be used when CSF is required for other procedures. Ruling out other causes of neurologic disease reduces the necessity of additional EPM testing.