Infection with serovars of Leptospira interrogans and Leptospira kirschneri is an important cause of abortion, acute renal failure, recurrent uveitis, and rarely neonatal disease in horses. An in-clinic rapid ELISA is marketed for dogs. This study evaluated the performance of the LipL32-based ELISA (IDEXX SNAP Lepto) compared with the microscopic agglutination test (MAT) using serum from experimentally and naturally infected horses.
Serum samples were obtained from a previous study of horses experimentally infected with Leptospira interrogans serovar Pomona (n = 97). Serum from naturally infected horses was randomly selected from samples submitted to the Animal Health Diagnostic Center at Cornell University that were identified as positive on the MAT in any serovar (n = 31). A random selection of MAT negative samples was also included for testing (n = 20). All samples (n = 148) were tested with the IDEXX SNAP Lepto. The performance of the test kits was compared to the MAT. The accuracy was measured in terms of the relative sensitivity and specificity with a cut-off point for positivity in the MAT of ≥ 100. The relationship between the MAT titer and the probability of positivity in the IDEXX SNAP Lepto was assessed using logistic regression analysis.
Results indicated that the test kits have high specificity (100%). Sensitivity was poor at titers ≤400 (0 – 36%) and moderate at titers 800-1600 (50%), but was excellent at titers ≥ 3200 (90-100%).
The IDEXX SNAP Lepto provides a rapid in-clinic test for evidence of antibody response to Leptospira species in horses, with excellent specificity and high sensitivity with increasing titers. Leptospirosis associated abortion and acute renal disease often result in MAT titers of ≥ 6,400. This test kit may allow for prompt stall-side or field determination of Leptospirosis status in these cases.
Large Animal Internal Medicine Resident
Cornell University School of Veterinary Medicine
Thursday, June 14
1:30 PM – 1:45 PM
Friday, June 15
2:15 PM – 2:30 PM
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