Validating a New Diagnostic Test for Leptospira spp Infection in Dogs

The microscopic agglutination test (MAT) has traditionally been used to diagnose Leptospira spp infection in dogs. However, the MAT—which requires highly trained team members, expensive equipment, and live cultures of reference strains—is a specialized procedure run only by select laboratories. Use of an ELISA would require a lower investment in equipment and labor and could reduce risk to personnel. 

L fainei shares the antigenic features of many Leptospira spp strains and serves as the basis of a newly developed ELISA for diagnosing Leptospira spp infections in humans, where it has shown a high sensitivity and specificity. 

This study examined the diagnostic sensitivity and specificity of an L fainei-based ELISA in dogs for diagnosis of acute leptospirosis. Researchers divided serum samples from 271 dogs into 5 groups and tested all dogs for serologic evidence of Leptospira spp infection using the MAT as well as the L fainei-based ELISA. 

MAT was performed using live cultures of 8 different Leptospira spp. All 92 dogs allocated to one test group manifested clinical signs of acute Leptospira spp infection and had a positive MAT of at least 400. In this group, the L fainei-based ELISA demonstrated a 95.6% sensitivity (88/92). In another group of dogs that were not showing signs but still had a positive MAT of at least 400, the L fainei-based ELISA demonstrated a poor (39%) sensitivity (13/33). All other groups were MAT negative and ELISA negative. 

As developed in this study, the L fainei-based ELISA would only be clinically useful to practitioners when a dog is presented with acute clinical signs of Leptospira spp infection.

Key pearls to put into practice:

The MAT test remains the gold standard for serologic testing for Leptospira spp infections in dogs.

Clinicians should talk with team members at the laboratories they use to learn what Leptospira spp serovars the MAT can identify.

An L fainei-based ELISA holds potential, but further study is necessary to validate its usefulness, especially in dogs that are not showing acute signs of infection.