ACVIM Abstracts: Genetic methods of detection may spur greater understanding, control of leptospirosis

Lptospirosis is a zoonotic bacterial disease found throughout the world. It is caused by infection with antigenically distinct serovars of the species Leptospira interogans sensu latu and L. kirschneri.

Bethany Howe

Leptospirosis infection in dogs manifests in many ways, from lethargy, depression, polyuria and polydypsia to uveitis, hepatic inflammation, severe renal failure and disseminated intravascular coagulation and death.

Diane Levitan

Leptospirosis is not only easily transmitted among dogs, but also is transmissible to humans.

Many techniques have been used for the diagnosis of leptospirosis (see Table 1). For various reasons, many have not proven practical, and the ones most used today have limitations.

Table 1 Comparing testing methods

The most widely used diagnostic test is the microscopic agglutination test (MAT). Samples are easily acquired; the test is readily available and results are quick.

However, evaluation of antibody levels can be complicated by vaccination, stage of disease (acute or chronic) or antibody cross-reactivity. All tests have been helpful for diagnosis; however, they have not provided enough information about the role of bacteria in the disease over time.

A recent abstract by K. Kasper, et al, titled: Development of a Real-Time PCR Assay for the Detection of Pathogenic Leptospires in Canine Urine, was presented at the 2006 ACVIM Forum. In it, they describe their work on the development of an assay and its usefulness. The results of the study indicated that the real-time PCR assay detected at least six leptospiral serovars (canicola, icterohaemorrhagiae, grippotyphosa, pomona, bratislava and hardjo) that are pathogenic in dogs, and that the assay is able to detect organisms in canine urine samples.

The test proved to be accurate, easy and cost effective. The tests were run on urine spiked with leptospiral organisms, however, and not on urine samples from infected dogs. Therefore, further documentationis needed to ensure that it will detect the leptospires in urine shed from infected animals.

Real-time PCR technology is a flexible, cost-effective, sensitive, specific and quantitative method for the diagnosis of infectious disease. K. Kasper, et al, say the development of this assay may prove to be a more sensitive, quantitative test for canine leptospirosis and that it may enhance our ability to diagnose the disease and provide an opportunity to compare the effects of different treatment protocols on shedding of organisms in the urine of infected dogs.

The abstract is another indicator that genetic methods of disease detection will likely improve the diagnosis, treatment and overall understanding of leptospirosis in addition to many other diseases we will attempt to diagnose in the future.

Dr. Howe is a resident in small animal internal medicine at The Center For Specialized Veterinary Care in Westbury, N.Y. Her interests include diagnostic ultrasound and renal physiology. A Ross University veterinary graduate, she completed her clinical training at Auburn University and a medicine and surgery internship at The Center For Specialized Veterinary Care.

Dr. Levitan graduated with honors from the University of Pennsylvania School of Veterinary Medicine in 1991. She did an internship in small animal medicine and surgery at the Animal Medical Center in New York City, and then completed a residency in Internal Medicine (small animal) at Tufts University School of Veterinary Medicine. Dr. Levitan has since been a consultant for Antech Diagnostics, owns Mobile Veterinary Ultrasound & Endoscopy, PC (a veterinary consulting service) and is the founder and director of the Center For Specialized Veterinary Care in Westbury, N.Y.