Veterinary Medicine - December 2007 - (Page 782)

2007 Highlights O Central Practical advice from the presentations A tip for interpreting Leptospira species titers There’s no easy way to definitively diagnose leptospirosis quickly in dogs—yet. But obtaining a negative result initially doesn’t mean you should stop antibiotic therapy. Here’s how to best interpret the titers. Richard E. Goldstein, DVM, DACVIM (small animal internal medicine), DECVIM-CA T o help confirm a diagnosis of canine leptospirosis, veterinarians today must rely on serologic testing with the microscopic agglutination test (MAT). The highest dilution of serum that agglutinates 50% of the Leptospira organism is the titer. Interpreting the test can be problematic, though, especially early on in the disease or in a recently vaccinated dog. AN EARLY NEGATIVE TITER SHOULDN’T DISSUADE YOU A low MAT titer could indicate previous vaccination against Leptospira species or possibly infection with another type of spirochete because cross-reactivity occurs. However, a titer > 800 for a nonvaccinal serovar along with appropriate clinical signs is suggestive of active disease. Also, a fourfold increase in titer in a convalescent serum sample indicates a recent Leptospira species infection.1 For example, you’re treating a sick dog (dogs with leptospirosis may have acute renal failure, vasculitis, disseminated intravascular coagulation, or hepatic disease) that has a titer > 800 for Leptospira pomona, but the dog was vaccinated two months earlier against L. Richard E. Goldstein, DVM, DACVIM, (small animal internal medicine), pomona. You submit another serum sample seven to 10 days later, and the titer is now > 3,200. This fourfold increase in titer indicates infection, most likely due to L. pomona during the illness. Keep in mind that because titers may decline quickly after antibiotic therapy, you may miss rapidly rising titers if a convalescent titer is drawn after the typical three-week interval. So if you suspect leptospirosis, don’t let an early negative titer result dissuade you; start treating and submit another sample for an MAT within seven to 10 days. to assess protection because at least one study has shown that dogs were wellprotected from a challenge with Leptospira organisms a full year after vaccination despite low serum MAT titers.2 A TEST ON THE HORIZON Veterinarians may someday have a better diagnostic test that will allow earlier diagnosis of canine leptospirosis. In people, ELISA tests are used as screening tools for leptospirosis, and similar types of tests are currently being evaluated in dogs. O REFERENCES 1. Greene CE, Sykes JE, Brown CA, et al. Leptospirosis. In: Greene CE, ed. Infectious diseases of the dog and cat. 3rd ed. Philadelphia, Pa: WB Saunders Co, 2006;402-417. 2. André-Fontaine G, Branger C, Gray AW, et al. Comparison of the efficacy of three commercial bacterins in preventing canine leptospirosis. Vet Rec 2003;153(6):165-169. DECVIM-CA Department of Clinical Sciences College of Veterinary Medicine Cornell University Ithaca, NY 14853 HOW LONG DO VACCINAL TITERS LAST? Leptospira species vaccinal titers may last six months to a year or longer. However, antibody testing may not be a good way 782 December 2007 VETERINARY MEDICINE ©iStockphoto.com/Provokator

Table of Contents Feed for the Digital Edition of Veterinary Medicine - December 2007

Veterinary Medicine - December 2007 Contents Letters Editors' Guest Thanking Our Valued Reviewers The Veterinary Medicine Interview: Dr. Joseph Harari Clinical Exposures Idea Exchange Answers to Three Commonly Asked Questions About Lyme Disease Practical Ideas for Managing Common Internal Medicine Problems A Tip for Interpreting Leptospira Species Titers Investigating Proteinuric Kidney Disease Counseling New Puppy Owners: Normal Play vs. Aggressive Tendencies 11 Guidelines for Conservatively Treating Chronic Kidney Disease CE Form Product Preview Advertiser Index Marketplace/Classifieds Mind Over Miller Merial Insert

Veterinary Medicine - December 2007

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