Today's Veterinary Practice

JAN-FEB 2018

Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.

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PEER REVIEWED 78 FOCUS ON LEPTOSPIROSIS signs, clinicopathologic abnormalities, and methods of organism detection, including MAT titers, acute and convalescent titers, PCR, culture, histopathology, and IDEXX SNAP Lepto Test ( idexx.com ). MAT titers. MAT is an antibody test that assesses the ability of serial dilutions of patient serum to cause agglutination of live leptospires via dark field microscopy. 2 The reported titer is the highest patient serum dilution causing 50% agglutination of leptospires in the reaction. 1 There is no consensus on the cutoff value for a negative titer. Natural infection should be strongly suspected with a single MAT titer of 1:800 or greater with consistent clinical signs and clinicopathologic abnormalities without leptospiral vaccination within the past 4 months. 2,3 MAT titers cannot be used to predict the infecting serovar due to cross-reactivity among different serogroups from shared leptospiral antigens. 1,5 Acute and convalescent titers. Dogs frequently have negative MAT results in the acute phase of infection. 1 If there is a high index of suspicion for disease, and the initial titer does not support infection, convalescent titers in 2 to 4 weeks should be performed. A 4-fold change (increase or decrease) in a titer supports recent infection with leptospirosis. 1–3 PCR testing. PCR can be used to detect pathogenic leptospiral nucleic acids. During the first 10 days of infection, organism numbers are highest in blood. Afterwards, they are found in the highest concentration in urine. 1 Because timing of infection is not often known, pairing blood and urine PCR testing may increase diagnostic sensitivity. False-negative results may occur with recent antimicrobial treatment or when the number of sampled organisms is low. 1 Recent vaccination does not interfere with PCR assays. 2 PCR testing should be paired with other diagnostic methods like MAT titers. 1 Culture. Leptospires can be cultured on special media; however, the diagnostic utility is limited because the organism is both fragile under transport conditions and slow growing (up to a 3- to 6-month incubation period). 1,2 Histopathology. Organisms may be visualized with silver stains, immunohistochemistry, or fluorescence in situ hybridization on biopsied kidney tissue. 6 SNAP Lepto Test. This point-of-care test detects antibodies to Leptospira species by enzyme-linked immunosorbent assay (ELISA) and reports a qualitative positive or negative result. Independent studies of its utility in field conditions have not yet been reported. Therapeutic Approach Appropriate supportive therapy should be provided to each patient based on the clinical manifestation of disease. IV fluid therapy must be initiated for the treatment of acute kidney injury associated with leptospirosis and to correct for dehydration. Urine output should be monitored and fluids adjusted accordingly once hydration is restored. Ideally, these patients should be hospitalized at 24-hour care facilities, and referral for dialysis should be offered for patients in oliguric or anuric renal failure. 7 Acute kidney injury in dogs has been comprehensively and practically reviewed elsewhere. 8 The current recommendation for treatment of leptospirosis is doxycycline 5 mg/kg PO q12h for 2 weeks. In clinically ill patients that cannot tolerate doxycycline, IV ampicillin can be administered to eliminate the leptospiremic phase. Once tolerated, a 2-week course of doxycycline is required to eliminate the organism from the renal tubules. 1,2 Madeline Fujishiro Madeline Fujishiro, DVM, is a small animal internal medicine resident at Texas A&M University College of Veterinary Medicine and Biomedical Sciences. She received her DVM from Colorado State University, followed by a 1-year small animal rotating internship at University of Georgia, before starting her residency at Texas A&M University. Kate E. Creevy Kate E. Creevy, DVM, MS, DACVIM, received her DVM from the University of Tennessee and completed a small animal rotating internship at the University of Minnesota before entering emergency practice for 4 years. She joined the University of Georgia (UGA) faculty as a clinical instructor in emergency medicine, subsequently completing both her master's degree in infectious disease and her residency in small animal internal medicine at that institution. She remained on the faculty at UGA through early 2016 and has recently joined the faculty at Texas A&M University, where she is an associate professor of small animal internal medicine.

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