Today's Veterinary Practice

JUL-AUG 2012

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| CANINE LEPTOSPIROSIS: A PERSPECTIVE ON RECENT TRENDS a single titer taken during the acute stages of dis- ease, along with compatible clinical signs, is often accepted as diagnostic. UÊSingle titer variations: Defining an acceptable cutoff for a single serum titer can be difficult and may vary based on the serogroup evaluated, pre- vious leptospiral vaccinations, and other infec- tions, which may result in false positive results. UÊReciprocal titer cutoffs: While a reciprocal titer of 800 is often used in the literature, prior vac- cination may produce a reciprocal titer of 6400, suggesting that a cutoff reciprocal titer should be set at 12,800.22,23 MAN VERSUS DOG: ZOONOTIC IMPLICATIONS A recent study evaluated the seropositivity of dog owners and veterinary staff that were in contact with dogs with clinical leptospirosis. The results showed that none of the people seroconverted, suggesting that the risk of zoonotic transmission from dogs is low.1 Determining Source. However, there are a number of well-documented cases of humans contracting lepto- spirosis from dogs. In fact, the asymptomatic carrier may pose a more significant risk to humans as individu- als may not take the same precautions (ie, wearing gloves, judicious hand washing) as when handling a dog showing clinical signs of leptospirosis. It should also be noted that humans and dogs may become infected from the same source, resulting in the incorrect assumption that the dog was the source of infection. Reducing Risk. Zoonotic risk can be reduced by vaccination; good hygiene (hand washing after contact with healthy or ill dogs); and avoiding contact with urine, saliva, or feces from infected dogs. Certain conditions and occupations may predispose humans to leptospiro- sis, including rodent exposure, unsanitary living condi- tions, water-related recreation (boating, triathlons, kayak- ing), abbatoir or sewer maintenance, work with livestock, and certain farming practices (sugar cane, rice). Assessing Disease Course. Although most infec- tions in humans are symptomless, when clinical, the most common presentation is acute, febrile illness that mimics influenza, with fever, chills, headache, nausea, and myalgia. Illness may be followed by resolution, transient improvement with relapse, or progressive disease. Those with progressive disease may develop recur- rent fever, aseptic meningitis, jaundice, renal failure, or uveitis. A smaller percent of cases may develop fulminant disease, which may include hepatic and renal disease (Weil's syndrome), hemorrhagic pulmonary syndrome, or septic shock. 1. Barmettler R, Schweighauser A, Bigler S, et al. Assessment of exposure to Leptospira serovars in veterinary staff and dog owners in contact with infected dogs. JAVMA 2011; 238(2):183-188. Results of the MAT have been used to suggest the epidemiologic prevalence of certain serogroups. UÊ oÜiÛiÀ]Ê ÀiVinÌÊ ÃÌÕ`iiÃÊh>ÛiÊ V>ÃÌÊ`oÕLÌÊonÊ ÌhiÊ reliability of the MAT to accurately predict the infecting serogroup in humans, with the MAT correctly identifying the infecting serogroup only 33% to 44% of the time.24,25 UÊ illiÀ]ÊiÌÊ>l]ÊÀiVinÌlÞÊÀi«oÀÌi`Ê`iÃm>lÊÀiÃÕlÌÃÊÜhinÊ looking at agreement of MAT results with 5 veteri- n>ÀÞÊ`i>}noÃÌiVÊl>LoÀ>ÌoÀiiÃÊ6 î]Ê>lÌhoÕ}hÊÌhiÊ true infecting serovar was not known.22 » /hiÊ6 ÃÊonlÞÊ>}Àii`ÊonÊ ÌiÌiÀÃÊ inÊΣ¯ÊovÊÛ>V- cinated, specific pathogen-free dogs and 27% of patients with clinical cases of leptospirosis. » Equally disturbing, over the course of long-term volloÜ-Õ«ÊÜiÌhÊÈÊ`o}Ã]ÊÌhiÊ6 ÃÊi`inÌivii`Ê`iv- ferent serogroups in each dog. » Although this did not affect diagnosis of lep- tospirosis in these dogs, the MAT did not pro- vide reliable information regarding the infecting serogroup—information that may be important in evaluating vaccine options. Polymerase Chain Reaction PCR has been shown to have good sensitivity and specificity in the diagnosis of leptospirosis.19,23 UÊSample selection: While a variety of body flu- ids (blood, urine, cerebral spinal fluid, aqueous humor) and tissues (kidney, liver) can be used, urine is most commonly used due to its ease of acquisition and high concentration of organisms in infected dogs, even those without acute kidney injury.26,27 UÊOrganism shedding: The onset of clinical signs in dogs is such that, at the time of presentation, the leptospiral organisms are being shed in the urine of most dogs. UÊSerovar identification: PCR cannot currently identify infecting serovars, but laboratories report the presence or absence of pathogenic lepto- spires. In the near future it appears that PCR will be able to identify serovars, vastly improving its utility by providing information with epidemio- logical significance. THERAPY There are 2 main therapeutic components for lepto- spirosis in dogs: UÊ ««Ào«Ài>ÌiÊ>nÌimiVÀoLi>lÊÌhiÀ>«Þ UÊ >n>}iminÌÊovÊoÀ}>nÊv>ilÕÀi°Ê Antimicrobial Therapy A number of antimicrobials have been demonstrated to be effective in killing leptospires, at least through in vitroÊÃÌÕ`iiÃ°Ê oÜiÛiÀ]ÊÌhiÊmoÃÌÊvÀiµÕinÌlÞÊÀiVom- mended antibiotics for dogs with leptospirosis are ampicillin and doxycycline. UÊAmpicillinÊÓÓÊm}Ék}Ê 6Ê+ÊnÊ 30 Today's Veterinary Practice July/August 2012 ®ÊiÃÊÀiVommin`i`Ê

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