LEPTOSPIROSIS GEORGE E. MOORE, DVM, MS, PHD, DACVPM, DACVIM College of Veterinary Medicine, Purdue University, West Lafayette, IN
(cont)
Thus, there appears to be some molecular mimicry between these serovars. At Purdue, we have not documented a case of leptospirosis attributable to serovar Bratislava or Autumnalis in a dog properly vaccinated with a 4-serovar product, again suggesting some cross- protection may occur between some serovars. 8 All leptospiral vaccines are similar in that they are bacterins. Recombinant leptospirosis vaccines do not exist. Bacterins can vary in the quantity of whole inactivated bacteria or cell wall antigens present, or in quantity of vaccine excipients (such as bovine serum albumin) remaining from vaccine
One limitation of PCR-based diagnosis is the inability of most PCR assays to identify the infecting serovar. While this may not be important for individual patient management, serovar identify has important epidemiological and public health value. Not all PCR tests are performed with the same methodology, and sensitivity and specificity may vary. Generally PCR tests are highly sensitive. False negatives are considered uncommon, but can occur with low/zero levels of leptospiruria or leptospiremia. Certain methodologies however may be more prone to reductions in specificity, causing false positive test results. A comparison study of two PCR methods reported there were 0% false- positives in one method but the same samples had 13% false-positives via an alternative methodology. PCR positive results however do not necessarily mean there is viable organism. 7 Serological evidence in the US clearly supports the use of 4-serovar (Icterohaemorrhagiae, Canicola, Grippotyphosa, and Pomona) vaccines, rather than 2-serovar vaccines; and the 2017 AAHA Canine Vaccination Guidelines do not recommend the use of 2-serovar products. Leptospiral vaccines are generally considered serovar-specific, and cross-protection between serovars is not believed to occur. This concept is being challenged in some research, however, and cross-protection may occur between selected serovars. Recent research suggests that MAT seropositivity for serovars Autumnalis, Grippotyphosa, Bratislava, and Pomona are strongly correlated.
production. This variation in exogenous protein/antigen most likely explains the occurrence – or lack of occurrence – of allergic reactions following leptospirosis vaccination and observed differences in the rate of these reactions among vaccines by different manufacturers. Nevertheless, current vaccines are much improved in safety compared to the biologicals produced more than a decade ago.
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