Viability of Leptospira spp. in deer kidney from a New Zealand abattoir, as a model for New Zealand’ wildlife

Abstract

Leptospirosis is a spirochetal zoonosis and can affect all domestic animals and humans, ranging in severity from mild infections to serious systemic diseases. Leptospirosis is an important zoonosis and can have a major economic impact on livestock industries. The goal of this research is to have a more robust estimate of how long leptospirosis survives in dead animal kidney tissue and how long after death leptospiral DNA can be extracted for PCR determination and till what time leptospiral culture can be isolated. Therefore, a cross-sectional study was carried out on slaughtered farmed red deer at a New Zealand abattoir from November 2015 to February 2016 to investigate the renal carriage rate, the viability of leptospires in dead kidney tissue, the seroprevalence and the serovar causing infection. Kidney that showed possible sign of leptospiral infection were target and blood samples were collected. Samples of 98 deer from 9 different farms were collected. The kidney samples were tested by quantitative real-time PCR (qPCR) and culture while serum samples (from coagulated blood samples) from positive animals were tested by microscopic agglutination test (MAT). The kidneys were left at ambient temperature and culture and PCR were repeated at intervals thereafter. In total, 2 out of 98 kidney samples (2%) tested positive by qPCR. The 2 kidneys that were PCR positive on day one, were found PCR negative at day 2 (after 48h). All kidneys were found culture negative. There are no MAT results from blood samples available. The number of leptospirosis positive tested animals is too low to state firm conclusions. Either the prevalence of leptospirosis in deer at the abattoir was low or the methods of testing that were used were not suitable.