Molecular demonstration of intermittent shedding of Leptospira in cattle and sheep and its implications on control

Abstract

For a long time, it has been stated that urine leptospiral shedding is intermittent, which was observed primarily by culturing. However, culturing presents serious limitations, mainly low sensitivity, and failure on detection of leptospires cannot be neglected. PCR presents several advantages, mainly higher sensitivity. The present study aimed to analyze the occurrence of intermittency on leptospiral shedding by PCR in naturally and experimentally infected animals. In this study two experiments were conducted, the first with 60 cows naturally infected from an endemic herd. The second one was conducted in three sheep experimentally infected, each one with a different strain of Leptospira (strains Copenhageni L1-130, Canicola LO-4 and Pomona Fromm). Considering cattle, 43.3% presented negative in all tests, the remaining (56.7%) were positive at least once. From these, only one (1.6%) was positive in all samples, and seven (11.8%) were positive only in the last sampling, making it impossible to evaluate the intermittency. Noteworthy, 26 cows (43.3%) presented the typical intermittent pattern of leptospiral shedding in urine. In sheep, all experimentally infected animals presented the typical intermittent shedding patterns, independently of the inoculated leptospiral strain. We considered that a careful serial analysis of urine samples for a more definitive and reliable individual diagnosis would be required for a successful antimicrobial therapy and control of leptospirosis on a herd.

Reproductive Disorders and Leptospirosis: A Case Study in a Mixed-Species Farm (Cattle and Swine)

“…Molecular diagnosis in blood and urine samples of cows did not contribute to a final diagnosis. On the other hand, bacteraemia is transient [ 17 ] and shedding in urine intermittent [ 18 , 19 ]. In the swine unit, the clinical scenario was less documented, albeit irregular cases of spontaneous abortions were noticed and a clear rat infestation problem was observed at the time of the site visit.…”

Rat in a Cage: Trappability of Urban Norway Rats (Rattus norvegicus)

“…However, an analysis of the rats caught outside of the seven-day window demonstrated that these rats were on average 138g (n=16), within the weight range assigned to "smaller rats". Additionally, while our study found that 12% of rats were positive for Leptospira spp., it is possible that this is an underestimate of the actual number of infected rats as previous studies in in other species found intermittent or decreasing shedding of Leptospira over time (Leonard et al, 1992;Rocha et al, 2017). However, in a study which evaluated Leptospira shedding by Norway rats over two months in Salvador, Brazil, the bacteria was shed consistently over time (Costa et al, 2015), and therefore the extent to which variations in shedding affects our study is unclear.…”

Dynamics of experimental infection with Leptospira serogroup Pomona in different sheep breed

“…The number of positive samples of vaginal fluid in the PCR was similar to the quantity of positive samples of urine in both groups; however it is probable that the intermittent elimination of the agent through the urine influenced negatively the evaluation of the elimination by this route (Costa et al, 2018;Rocha et al, 2017;Rocha et al, 2018). With this in mind, this hypothesis is further reinforced by the fact that the majority of the sheep having been renal bearers of the agent.…”