Detection and Characterization of Leptospira Infection and Exposure in Rats on the Caribbean Island of Saint Kitts

SIMPLE SUMMARY: Leptospirosis is a widespread zoonotic and potentially life-threatening disease in humans and animals. Many animal species maintain Leptospira, the bacterial agent causing this disease, in the kidneys and they shed the bacteria in urine. These animals act as a source of infection and environmental contamination. Leptospira infection has been previously reported in several animals on the Caribbean island of Saint Kitts, yet, no data is currently available on rats, a significant reservoir host of this pathogen. The main goal of this study was to detect Leptospira infection and exposure in two species of rats on Saint Kitts, by using a complementary set of diagnostic tools. Infecting Leptospira strains were subsequently characterized with a combination of serologic, molecular, and genomic techniques. Results show a relatively high prevalence of infection with L. interrogans (serogroup Icterohaemorrhagiae) and L. borgpetersenii (serogroup Ballum), with evidence supporting mixed infection with both species in some rats. Our study suggests the use of multiple diagnostic tests to enhance the results of Leptospira surveillance studies and diagnostic investigations. ABSTRACT: In this study, we detected and characterized Leptospira infection and exposure in rats on the Caribbean island of Saint Kitts for the first time. We detected Leptospira infection in 17/29 (59%), 14/29 (48)%, and 11/29 (38)% of rats by RT-PCR, culture, and immunofluorescence assay, respectively. Whole genome sequencing (WGS) and analysis and serogrouping of 17 Leptospira strains isolated from rats revealed their close relationship with L. interrogans serogroup Icterohaemorrhagiae (n = 10) and L. borgpetersenii serogroup Ballum (n = 7). WGS, serogrouping, and additional PCR tests on rat kidneys confirmed mixed infections with L. interrogans and L. borgpetersenii in the kidneys of three rats. Microscopic agglutination test (MAT) was positive for 25/29 (87%) of the rats tested, and the response was restricted to serovars Icterohaemorrhagiae {24/29(83%)}, Mankarso {4/29(14%)}, Copenhageni {4/29(14%)}, Grippotyphosa {2/29(7%)}, and Wolffi {1/29(3%)}. Interestingly, there was no agglutinating antibody response to serovar Ballum. We observed a similar pattern in the serologic response using Leptospira isolates obtained from this study with each of the rat sera, with strong response to L. interrogans isolates but minimal reactivity to L. borgpetersenii isolates. Our findings suggest the use of multiple complementary diagnostic tests for Leptospira surveillance and diagnosis to improve the accuracy of the data.