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

In this study, we detected and characterized infection and exposure in rats on the Caribbean island of Saint Kitts for the first time. We detected 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 strains isolated from rats revealed their close relationship with serogroup Icterohaemorrhagiae ( = 10) and serogroup Ballum ( = 7). WGS, serogrouping, and additional PCR tests on rat kidneys confirmed mixed infections with and 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 isolates obtained from this study with each of the rat sera, with strong response to isolates but minimal reactivity to isolates. Our findings suggest the use of multiple complementary diagnostic tests for surveillance and diagnosis to improve the accuracy of the data.