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

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.

Leptospira Infection in African Green Monkeys in an Endemic Area: An Opportunity for Comparative Studies in a Natural Environment

“…Only one of these samples was evaluated by histopathology, but only mild multifocal interstitial nephritis was observed in this case and this animal was negative by microscopic agglutination test. This is not surprising as we have observed similar findings in other animal species where antibody response or lesions were minimal despite the presence of organisms [12,13,18]. It is roughly estimated that 50,000 AGMs inhabit Saint Kitts, a small island with a 168 km 2 area.…”

“…In rats from which we isolated L. interrogans serovar Copenhageni, the highest exposure was documented for serovar Icterohemorrhagiae but not for the infecting serovar Copenhageni. Exposure to serovar Ballum, a commonly found serovar in Saint Kitts rats [13] and mice (unpublished data), was also observed in this group of AGMs tested. The wild and captive AGMs are in contact with the rodents, and direct or indirect transmission from these highly infected vectors is possible in AGMs.…”

“…Out of two PCR-positive samples one was positive for six Leptospira serovars with MAT titers ranging from 50-200, suggestive of a potential early active infection. We have isolated L. interrogans serovar Copenhageni from rats, mongooses, and a dog from the island [12,13,15]. In rats from which we isolated L. interrogans serovar Copenhageni, the highest exposure was documented for serovar Icterohemorrhagiae but not for the infecting serovar Copenhageni.…”

“…Proximity to the Leptospira infected animals can be a potential risk factor for other animals and humans. Our studies have also documented Leptospira infection and exposure in other animal species on the island [12][13][14][15][16]. In this pilot study, we investigated whether the African green monkeys (AGMs) could potentially serve as an asymptomatic source of infection and whether there is any association between Leptospira infection or exposure and the presence of renal pathology in a set of AGMs.…”

Seroepidemiological investigation of animal leptospirosis and molecular characterization of the first Leptospira strain isolated from Fernando de Noronha archipelago, Brazil

“…interrogans serogroup Pyrogenes, and no serum antibodies against Leptospira could be identified in the rat that leptospires could be recovered. Similar lack of correlation has also been reported in an insular environment (Rajeev et al., 2020), and further attempts to isolate leptospires from rats should be performed in future studies. Pyrogenes strains have been isolated from humans in New Caledonia (Thibeaux et al., 2017), Philippines (Villanueva et al., 2014), Costa Rica (Valverde et al., 2013) and Mayotte islands (Bourhy et al., 2010).…”