Abstract
BackgroundLeptospirosis has gained much attention in Sri Lanka since its large outbreak in 2008. However, most of the cases were clinically diagnosed and information on Leptospira genotypes and serotypes currently prevailing in the country is lacking.Methodology/Principal findingsWe retrospectively analyzed 24 Leptospira strains from human patients as well as isolated and characterized three Leptospira strains from black rats using the microscopic agglutination test with antisera for 19 serovars and multilocus sequence typing. The isolates were identified as Leptospira borgpetersenii sequence types (STs) 143 and 144; L. interrogans STs 30, 34, 43, 44, 74, 75, 80, 308, 313, 314, 316, and 317; and L. kirschneri ST318. Six of the 15 STs were identified for the first time in this study. Five serogroups such as Autumnalis, Grippotyphosa, Hebdomadis, Javanica, and Pyrogenes were detected among the isolates. Contrary to previous studies, various genotypes including novel STs were isolated during an outbreak in Southern Province. L. borgpetersenii serogroup Javanica ST143 was isolated both from a human and black rat.Conclusions/SignificanceThis study revealed that genetically diverse Leptospira strains currently circulate in Sri Lanka: some genotypes have been circulating and others have emerged recently, which may explain the recent surge of leptospirosis patients with varying clinical manifestations and frequent outbreaks of leptospirosis. Black rats were identified as the source of infection for humans, but reservoir animals for other genotypes remain unknown.
Highlights
Leptospirosis is a zoonotic disease caused by pathogenic spirochaetes of Leptospira spp. belonging to subclades P1 and P2 [1,2,3,4]
This study revealed that genetically diverse Leptospira strains currently circulate in Sri Lanka: some genotypes have been circulating and others have emerged recently, which may explain the recent surge of leptospirosis patients with varying clinical manifestations
We revealed that genetically diverse Leptospira strains presently cause human leptospirosis in this country
Summary
Leptospirosis is a zoonotic disease caused by pathogenic spirochaetes of Leptospira spp. belonging to subclades P1 and P2 [1,2,3,4]. Recent molecular investigations detected L. borgpetersenii, L. interrogans, L. kirschneri, and L. weilii in clinical samples of febrile human patients and regional differences of predominant Leptospira species in the country [13, 15,16,17,18]. Leptospira DNAs belonging to L. borgpetersenii, L. interrogans, and L. kirschneri have been recently detected in cattle kidney or urine samples collected in distinct areas [14, 19]. Leptospira strains were isolated from humans, rodents, shrews, and dogs in 1960s and early 1970s [20, 21], only one report of culture isolation of L. interrogans unidentified serogroups has been published in Sri Lanka during the past 40 years [22]. Most of the cases were clinically diagnosed and information on Leptospira genotypes and serotypes currently prevailing in the country is lacking.
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