Human leptospirosis in Seychelles: A prospective study confirms the heavy burden of the disease but suggests that rats are not the main reservoir

• Published in: PLOS Neglected Tropical Diseases
• Main Authors: Biscornet, Leon, Dellagi, Koussay, Pagès, Frédéric, Bibi, Jastin, de Comarmond, Jeanine, Mélade, Julien, Govinden, Graham, Tirant, Maria, Gomard, Yann, Guernier, Vanina, Lagadec, Erwan, Mélanie, Jimmy, Rocamora, Gérard, Le Minter, Gildas, Jaubert, Julien, Mavingui, Patrick, Tortosa, Pablo
• Other Authors: Seychelles Public Health Laboratory, Ministry of Health Mozambique, Processus Infectieux en Milieu Insulaire Tropical (PIMIT), Université de La Réunion (UR)-Institut National de la Santé et de la Recherche Médicale (INSERM)-IRD-Centre National de la Recherche Scientifique (CNRS), Centre de Recherche et de Veille sur les Maladies Émergentes dans l'Océan Indien (CRVOI), Université de La Réunion (UR), Cyclotron Réunion Océan Indien (CYROI), Université de La Réunion (UR)-Centre Hospitalier Universitaire de La Réunion (CHU La Réunion), Regional Office of the French Institute for Public Health Surveillance, Institut de Veille Sanitaire (INVS), Ministry of health of Seychelles, Ministry of agriculture and fisheries, Université des Seychelles, Groupe Hospitalier Sud Réunion (GHSR)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2017
• Subjects: Leptospira interrogans; Seychelles; Leptospirosis; Leptospira; Bacterial pathogens; Infectious disease epidemiology; Islands; Polymerase chain reaction; [SDV.SPEE]Life Sciences [q-bio]/Santé publique et épidémiologie; [SDV.MHEP.MI]Life Sciences [q-bio]/Human health and pathology/Infectious diseases; Rattus rattus
• Online Access: https://hal.univ-reunion.fr/hal-01592503; https://hal.univ-reunion.fr/hal-01592503/document; https://hal.univ-reunion.fr/hal-01592503/file/journal.pntd.0005831.pdf; https://doi.org/10.1371/journal.pntd.0005831

International audience Background: Leptospirosis is a bacterial zoonosis caused by pathogenic Leptospira for which rats are considered as the main reservoir. Disease incidence is higher in tropical countries, especially in insular ecosystems. Our objectives were to determine the current burden of leptospirosis in Seychelles, a country ranking first worldwide according to historical data, to establish epidemiological links between animal reservoirs and human disease, and to identify drivers of transmission.Methods: A total of 223 patients with acute febrile symptoms of unknown origin were enrolled in a 12-months prospective study and tested for leptospirosis through real-time PCR, IgM ELISA and MAT. In addition, 739 rats trapped throughout the main island were investigated for Leptospira renal carriage. All molecularly confirmed positive samples were further genotyped.Results: A total of 51 patients fulfilled the biological criteria of acute leptospirosis, corresponding to an annual incidence of 54.6 (95% CI 40.7–71.8) per 100,000 inhabitants. Leptospira carriage in Rattus spp. was overall low (7.7%) but dramatically higher in Rattus norvegicus (52.9%) than in Rattus rattus (4.4%). Leptospira interrogans was the only detected species in both humans and rats, and was represented by three distinct Sequence Types (STs). Two were novel STs identified in two thirds of acute human cases while noteworthily absent from rats.Conclusions: This study shows that human leptospirosis still represents a heavy disease burden in Seychelles. Genotype data suggests that rats are actually not the main reservoir for human disease. We highlight a rather limited efficacy of preventive measures so far implemented in Seychelles. This could result from ineffective control measures of excreting animal populations, possibly due to a misidentification of the main contaminating reservoir(s). Altogether, presented data stimulate the exploration of alternative reservoir animal hosts.