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Rodent abundance dynamics and leptospirosis carriage in an area of hyper-endemicity in New Caledonia.

ABSTRACT: BACKGROUND: Widespread but particularly incident in the tropics, leptospirosis is transmitted to humans directly or indirectly by virtually any Mammal species. However, rodents are recognized as the most important reservoir. In endemic regions, seasonal outbreaks are observed during hot rainy periods. In such regions, hot spots can be evidenced, where leptospirosis is "hyper-endemic", its incidence reaching 500 annual cases per 100,000. A better knowledge of how rodent populations and their Leptospira prevalence respond to seasonal and meteorological fluctuations might help implement relevant control measures. METHODOLOGY/PRINCIPAL FINDINGS: In two tribes in New Caledonia with hyper-endemic leptospirosis, rodent abundance and Leptospira prevalence was studied twice a year, in hot and cool seasons for two consecutive years. Highly contrasted meteorological situations, particularly rainfall intensities, were noted between the two hot seasons studied. Our results show that during a hot and rainy period, both the rodent populations and their Leptospira carriage were higher. This pattern was more salient in commensal rodents than in the sylvatic rats. CONCLUSIONS/SIGNIFICANCE: The dynamics of rodents and their Leptospira carriage changed during the survey, probably under the influence of meteorology. Rodents were both more numerous and more frequently carrying (therefore disseminating) leptospires during a hot rainy period, also corresponding to a flooding period with higher risks of human exposure to waters and watered soils. The outbreaks of leptospirosis in hyper-endemic areas could arise from meteorological conditions leading to both an increased risk of exposure of humans and an increased volume of the rodent reservoir. Rodent control measures would therefore be most effective during cool and dry seasons, when rodent populations and leptospirosis incidence are low.

SUBMITTER: Perez J

PROVIDER: S-EPMC3201910 | biostudies-literature | 2011 Oct

REPOSITORIES: biostudies-literature

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Rodent abundance dynamics and leptospirosis carriage in an area of hyper-endemicity in New Caledonia.

Perez Julie J Brescia Fabrice F Becam Jérôme J Mauron Carine C Goarant Cyrille C

PLoS neglected tropical diseases 20111025 10

<h4>Background</h4>Widespread but particularly incident in the tropics, leptospirosis is transmitted to humans directly or indirectly by virtually any Mammal species. However, rodents are recognized as the most important reservoir. In endemic regions, seasonal outbreaks are observed during hot rainy periods. In such regions, hot spots can be evidenced, where leptospirosis is "hyper-endemic", its incidence reaching 500 annual cases per 100,000. A better knowledge of how rodent populations and the ...[more]

PMID: 22039557

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Project description:BackgroundLeptospirosis is a major public health concern in New Caledonia (NC) and in other tropical countries. Severe manifestations of the disease are estimated to occur in 5-15% of all human infections worldwide and factors associated with these forms are poorly understood. Our objectives were to identify risk factors and predictors of severe forms of leptospirosis in adults.Methods and findingsWe conducted a retrospective case-control study of inpatients with laboratory-confirmed leptospirosis who were admitted to two public hospitals in NC in 2008-2011. Cases were patients with fatal or severe leptospirosis, as determined by clinical criteria. This approach was meant to be pragmatic and to reflect the routine medical management of patients. Controls were defined as patients hospitalized for milder leptospirosis. Risk and prognostic factors were identified by multivariate logistic regression. Among the 176 patients enrolled in the study, 71 had criteria of severity including 10 deaths (Case Fatality Rate?=?14.1%). Three risk factors were independently associated with severe leptospirosis: current cigarette smoking (OR?=?2.94 [CI 1.45-5.96]); delays >2 days between the onset of symptoms and the initiation of antibiotherapy (OR?=?2.78 [CI 1.31-5.91]); and Leptospira interrogans serogroup Icterohaemorrhagiae as the infecting strain (OR?=?2.79 [CI 1.26-6.18]). The following post-admission laboratory results correlated with poor prognoses: platelet count ?50,000/µL (OR?=?6.36 [CI 1.79-22.62]), serum creatinine >200 mM (OR?=?5.86 [CI 1.61-21.27]), serum lactate >2.5 mM (OR?=?5.14 [CI 1.57-16.87]), serum amylase >250 UI/L (OR?=?4.66 [CI 1.39-15.69]) and leptospiremia >1000 leptospires/mL (OR?=?4.31 [CI 1.17-15.92]).ConclusionsTo assess the risk of developing severe leptospirosis, our study illustrates the benefit for clinicians to have: i) the identification of the infective strain, ii) a critical threshold of qPCR-determined leptospiremia and iii) early laboratory results. In New Caledonia, preventative measures should focus on early presumptive antibacterial therapy and on rodent (reservoir of Icterohaemorrhagiae serogroup) control.

Dataset Information

Rodent abundance dynamics and leptospirosis carriage in an area of hyper-endemicity in New Caledonia.

Publications

Rodent abundance dynamics and leptospirosis carriage in an area of hyper-endemicity in New Caledonia.

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