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Leptospirosis in the western Indian Ocean islands: what is known so far?

Desvars A, Michault A, Bourhy P - Vet. Res. (2013)

Bottom Line: The clinical signs of the human disease are generally similar to an influenza-like syndrome, but acute forms of the disease are reported and mortality remains significant in this region.In animals, clinical forms are mainly asymptomatic but leptospirosis reduces the fertility of livestock, resulting in economic losses.The rat is recognized as the major reservoir host for the bacteria on all islands, but recent data from Reunion Island indicates that almost all mammals can be a source of contamination.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institut Pasteur, Unité de Biologie des Spirochètes, Centre National de Référence de la Leptospirose, Paris, France. pbourhy@pasteur.fr.

ABSTRACT
In the past decade, leptospirosis has emerged as a major zoonosis with a worldwide distribution. The disease is caused by bacteria of the genus Leptospira. The western Indian Ocean includes more than one hundred tropical or subequatorial islands where leptospirosis constitutes a major public health problem. The clinical signs of the human disease are generally similar to an influenza-like syndrome, but acute forms of the disease are reported and mortality remains significant in this region. In animals, clinical forms are mainly asymptomatic but leptospirosis reduces the fertility of livestock, resulting in economic losses. The data available about human and animal leptospirosis in the western Indian Ocean islands are diverse: human leptospirosis has been extensively studied in Reunion Island, Mayotte, and the Seychelles, whereas the human clinical disease has never been described in Madagascar, Comoros, Mauritius, or Rodrigues, mainly because of the deficiency in appropriate medical and diagnostic structures. The rat is recognized as the major reservoir host for the bacteria on all islands, but recent data from Reunion Island indicates that almost all mammals can be a source of contamination. The incidence of leptospirosis in humans is highly seasonal, and linked to the rainy season, which is favorable for the environmental maintenance and transmission of the bacteria. The epidemiology of leptospirosis is fully island-dependent, related to the number of mammalian species, the origins of the introduced mammalian species, the relationships between humans and fauna, and environmental as well as cultural and socio-economic factors.

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Global methods of investigation of leptospirosis. Islands are small (except Madagascar) closed territories in which the number of mammal species is known (except in Madagascar) and each can be studied. Transdisciplinary approaches, incorporating diverse disciplines and approaches specific to leptospirosis should contribute to a better understanding of the mechanisms of transmission in the different ecosystems across the region. Interaction and data exchange between the various research teams of the western Indian Ocean islands is crucial.
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Figure 2: Global methods of investigation of leptospirosis. Islands are small (except Madagascar) closed territories in which the number of mammal species is known (except in Madagascar) and each can be studied. Transdisciplinary approaches, incorporating diverse disciplines and approaches specific to leptospirosis should contribute to a better understanding of the mechanisms of transmission in the different ecosystems across the region. Interaction and data exchange between the various research teams of the western Indian Ocean islands is crucial.

Mentions: The incidence of leptospirosis in humans is affected by rainfall, particularly in tropical regions [81-83]. In Reunion Island, cases of leptospirosis are reported all year round, but epidemics mostly occur during the rainy season [26,28,31,84]. Therefore, despite popular belief, the peak incidence of leptospirosis in Reunion Island is not during the sugar cane harvest (July to December) [84]. This seasonality in leptospirosis cases is also observed in Mayotte where almost all cases are reported during the rainy season [21]. In the Seychelles, the relationship between rainfall and leptospirosis cases is weaker than in Mayotte or Reunion Island, probably because the rainy season is not well-defined [30]. A prediction model could be a useful tool for the identification of cases and, obviously, for predicting epidemics; this may facilitate improved diagnosis and treatment of leptospirosis to reduce lethality rates [85,86]. Statistical modeling should include the number of cases, meteorological factors, and data on animal and human population density (Figure 2).


Leptospirosis in the western Indian Ocean islands: what is known so far?

Desvars A, Michault A, Bourhy P - Vet. Res. (2013)

Global methods of investigation of leptospirosis. Islands are small (except Madagascar) closed territories in which the number of mammal species is known (except in Madagascar) and each can be studied. Transdisciplinary approaches, incorporating diverse disciplines and approaches specific to leptospirosis should contribute to a better understanding of the mechanisms of transmission in the different ecosystems across the region. Interaction and data exchange between the various research teams of the western Indian Ocean islands is crucial.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3852700&req=5

Figure 2: Global methods of investigation of leptospirosis. Islands are small (except Madagascar) closed territories in which the number of mammal species is known (except in Madagascar) and each can be studied. Transdisciplinary approaches, incorporating diverse disciplines and approaches specific to leptospirosis should contribute to a better understanding of the mechanisms of transmission in the different ecosystems across the region. Interaction and data exchange between the various research teams of the western Indian Ocean islands is crucial.
Mentions: The incidence of leptospirosis in humans is affected by rainfall, particularly in tropical regions [81-83]. In Reunion Island, cases of leptospirosis are reported all year round, but epidemics mostly occur during the rainy season [26,28,31,84]. Therefore, despite popular belief, the peak incidence of leptospirosis in Reunion Island is not during the sugar cane harvest (July to December) [84]. This seasonality in leptospirosis cases is also observed in Mayotte where almost all cases are reported during the rainy season [21]. In the Seychelles, the relationship between rainfall and leptospirosis cases is weaker than in Mayotte or Reunion Island, probably because the rainy season is not well-defined [30]. A prediction model could be a useful tool for the identification of cases and, obviously, for predicting epidemics; this may facilitate improved diagnosis and treatment of leptospirosis to reduce lethality rates [85,86]. Statistical modeling should include the number of cases, meteorological factors, and data on animal and human population density (Figure 2).

Bottom Line: The clinical signs of the human disease are generally similar to an influenza-like syndrome, but acute forms of the disease are reported and mortality remains significant in this region.In animals, clinical forms are mainly asymptomatic but leptospirosis reduces the fertility of livestock, resulting in economic losses.The rat is recognized as the major reservoir host for the bacteria on all islands, but recent data from Reunion Island indicates that almost all mammals can be a source of contamination.

View Article: PubMed Central - HTML - PubMed

Affiliation: Institut Pasteur, Unité de Biologie des Spirochètes, Centre National de Référence de la Leptospirose, Paris, France. pbourhy@pasteur.fr.

ABSTRACT
In the past decade, leptospirosis has emerged as a major zoonosis with a worldwide distribution. The disease is caused by bacteria of the genus Leptospira. The western Indian Ocean includes more than one hundred tropical or subequatorial islands where leptospirosis constitutes a major public health problem. The clinical signs of the human disease are generally similar to an influenza-like syndrome, but acute forms of the disease are reported and mortality remains significant in this region. In animals, clinical forms are mainly asymptomatic but leptospirosis reduces the fertility of livestock, resulting in economic losses. The data available about human and animal leptospirosis in the western Indian Ocean islands are diverse: human leptospirosis has been extensively studied in Reunion Island, Mayotte, and the Seychelles, whereas the human clinical disease has never been described in Madagascar, Comoros, Mauritius, or Rodrigues, mainly because of the deficiency in appropriate medical and diagnostic structures. The rat is recognized as the major reservoir host for the bacteria on all islands, but recent data from Reunion Island indicates that almost all mammals can be a source of contamination. The incidence of leptospirosis in humans is highly seasonal, and linked to the rainy season, which is favorable for the environmental maintenance and transmission of the bacteria. The epidemiology of leptospirosis is fully island-dependent, related to the number of mammalian species, the origins of the introduced mammalian species, the relationships between humans and fauna, and environmental as well as cultural and socio-economic factors.

Show MeSH
Related in: MedlinePlus