Biodiversity and leptospirosis risk: A case of pathogen regulation?

School of Population Health, Level 2 Public Health Building, University of Queensland, Herston Qld 4006, Australia.
Medical Hypotheses (Impact Factor: 1.07). 06/2011; 77(3):339-44. DOI: 10.1016/j.mehy.2011.05.009
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Well balanced ecosystems have an essential role in disease regulation, and consequently their correct functioning is increasingly recognised as imperative for maintaining human health. Disruptions to ecosystems have been found to increase the risk of several diseases, including Hantavirus, Lyme disease, Ross River virus, malaria and Ciguatera fish poisoning. Leptospirosis is a globally important emerging zoonosis, caused by spirochaete bacteria, borne by many mammalian hosts, and also transmitted environmentally. We propose that leptospirosis incidence in humans is also linked to ecosystem disruption, and that reduced biodiversity (the diversity of species within an ecological community) may be associated with increased leptospirosis incidence. To investigate this hypothesis, the relationship between biodiversity levels of island nations and their annual leptospirosis incidence rates (adjusted for GDP per capita) was examined by linear correlation and regression. Supportive, statistically significant negative associations were obtained between leptospirosis incidence and (a) total number of species (r2=0.69, p<0.001) and (b) number of mammal species (r2=0.80, p<0.001) in univariate analysis. In multivariable analysis only the number of mammal species remained significantly associated (r2=0.81, p=0.007). An association between biodiversity and reduced leptospirosis risk, if supported by further research, would emphasise the importance of managing the emergence of leptospirosis (and other infectious diseases) at a broader, ecosystem level.

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    • "Thus, a higher percentage of ticks that bite humans are infectious, linking biodiversity loss directly to disease emergence (Ostfeld and Keesing, 2000). It is tempting to generalise from this example that biodiversity conservation is protective against infectious disease emergence, and many other examples indeed support that this is the case (Ostfeld, 2009), chiefly for arthropod mediated infections, but also for directly transmitted zoonoses (Derne et al., 2011). However, a recent review article (Randolph and Dobson, 2012) and meta-analysis (Salkeld et al., 2013) have seriously questioned the generalisability of the statement " biodiversity protects against disease " (Randolph and Dobson, 2012). "
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    ABSTRACT: It is well known that the degradation of ecosystems can have serious impacts on human health. There is currently a knowledge gap on what impact restoring ecosystems has on human health. In restoring ecosystems there is a drive to restore the functionality of ecosystems rather than restoring ecosystems to ‘pristine’ condition. Even so, the complete restoration of all ecosystem functions is not necessarily possible. Given the uncertain trajectory of the ecosystem during the ecosystem restoration process the impact of the restoration on human health is also uncertain. Even with this uncertainty, the restoration of ecosystems for human health is still a necessity.
    Science of The Total Environment 01/2015; 502:276–279. DOI:10.1016/j.scitotenv.2014.09.028 · 4.10 Impact Factor
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    • "This observation contrasts with that of Redetzke and McCann (1980), who found a density-dependent relationship. Leptospira maintenance and transmission in Janos may depend on several factors, including temperature, frequency of droughts and rainy periods, and the accessibility of humid environments for Leptospira survival and reproduction (Derne et al. 2011). "
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    ABSTRACT: Abstract Interest in the study of infectious diseases of wildlife has grown in recent decades and now focuses on understanding host-parasite dynamics and factors involved in disease occurrence. The black-tailed prairie dog (Cynomys ludovicianus) is a useful species for this type of investigation because it lives in heterogeneous landscapes where human activities take place, and its populations are structured as a metapopulation. Our goal was to determine if colony area, density, and proximity to human settlements are associated with prevalence of antibodies to Leptospira interrogans in black-tailed prairie dogs of northwestern Chihuahua State, Mexico. We captured 266 prairie dogs in 11 colonies in 2009 and analyzed 248 serum samples with the microscopic agglutination test (MAT) for antibody to any of the 12 pathogenic serovars of L. interrogans. Serologically positive test results for only serovars Bratislava, Canicola, Celledoni, and Tarassovi were considered for statistical analysis. Almost 80% of sera were positive for at least one pathogenic serovar (MAT titer ≥1∶80). The highest recorded antibody prevalences were to serovars Bratislava and Canicola. Correlation analysis showed a negative relationship between L. interrogans antibody prevalence and colony area (r = -0.125, P<0.005), suggesting that animals living in larger colonies were at a lower risk than those in smaller colonies. The correlation between the serovar Canicola and distance was negative (r = -0.171, P<0.007), and this relationship may be explained by the presence of domestic dogs associated with human dwellings. This is the first study of Leptospira spp. antibody prevalence in prairie dogs, and it provides valuable insights into the dynamics of leptospirosis in threatened wildlife species. Further studies are needed to evaluate the impact of Leptospira serovars in metapopulations of prairie dogs and other domestic and wild mammals in grassland communities.
    Journal of wildlife diseases 11/2014; 51(1). DOI:10.7589/2013-10-259 · 1.36 Impact Factor
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    • "Morse (1993) termed this 105 pathogen diversity in wildlife hosts the 'zoonotic pool'. In the liter- 106 ature, most studies emphasized the links between biodiversity loss 107 and the risk of pathogen emergence and transmission (Keesing 108 et al., 2009; Derne et al., 2011), whereas very few investigated 109 the role of parasite diversity, or the size of the 'zoonotic pool', in 110 the risk of emergence. "
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    ABSTRACT: Interest in bat-borne diseases and parasites has grown in the past decade over concerns for human health. However, the drivers of parasite diversity among bat host species are understudied as are the links between parasite richness and emerging risks. Thus, we aimed at exploring factors that explain macro and microparasite species richness in bats from Southeast Asia, a hotspot of emerging infectious diseases. First, we identified bat species that need increased sampling effort for pathogen discovery. Our approach highlights pathogen investigation disparities among species within the same genus, such as Rhinolophus and Pteropus. Secondly, comparative analysis using independent contrasts method allowed the identification of likely factors explaining parasite and viral diversity of bats. Our results showed a key role of bat distribution shape, an index of the fragmentation of bat distribution, on parasite diversity, linked to a decrease for both viral and endoparasite species richness. We discuss how our study may contribute to a better understanding of the link between parasite species richness and emergence.
    International Journal for Parasitology: Parasites and Wildlife 08/2014; 3(2). DOI:10.1016/j.ijppaw.2014.06.003
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