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Evol Appl. 2017 Feb 23;10(4):323-337. doi: 10.1111/eva.12449. eCollection 2017 Apr.

Using fine-scale spatial genetics of Norway rats to improve control efforts and reduce leptospirosis risk in urban slum environments.

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Department of Biology Providence College Providence RI USA.
Department of Ecology & Evolutionary Biology Yale University New Haven CT USA.
Centro de Pesquisas Gonçalo Moniz Fundação Oswaldo Cruz Ministério da Saúde Salvador Brazil.
Centro de Controle de Zoonoses Secretaria Municipal de Saúde Ministério da Saúde Salvador Brazil.
Instituto de Saúde Coletiva Universidade Federal da Bahia, UFBA Salvador Brazil.
Department of Epidemiology of Microbial Disease Yale School of Public Health New Haven CT USA.
Centro de Pesquisas Gonçalo MonizFundação Oswaldo CruzMinistério da SaúdeSalvadorBrazil; Department of Epidemiology of Microbial DiseaseYale School of Public HealthNew HavenCTUSA.


The Norway rat (Rattus norvegicus) is a key pest species globally and responsible for seasonal outbreaks of the zoonotic bacterial disease leptospirosis in the tropics. The city of Salvador, Brazil, has seen recent and dramatic increases in human population residing in slums, where conditions foster high rat density and increasing leptospirosis infection rates. Intervention campaigns have been used to drastically reduce rat numbers. In planning these interventions, it is important to define the eradication units - the spatial scale at which rats constitute continuous populations and from where rats are likely recolonizing, post-intervention. To provide this information, we applied spatial genetic analyses to 706 rats collected across Salvador and genotyped at 16 microsatellite loci. We performed spatially explicit analyses and estimated migration levels to identify distinct genetic units and landscape features associated with genetic divergence at different spatial scales, ranging from valleys within a slum community to city-wide analyses. Clear genetic breaks exist between rats not only across Salvador but also between valleys of slums separated by <100 m-well within the dispersal capacity of rats. The genetic data indicate that valleys may be considered separate units and identified high-traffic roads as strong impediments to rat movement. Migration data suggest that most (71-90%) movement is contained within valleys, with no clear source population contributing to migrant rats. We use these data to recommend eradication units and discuss the importance of carrying out individual-based analyses at different spatial scales in urban landscapes.


epidemiology; favela; individual‐based sampling; intervention; landscape genetics; population genetics; public health; reservoir host; spatial scale; urban ecology; vector control

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