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Background: The presence of synanthropic rodents, such as Rattus norvegicus, in urban environments generates high costs of prophylaxis and control, in large part due to the environmental transmission of the pathogenic spirochete Leptospira interrogans, which causes leptospirosis. In Salvador, Brazil, The Center for Control of Zoonosis (CCZ) is responsible for planning and implementing Rodent Control Programs (RCP) which are based on chemical rodenticide. However, these strategies have not been standardized for use in developing countries. Aim: This study aimed to identify the effect of a chemical control campaign on the demographic variables of urban R. norvegicus, analyzing relative abundance, sex structure, body mass, and age of the population, as well as the characterization of spatial distribution among households, rodent capture campaigns and interventions. Methods: This study was carried out during 2015 in three valleys of an urban poor community in Salvador. Individuals of R. norvegicus were systematically captured before (Pre-intervention) and three months (1st post-intervention) and six months (2nd post-intervention) after a chemical control intervention conducted by the CCZ in two valleys of the study area while the third valley was not included in the intervention campaign and was used as a non-intervention reference. We used analysis of variance to determine if intervention affected demographic variables and chi-square to compare proportions of infested households (Rodent infestation index–PII). Results: During the chemical intervention, 939 households were visited. In the pre-intervention campaign, an effort of 310 trap nights resulted in 43 rodents captured, and in the 1st and 2nd, post-intervention campaigns resulted in 47 rodents captured over 312 trap nights and 36 rodents captured over 324 traps-nights, respectively. The rodent infestation index (PII) points did not show a reduction between the period before the intervention and the two periods after the chemical intervention (70%, 72%, and 65%, respectively). Regarding relative abundances, there was no difference between valleys and period before and two periods after chemical intervention (trap success valley 1: 0,18; 0,19; 0,18 / Valley 3 0,15; 0,17; 0,13/ P>0,05). Other demographic results showed that there was no difference in demographic characteristics of the rodent population before and after the intervention, as well as there being no influence of the application of rodenticide on the areas of concentration of capture of rodents between the campaigns. Conclusion: Our study indicates that the chemical control was not effective in controlling the population of R. norvegicus and provides evidence of the need for re-evaluation of rodent control practices in urban poor community settings. [ABSTRACT FROM AUTHOR]

In this study, we genotyped samples from environmental reservoirs (surface water and soil), colonized rat specimens, and cases of human severe leptospirosis from an endemic urban slum in Brazil, to determine the molecular epidemiology of pathogenic Leptospira and identify pathways of leptospirosis infection. We identified a well-established population of Leptospira interrogans serovar Copenhageni common to human leptospirosis cases, and animal and environmental reservoirs. This finding provides genetic evidence for a potential environmental spillover pathway for rat-borne leptospirosis through the environment in this urban community and highlights the importance of environmental and social interventions to reduce spillover infections. [ABSTRACT FROM AUTHOR]

Background: We address some critical but unknown parameters of individuals and populations of Norway rats (Rattus norvegicus) that influence leptospiral infection, maintenance and spirochetal loads shed in urine, which contaminates the environment ultimately leading to human infection. Methodology/Principal Findings: Our study, conducted in Salvador, Brazil, established the average load of leptospires in positive kidneys to be 5.9 x 106 per mL (range 3.1-8.2 x106) genome equivalents (GEq), similar to the 6.1 x 106 per ml (range 2.2-9.4 x106) average obtained from paired urines, with a significant positive correlation (R2=0.78) between the two. Based on bivariate and multivariate modeling, we found with both kidney and urine samples that leptospiral loads increased with the age of rats (based on the index of body length to mass), MAT titer and the presence of wounding/scars, and varied with site of capture. Some associations were modified by sex but trends were apparent. Combining with data on the demographic properties and prevalence of leptospiral carriage in rat populations in Salvador, we estimated that daily leptospiral loads shed in the urine of a population of 82 individuals exceeded 9.1 x 1010 leptospires. Conclusions/Significance: These factors directly influence the risk of leptospiral acquisition among humans and provide essential epidemiological information linking properties of rat populations with risk of human infection. Author Summary: Leptospirosis is a human disease caused by the bacterium Leptospira. It is often acquired through contact with water/soil contaminated with leptospires shed in the urine of rats, the most important reservoirs in urban environment. We evaluated how location, sex, age and other rat characteristics can influence the amount of leptospires shed into the environment. We found that rats from different locations were able to shed different concentrations of leptospires. Rat populations were able to shed more than one billion leptospires per day. The findings of this study provide information linking rat population and the risk of human leptospirosis. [ABSTRACT FROM AUTHOR]

We examine coinfection between helminth species and the bacterium Leptospira interrogans in a natural population of the Norway rat, Rattus norvegicus. We ask whether coinfection can influence the probability and intensity of infection of these enzootic and zoonotic parasites in urban rats, which may affect the loads of parasites excreted into the environment. Rodent sampling was carried out during two seasons in 2014 in a Brazilian urban slum. We sampled rats' feces, kidney imprints, and urine to identify and quantify helminth eggs/larvae and infection by L. interrogans. Eleven species/groups of helminths and L. interrogans were identified among 299 captured rats. Simple correlation tests and generalized linear models were performed to identify general patterns of coinfection and potential direction of effects, respectively, after controlling for consolidated environmental and host biotic variables. Significant associations were illustrated in an interaction network. Focusing on parasites with the potential to cause zoonoses among humans, we observed that coinfection between L. interrogans and the nematode Angiostrongylus cantonensis was significantly more frequent than expected. Reduced prevalence of A. cantonensis was found in the presence of Nippostrongylus brasiliensis, and N. brasiliensis intensities (eggs per gram of feces) were increased with greater intensities of both L. interrogans and Strongyloides sp., the latter of which was, in turn, found to increase the intensities of A. cantonensis. A higher probability of finding L. interrogans was associated with infection by Strongyloides sp. Our study provides a novel perspective on evaluating helminth coinfection profiles in populations of naturally infected urban rats, moving beyond previous studies which have been limited to descriptions of co‐occurrence. Noticeably, infection risk was dependent on coinfection and this should be accounted for when targeting the control of zoonotic pathogens in natural populations. [ABSTRACT FROM AUTHOR]