Basic urban services fail to neutralise environmental determinants of 'rattiness', a composite metric of rat abundance

Globally, low-income urban communities suffer from poor provision of services and degraded environments, favouring opportunistic zoonotic reservoirs, such as rats. Large-scale infrastructural improvements in these contexts are limited, but targeted control of disease reservoirs has sometimes been achieved. A starting point for the targeted control of rats is assessing the impact of existing basic services on rat abundance. However, there is no gold-standard metric for rat abundance, and studies have used different or multiple metrics. Here, therefore, in four low-income urban Brazilian communities, we address the question of whether basic urban services (BUS) - trash collection, rodenticide application and health community agent visits - affect rat abundance, through the first application of the rattiness modelling framework. This recently-developed geostatistical method combines multiple abundance metrics (here, three) to generate rattiness, a proxy for rat abundance, a spatially-continuous latent process common to all metrics. In a cross-sectional study, we exploited spatial heterogeneities in BUS to evaluate its association with the presence of rat signs, rat marks on track plates, and live-trapped rats, and with rattiness, which combined these three imperfect metrics. Rattiness proved to be a useful tool for pooling information among the three metrics and was associated with a greater range of baseline predictors than any single metric. Rat signs and rattiness were positively associated with higher levels of BUS provision and environmental variables known to provide resources for rats. The strong association of baseline environmental variables with rat abundance highlights the need for targeted, small-scale environmental modifications to reduce resources for rats.

Automated summary

Globally, low-income urban communities suffer from poor provision of services and degraded environments, creating favorable conditions for the spread of zoonotic diseases through animals such as rats. This study in low-income urban communities in Brazil investigated the impact of basic urban services on rat abundance using a rattiness modeling framework. The study found that rattiness, a proxy for rat abundance, was associated with higher levels of basic urban services provision and environmental variables that provided resources for rats. The findings highlight the need for targeted environmental modifications to reduce rat resources.