Miller, Poppy

Identifying hotspots of rat activity and quantifying their effect on the risk of leptospirosis in urban slums

Poppy Miller1,2, Chris Jewell1, Peter Diggle1, and Kate Hacker3

1. Lancaster University, United Kingdom

2. AgResearch, Palmerston North

3. Yale University, New Haven, Conneticutt

Leptospirosis is much more prevalent in urban slums than in most other parts of the world. It is suspected that one of the key predictors of leptospirosis risk is exposure to rats. However, rodent control has so far been largely ineffective at reducing the burden of leptospirosis in urban slum environments where Norway rats (Rattus norvegicus) are the primary reservoir hosts.

Our study aims to quantify the risk attributable to rat exposure compared to other known risk factors in an urban slum. As part of this, we estimate a spatio-temporal rat activity surface over the study area which can be used to target rodent control more effectively.

The study design was a spatially continuous constrained random sample (340 points) at locations throughout a Brazilian urban slum community. An additional 100 random points were added at close range, to distinguish between short range spatial variation and underlying noise, allowing identification of hotspots at very small ranges. Tracking boards at each study location detect if a rat crosses them. All residents of the study area were asked to participate in the study, and their leptospirosis infection status was measured every 6 months.

At all points, we performed environmental surveys and used satellite imagery to derive spatially relevant covariates. We analyzed the rat activity data using a generalised linear spatial model to evaluate the association between rat activity and nearby environmental characteristics, and to create high-resolution predictive maps of relative rat activity/abundance. This allowed identification of defined environmental features of slum communities, which predict rat abundance.

We then predicted rat abundance near each study participants homes, and used these to quantify of the risk of leptospirosis attributable to nearby rat abundance compared to other risk factors.

NZSAStudent This presentation is eligible for the NZSA Student Prize.