Hotspots: are some areas of sewer network prone to re-infestation by rats (Rattus norvegicus) year after year?

Abstract

The records of sewer baiting work for three London boroughs were examined to see whether there were locations that exhibited 'rat' (Rattus norvegicus) activity more often than would be expected by chance, a feature we dubbed 'hotspots'. More than 100000 baiting records were checked covering 15 years of the London Borough of Enfield (Enfield) and 5 years each of the London Borough of Barnet (Barnet), and the Royal Borough of Kensington and Chelsea (RBKC). The additional boroughs were included for comparison to see whether any effect observed was confined to Enfield or was a feature that could be found in both inner and outer city locations. Each borough was divided into kilometre squares corresponding with those found both on Ordnance Survey maps and also Thames Water Utilities Asset maps. The number of records per square were logged and then the number of positive records for all the manholes in that square on a year-on-year basis. We examined 350 km2 in Enfield, 377 km2 in Barnet and 66 km2 in RBKC. The data were subjected to a weighted analysis (i.e. allowing for the number of manholes per square and the varying total rat population from year to year). Some areas were shown to exhibit significantly higher amounts of activity than others suggesting that their distribution is not random and that there must be environmental and other factors, which make certain locations attractive to rats. Squares with very high activity, repeating year-on-year, 'hotspots', were found in all three boroughs, suggesting that the phenomena are widespread.

Socioeconomic and environmental risk factors for urban rodent infestation in Sao Paulo, Brazil

“…Nevertheless, the Norway rat was the predominant species in Europe (Austria, Denmark and United Kingdom) and in USA (Leirs et al 2004;Traweger et al 2006;DEFRA 2005;Easterbrook et al 2007). This difference may be due to several factors: roof rat seems to be the predominant species in developing countries, maybe due to precariousness of habitations and environmental sanitation, and the Norway rat in developed countries, where it lives mainly in natural places, such as stream banks, sewer system, vacant lots, parks, gardens, and farms (DEFRA 2005;Traweger and Slotta-Bachmayr 2005;Channon et al 2006;Traweger et al 2006); on the other hand, roof rat seems to be related to warm climates, while Norway rat may dominate in cities with cold climates, as pointed out by Cavia et al (2009). Although these are attractive hypotheses, they still need supporting evidence studies, since there are some conflicting results: in Durban (South Africa), the main species is the Norway rat (Taylor et al 2008) and, even in Sao Paulo city, different boroughs present different infestation patterns by species.…”

Environmental conditions and rodent infestation in Campo Limpo district, São Paulo municipality, Brazil

“…The size of a rodent population in a given area is directly related to the maintenance of a favorable environment, to limiting factors such as food, water, harborage, parasites/diseases, predators and competitors (Jackson 1997;Channon et al 2006). Concerning these aspects, poor environmental conditions favor the growth of this population of animals, since under these conditions a large variety of resources, such as food and harborage are available (Perret et al 2005).…”

Rat infestation associated with environmental deficiencies in an urban slum community with high risk of leptospirosis transmission

“…It has been shown that R. norvegicus prefers environments with available water, and their presence has been associated with sewers 11,19,31 . In addition, GAM analysis found that households had a higher risk of rat infestation when situated within 25 meters from an open sewer (Figure 4) or at the lowest point in the valley ( Figure 5).…”

“…Campaigns for rodent control, based on the use of chemical rodenticides, have been a major strategy for preventing urban leptospirosis 10 . However, chemical interventions are not effective for long-term control of rodent infestations 11 and have important limitations such as the development of rodenticide resistance and potential adverse impacts on non-target species 12 . A few major cities in Brazil (São Paulo, Salvador, Recife and Curitiba) have shifted the focus of their interventions from rodenticide-focused pest control to a more holistic approach of integrated interventions (e.g., education, poisoning and environmental modifications).…”