Public Health Significance of Urban Pests
405
be cost effective. Control of rodent infestations should not be treated simply as a question of killing the rodents. The problem must be seen more broadly, as an infestation within
a vulnerable and more often than not, degraded urban environment. Once the risk fac- tors that contribute to infestations and subsequent public health threats are identified, as
in case study 1 subsection 12.4.4.1, a plan to provide long-term solutions can be develo- ped and implemented. The following case study provides an example of threat assess-
ment and the actions required for an effective intervention.
12.5.1. Case study 2: Fairhill case study
The Fairhill neighbourhood of Philadelphia was selected for intervention because of the existence of a number of risk factors for rat bites. The area included 50 square blocks
with 1520 premises, consisting of residential, commercial and vacant buildings. Single- family attached row houses dominated the neighbourhood, and about 10 000 people resi-
ded in it. The population was young, with less than 10 of the residents over 55 years of age Hirschhorn, 2005.
Three objectives were the basis of this intervention: 1.to deliver a comprehensive environmental improvement, rodent control and safety pro-
gramme to residential properties in the target area; 2.to coordinate with other city agencies and community partners, to improve the quality
of life in the target area; and 3.to solicit community cooperation, to improve substandard conditions and maintain a
healthy and safe environment. A survey was conducted to provide an accurate assessment of conditions and problems.
All exterior areas and 60 of the interior areas were inspected. Twenty environmental and safety factors were examined as part of the survey. Surveys of exterior areas exami-
ned rodent infestations, structural damage, unapproved refuse storage, abandoned auto- mobiles and large accumulations of refuse. Surveys of interior areas focused on evidence
of rat, mouse and insect infestations, points of rodent entry and harbourage, actual or potential food sources, building condition, and points of disrepair. City health depart-
ment staff performed repairs inside the residential units, to seal off points of entry and harbourage for vermin, and used non-chemical methods to eliminate active rodent and
cockroach infestations. At the same time, public education was provided to help the resi- dents understand how they could combat the rodent problems and reduce the environ-
mental and safety hazards that contributed to the risk of infestation. Also, local building and sanitation codes were explained and enforced, and sewers were inspected and repai-
red. The contributions to rat bites of various housing and environmental conditions are shown in Fig. 12.3.
This abatement and intervention effort required the cooperation of many city agencies. As a result the programme reduced rat complaints by more than 50, reduced unintentional
injuries in residential areas and led to safety improvements, including protection from fires.
Commensal rodents
404
of baiting rounds, where bait laced with a single-dose anticoagulant is set out for a per- iod of 3–13 days and then removed for 7 days. Death is usually delayed by three or more
days. After the seven-day period, the bait is set out again. This technique accommodates the hierarchical feeding common to rats, by allowing the older dominant rats to die before
replacing the bait, providing the less dominant rats with an opportunity to eat the bait. Bait conservation is also achieved, in that rats that have already ingested enough poiso-
ned bait to insure death do not continue to consume bait at the stations. Three baiting pulses can remove almost an entire population CIEH, 2003.
Current practices of rodent control in Europe and North America, based on complaints by members of the public, are not the best and most sustainable pest management prac-
tices available to protect public health. However, it has been suggested that, where the rate of infestation is 1 or less, it is not worthwhile replacing a system that relies on com-
plaints with a more structured approach of systematic surveys, because the costs of secu- ring any significant improvement in the rate at which infestations are discovered and
treated would be prohibitive Drummond, 1970. Thus, priority areas should be those where infestation rates are above 1. This implies, however, that the municipal autho-
rity has adequate information on which to make that assessment.
As part of a coherent strategy, rodenticides are an essential means of effectively control- ling rat populations in sewers Colvin, Swift Fothergill, 1998, when coupled with
maintenance and repair of the underground sewerage infrastructure. The successful use of rodenticides over the past 50 years has been managerially convenient, so that rodent
control can be reduced to routine, fixed-price procedures with an apparently predictable outcome. In many countries, rodenticides are seen as an immediate, economical and rela-
tively easy way of addressing infestations in urban areas. This practice has unfortunately led to an over-reliance on this approach. This over-reliance is understandable, however,
in complex situations where there are many different agencies, in addition to individual homeowners, involved in securing the necessary changes to the environment to reduce
infestations in the longer term. Reliance on this technical solution has thus led to a mini- mization of strategic thinking.
Apart from surveillance of specific individual premises, such as high-risk food shops and restaurants, rodent management is essentially driven by a complaint procedure within
municipal authorities Richards, 1989. The reported level of infestations in the urban ecosystem depends on public perception. In effect, this means that if the residents of some
urban areas are more tolerant of rats than others, a less stringent or perhaps no control strategy will be implemented. The failure to have an effective control strategy means the
overall level of control will not be optimized Meyer Drummond, 1980. Furthermore, little attention has been paid to deciding what level of infestation, if any, represents satis-
factory control.
The problems caused by rodents should not be viewed as only belonging to the indivi- duals affected, but they should be seen as community problems that need to be addres-
sed by the community as a whole. Attempts to solve rodent infestation problems across wider areas need to be addressed on a community-wide basis if the effort invested is to
Public Health Significance of Urban Pests
407
These provisions will include approved methods and materials, which take into account operator safety and protection of non-target species. The legislation should provide for
controls over the use of rodenticides, including approval of formulations, and prescribe the circumstances and safe manner in which they can be used. Within the EU, the
European Biocidal Products Directive 988EC European Commission, 1998 has intro- duced an authorization scheme for placing biocidal products which include rodentici-
des on the market and for their subsequent use. The key aims of the Directive are to establish a single European market in biocidal products and, at the same time, to ensure
that people and the environment are highly protected.
As an example, in the United Kingdom, before any person other than a householder in their own premises can carry out any rodent control work, they must conduct an assess-
ment, as required by the Control of Substances Hazardous to Health Regulations 2002 the COSHH assessment HSE, 2003. The purpose of the COSHH assessment is to
make sure that any product selected will control rodents effectively when used in accor- dance with the specified method, while at the same time minimizing risks to both the
operator and any other person or animal non-target species that might come in contact with the rodenticide.
The legal framework that relates to the presence of commensal rodents on land and beneath the surface will depend on the legal history and the legal system within the state.
For example, in England, the law that relates to the control of rats and mice Prevention of Damage by Pests Act of 1949 was drafted at a time of relative food shortage and was
aimed at protecting foodstuffs from damage. It gave power to local authorities to require occupiers to deal with infestations, but did not impose a statutory duty on the authority
to provide a pest control service. In practice, most local authorities in the United Kingdom do provide such a service, but there is no duty to do so. On behalf of the authority, a com-
mercial pest control company may deliver this service under contract. In some cases, local authorities in England and Wales have also introduced charges for what had previously
been a free service. The tariff and charging structure varies from authority to authority, with so-called public health pests treated free of charge and a service charge made for
the treatment of nuisance pests Battersby, 2002; Murphy, 2002; CIEH, 2003. Across authorities, there is no general agreement as to what is a public health pest, so that in some
municipalities domestic mice are seen as public health pests and in other areas they are not. This confused situation makes effective urban rodent control more difficult Murphy
Battersby, 2005.
Where private companies perform public services under contract, the terms of the contracts are critical. For example, in England and Wales, much of the sewerage net-
work is the responsibility of privatized companies, which have no clear legal obligation as part of this service to control rats in their sewers. Where they invest in such controls,
these private companies incur the direct costs, but do not gain any direct benefits. Also, these companies do not incur the costs that result from increased rat infestations above
ground, even though these may be the result of their failure to control infestations and maintain the sewerage infrastructure.
Commensal rodents
406
The study demonstrated that a prerequisite for an effective public health rodent control programme is cooperation between agencies and the cooperation of the community with
those agencies. Public education and information are important. This in turn demons- trates the need for a high level of management and commitment within public authori-
ties.
12.6. Legal framework
