Today's urban pest problems have to be addressed within the wider context of national economic and public health liabilities. There is a compelling argument that the UK is lacking up-to-date, accurate, comparable data on the true extent of its rodent problem. With this in mind, Tracey Khanna looks at the CIEH's proposals for a major study on the subject.

The 1993 "National commensal rodent survey" was undertaken with the direct objective of determining whether levels of infestation by commensal rodents had changed in England and Wales since the previous reliable surveys had been undertaken in the mid-to-late 1970s. The results were published in the Environmental Health Journal alongside the Chartered Institute of Environmental Health's comments and recommendations (EHJ, June 1995, page 125).

In summary, the survey found an increase of 39 per cent in the levels of rat infestations in domestic premises; an increase of 48 per cent in rural areas; a general increase in mouse infestation; that infestations vary according to business and domestic use; and that a higher percentage of infestations were going untreated compared with the 1970s.

Nearly six years on from the publication of these results, and the situation with regard to pest control is little changed. Some of the issues that became the catalyst for the 1993 commensal rodent survey still hold true today: reported increases in the number of infestation complaints received by local authorities; changes in the incidence of complaints being affected by high media profile; and the need to determine the real levels of change through soundly based random surveys of actual infestation.

Many of the recommendations put forward by the CIEH in 1995 are also still in need of being comprehensively addressed today: the need for accurate and reliable information on infestation rates; sample survey methodology to be created to provide reliable data on a regular basis; one government department to take overall responsibility for the co-ordination of policies and rodent control strategy; a common and consistent policy from water companies; and vital, continual research to be an integral part of the policy making process. Says Graham Jukes, director of professional services at the CIEH: "The issue on rats is really about at what level should we be providing rodent control, how do we measure that and how do we measure that as a cost effective equation?" In other words, what is the publicly acceptable level of rats in an environment, and why should local authorities put a certain amount of resources into controlling rodents in an area if there are no demonstrable negative health effects?

As society has evolved, there has been an ever increasing demand for higher sanitation standards. As Mr Jukes points out: "A lot has to do with the public's concern about their environment. If people see rats running around their area they have an instinctive feeling that it is unhealthy. In the main, they are probably right." The scientific facts are that rats carry a wide range of zoonotic species (see article, this issue, page 109) and it is clear that there does exist a public health threat which needs to be managed. The question is, is there a direct correlation between numbers of rats and levels of public health?

In addition to the issue of health hazards, economic damage by rodents can take many forms. This ranges from the contamination and spoilage of food and materials by droppings and urine, damage to buildings and materials through continued gnawing, to burrowing activity which can cause subsidence to structures. A huge problem to the Government and concerned agencies is the lack of accurate and meaningful information on the extent of such damage. Without this, the prioritising of funding and resources is extremely difficult.

It is against this background that the CIEH, in its capacity as a collaborating centre for environmental management, is in discussion with the World Health Organisation regional office for Europe (WHO) on ways and means to undertake a major project on the subject of urban pest control. The WHO plans to produce a report by the end of 2003, which will encompass cockroaches, ants, flies and birds as well as rats and mice. However, the findings should help government departments, local authorities and environmental health professionals to set adequate priorities with specific regard to rats and mice where these pests are of major issue.

In short, the proposed study will:

• collect and evaluate the health hazards from public health pests by reviewing the scientific evidence available from universities, hospitals and other genuine sources;
• quantify the economic damage caused by public health pests, including days lost to industry through illness caused by allergies and food borne illnesses;
• provide elements for designing benchmarks for pest control. In environmental terms, this means providing a system of ascertaining how successful countries have been in controlling public health pests and establishing a level of service against which others can measure what they are doing; and
• recommend, if needed and deemed legitimate, specific treatment regimes to achieve successful pest control.

The importance of introducing benchmarking is clearly defined in the report proposal, which says: "if data is to be collected and used to ensure pest management programmes are in place, it is essential that the basis for this data is capable of comparison and in the right form." A standard benchmark system is vital in the promotion of useful surveys.

With regard to the implementation of modern pest control techniques the development of better risk assessment and risk management programmes is needed. According to Andrew Griffiths, assistant secretary at the CIEH, "local authorities deal with individual infestations and there is little co-ordination between authorities. There is a need to look at the implications of individual pest control treatments across local authority boundaries." Mr Jukes goes on to add: "What is needed is information which allows a local authority to make a conscious decision as to the acceptable population of rats in an area, then to draft a plan to keep this to a determined level over a certain period of time." At present, this information does not exist and local authorities are simply being reactive to numbers of complaints. As Mr Jukes points out, "such a plan would enable local authorities to target resources more efficiently."

Once the proposed WHO report is made available, it is clear that central government will have to determine which department should take full responsibility to deal with the problem. Unfortunately, this is not a political issue and it seems unlikely that any serious commitment will be made by the Government in tackling the issues and providing adequate resources without some detailed research demonstrating a specific link between rats and population levels, and public health.