Rodents are the species most commonly associated with pest control. The full extent of the rodent problem is not known but there are estimated to be between 10 and 20 million brown rats inhabiting Britain’s streets, sewers and waterways. All the more reliable survey evidence suggests that numbers are increasing, particularly in inner city areas.
The range of organisms known to be carried by rodents and the severity of some of the diseases they cause should be enough to demonstrate the importance of preventing rodents from entering areas where people live, work or play. However, there are also significant economic factors to consider, such as the effect on degraded environments.
Certain insects also pose dangers. Flies and cockroaches, in particular, can spread numerous disease-causing bacteria, viruses and protozoa. The free movement of flies, cockroaches and other insects from unsanitary to sanitary areas allows them to carry infections. Many common allergic reactions, notably asthma and eczema in children, may start as a result of exposure to pests such as cockroaches and house dust mites.
In addition to existing problems relating to pests already native to the UK, pests are associated with a number of emerging diseases. Rising atmospheric CO2 and climate change due to global warming will undoubtedly affect the distribution and proliferation of insects and the diseases they carry.
Several diseases could become more prevalent if warmer temperatures enable insects such as mosquitoes to become established further north, leading to the spread of malaria, yellow fever, dengue fever and encephalitis. Southern regions of England may become warm enough to support mosquitoes carrying such diseases.
Various tick-borne diseases, such as Lyme disease, which is already present in the UK, could also spread with milder winters and extended spring and autumn seasons. Even now, accidental introductions of these species could cause serious outbreaks of diseases resulting in vast public expenditure on treatment and eradication.