Why rodents are a pest and how to control them

Learn more about the techniques to control a rat problem.

The commensal rodents, those usually found associated with people, the brown rat (Rattus norvegicus), and the house mouse (Mus musculus musculus and Mus musculus domesticus). They have been pests since time immemorial and have resisted all attempts to eradicate them. Rats and mice are highly adaptable, omnivorous creatures with tremendous reproductive potential, acute senses and a high degree of athleticism. Moreover, as recent studies such as the 2009 Rodent Survey in the UK demonstrate, their numbers are not diminishing.

The cost attributable to rats and mice in both financial terms and in human suffering are enormous. At Bailey Pest Control rodent control is given high priority in order to protect businesses and house holders.

Rodent Pests’ Life cycles


In Britain Mus domesticus is common, whereas in the rest of Europe, Mus musculus musculus is the predominant species. The house mouse weighs around 25-30gm and measures 60-90mm, its tail being 80-100mm long. Mice live indoors and outdoors, its diet consisting mainly of cereals. It can survive without drinking water, gaining sufficient moisture from its food. Mice only eat small amounts of any one thing at a time; its total food consumption is some 5gm per day.


Rattus norvegicus the brown, common or Norway rat weighs in at 500gm and measuring 200-300mm, the length of the tail being 150-200mm. A rat has small eyes, rounded snot and is truly omnivorous, eating 50gm of food a day. Found living near water, in buildings and in sewers, it nests in burrows underground. A rat lives for 9-18 months and produces around 7 litters a year with 8-10 young each.

Spread of disease by rats, mice and other rodent pests

The main commensal rodent species, the brown rat and the house mouse are all adapted extremely well to take advantage of the environments where food is grown, reared, stored, processed, prepared and sold. In addition to the vast amount of damage done directly to that food through consumption, rats and mice have the capability to spread human pathogens.

Salmonella spp

In the Uk there are around 20,00 to 30,000 cases of salmonellosis reported each year. The three main species of salmonella are responsible for these S. enteriditis, S. typhimurium and S. Dublin. In a number of scientific investigations carried out between the 1950’s and the 1990s, it has been shown that anything between 2 and 25% of the rat population and between 2 and 18% of the mouse population can be carrying Salmonella.

Escherichia coli

Around 40% of the rat population is infected with E. coli and many of the hundreds of reported cases on E.coil infection could possibly be related to rat transfers of this pathogen.

Leptospira spp

Weil’s disease, caused by the bacterium Leptospira interohaemorrhagiae, is world wide in its distribution, with rodent’s urine being the prime source of human infection. The infection is picked up by human’s ether by contact with the urine or through contacting contaminated soil.

The solution to rat problems

Bailey Pest Control use control techniques that are designed to eliminate the infestation completely, since any remaining rats or mice will produce a rapid infestation. Control techniques can be chemical and non-chemical. Non-chemical control techniques may be used on there own, such as the utilisation of live traps, glue boards and traditional back breakers but more often these methods are used to complement chemical control.

Acute rodenticides are employed in certain situations but can cause bait shyness and thus their usefulness is limited. Bait shyness is caused when rodents ingest sub-lethal quantise of bait, which are nevertheless enough to produce unpleasant symptoms.

The most effective rodenticides are anticoagulants, which are slow acting and thus do not induce bait shyness. They have a specific antidote in case of poisoning, namely Vitamin K! (phytomenadione).

All of the Rodenticides products used by Bailey Pest Control have an additional ingredient, Bitrex, an extremely bitter taste deterrent, which is include to decrease the likelihood of consumption by humans.

The active ingredients are usually formatted as grain baits, pellets or blocks. The latter contain a certain proportion of paraffin wax and have the advantage of being more weather resistant and less attractive to non – target animals.

The application of rodenticides requires a planned, struched approach involving regular visits and if necessary replenish bait or modify the control technique. Even after an infestation has been eliminated, continues monitoring may be required to detect signs of reinfestation as early as possible.

Bailey Pest Control always applies rodenticides in accordance to label instructions.

Integrated pest control management

Effective rodent control requires a combination of measures including surveys, proofing, habitat manipulation, sanitation and control techniques in order to avoid creating neophobic conditions, delaying bait takes.

1) Pest Control Survey

A survey is necessary to identify the type and extent of the infestation in order to allow informed decisions to be made with regard to the proofing and hygiene measures required and the type of control techniques to be employed. Visible signs include droppings, smear marks, tracks and urine pillars.

2) Pest Proofing

Eliminating rats and mice from the inside for a building will only be as short – term solution if there are others outside that can then get in. Rats are good climbers and can climb drain pipes or trees and enter through high apertures. Brown rats can burrow in or enter via drains and sewers and a young mouse can get through and hole with a diameter greater than 6mm. As many of the potential entry routes as possible should be blocked using rodent-resistant filling materials and nylon bristlestrip.

3) Habitat Manipulation

Eliminating rodent harbourages will also help reduce populations. Rats need somewhere to hide and breed and any such areas should be indentified and eliminated or made inaccessible.

4) Sanitation

Good sanitation is essential both inside and outside buildings. All rubbish and food spillage should be removed immediately as should and old tins or tyres capable of collecting rain water. Refuse bins and skips should be kept covered and water leaks repaired.