Rats

The Brown Rat (the Common Rat) is of particular public health significance because of its close association with man. Rats are known carriers of disease and in this country the most infamous disease carried by rats is Leptospirosis (Weils Disease).

This bacterium lives in the kidneys of rats and is passed into the environment by rats' urine. The tiny bacteria may enter a person's body through cuts and grazes in the skin or through the membranes of the nose, ears and mouth.

Another common disease carried by rats is Salmonellosis, a type of food poisoning. Humans may be infected as a result of eating food which has been contaminated with rat excrement.

Gnawing is part of the routine for the rat and in the home, plumbing, electric cable and insulation materials are therefore all susceptible to damage.

Two species of rat can be found in the UK:

·       The Brown Rat or Sewer Rat (Rattus norvegicus).

·       The Black Rat or Ship Rat (Rattus rattus).

These species have become well adapted to living in close association with man and our resources may be used for food or shelter.

Description

There are a number of features that separate the Brown Rat from the Black Rat:  The Black Rat has larger ears and larger eyes than the Brown Rat. Its tail is longer in proportion to its body which is slender with finer features and generally smaller in size.

Distribution

The Brown Rat is found in rural and urban areas, and can be found both indoors and outside. It is often associated with sewer systems.

The Black Rat is now rare and is confined mainly to port areas. In Britain it lives only indoors.

Life cycle

Rats can breed more efficiently than rabbits so infestations can develop very quickly from a single pair.

In favourable conditions e.g. surplus food, adequate water, suitable temperature and good undisturbed harbourage, a rapid population increase is inevitable.

Female rats are able to reproduce at approximately 3 months and gestation (pregnancy) lasts about 21 days with each litter averaging 4 - 6. The young are weaned at between 3 - 4 weeks and reach maturity at around 3 - 4 months of age.

Rats do not have to wait until the original litter is weaned before being able to conceive again.

Prevention and control

Rat control begins with good housekeeping in that rubbish and overgrown vegetation should be completely removed from around the outside of buildings. Deny a rat cover and you may well deny it access. Good housekeeping is also important indoors. Loose foods should be kept in rodent-proof containers.

All edible refuse should be disposed of in a suitable waste bin with a tight fitting lid. If an infestation occurs the only consistently effective method of control is the use of chemical poisons. This type of treatment should be carried out by a Professional Pest Control Technician.