Mice and Rats

The rodents most likely to invade domestic premises and commercial kitchens will be mice. Although rats are less likely to invade such premises they are still a serious threat. Both will be attracted to the building by the possibility of shelter, food and the opportunity to breed.

Mice and rats are extremely fast breeders! Mice have a gestation period of three weeks, an average litter size of twelve and can produce up to eight litters per year. That’s ninety-six offspring per year! Rats also have a short gestation period, an average litter size of eight and produce up to six litters per year. That’s fifty offspring or more per year! So,unless the problem is tackled fast, it can quickly get out of control.

Why are they such a problem?

Rodents are mammals with teeth that grow continuously; these are called incisor teeth. The grinding action of the upper incisors over the lower incisors keep their length under control. To prevent overgrowth the mice need to gnaw or chew on fairly hard surfaces on a daily basis. Since many commercial buildings contain a lot of computer and electrical equipment, business  activity would be seriously disrupted if rodents were to gnaw through any of the electrical cables within the building.

Another risk rodents pose is that of disease. Mice and rats can carry leptospiral jaundice (Weil's disease) in their urine. Their urine is not highly visible and there is the possibility of contamination of food preparation surfaces and other kitchen equipment. Businesses which are food premises can quickly lose custom or be closed by Environmental Health departments if infested with mice or rats.

Rodents also contaminate food and paper products by gnawing and with their droppings. They can climb inside cupboards, vending machines and food stores, and damage the goods within. They can also chew paper and boxes to make nests.

I have a rat or mouse problem and would like your help    

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Rats: What the scientists say

Damage to sewers by Norway rats (Rattus novegicus) is minimal compared to the harm they have caused as a vector of human diseases. Rat-borne diseases are alleged to have taken more human lives than all the wars in the history of humanity combined (Lowery, 1974).

In a recent survey of Norway rats from the United Kingdom, Webster and Macdonald (1995) reported 13 zoonotic and 10 non-zoonotic parasite species from a total of 509 specimens trapped on the surface in an agricultural setting in the United Kingdom. They found the zoonotic helminths Capillaria spp., Hymenolepis diminuta and H. nana in 23%, 22% and 11% of the specimens examined respectively.

They also found the zoonotic bacteria Leptospira spp., which causes Weil's disease, in 14% of the specimens examined (lower than the commonly believed level). They also found Listeria spp., which causes listeriosis, in 11% of the specimens examined; Yersinia enterocolitica, which causes yersiniosis, in 11% of the specimens examined; Pasturella spp., which causes pasturellosis, in 6% of the specimens examined; and Pseudomonas spp., which causes meilioidosis, in 4% of the specimens examined.

The protozoans Cryptosporidium parvum, which causes cryptosporidiosis, were found in 63% of the specimens examined and Toxoplasma gondii, which causes toxoplasmosis, in 35% of the specimens examined. Interestingly, they also found antibodies to the rickettsian Coxiella burnetii, which causes Q fever, in 34% of the specimens examined and to the virus Hantavirus which causes Hantaan-fever or haemorrhagic fever, in 5% of the specimens examined.

They found no evidence of Salmonella among specimens examined in the United Kingdom. Low percentages of Salmonella have been reported from other populations of Norway rats (Davis, 1948; Davis, 1951; Nakashima et al., 1978).

Microbee's own scientists (Channon, D., Cole, L. and Cole, M.) carried out an analysis of nearly thirty-six thousand baiting records over thirteen years which showed the sewer rat population of part of London to be in long-term decline. The results suggested that sewer rat numbers were nowhere near as high as is commonly believed and this suggested that they were much less likely to be the source of surface infestations. Read it in Epidemiology & Infection (2000) 125, 441-445.

I have a rat problem in the sewer and would like your help    

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Squirrels

This section refers to grey squirrels. Red squirrels are protected in the UK under the Wildlife & Countryside Act and should not be disturbed.

Grey squirrels are a non-native species, originally imported from the Americas. They have taken over most of the habitat of the red squirrel.

They do a great deal of damage to houses; usually entering lofts, making nests out of loft insulation and chewing holes in soffits and through electrical cables. They look very cute and many people are opposed to any form of control – mostly those whose houses have not been damaged.

Squirrels must not be encouraged to visit bird feeders. The presence of abundant food is soon followed by a search for a nest site and that is then followed by the production of a lot more squirrels.

They have pest status in the UK and can be controlled by legal methods, including shooting, trapping and poisoning.

Shooting is possible but difficult in towns. Poisoning must be done from special food hoppers attached to trees.

The easiest method of control is by trapping. It requires a great deal of care and supervision and is expensive. All traps have to be regularly checked and trapped animals dispatched quickly since it is illegal in the UK to be wantonly cruel, even to a pest animal.

I have a squirrel  problem and would like your help  

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