All about pests

Mice

First the danger. Mice are more of a problem in buildings because they live indoors. They are more liable to cause fires by gnawing cables and they can damage insulation in animal housing causing costly heat loss and expensive replacement.

Mice carry diseases such as Salmonella and they can also transmit a type of Leptospirosis, but not Weil's disease. Their continual dribble of urine contaminates food and feedstuffs. They are a particular problem in poultry units and pig housing and a very real pest in grain stores, warehouses, shops, hospitals and even domestic premises.

Being so small they are very easily carried, unnoticed, in egg boxes, food packaging, laundry baskets, etc. Entering a new location through gaps as small as 6mm, mice build nests which are hard to find, populating an area with new colonies quickly with devastating effect. Because mice can reach sexual maturity 42 days after birth, populations grow much faster than those of rats, which take about twice the time to reach maturity.

The difficulty of preventing access, coupled with the rapid population growth and natural dispersal of mice, means that a large building may contain a number of colonies.

Mus domesticus

Common Names: House mouse Adult Weight: 15 grams Length (head + body): 60-90mm Length (tail): 80-100mm, usually longer than head and body. Fur, colour: Brownish grey. Lighter shades occur Ears, hearing: Large with some hairs. Excellent sense of hearing. Eyes, sight: Small. Poor sight, colour blind. Snout, smell and taste: Pointed, Excellent sense of smell and taste. Droppings: Scattered. Rod shaped, 3-6mm long. Habits, habitat: Sometimes burrows. Lives indoors and ourdoors but is almost unknown in sewers. Nests generally within stored materials but may burrow. Climbs. Erratic in habit. Inquisitive towards new objects. Range 1.5-5 metres. Feeding habits: Nibbles. Prefers cereals. Consumes 3 grams per day. Unlike rats, can survive with very little water and often obtains sufficient water in food without the need to drink. Life cycle: Span: 9-12 months. Sexual maturity: 6 weeks. Litter size: 5-6 offspring. Maximum reproduction rate: 8 litters per year.

Rats

Rats are a worldwide pest due to their capacity to cause structural damage, to spread life-threatening diseases, and to compete with man for food.

The species most commonly found in Europe is known as the Norway Rat (Rattus norvegicus). A less commonly found species, the Black or Roof Rat, (Rattus rattus), is largely restricted to port areas.

Rats live alongside man, invading his buildings and eating his food. Rats transmit disease which are potentially fatal to man such as Weil's disease and murine typhus. They also carry organisms which can damage man's health such as Salmonella bacteria, viruses and parasites such as nematodes and worms.

Damage by rats to the fabric of buildings can be costly. Fires can easily be started after a rat has gnawed a cable. Gas and water pipes are also at risk and rat burrowing can undermine foundations and damage water courses.

Physically very strong, rats have been known to survive for two days in open water, to swim a mile in open sea and to get through a gap of less than 25mm.

Rattus norvegicus

Common Names: Norway rat; Common rat; Brown rat; Wharf rat; Sewer ratAdult Weight: 300 grmsLength (head + body): 200-250 mmLength (tail): 150-200mm, shorter than head and body.Fur, colour: Harsh and shaggy. Brown and black on upper head and body, grey or off-white underneath.Ears, hearing: Thick, opaque, short with fine hairs. Excellent sense of hearing.Eyes, sight: Small. Poor sight, colourblind.Snout, smell and taste: Blunt, Excellent sense of smell and taste.Droppings: In groups, but sometimes scattered. Ellipsoidal capsule shaped, about 20mm long.Habits, habitat: Does burrow. Lives outdoors, indoors and in sewers. Nests in burrows. Can climb though not agile. Very good swimmer. Conservative, somewhat predictable in habit. Will avoid unfamiliar objects, e.g. bait trays, placed on runs, for some days. Range 50 metres.Feeding habits: Omnivorous, more likely to eat meat than Rattus rattus. Consumes up to 30 grams per day, drinks water or eats food with high water content.Life cycle: Span: 9-18 months.Sexual maturity: 2-3 months.Litter size: 8-10 offspring.Maximum reproduction rate: 7 litters per year.

Rattus rattus

Common Names: Ship rat; Black rat; House rat; Roof rat. Adult Weight: 200 grams Length (head + body): 150-220mm Length (tail): 180-250mm, usually longer than head and body. Fur, colour: Smoother and softer than Rattus norvegicus. Usually black or grey Ears, hearing: Thin, translucent, large and hairless. Excellent sense of hearing. Eyes, sight: Large and prominent. Poor sight, colour blind. Snout, smell and taste: Pointed, Excellent sense of smell and taste. Droppings: Scattered. Spindle or banana-shaped, about 12mm long. Habits, habitat: Non-burrowing. Nests mainly in walls, attics, vines and trees. Active agile climber, rarely found in sewers. Rather more erratic and unpredictable in habit than Rattus norvegicus. Less wary of new objects than Rattus norvegicus. Range 30 metres. Feeding habits: Omnivorous, mainly fruits, nuts, grains and vegetables. Consumes 25-30 grams per day, drinks water or eats food with high water content. Life cycle: Span: 9-12 months. Sexual maturity: 2-3 months. Litter size: 6-10 offspring. Maximum reproduction rate: 6 litters per year.

Ants

In the UK, the Common black ant (Lasius niger) nests outdoors - often under lawns, within decaying trees, under building foundations and within wall cavities of our homes. Ants, like wasps, are social insects living in organised colonies controlled by a queen. The workers will forage widely in search of food. In doing this , they tend to follow well-defined trails and cluster around the source of food. Sweet foods are of particular attraction, hence the ant's interest in kitchens, storerooms and warehouses. Pharaoh's ants (Monomorium pharaonis), which are smaller than black ants and yellow-brown in colour, are more commonly found in hospitals - attracted by soiled linen and excrement - and are more likely to spread infection.

Cockroaches

Cockroaches present one of the most significant public health risks, carrying diseases such as dysentery, gastroenteritis, diarrhoea, typhoid, poliomyelitis and salmonella. They are most commonly found in commercial premises in which food is produced or handled, such as restaurants and catering establishments. However, they are not uncommon in domestic situations where they live in kitchens and drains.

The three most important species are the Oriental cockroach (Blatta orientalis), the German cockroach (Blattella germanica) and the American cockroach (Periplaneta americana).

The Oriental cockroach reaches 20-24mm in length in its adult stages, is almost black in colour and is largely found in cooler, less humid areas than its German counterpart, which, at 9-14mm long is markedly smaller. Blattella germanica, yellowy-brown in colour, is a better climber than the Oriental cockroach and thrives particularly well in kitchens and canteens. The largest of the species, the American cockroach, is red-brown in colour and can reach 30-35mm in length. This species survives well in drains and sewers.

Cockroaches are nocturnal creatures, which spend the daytime hours hiding in cracks and crevices around sources of food and water such as cookers and sinks. Complex pipework systems and underground ducts in larger buildings can make their control all the more difficult. Food contamination occurs when the cockroach moves from refuse to food preparation areas. Cockroaches will eat practically anything from human food to leather, wallpaper and even other cockroaches.

Fleas

The cat flea (Ctenocephalides felis) is the cause of over three-quarters of all flea infestations. At 2-3mm long, it is often found in host bedding and, in instances of infestation in commercial premises, can often be traced to a feral cat problem. Human and dog fleas are less common and the majority of human flea bites come from cat fleas Adult fleas live off the blood of a variety of warm blooded-animals and birds. They are more nest than host specific and will feed on other animals in the absence of the preferred host. Fleas are carriers of both disease, such as typhus and bubonic plague, and also parasitic worms. Rodent fleas, in particular, are a prevalent source of murine typhus. In the UK, fleas are less of a concern from a disease perspective but their bites - visible as small deep-red spots within a reddened area - are painful and irritating and carry a social stigma. Flea larvae develop easily in typical living room conditions with wall to wall carpeting and central heating.

Flies

The Common Housefly (Musca domestica) can remain active and reproduce throughout the year in warm environments although, more commonly, they tend to stop breeding during the winter months.

As potential vectors of typhoid, cholera, tuberculosis, gastroenteritis and dysentery, they must be controlled. Solid foods are liquefied by regurgitating digestive juices on the surface of the food. Rotting food is of particular attraction and decaying household refuse provides an ideal environment for laying eggs. House flies have been known to cover distances as large as 9 miles.

Bed Bugs

5mm long, and looking like a small, flat red-brown disc, the common bed-bug (Cimex lectularius) is found in human habitations world-wide. It feeds on the blood of humans, emerging at night from cracks in furniture joints, bed frames, wallpaper and skirting boards to bite humans, its principal host, and to leave its characteristic speckled excrement. Bed bugs leave a characteristic almond-like smell in rooms where they are active. Bites can be painful, giving rise to hard whitish swelling.

Pest information supplied by Sorex.