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Writing Word Macro Viruses

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The Roof Rat (Rattus rattus), also known as the ship, black, or house rat, is usually found inside buildings, preferring the upper parts of these properties, possibly as a result of its tree-dwelling origins before it adapted to its current pest lifestyle. The Roof Rat is also the rodent species most closely associated with plague outbreaks, carrying fleas capable of spreading this disease to man.

Roof Rats typically grow to 17-20cm long, plus a tail 20-25cm long. Bodyweight ranges between 200-300g and this may help to explain why this rat is more agile than the heavier Norway Rat. A Roof Rat's tail, unlike the Norway Rat, is longer than the combined length of its head and body, and is all one colour. This longer tail aids the Roof Rat in climbing, helping to balance the body or adding extra purchase to its grip.

The Roof Rat is an extremely agile climber, probably as a result of its arboreal (tree-dwelling) origins. The origin of the name 'Roof Rat' stems from this ability as these rats tend to live in the upper floors of the buildings they infest.

The eyes are specialised for nocturnal vision, although sight is not as important as it is to humans. Because of their adaptation to low-light vision, rats are almost certainly colour blind. Touch is a far more important sense to rodents. The vibrissae, or whiskers, are the most important organ for this sense, although tactile hairs are found all over the fur. This sense enables rodents to find their way in the dark places they inhabit.

A rodent’s sense of taste is apparently similar to a human’s. However, they are not particularly sensitive to a substance (trademarked ‘Bitrex’), which is the most bitter substance known to man. This enabled its incorporation into rodenticides to reduce the risk of accidental ingestion by humans (especially children), whilst maintaining the effectiveness of the rodenticide.

Although sensitive to sounds of a frequency that humans can hear (up to 20 kHz), rats are also able to hear sounds of a much higher frequency (up to 100 kHz, with a peak sensitivity at 40 kHz). Rats also make many ultrasonic vocalisations as a form of communication between individuals. It has been suggested that ultrasonic sound generators could be used to exclude rodents from buildings, but their usefulness remains to be proved.

Rodents have continuously growing incisor teeth, which they wear down and keep sharp by gnawing. Anything can be gnawed, even some metals. On Moh's scale of hardness, the lower incisors of a Norway Rat score 5.5, whereas steel only rates a 4. In practice though, rats usually gnaw on materials softer than this. The incisor teeth keep growing throughout their life, in order to replace wear caused by gnawing on these hard materials.

Whereas the Norway Rat is basically omnivorous, and can make good use of the foodstuffs people discard, Roof Rats prefer fruits, seeds and grain. It is a serious pest of orchards and plantations in many regions of the world.

The Roof Rat has a litter size of between five and ten pups, after a gestation (pregnancy) period of three weeks. The young can be weaned as early as three weeks later, and can breed themselves after only 12 weeks. Although capable of producing more, a female rat usually produces no more than six litters a year.

Holes are often gnawed by rats in doors and even walls to allow access to a building. These holes, showing distinct grooves - the tooth marks - are the most easily seen signs of rat activity. Droppings (12 - 15 mm long) may also be seen scattered throughout the infested area. Rats are creatures of habit, and will often wear visible paths between their burrows and food sources. Inside buildings, rats will also leave behind ‘smear marks’, accumulations of grease and dirt smeared off their fur. These are a sure sign of a serious rodent infestation.

Pest rodents are important vectors for the spread of many diseases to humans, several of which produce flu like symptoms. Some of these diseases can be fatal. The Roof Rat is most famously associated with plague outbreaks. The bacterium responsible infects man via the bite of rat fleas, which are in turn infected from rats. It is usually only when the rat population succumbs to the disease that the fleas seek an alternative host and feed on humans. Among the most common illnesses passed along in recent times are rat bite fever or Haverhill fever, which is transmitted through the teeth and gums of a rat infected with bacteria. This disease is highly infectious, characterized by high fever and has a fatality rate of seven to 10 percent if untreated. Weil's disease or leptospirosis occurs when an individual becomes infected by direct or indirect contact with infected rodent urine. Organisms in the urine enter the body through the mucous membranes or through small cuts or abrasions in the skin. This disease is seldom fatal.

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