There are two species of rats found in the UK: The Brown Rat and the Black Rat. The difference in the two species is not the colour, as they are both the grey-brown colour of the rats often seen mooching around waste bins.
The brown rat is the common rat, the ones that plague us in our homes and work places; the black rat is very rare (thank heavens!) now in the UK - the odd few can be found in dock areas and around wharfs close to the sea or river ports.
The Black Rat (Rattus rattus) was the host species of the fleas that caused the Bubonic plague in the middle ages.
Black rats thrived in the thatching used in roofs in the bygone days. They are excellent climbers that feed on fruit and vegetables by choice, although they will take grains and cereals if there is a shortage of their preferred food source. This species is very sleek in its body, the tail is longer than the head and body combined, the face is long and pointed and the ears are large in proportion to the head. Should you see one, send me a photo, I have never been lucky enough to have even caught a glimpse of one in the wild!
The rat which we all see, the species that gnaws cables, infests homes, gardens, factories, sewers and just about everywhere else in the UK will be the Brown Rat (Rattus Norvegicus).
This species has six to ten babies per litter, the female is pregnant for twenty one days and, believe it or not, she can be pregnant again just ten hours after giving birth!
An adult female brown rat will have six to eight litters per year, her kits will be weaned at twenty-one days old, just in time for the second litter to be born. In three to four months, the young females will be in breeding condition and capable of bearing six or more babies every twenty one days, this explains why one rat appearing at a site can become a huge infestation in a few months.
Brown rats are capable of squeezing through a gap of twelve millimetres; if you can get your thumb into a hole, a rat will be able to crawl through it. Their teeth continually grow throughout their life and have to be kept to the optimum length and sharpness by gnawing. They are slightly harder than mild steel, allowing brown rats to chew their way through most of our building fabrics, including concrete, to get to a food source.
Brown Rats are omnivores, eating just about anything. We have controlled rats that had been living on organic soap bars in a warehouse, through to rats that had gnawed their way through a floor into a restaurant kitchen.
There are various methods of control used, anticoagulants are the most common. These fall into two categories - first and second generation - first being Warfarin, Coumatetralyl and Chlorophacinone.
Resistance to Warfarin is now widespread in the UK, whilst Coumatetralyl still works very well and is not as toxic as the second generation active ingredients to birds of prey, should they eat a dead or dying rat.
Second generation baits include Bromadiolone and Difenacoum. These are the only second generation baits that can be legally used outside. Always read the label on the bait tub if you choose to control rats yourself. Many are professional use only; you can buy them, you just can't use them unless you have been suitably trained.
When baiting, you must make sure the baits are covered to ensure non-target species, such as dogs, cats etc., cannot get access to it.
Unless you are totally confident in your skills using baits, I would recommend calling in a professional pest control company to do the work for you. You may be able to find an independent pest controller that offers competitive prices in your area by logging on to www.ukpestcontrollers.org and searching the map.
Break back traps will often catch the odd juvenile rat; adults will be too long in the tooth to be caught, unless the trap is set perfectly. Live catch traps are helpful if there is a chance of catching a non-target species that has to be released by law. Trapping is not really a suitable way of controlling a rat population which has become established.
There are many sonic repellers for rats on the market - these are fantastic for throwing at rats, and that is about all - none of them work to any degree of satisfaction, so don't be fooled into buying any.
Rats are neophobic, which means they have a fear of new things. Bear this in mind if you use bait safes - it can take up to a month before a rat feels safe enough to enter a box to feed on your bait.
A rat infestation will need three things to survive: food, water and somewhere to live safely. The only one of these we can manage is the food source - find out where they are feeding and deny them access to it, by removing it or putting it into rodent-proof containers high up, away from the intruders. Under no circumstances should rubbish, or whatever the rats are hiding in, be moved before full control has been achieved; moving the harbourage will only move the rats to somewhere else, possibly a more sensitive location, such as a kitchen.
Rat population in the UK is steadily increasing - composting, decking, bird tables and our throw away society are giving rats a real heads up.
Rats carry a deadly disease called Leptospirosis (Weil's disease), this can be transferred to humans by contact with rats' urine or faecal pellets or through cuts and grazes. Leptospirosis can live in water for many days, so always be careful when working in areas where rats have been active. Never smoke, drink or eat while dealing with rats, and always cover cuts and grazes with a suitable waterproof plaster.
The symptoms of Leptospirosis are very similar to having the Flu; with the problems we are having with swine flu at the moment I would suggest you ask your doctor to take a blood test for Leptospirosis if you go down with the flu and are working in areas where rats are present.
Don't forget, you can always ask me for advice on pest control.
Andy Beddoes - www.abcomplete.co.uk
Leptospirosis (Weil's Disease)
Leptospirosis is notifiable in the UK under the Public Health (Infectious Diseases) Regulations 1988.
Human leptospirosis can be a difficult infection to describe, as the symptoms can vary dramatically between patients. Some symptoms are extremely common, but only a small number of patients will experience the severe life-threatening illness known as Weil's disease. The severity of the infection depends on the age and general health of the patient, plus the serovar (strain) of bacteria involved and the number of bacteria that entered the patient's body.
The infection is usually systemic (affecting the whole body) and causes a sudden fever. In mild cases it lasts a few days, following a pattern similar to flu but often in two phases - a period of illness lasting a few days, then a slight recovery, then a second period of illness. In mild cases the second phase lasts a short time and the patient recovers, but in severe types the illness develops and progresses rapidly, leading to organ failure and often death if not treated with intervention and support.
With human leptospirosis this is typically 3 to 21 days, with most patients developing illness after about 3 to 14 days. It does not usually take more than 28 days but, in rare cases, very long incubation periods have been reported. It generally cannot show illness in less than 24 hours unless the volume of bacteria taken into the bloodstream was massively larger than normal.
Leptospirosis starts suddenly, with a severe headache, redness in the eyes, muscle pains, fatigue and nausea and a fever of 39°C (102°F) or above. There is sometimes a red non-blanching pinprick rash on the skin, similar to that seen in meningitis. Young children can be tired or distressed and may show an aversion to bright light. The severe headache is almost always present and can be incapacitating. Nausea may or may not cause vomiting. Muscle pains can be extreme and are often particularly bad in the calf and back areas - muscles will be sore to move and to touch. A rapid pulse is also common in the first few days.
The skin rash develops in the first one or two days and often the skin is warm and pink just beforehand, with the patient complaining of feeling warm. Rashes can occur anywhere but, in some cases, are confined to local regions of skin such as the front of the legs. Sometimes they will be itchy, but rashes are only seen in about 30% of all cases so the lack of any rash is not too significant.
Psychological changes are often seen, with patients feeling depressed, confused, aggressive and sometimes psychotic - with schizophrenia and hallucinations, personality changes and violence. This phase lasts between three and five days, then the patient (temporarily) recovers. During this phase the bacteria are active in the patient's bloodstream (so it is sometimes called the septecaemic phase) and so can be detected by lab tests.
In many mild cases this doesn't happen at all but, where the infection is more severe, the patient enters a second phase of illness after a few days of apprent recovery. The initial symptoms and fever return, accompanied with chest and abdominal pain, some renal problems and psychological changes. Increased symptoms of meningitis are often seen with neck stiffness and vomiting but, in most mild cases, the patient will not suffer kidney or liver failure and will eventually recover. There may be a sore throat and dry cough, with a litle blood. With treatment, mild cases will recover within a few weeks.
During this second phase the bacteria are only really active in the tissues of the patient, and so can be difficult to find in the bloodstream, making lab tests a problem. This second phase is usually called the 'tissue' or 'immune' phase.
In cases of particularly virulent serovars or patients with poor health, the infection follows a different pattern and the patient develops very rapid and severe symptoms from the start, without much of a remission. Symptoms are the same as for the mild type but more pronounced, and multiple organs are damaged - liver and kidney failure can occur within 10 days, leading to jaundice and death if not treated. Haemorrhages are common (including bleeding from the mouth, eyes and other mucous membranes), plus infection of the heart and significant internal bleeding. Death, when it occurs, is usually due to heart, liver or respiratory failure. Severe infections are often called 'icteric' because of the presence of jaundice, and these are the only cases that can really be called Weil's disease.
Patients with mild infections recover quite quickly, so are usually feeling OK after a few weeks, but they can suffer from fatigue and depression for a while and may be at risk from persistent infection. Patients with the more severe infections can take several weeks to recover, as removing the bacteria is not the problem - they will have caused damage to the body's tissues that take time to heal. Although some patients can die, with medical treatment the chances of survival are good - though patients that have had a severe illness may suffer long-term symptoms due to organ damage that cannot completely heal. Psychological changes (mood swings, depression, psychoses) are common for a few months following recovery.