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Rats are very prone to respiratory problems of various kinds. Some of these are due to infection: and a severe infection can scar the lungs and lead to chronic problems and reinfection. A marked nasal or lung infection (i.e. a snuffle or a wheeze) which persists for more than a few days should be treated with antibiotics to prevent such scarring.
Most kinds of chestiness are at their worst between about 1am and 4am.
I have heard of two or three cases in which a rat has actually haemorrhaged (bled heavily) from the nose due to some sort of circulatory problem, but the red crust often seen around a snuffly rat's nose and eyes is not blood. When Norway rats' noses and eyes run the discharge just contains red chemicals called porphyrins. Sometimes this is due to respiratory infection; sometimes to some sort of mechanical irritation (see section on sore eyes for possible causes of such irritation).
Like cats, a high proportion of elderly rats develop kidney failure. Obvious signs of this are weight-loss and excessive urination.
According to an American renal specialist the chronic wheezing which is often seen in older rats is also a symptom of renal failure, and is due to oedema (excess fluid in tissues, in this case in the lungs). Some other sources think that the respiratory problem comes first, and leads to chronic heart failure which itself then damages the kidneys.
Heart-failure is itself a cause of laboured breathing. Check for blueness of the tail-tip, fingers and toes, and in some cases a build-up of fluid (oedema) under the skin and/or around the abdomen. If you aren't sure whether a rat which is breathing heavily is really wheezing or not, stick the rat's nose down your ear and listen: if you can hear an obvious wheezing, roaring or bubbling the problem is in the lungs or nose (though in some cases there may be heart trouble as well).
Respiratory infection can be treated with antibiotic (if severe enough to warrant it) and decongestants, and heart-failure with digitalis (see below) and ACE (angio-tensin converting) inhibitors. Kidney failure is incurable, though a low-protein diet (no nuts or meat) and lots of vitamin B may help alleviate the condition. It does in cats.
Congestive heart failure in rats can be either hypertrophic cardiomyopathy (in which the muscle-wall of the left ventricle thickens due to overwork, reducing the size of the chamber and leading to a stiff, inefficient pumping action) or dilated cardiomyopathy (an enlarged but flabby heart). Hypertrophic cardiomyopathy leads to oedema (i.e. build-up of fluid) in the lungs: dilated cardiomyopathy leads to oedema of the skin and sometimes around the abdomen.
Debbie Ducommun, an American rat expert, states that the recommended treatment for heart failure is a low sodium diet, a diuretic (to reduce fluid in the lungs) such as Lasix (dose 1-2 mg/lb 1-3 times a day), and the ACE inhibitor enalapril (dose 0.25 mg/lb once a day), which lowers the blood pressure and makes it easier for the heart to beat.
If it is certain that the heart is dilated (as indicated by skin oedema or by x-ray) rather than hypertrophic, Cardoxin, a digitalis-derivative which helps the heart beat more strongly, can be added to the treatment. It must never be used for a hypertrophic heart, however, as in this case making the heart-beat stronger would simply increase the thickening of the heart wall, and could be fatal.
The dose for Cardoxin is 0.001-0.0025 mg/lb twice a day: the precise dose often has to be increased as time goes on. My vet, however, recommends sticking with ACE inhibitors alone for as long as possible, as they are much safer than digitalis. His favourite is Vasotop, which seems to be both effective and palatable enough that you don't have to go three rounds to get the rat to take it.
Debbie has found that some dietary supplements which are suggested for humans with congestive heart failure are also helpful for rats, at about a tenth of the human doses. She suggests omega-3 oils in flax oil (25 mg/day), co-enzyme Q10 (10-30 mg/day), L-carnitine (25 mg/day), and taurine (50 mg/day).
Whether the condition is due to infection, allergy or kidney-failure, the symptoms of respiratory problems (i.e. wheezing and/or blockages of nose or lungs, as opposed to heart-failure) can be eased in several ways. With proper care most affected animals will survive for a long time and still have a good quality of life.
Mild wheezing and stuffiness can be alleviated by sprinkling the patient's cage with the sort of herbal decongestants sold for human babies e.g. Karvol or Olbas Oil, or similar (Olbas Oil is cajuput, eucalyptus, juniper, menthol and wintergreen).
More serious chestiness can be eased with the decongestant Bisolvon, which is obtainable from your vet and comes either in an injectable form or as a powder.
The powdered form can be given mixed into e.g. butter or liver paté (British liver paté, that is, which is like what Americans call liverwurst only squishier), or if the rat won't take it that way then it should be mixed with water and squirted into the mouth using a needle-less syringe. The drug is so safe that exact dosage isn't very important, but an appropriate level would be between half a mil and a mil of powder mixed with about the same amount of water. It works very rapidly, but the effects only last about 1½ to 2 hours per dose, so you may need to get up in the night to give a second helping. A dose at 1am and at 3am should be sufficient to see the rat through the night: though in some very severe cases you may initially need to give two or three doses within the first half-hour.
N.B. The instructions on the box that injectable Bisolvon comes in say "Small animals 1-5ml". Bisolvon is primarily a horse drug: "Small animal" in this case means a dog. The proportionate dose by weight for a rat is about 0.03 to 0.05ml: though you can safely go up to 0.3ml for a large rat or 0.2ml for a small one if the animal is very chesty.
Also note that Bisolvon loosens and liquefies secretions in the lungs. If the animal is already very "bubbly", give only a small dose at first, to avoid building up an excessive amount of fluid.
For emergency relief of serious chestiness you can set up a steam-tent.
Put the rat in an open wire cage (to enable it to inhale the medicated steam while keeping it safely away from the hot water) and cover the cage completely with a thick cloth, so that there are no gaps around it. Underneath the cloth, next to the cage, place a bowl of very hot (i.e. just off the boil) water with a dash of e.g. Olbas Oil or Friar's Balsam in it. Renew the bowl of hot water as it cools (i.e. about every 10 minutes). 15 or 20 minutes in a steam tent usually brings considerable relief.
Steam can be burning hot, so put your own hand or face over the bowl before putting it in with the rat, to make sure it has cooled enough to breathe safely. The water needs to be hot enough to give off a good cloud of steam, but the steam itself should be no more than warm.
A nebulizer such as is used by human asthmatics does the same thing only better - if you can afford it (about £80: but you'll always have it there for future use). It creates a mist which eases breathing in the same way as steam: and it can be used to aerosol a mixture of antibiotic and saline (about 1 ml by volume - i.e. a fifth of a teaspoon - of salt to 100 ml of cold boiled water) so that the rat breathes in a cloud of antibiotic-laden mist which coats the lungs, getting right to the site of the infection. This is more effective against respiratory infection than antibiotic given by mouth or by injection.
A standard nebulizer consists of a toaster-sized box of electronics which generates compressed air, connected by a thin flexible tube to a cylinder slightly bigger than an asthmatic's inhaler, with a switch on the side and a detachable mouthpiece at the top. The cylinder houses the medicine-tank and nebulizer head.
If you take off the mouthpiece you see a short, wide, rigid plastic tube or nozzle which normally joins the cylinder to the mouthpiece. I have a plastic carrying-box with a hole bored in the side the right size and position to fit this nozzle, with the cylinder standing upright against the side of the box. The ventilation-surface of the box (e.g. pierced lid) should be partly covered to reduce air-circulation and encourage a build-up of mist when the nebulizer is turned on. The rat then sits in the box with the nebulizer running, and breathes in the mist for 15 to 30 minutes.
The person who introduced me to nebulizers for rats used the powerful antibiotic gentamicin (trade names Genticin and Pangram), which is particularly effective against gram negative bacteria often found in chest infections. Her vet prescribed a mixture of 25mg of gentamicin (e.g. 0.5ml of strength 50mg per ml) in 5ml of saline, to be used in the nebulizer for half an hour twice a day.
If given repeatedly over a period of weeks Genticin can cause deafness, but there should be no problems with short-term use. I would be wary of using Baytril in a nebulizer, as it tends to kill skin-cells on contact, and so might do more harm to the lungs than good.
N.B. The nebulizer is generally less pleasant for the rat than a steam-tent, as it is colder and makes a loud noise. Some nervy rats may be so stressed by it that it makes them pant and does nearly as much harm as good. If your rat really doesn't like it it's better to stick to a steam-tent, unless the animal's condition is so bad that it is imperative that antibiotic be delivered directly into the lungs.
If the rat's lungs are thickly congested you can follow up steam or nebulizer treatment by using coupage - the massage technique used to loosen secretions in the lungs of human cystic fibrosis patients.
As soon as you take the rat out of the steam tent or nebulizer box, place the animal on its stomach on a flat surface, facing away from you.
Using your fingertips, gently "thump" both sides of the rat, over the ribs. If you get the rhythm right the lungs will resonate, loosening the congealed matter which is causing the chestiness.
This will only work with a congestive respiratory problem involving thick secretions: check with your vet if in doubt as to the rat's precise condition.
Do not attempt this if the rat has recently been injured and there is any possibility of a broken rib.
WARNING: this technique requires either an extremely cooperative rat or three hands.
Because older rats often do have some respiratory problems, they are not suitable pets for heavy smokers.
Norway rats are rather prone to hiccups (i.e. spasming of the diaphragm): the affected rat will usually be hunched up, and will certainly be twitching rhythmically and making a little ip ip ip noise in time with the twitches. You really can cure a rat of the hiccups by giving it a mild fright: I usually creep up behind the affected animal and clap my hands sharply.