`I can't part with my cats even if my life is at stake. I can't live without them.' ANONYMOUS 43-year-old asthma patient

They're cuddly and loveable and keep us entertained with their antics. But as the recent news of a man dying from a hamster bite shows, pets can also be deadly.

``Listen to me. If you keep on living like this, you'll have an asthma attack that will kill you,'' a doctor told one of his female patients in June. Seeing the alarmed expression on her usually calm family doctor's face, the 43-year-old realized he wasn't kidding.

She had staggered to the hospital shortly after midnight three days earlier after suffering a severe asthma attack. She said the agony was unlike anything she had ever felt before.

She had a slight cold a few days before the attack. She still wasn't feeling very well. After she brushed her two cats late that night, her throat began to bother her. Her breathing became labored.

``My pulse quickened, and I became very alarmed. The situation seemed serious,'' she recalled. ``I couldn't find my inhaler to steady my breathing. I remembered a friend who died from an asthma attack. I began to panic.''

There was a general hospital offering nighttime emergency care five minutes away. She managed to get there and whispered to the receptionist that she couldn't breathe.

The doctor on duty treated her with steam inhalation and administered a drug intravenously to open the bronchi. Her condition improved. But the doctor told her she'd had a close shave.

She was discharged the following evening, but not before she was examined by her family doctor.

The woman is single, and her cats are like her children. But in this case, dangerous children, and the source of her asthma. Her doctor reiterated what she'd learned years earlier-that she was allergic to cats. He told her she now had no choice but to find another home for her pets.

But even with death creeping in on little cats' feet, she refused. ``I can't part with my cats even if my life is at stake,'' she said. ``I can't live without them.''

She learned of her allergy six years ago, five years after she began keeping a cat. The cat allergy was diagnosed when she went to a hospital for a persistent cold. ``At that time, I was still optimistic. I thought my body would get used to the cats,'' she said.

But when she adopted a stray-doubling her cat exposure-her allergy became worse, irritating her eyes and making her nose run.

Once, when she rubbed her eyes after touching one of the cats, her eyes swelled up like jelly.

Again she was told to dump the felines, this time by an eye doctor. Again she didn't listen. She kissed the cats; she buried her face in their bellies. She paid the price: Her lips swelled up, her eyes turned red and she experienced minor asthma attacks.

Her allergy rapidly grew worse. In February, she had a blood test to test the extent of her allergic reactions to certain substances.

She tested normal for her reactions to mold and dust mites. But she said she was horrified to learn that her results for cat dander and animal epithelium (the outer layer of skin) were more than 300 times normal levels. Her beloved pets could potentially kill her.

``The doctor who carried out the test told me the results were clearly abnormal,'' she said, before launching into another chorus of her death defying refrain. ``I can't let my cats go, even though I'm risking my life to keep them.''

If this woman ultimately becomes a feline fatality, she can't complain-from the grave-that she wasn't warned. However, many pet owners are unaware of the risks.

Allergies are caused by substances called allergens. Allergens found in mammals such as cats and dogs are protein particles produced in the sebaceous glands. These microscopic allergen particles can become airborne.

The protein is found on the hair and in the dander of cats and dogs and can enter the human body through the mucous membranes. If an individual has high levels of antibodies, the body will react to the foreign substance and trigger an allergic reaction.

The amount of allergens found in the home of a cat or dog owner is more than 50 times the level of dust mite allergen, which can cause childhood asthma, according to a study conducted by Masahiro Sakaguchi of the Riken Research Center for Allergy and Immunology (RCAI) in Yokohama. The air in such homes contains 154 times more cat allergen and 463 times more dog allergen compared to dust mite allergen, the study showed. A cat crawling under the bed covers was found to leave behind 60 times the amount of allergen usually generated by dust mites in a bed.

``If you have dogs or cats that move about indoors, the amount of allergens in the air increases compared to the level of dust mite allergen,'' Sakaguchi said.

Studies conducted in the United States and Japan have found more people are allergic to cats than dogs.

``It is believed that since cat allergen particles in the air are smaller, they tend to trigger more asthmatic symptoms than dog allergen,'' Sakaguchi said.

Whether a person will develop an allergy depends largely on his or her physical constitution. Yet it is believed that the greater the exposure to allergens, the higher the odds of developing an allergy.

Whether a pet is likely to cause an allergy depends on the kind of animal. Those that carry a particularly vicious form of allergen are hamsters of the same breed as the pet that made headlines recently by killing its owner in Saitama Prefecture. The man had kept the pet-a gray Jangarian hamster, an endearing creature only about 10 centimeters long with stripes on its back-for about four years. Of the nearly 1 million hamsters imported into Japan in 2001, the Jangarian is the most popular.

The man had a longstanding asthmatic condition. In February, immediately after he was bitten on the middle finger of his left hand, he began coughing. When his wife found him 30 minutes later after getting out of the bath, he had already passed out. By the time the ambulance arrived, his heart had stopped and he was no longer breathing. He died shortly after.

The man had gone into anaphylactic shock, in which the body overreacts to allergy-causing substances, causing such symptoms as difficulty in breathing, a rash and a drop in blood pressure.

``The allergen, which normally finds its way into the body through the mucous membranes, entered the blood vessels directly and in large amounts through the hamster's saliva. Since allergies appear in the parts of the body that are most sensitive to them, the man's bronchi, which were already sensitized by asthma, suffered a severe shock,'' said Yuji Maeda, head of the respiratory department at the National Hospital Organization Sagamihara National Hospital in Kanagawa Prefecture.

Eighteen cases of anaphylactic shock caused by hamsters and other rodents have been reported, including the case in Saitama Prefecture. In many of the cases, the hamster allergen had already triggered asthma.

In 2001, a woman in her 40s was taken to Hiroshima University Hospital after being bitten by a hamster and fell into a coma. The woman began keeping Jangarians and other types of hamsters in 1998.

She developed asthmatic symptoms three months later and was treated with intravenous drugs at the hospital after suffering a major attack. Nevertheless, she hung on to the rodents.

In the Saitama Prefecture case, the man who died was not only asthmatic, but also a heavy smoker. ``Smokers are more likely to develop asthma caused by a hamster allergy,'' Maeda said. ``Their bronchi, which are constantly in a sensitized state, constrict easily.''

The danger of hamsters lies in the fact that they carry stronger allergy-causing substances than cats and dogs.

According to Maeda, tests to measure allergic tendencies showed about 80 percent of people whose blood tested positive for an allergic reaction to cat and dog allergens could expect to develop an allergy if they kept these pets. That figure jumped to 100 percent in the case of hamsters and other rodents.

In another study to see if a subject would develop an allergy if they inhaled an extract of an allergy-causing substance, substances derived from hamsters caused stronger reactions than those from cats and dogs.

``Since cats and dogs rarely bite, they are not likely to cause anaphylactic shock. You must be careful with hamsters since they are small, timid and bite a lot,'' Maeda said.

It's not just rodent saliva that's deadly. Rodent urine is also problematic. Compared to humans, hamster urine contains a higher concentration of protein. This concentration is so high, that if an equivalent amount were present in a human patient, he or she would most likely die of kidney failure.

Minute particles of hamster urine can become airborne and attack a pet's owner. ``So there is a chance of being exposed to allergens floating about in a room even if you don't touch the hamster directly,'' Maeda said.

Keeping a hamster for only a few months is believed to be enough to trigger an allergic reaction. Blood tests can warn individuals about their risks, but they are not fail-safe.

``Although tests can determine whether a person is allergic to dogs or cats quite easily, things are not so simple for hamsters, in particular the Jangarian type,'' Maeda said. ``You shouldn't feel you're in the clear even if you test negative. The safest option is to just not keep hamsters. If you're in any doubt at all, leave your hamster with a friend and spend some time away from it.''

Allergies are not the only risk involved in keeping pets. Some infections that can be spread by animals to humans are potentially deadly. In Japan, there are about 20 infections that can be spread by pets.

One example is the pasteurella infection. A man in his 70s startled a sleeping poodle and was bitten on the finger. The bite became so badly infected that the bone eroded. In this case, the man lucked out. He was able to avoid having his digit amputated. Other people have not been so fortunate and have died from this type of infection.

The pasteurella germ is highly prevalent among cats and dogs. There is roughly a 100 percent chance of finding it in a cat's mouth, a 20 to 25 percent chance of a cat carrying it on its claws and a 75 percent chance of finding it in a dog's mouth.

``Of the communicable diseases common to man and animals, the pasteurella germ is the most likely to be found in the oral cavity of animals. Yet not many people have heard of it,'' said Yasutomo Arashima, a doctor at Nihon University School of Medicine in Tokyo's Itabashi Ward. Arashima's research team found that in 60 percent of cases, the pasteurella germ can cause infection of the respiratory system from the nose to the lungs, followed by the formation of pus on the skin. It can also cause inflammation of the bone marrow and outer ear or severe generalized infections, including blood poisoning and cerebral meningitis.

When pasteurellosis occurs, swelling accompanied by acute pain and effusion of a fluid develops about 30 minutes to a few hours after the person is bitten or scratched, Arashima said. These symptoms are particularly likely to develop if the person is diabetic.

``If you are in your 40s or older and suffer from a chronic illness such as diabetes and are therefore immune-compromised, the symptoms of pasteurellosis can be much worse. You have to be careful,'' Arashima warned.

Furthermore, cat owners shouldn't be fooled by the innocuous-sounding name of another illness, known as ``cat-scratch fever,'' which results from a cat scratch or bite. Transmitted from cats to humans by fleas, the disease is more likely to develop in the summer. Its main symptom is the painful swelling of the lymph nodes.

About 60 percent of those infected with cat-scratch fever are women, especially those in their 40s. The percentage of cats that carry the disease is higher in the north than the south of the country-20 percent in Okinawa Prefecture and 12 percent in Kagoshima Prefecture, but 0 percent in Miyagi Prefecture and Hokkaido-according to research conducted by Soichi Maruyama, assistant professor at Nihon University College of Bioresource Sciences in Fujisawa, Kanagawa Prefecture.

Although the disease is treatable with drugs, Maruyama warned that people with weakened immune systems must be careful. ``It is important to clip cats' claws and rid them of fleas on a regular basis,'' he said.

Other infectious diseases include parrot fever, an infection spread mainly by birds that causes flulike respiratory symptoms and eventually pneumonia; Q fever, which is spread by cats; and echinococcosis, an infection spread by foxes and dogs.

Caution is also required by those who keep faddish exotic animals as pets.

``People should not keep imported wild animals,'' said Tsuneo Kamiyama of the National Institute of Infectious Diseases. Reptile droppings contain salmonella, which can stick to the surface of the animals' bodies, he explained. If the animals are turned loose in a room, they will spread salmonella germs and cause food poisoning. Kamiyama said there are many unreported cases of such infections.

Other pets pose even more serious risks. ``Monkeys should absolutely not be kept as pets,'' Kamiyama said. ``Since they are closely related to humans, there is the risk of human diseases being transmitted to the monkeys, and then boomeranging back to people in a more powerful form and spreading.''

Although there are no accurate records of the incidence of infectious diseases spread by pets to humans, the number of cases is thought to be on the rise. Arashima advised owners to inform their doctors of the kind of environment in which their pets are kept.

``It's a good idea to put this in writing when visiting the doctor,'' he says. He suggested pet owners write a chronological account of their past health and a history of their contact with animals and hand it to the doctor with a brief explanation.

``There are very few vaccines against diseases that can spread from animals to humans,'' Arashima said. ``So from now on, people must use the `knowledge vaccine' by acquiring knowledge and arming themselves with information.''

--Motohiro Onishi, Shukan Asahi and Kaori Fujimura, Contributing Writer(IHT/Asahi: October 30,2004) (10/30)