There's good news and bad news about how pets may be related to your health.

But, by and large, it's more good than bad. A lot of it depends on how much you love or hate animals -- almost nobody has a take-them-or-leave-them attitude about pets.

First the good news:

Pets, according to some studies, can help you live longer.

Scientists aren't altogether certain why, but a pet(fish or bird, dog or cat) seems to have a perceptible beneficial effect on people with heart conditions or high blood pressure.

In a study conducted at the University of Maryland and the University of Pennsylvania, researchers found that cardiac patients with pets had a better survival rate than those who lived alone, or only with other people.

The scientist discovered that when hypertensives talked to people their blood pressure tended to rise, but when they talked to dogs it either stayed the same or dropped.

Some reasons, speculate the researchers, may involve being needed, being loved, being cheered by (as in songbird) and being relaxed by (as in watching a tankful of fish). Or the security of a noisy dog, or the required sharing of exercise with a dog . . . again, the studies indicate it really didn't matter the kind of pet; just its existence seemed to help. Not a lot, mind you, but measurably.

On the other hand, there are a few people around, including some doctors, who feel that pets may be dangerous to yuor health and to that of your children. (Some are not animal lovers, and this should be taken into consideration.)

However, three veterinarians -- who do tend to be animal lovers -- of the Center for Disease Control in Atlanta, Ga., are involved in the study of parasites and diseases, viral and bacterial, which may be transmitted from pet to human.

The CDC vets take special pains tonote that the incidence of these ailments, some of which can have grave effects in humans, range from the unusual to the extremely rate. They deal with "potentials."

But even this relatively negative side of pethood has its cheery aspects. Many of the so-called "zoonoses" can be either treated or prevented altogether.

Even rabies, that most deadly of all illnesses people share with animals, has been dealt another blow with last June's approval for use in the United States of a more effective, safer and not nearly as traumatic vaccine as the old "duck" vaccine, to which those bitten by rabid animals had to be subjected. o

Although cats and dogs are required to be vaccinated against rabies, enforcement is often lax, says Dr. William Winkler, chief of the CDC Resspiratory and Special Pathogens Brance and a specialist in pet-human viral illnesses, of which rabies is one.

Animal rabies is increasing, he says, primarly in the skunk population. The result is more "secondarily-affected animals like dogs and livestock."

"Let me put in my pitch," says Winkler. "We try to make a point of discouraging wild animals as pets, mainly because of rabies. Somebody buys a cute little skunk at the pet shop and is told it was born and raised in captivity. We've had a number of instances where these animals do come down with rabies . . . and invariably, multiple people have to take rabies treatment."

"Well," says Dr. Arnold Kornblatt of CDC's Bacterial Zoonoses Branch, "I'll tell you right off, there are a lot of diseases transmittable the basic recommendation -- the bottom line -- is maintain adequate hygiene.

"Even though I grew up with animals lickimg me and crawling all over me," says Kornblatt, the son of a veterinarian, "when I went to veterinary school, I said, 'Oh boy, how did I make it this far?'"

Among illnesses Kornblatt is studying:

Cat Scratch Fever: "We don't really know what causes it. It usually occurs at a certain time of year -- early fall to late winter -- and some cases are not connected to cats." The ailment usually involves mild fever and swollen lymph nodes under the arms.

Campylobacter: A bacterial infection causing diarrhea. Has been found in dogs, but more often associated with chimpanzees which, Kornblatt notes, "are not a pet you'd want to have" because of all the potential diseases they carry.

Salmonellosis: Once widely associated with pet turtles, but on the decrease from that source. A bacteria that grows in animal food products not refrigerated properly, or utensils not properly cleaned.

Psitticosis: From (mostly imported) birds. Be certain, when you buy a bird, advises Kornblatt, that it has its full 45 days of treatment in quarantine. And if the shop is a mess, it's probably not a good place to get a healthy pet. Only about 150 cases of this illness are reported annually.

Anypical Mycobacteria: A bacterium which grows occassionally in fish tanks and causes skin lesions. Wearing plastic gloves when cleaning the tank can prevent this minor ailment.

Dogs' mouths also harbor bacteria which can cause a dog bite to become infected.

Among animal parasites potentially serious for humans it toxplasmosis, an organism connected primarily with eating rare or inadequately cooked meat -- mostly lamb or pork -- occording to Dr. Dennis Juranek of CDC's Parasitic Diseased Division.

The parasite now has been found in the intestines of cats and studies are underway, including one in Baltimore, to determine the extent of the cat connection.

"The relative importance of cats versus meats as a source of infection for humans is not known," says Juranek. The infection is rare, but serious. If a pregnant woman is infected it could have much the same devastating effect on the fetus as rubella. It can also cause eye infection.

Finally, says Juranek, researchers are beginning to believe that human infection -- especially of toddlers -- by roundworms commonly found in dogs is a greater problem than had been believed. These worms occasionally migrate to the eyes and can, untreated, cause blindness. They have been mistaken for retinal cancer, but a blood test is now available to help make the distinction. r

Control of infection lies in "reeducation of veterinarians to treat puppies at an earlier age," at about 2 weeks, rather than the more usual 6 or 7.

And, as all three vets emphasize, keep animal areas and litter boxes clean -- and small children out of them.

Finally, advises Dr. Kornblatt, "Love your pet, just don't sleep with it."