Q: I have a 9-month-old dog who is not on any sort of heartworm medication. I live in Maryland and wondered whether I need bother to put him on anything for heartworm. If you think it is necessary, when should I start? I also have three adult cats. Are they at risk, too?

A: According to the American Heartworm Society, 27 million dogs are in danger of becoming infected with heartworm because they are not on a heartworm preventive medication. A study by this society in conjunction with the drug company Merial, makers of Heartgard tablets, found that at least 250,000 dogs and cats tested positive for heartworm in 2001 in reports from 18,000 veterinary clinics.

It does not take much for a dog to become infected. Eight to 10 larvae can be transmitted in one bite from an infected mosquito, and within three months the larvae become adult worms and the dog may exhibit clinical signs. In some cases, it may take as long as seven months before a dog tests positive for heartworm depending on the number of parasites present.

Cats appear to be more resistant to heartworm infection than dogs, as fewer heartworm larvae become adult worms. In coastal regions, 30 percent to 40 percent of cats will have been exposed to infection as is shown by the presence of antibodies, although few showed any clinical signs. An interesting finding was that 28 percent of totally indoor cats had also been exposed to heartworm larvae.

Once a dog shows clinical signs of heartworm infection, which include a persistent cough, reduced appetite, weight loss, fatigue and reluctance to exercise, the treatment, although possible, is expensive and complicated. An infected dog may take several months to recover.

In some cases, the dog dies as a result of the treatment, as the dying worms can cause a serious or fatal anaphylactic reaction in the dog.

It is much better to use preventive measures. A number of treatments are available, including daily or monthly tablets or chewables, as well as monthly topical applications.

In order not to forget to dose our dogs, I always gave them their medication on the first of the month, and I kept it up all year. Because the weather is so unpredictable in this area, it takes only a couple of warm days in midwinter for mosquitoes to hatch. Furthermore, by dosing them all year, I did not have to take an annual blood sample from the dogs to check for larvae.

In the case of your young dog, it is advisable to have a blood sample checked for microfilaria before dosing him for the first time. Most of the tablets and chewables are highly palatable, and our Labradors were happy to eat them, regarding them as treats and even as a reward for good behavior.

There is a topical flea and tick product available that also is said to repel mosquitoes, but I still think it is important to have a medication specific for heartworm. As a plus, heartworm oral medication will also prevent roundworm and hookworm infection, but not tapeworms. Your veterinarian is the best person to recommend and prescribe the correct heartworm treatment for your dog.

There are special tablets and topical treatments available for cats, too. Do not use medicine prescribed for dogs on the cats, as it is too strong. The chances of your cats having a heartworm problem are not very high. Dogs are far more vulnerable to infection.

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Q: I have a toy poodle puppy who yaps or barks at everything and everybody. I am afraid that this is going to become very annoying as she gets older. What can I do to nip it in the bud?

A: Toy breeds, especially toy poodles, are renowned for their ability to have a high-pitched yap, which they use to full effect.

As soon as your puppy is old enough, she needs to be enrolled in a well-run positive puppy training class so she gets used to interacting with other people and dogs and where good behavior is rewarded rather than bad behavior punished.

Dogs generally do better when told what to do rather than what not to do. By this I mean "come, sit" rather than "stop barking" is likely to be more effective. Dogs can do only one thing at a time; therefore, the command to come and sit will make her think and give her something positive to do rather than the mindless barking.

Reward her obedience with a little treat. Do not shout at her when she starts barking, as this will only reinforce the noisy behavior. In her mind, your shouting is an encouragement to make even more noise.

Dr. Jill Bowen has practiced veterinary medicine in England and Texas and taught at Texas A&M. She lives with her veterinarian husband, three cats and a chocolate Labrador retriever in Blacksburg. If you have a question, please write to her in care of The Roanoke Times' New River Current, P.O. Box 540, Christiansburg, VA 24068, or send an e-mail to mjbowen@radford.edu. Jill Bowen regrets that she cannot answer readers' letters personally. All sick animals should, of course, be taken to a veterinarian.