Pet Connection by Dr. Marty Becker, Kim Campbell Thornton and Mikkel Becker

Inside Heartworm

The incidence of the spaghettilike parasites is up by more than 20 percent since 2013

By Kim Campbell Thornton

Andrews McMeel Syndication

Climate change, failure to give preventive, and the beginnings of resistance to preventive products are among the reasons why veterinarians are seeing more cases of heartworm disease in dogs -- and cats. When the American Heartworm Society performed its triennial incidence survey last year, it found that while the highest incidence remains in the southern United States, no state is free of the harmful internal parasites, spread by the bite of an infected mosquito or, in the case of states such as Alaska, arriving by way of already-infected dogs brought from out of state.

Dogs are natural hosts for heartworms. Once an infected mosquito injects microfilaria -- microscopic baby heartworms -- into a dog’s bloodstream, the worms begin to mature and reproduce. As they get larger -- heartworms can achieve a length of 1 foot during their 5-to-7-year lifespan -- and increase in numbers, they clog the heart, lungs and associated blood vessels, causing heart failure, lung disease and other organ damage.

Cats are more resistant to the parasites, but they can acquire them. Clinical signs include weight loss, exercise intolerance, vomiting, diarrhea, coughing, gagging, difficulty breathing and wheezing. Even indoor cats are at risk. Approximately 25 percent of indoor cats are heartworm positive, according to the American Heartworm Society.

Heartworm disease is easy to prevent with a monthly pill or topical treatment, and it's comparatively less expensive than treating a pet with heartworms. But people forget to give preventive, or they don’t give it year-round, giving infective mosquitoes a shot at spreading the parasites. Cool or dry weather slows transmission, but it doesn’t eliminate it.

“Most people think they don’t need to give it in the winter,” says Craig Prior, DVM, owner of Murphy Road Animal Hospital in Nashville, Tennessee. For instance, he says, dogs should stay on preventive for two months after the last exposure to mosquitoes and go on it one month before mosquitoes become active again. With climate change, some species are staying active longer throughout the year and venturing into new areas.

For those reasons, parasitologists recommend treating pets with parasite preventives year-round.

An associated concern is the beginning of resistance to preventive products. Some populations of heartworms, primarily in the Mississippi Delta area so far, are becoming resistant. “By keeping pets on year-round preventive, we decrease the risk of developing more resistant populations and increase the effectiveness of the preventives,” says Leni K. Kaplan, DVM, community practice service lecturer at Cornell University College of Veterinary Medicine in Ithaca, New York.

Adding a dog-safe mosquito repellent (avoid anything containing DEET) to your dog’s arsenal against mosquitoes can beef up his protection. Research published in 2016 found that the combination of heartworm preventive with the mosquito repellent in the study, Vectra 3D, was 100 percent effective in blocking transmission of immature heartworms from dogs to mosquitoes -- one of the stages of the heartworm lifecycle -- and more than 95 percent effective in repelling and killing mosquitoes for 28 days after treatment.

“The addition of a topical product that prevents mosquito feeding adds a second element of protection to the pet,” says Byron Blagburn, Ph.D., a parasitologist at Auburn University College of Veterinary Medicine. “So not only do you prevent heartworm infection if the pet is on prevention, but you prevent the likelihood that the pet will see a mosquito.”

While Vectra 3D isn’t safe for cats, the good news is that if the repellent is used on a dog in the same household, the cat will share in protection because fewer mosquitoes will be present.


How to introduce

pocket pet and dog

Q: My child wants a pet chinchilla. Do you have any advice on introducing him to the family golden retriever and making sure he stays safe?

A: You can’t take new pets to couples counseling to ensure happy cohabitation, but you can take steps to keep tensions to a minimum. They may or may not become best friends, but they can live together safely.

Start slow. Ritual, structure and scent are important to animals. With your chinchilla securely caged, let your dog get used to the smell of his new roomie (this works with other pets, too). Interact with the chinchilla (still caged) so your dog knows you are aware of the new animal’s presence. After a day or two, let your dog check out the cage up close so he can combine sight and smell of your home’s new occupant. Most small pets will feel secure in their cage, more calm than your dog in many cases. They may even sniff back at your dog -- odor is important to them, too.

Praise and reward your dog for behaving calmly in the chinchilla’s presence. Friendly sniffs are a good sign; staring or snapping signal that it’s best to keep them safely apart. Many goldens are laid-back, and yours may not show much interest in the new chinchilla once he’s had a few sniffs.

When you’re not home to supervise interactions, keep your chinchilla in his cage in a separate room with a closed door. Never leave his cage on the floor or some other area where your dog could investigate unsupervised. Make sure the cage is securely latched to prevent chinchilla escape attempts.

Can your dog and chinchilla snuggle and play? It happens, but I think there’s too much risk of a dog accidentally injuring the smaller animal, so I don’t recommend it. -- Dr. Marty Becker

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Have pet care plan

in case of disaster

-- Got a disaster plan in the event of a wildfire, hurricane or other natural disaster? Work out a buddy system with friends, neighbors, relatives or your pet sitter. Set up a plan to collect and care for each other’s pets in the event that one of you is traveling or at work and can’t get home to rescue pets. Exchange house keys, and make sure you have contact information to facilitate a reunion. If you’re home and must evacuate, always bring pets with you. Never assume that you’ll be able to go back in and get them.

-- With the help of a $2.8 million grant from Maddie’s Fund, researchers from the University of Tennessee’s colleges of veterinary medicine, social work, business and the department of public health are working together to develop a health care system that will improve access to veterinary care for families with limited financial resources. Ensuring that all pets have good health care not only benefits the animals and their families, but also improves public health. Called “AlignCare,” the one-health model will promote interprofessional collaboration that takes into account the influence of pets on family health and well-being and help to keep pets in homes while providing needed care.

-- Does your cat love playing in water? Whether they dabble their paws beneath a running faucet, splash in their water dish, swim in your pool or join you in the shower, more cats than you might think are true water babies. Among the breeds known to play on the wet side are Turkish vans (nicknamed “swimming cats” in their homeland of Turkey), Turkish Angoras, Savannahs, American bobtails, Bengals, Japanese bobtails and Manx (both island cats), Abyssinian (which originated in Indian Ocean coastal areas), Norwegian forest cats (descended from viking cats) and Maine coons. -- Dr. Marty Becker, Kim Campbell Thornton and Mikkel Becker


Pet Connection is produced by a team of pet-care experts headed by "The Dr. Oz Show" veterinarian Dr. Marty Becker and award-winning journalist Kim Campbell Thornton. They are affiliated with and are the authors of many best-selling pet-care books. Joining them is dog trainer and behavior consultant Mikkel Becker. Dr. Becker can be found at or on Twitter at DrMartyBecker. Kim Campbell Thornton is at and on Twitter at kkcthornton. Mikkel Becker is at and on Twitter at MikkelBecker.