Heartworm survey: No change in 10 years

'Every now-and-then profession needs wake-up call; this is a good one'
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Jul 01, 2002

Atlanta-Widespread use of heartworm preventive has not changed rates for infection of the disease in the last 10 years, according to a Gallup survey to 18,000 veterinary clinics nationwide.

Even more alarming, officials say, is the significant drop in the number of dog owning households using heartworm prevention. The survey indicates 55 percent of U.S. dog-owning households are on heartworm preventive, which is down from a high of 66 percent in 1998.


Heartworm Disease Hot Spots
The comprehensive survey of veterinarians was sponsored by Merial in collaboration with the American Heartworm Society and is considered the largest undertaking on heartworm disease since the 1950s.

Despite the annual push on heartworm awareness, veterinary officials still believe the decline is nothing more than a problem of awareness, and is not a result of a lingering economic recession.

Overall, the survey shows that 240,000 dogs and 3,095 cats tested positive for heartworm infection nationwide in 2001. Heartworm was also diagnosed in every state in the country. The results are significant, and experts believe the numbers are probably very conservative.


An estimated 240,000 dogs and cats were diagnosed with heartworm disease last year, a Gallup survey says. DVMs fear the number is low.
Dr. Don Doiron, president of the American Heartworm Society says, "I think the incidence is significantly higher than 240,000."

Doiron says, "We have a disease that is 100 percent preventable when medications are given when recommended, and yet we still have a pretty significant number of dogs developing heartworm disease."

Official estimates are that 27 million dogs are not on heartworm preventive and may not have been tested, which could also translate into a much higher number of positive tests.

Get the message out Dr. Doug Carithers, director of veterinary professional services for Merial says the downward trend in use of heartworm preventives is nothing more than pet owner awareness and that a constant reminder system is needed to keep the message in front of owners.


Table 2: Top 10 states reporting heartworm disease
Carithers says that people become complacent over time and lax in some cases because they don't feel this preventable disease could impact them.

"Every now and then any profession needs a wake up call. And I think this is a good wake-up call. We have a need out there and just awareness helps build the story and confidence in discussing it with clients," Carithers says. "It gives them a valuable new tool to show their clients how they can best manage the health of their pet," he adds.

Doiron, who owns a veterinary practice in Lafayette, La., adds, "Without proper prevention, it is possible that 50-90 percent of dogs could be at risk for contracting heartworm disease every year, depending on which area of the country they live in."

Look at the states While the incidence numbers have not yet all been compiled, heartworm infection rates were pretty predictable. Infection rates in southern climates were greater than in northern states, and infection rates were typically higher along the Mississippi and Ohio rivers. The top 10 states included:

  1. Texas: 38,535 dogs, 362 cats
  2. Florida: 29,749 dogs, 743 cats
  3. Louisiana: 18,700 dogs, 158 cats
  4. North Carolina: 17,338 dogs, 200 cats
  5. Georgia: 13,896 dogs, 133 cats
  6. Mississippi: 11,522 dogs, 107 cats
  7. Tennessee: 10,324 dogs, 39 cats
  8. South Carolina: 9,387 dogs, 131 cats
  9. Alabama: 9,308 dogs, 95 cats
  10. Indiana: 8,348 dogs, 107 cats

Keep in mind there is always bias in surveys, but it does provide a very useful snapshot of which areas are at risk and it definitely brings to the forefront that client compliance is an issue, Doiron adds.

What is unknown is whether or not clients are not following through once heartworm medication is prescribed or whether clients are just refusing the medication and gambling that their pets won't get the disease.

Doiron explains, "A lot of those cases may be stray animals and ones that have just never been to a veterinarian. We don't know how many people just aren't giving the medication when prescribed. I am concerned with those kinds of numbers; that it is a pretty significant percentage."

In addition, areas not typically thought to be heartworm states are reporting infections simply because of the increasing mobility of our society, Doiron explain. Travelers from non-endemic to heartworm endemic states have been a long-established trend, and pets are picking up infection. He adds there is reason for veterinarians even in non-endemic states to discuss heartworm prevention especially for travelers and people who spend their winters in warmer climates.

Bring it home Doiron says that the key to prevention of this disease is education, which will help compliance problems.

"There are, of course, a lot of things that we could do to combat compliance problems," Doiron says. "We have some areas of the country that transmission could be six to eight months of the year. They still recommend year-round preventive just to get clients to comply better." He adds that the injectable heartworm preventive will be important for clients having difficulty complying with the chewable medications.

As a follow-up program to the survey, Merial launched a new consumer education push "For Healthy Pets, Visit the Vet" campaign. This yearlong initiative is designed to encourage pet owners to visit their veterinarian. For more information, pet owners are directed to go to www.healthpet.com or call (866) ASK-VETS.

Veterinarians will get a poster depicting what is going on in their counties. The idea is to spur questions from pet owners. "If someone asks a question, they will listen far more intently than if you are up there telling people what could happen," Carithers says.