Preventive Pet Care Amid Uncertainty


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Veterinarians are concerned that the limitations COVID-19 has placed on veterinary services could lead to a decline in preventive health care for pets.

Pandemic or no now is not the time for the veterinary community to take its collective eye off the importance of heartworm prevention. That was the message of the American Heartworm Society (AHS) this spring as it announced the results of the 2019 AHS Heartworm Incidence Survey and unveiled a new heartworm incidence map drawn from the data of nearly 6,000 U.S. veterinary practices and shelters last year.

Southeast remains “hotbed” for heartworm

The AHS Heartworm Incidence Survey is conducted every three years, using data from animals tested over the previous 12 months. The 2019 survey reflected data from more than 5.5 million heartworm tests conducted over the course of a year.

No state in the U.S. was heartworm-free in 2019, according to the AHS survey, which determined that the top five states in heartworm incidence were Mississippi, Louisiana, South Carolina, Arkansas, and Alabama – all states that have been in the top tier since the AHS began tracking incidence data in 2001.

In Mississippi, almost 10% of dogs tested for heartworms were heartworm-positive in 2019; in Louisiana, just under 8% of dogs tested were positive.

Rounding out the top 10 states were Texas, Tennessee, Georgia, North Carolina, and Oklahoma.

“When veterinarians compare the 2016 heartworm incidence map to the 2019 map, it’s clear that the big picture hasn’t changed,” said AHS president Chris Duke, DVM. “The Southeast remains a hotbed for heartworm infection, but states in the Northeast, Midwest, and West have continued to see many cases as well.”

AHS’s survey also polled veterinarians on trends noted in the previous three years. According to those findings, 11% of veterinary practices and shelters surveyed reported seeing no heartworm cases, compared to approximately 13% three years ago. When asked whether they perceived the trend of heartworm incidence to be up or down over the previous three years, 26% of veterinarians saw an upward trend, while 16% noted a downward trend, and 57% of practices and shelters saw no change.

Respondents who reported an upward trend were most likely to cite “an influx of heartworm-positive patients into their practice area” and “poor compliance” (pet owners failing to administer heartworm preventives year-round and skipping doses). Respondents who noted decreases in heartworm incidence cited “improved preventive compliance among users” and “more owners giving heartworm preventives” as the leading reasons.

The COVID-19 crisis

Veterinary Advantage reached out to the American Heartworm Society for how veterinarians thought heartworm testing and preventive medicine were being affected by the COVID-19 pandemic, and how veterinarians were trying to maintain a continuity of care. Dr. Chris Duke, President of the American Heartworm Society, responded to the following questions.

Veterinary Advantage: Amid COVID-19, what were you hearing from veterinarians in regards to maintaining heartworm prevention? How was COVID-19 impacting compliance?

Dr. Chris Duke: I want to first stress that the AHS has no quantitative data on this. Compliance is never easy to track; the best we can typically do is make assumptions about compliance based on client purchases of preventives. Even before the COVID-19 crisis, we knew that heartworm compliance was far from where we would like it to be. CEVA conducted a consumer survey last year revealing that, among dog owners surveyed, 1 in 4 used preventives “consistently,” which was defined as at least 8 months/year, and 57% of respondents didn’t use preventives at all, either by intent or because they were giving another parasite preventive they mistakenly believe was preventing heartworms.

Veterinarians like me are naturally concerned that the pandemic and the limitations it has placed on veterinary services could lead to a decline in preventive health care for pets. For that reason, the AHS put together a series of recommendations veterinarians could follow to help ensure pet owners would keep their pets on heartworm prevention, even if they had to delay their pets’ annual heartworm tests for a time.

Meanwhile, I can offer some anecdotal feedback on this question, I was able to pull together after sharing your questions with the AHS Board of Directors (which includes a number of veterinarians in practice). Some of us, in turn, shared the questions with friends and colleagues of ours. We heard from veterinarians from a wide range of practices – from high-end urban practices to suburban and small-town practices to spay-neuter clinics. Following is some of that feedback:

  • One trend is that a number of owners stocked up on products like heartworm preventives early on, whether because they wanted to curtail visits to the veterinary clinic for a time or because they were concerned the products might be in short supply at some point in the future. As one of our board members put it, a number of owners who normally would buy one month’s worth of product switched to buying six months or a year’s worth. It’s possible that having products on hand could positively affect compliance, but it’s hard to know. In addition, companies have been offering rebates that have helped drive sales of preventives.
  • Across the board, veterinarians who are seeing patients for routine care say their clients are leaving with preventives – and in some cases, preventives sales have actually increased vs. the same time last year.
  • Nevertheless, declines in wellness visits do affect sales of heartworm preventives for some (not all) practitioners we talked to, especially in the first month or so of the crisis. However, services such as boarding, grooming, dentistry, etc. were more significantly affected than dispensing of heartworm preventives.
  • Several practitioners mentioned that clients able to work from home were spending more time with their pets and were, therefore, very focused on their pets’ health – a good thing. Not surprisingly, clients who are out of work are the clients most likely to forego prevention right now.
  • Another clear trend is an increase in clients wanting products shipped directly to them, whether from their clinics’ own online stores or through channels like Chewy or 1-800 Pet Meds. The spay/neuter practice we talked to noted that online pharmacy sales have doubled in their office.

Veterinary Advantage: What were veterinarians doing to try to maintain continuity of care?

Duke: Again, I can only answer this question anecdotally, since we have no quantitative data on this.

It’s important to keep prevention messages in front of owners. Some ways we do this include using social media, calling our clients, and public service announcements on local T.V. and radio stations.

Again, home delivery of products is a significant opportunity, and some veterinarians are focused on creating or leveraging their own programs to make this happen. Related to this, clinics are also offering coupons for their practices’ own online pharmacies to help facilitate prescription refills without clients’ having to stop in the clinic.

For patients that come in, veterinarians offer curbside service as well as phone consults, FaceTime calls, and Zoom calls to allow families to see their pets inside the hospital.

In my own practice, we hold weekly team meetings so we can continually be looking at processes that need to be adjusted. We initially split our team into two teams, so we wouldn’t have to shut down the practice if a team member became ill. Fortunately, that hasn’t happened, and we recently were able to consolidate our team into one and began offering elective surgeries and procedures once again. However, I realize this is not possible nationwide.

Veterinary Advantage: What will veterinarians need to do once businesses begin to reopen?

Duke: Preventive health care is so important for our patients. I’m hopeful that, more and more, practices will be able to offer wellness exams, heartworm testing, etc. as businesses open up. Again, I would refer you to our COVID-19 recommendations, which outline guidelines on heartworm testing delays. Annual heartworm testing is a standard of care in veterinary medicine and is critically important, so we would like to get our patients back on schedule.

A great deal is unknown at this point – we don’t know how long the pandemic will go on, but we know it will be months at the least before we’re back to anything close to “normal.” For that reason, we will be revisiting our recommendations by summer and considering what adjustments need to be made to help veterinarians and clients work together to keep pets healthy – while protecting the health of clients.

Infographic of the rise of heartworm incidence representative of preventive pet care.

Veterinary Advantage: How do you think this will affect heartworm incidence? Did we miss a critical window for prevention due to COVID-19? With shelter-in-place orders, could incidence rates actually go down as a result?

Duke: For clarification, the AHS conducts its incidence survey every three years, not annually. With or without that survey, we won’t know how the pandemic has affected heartworm incidence for some time, given the delay between a missed dose and the possibility of a heartworm-positive test result. It’s very much dependent on what clients do NOW. If they continue to value heartworm prevention and keep their pets on preventive, a significant uptick in heartworm cases can be avoided. And given the high costs of heartworm treatment vs. prevention, that would be best for everyone’s bottom line as well. I urge veterinarians to continue stressing the importance of prevention to clients, even if they need to get more creative with client education. Taking advantage of AHS resources – many of which are designed for online use – can help. A very simple step would be for clinics to “like” the AHS Facebook page ( and share the many posts that stress prevention.

Regarding shelter-in-place and a possible reduction in heartworm cases, that would only be possible if it somehow leads to better heartworm compliance due to an increased focus on pets and pet health. Dogs will continue to be exposed to mosquitoes, whether it’s when they’re on bathroom breaks or on walks with owners, so there is unlikely to be a reduction in exposure.