AHS Board Speaks Out

Tom Nelson, DVM, Medical Director
VCA Animal Medical Center of Northeast Alabama

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Dear AHS,
A 4-year old neutered Golden Labrador heartworm patient whose last melarsomine injection was administered 6 months ago came in for a recheck. While the microfilaria test was negative, the antigen test was positive. Should I re-administer adulticide therapy? -Dr. V.

THE SHORT ANSWER
Retest patients that have undergone heartworm treatment at 9 months post-adulticide treatment vs. 6 months.

Chris Duke, DVM
Bienville Animal Medical Center, Ocean Springs, Mississippi

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Dear AHS,
I have a client whose 6-year-old Golden Retriever was diagnosed with heartworms late last year. At that time, the dog was given preventive and started on doxycycline. However, the owner was in the midst of a job change and failed to bring the dog back for adulticide administration. While she is now willing to resume treatment, my question is, do I need to re-start the doxycycline—or can I move on to melarsomine? -Dr. M.

THE SHORT ANSWER
If the time span between giving doxycycline and starting melarsomine has been 12 months or less, you can proceed with adulticide treatment.

Angele Bice, DVM
Owner, Summerville Pet Clinic Summerville, South Carolina

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Dear AHS,
A local shelter treats heartworm-positive patients with a protocol consisting of a month of doxycycline immediately followed by two consecutive melarsomine injections that are administered during one two-day stay. We typically see  patients several months after they’ve been adopted. How should these patients be managed at this point? -Dr. H.

THE SHORT ANSWER
While a 2-dose adulticide protocol only reduces the worm burden by 90% vs. the 98% achieved with a 3-dose protocol, there are alternatives to giving additional doses of melarsomine to this dog at this time.

Brian DGangi, DVM, DABVP (Canine & Feline Practice, Shelter Medicine Practice)
Senior Director Of Shelter Medicine, ASPCA

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Dear AHS,

I work with a local rescue that wants to rehome several recently abandoned dogs, one of which has tested antigen-positive and microfilaria-positive. The dog is two years old, asymptomatic, and—with the exception of fleas—otherwise healthy. The rescue would like to send this dog to a shelter out-of-state where he can be adopted. Is this advisable? -Dr. B.

THE SHORT ANSWER
Following several simple steps can ensure dogs can be safely transported without posing a risk for further heartworm transmission.

Jennifer Rizzo, DVM
Friendship Pet Hospital
San Antonio, Texas

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Heartworm Outreach: Client Education in the Age of Covid-19

Educating clients without face-to-face communication has emerged as a new challenge in veterinary practices today. Whether a client has a new puppy or is the seasoned owner of a senior cat, understanding the need for year-round, on-time heartworm prevention and annual testing can mean life or death for pets.

Q. How can veterinarians stay engaged with pet owners if we’re not seeing them face-to-face?

A. With full appointment schedules and curbside-only service, it can be harder than ever to deliver effective client education. Yes, we have phone calls, FaceTime and Zoom, but the time we can devote to these may be limited.

In our practice, we have dedicated a cell phone to sending and receiving texts from clients with appointments. This phone also serves as a client education portal for:

• Texting clients prior to visits. If it’s a wellness visit, I can send articles about heartworm disease, vaccines and nutrition.
• Demystifying appointments. During visits, we send photos of the pet with the technician or veterinarian to clients so owners can see what’s happening while they sit outside in the car. I also
• send lab reports, including heartworm test results. Finally, we text owners a link to our preferred online pharmacy so they can have refills sent to their homes.
• Sending follow-up reading. In addition to sending home handouts, we direct clients to relevant website articles or YouTube videos.

Lindsay Starkey, DVM, PhD, DACVM - Parasitology
Assistant Professor, Department of Pathobiology
Augurn University College of Veterinary Medicine 

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Heartworm Diagnostics: Antigen Tests Alone Aren’t Enough

The American Heartworm Society (AHS) recommends heartworm antigen testing to screen dogs without clinical signs and verify suspected heartworm infections. While patient-side antigen tests provide a vital tool for the practice, a full understanding of their role in heartworm diagnosis is essential.

Q. Today’s commercial antigen tests have great utility in heartworm screening. Nevertheless, these tests also have certain limitations, don’t they?

A. Antigen tests detect circulating heartworm antigen from adult worms and are nearly 100% specific. While highly accurate in the vast majority of cases, even the most sensitive heartworm test can fail to detect the presence of antigen when levels of circulating antigen are low due to the presence of immature worms, male-only infection or few female worms. In other cases, sufficient antigen is present but bound by the antibodies produced as part of the body’s response to infection. This is known as an immune complex formation.

Chris Duke, DVM, President, AHS
Bienville Animal Medical Center
Ocean Springs, Mississippi

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Since 2002, the American Heartworm Society has conducted a triennial nationwide survey of veterinary practices and animal shelters that tracks heartworm incidence. Nearly 6,000 practices and shelters participated in the latest survey, which reflected data from the 2019 calendar year. These data were also used to produce the 2019 AHS heartworm incidence map.

Q. What did the latest AHS survey reveal? What stands out?
A. There’s no question that heartworm disease is more common in some areas than others, and the states with the highest percentages of positive cases continue to be in the Southeastern and Gulf Coast regions, where the climate creates ideal conditions for heartworm transmission. Sadly, my home state of Mississippi has been the #1 state in heartworm incidence for the past six years. The remaining states in the top 10 were Louisiana, South Carolina, Arkansas, Alabama, Texas, Tennessee, Georgia, North Carolina and Oklahoma.

Chris Duke, DVM, President, AHS
Bienville Animal Medical Center
Ocean Springs, Mississippi

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It’s spring—the season when many clients come to your clinic for heartworm checks, medication refills and their annual dose of heartworm education. As you think through how to once again
make a compelling case for heartworm prevention, consider the following: 

1. Clients learn best when there is a perceived need.

Pet owners must see a payoff if they’re going to make the effort to learn about heartworms. I emphasize that heartworm disease is preventable and position preventives as “insurance policies” against it. Using a life cycle diagram, I explain that heartworms undergo three life stages inside the pet and two stages within the mosquito vector—then show clients how heartworm preventives interrupt this cycle.

I admit that I’m often tempted to tell my clients everything I know about heartworms. However, I’ve learned it is better to limit my talking points to essential information and to save the “nice to know” scientific facts for clients who demonstrate genuine interest.

2. Use visuals to facilitate understanding.

Most clients learn better if I combine visuals with my heartworm talk. That’s why I keep copies of the AHS heartworm incidence map in every exam room. Clients are always drawn to the color of our locale on the map and it helps them understand the implications for their pets. I’ve also had clients point to parts of the country where they didn’t expect heartworms to be endemic and say, “Wow. I’m going to tell my friend Mary that she’d better be giving her pets heartworm prevention!” 

Marisa Ames,DVM, DACVIM (cardiology)
Associate Professor
Colorado State University,
College Of Veterinary Medicine

Managing Dogs with Severe Heartworm Disease

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Managing Dogs with Severe Heartworm Disease

Fortunately, most infected dogs have no clinical signs or only mild signs of heartworm disease (HWD) and tend to undergo adulticide therapy with few major complications. The likelihood of complications associated with HWD increases with the chronicity of infection. Prognosis is dependent on stabilization, the ability to administer subsequent adulticide therapy and the ability of the family to commit to treatment of chronic conditions. Following is a brief overview of these complications, including clinical signs, diagnosis and treatment. For information on drug dosages, please visit www.heartwormsociety/treating-severe-HWdisease.

Stephen Jones, DVM
Immediate Past President, American Heartworm Society
Lakeside Animal Hospital
Moncks Corner, South Carolina

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Q. You have studied the short- and long-term effects of heartworm disease in dogs in order to better understand the pathology it causes. What have you learned?

A. By conducting necropsies of experimentally infected dogs and documenting my findings, I’ve learned that heartworm disease actually begins long before clinical signs are evident—in fact, the damage to the pulmonary vasculature begins before heartworms can be diagnosed with standard antigen tests.

Once the worms reach their adult length of 10 to 12 inches, the larger pulmonary arteries are affected and the disease progresses, with the number of worms present, the duration of the infection, and the activity level of the dog all affecting disease severity. Given time, heartworm infection leads to a significant thickening of the pulmonary arteries, obstructive disease, perivascular inflammation and fibrosis, while natural, random worm death can cause dramatic embolic and inflammatory disease with significant acute and long-term consequences.