Study: Increasing Access to Heartworm Treatment for Dogs in Shelters

A new study in partnership with the University of Florida Shelter Medicine Program, Toronto Humane Society, and Lucky Dog Animal Rescue, made possible by a grant from PetSmart Charities, has the potential to change the way animal shelters across the United States treat heartworm infected dogs.

Heartworm disease — An unsolved challenge for animal shelters

Canine heartworm infection is present in all 50 states, but is most prevalent where mosquitoes capable of transmitting infection thrive in the warm and humid climate of the South. Since heartworm occurs most frequently in dogs with poor access to preventive healthcare, animal shelters that take in lost and unwanted dogs commonly encounter high numbers of infected dogs.

The longer dogs carry heartworms, the more damage to the lungs and heart occurs. This damage progresses undetected in many dogs, but may also lead to a poor quality of life accompanied by cough, exercise intolerance, and shortened lifespan. Heartworm infected dogs can also transmit it to other dogs via mosquitoes. Adopters often shy away from adopting heartworm positive dogs due to the cost and inconvenience of managing a dog through heartworm treatment.

Study participant

Meet Meatball!

Meatball was once a treasured family member until his person passed away. The surviving family members came into town, cleared out the house, put him outside, and left. Meatball was terrified and alone until a neighbor noticed him living under the porch and brought him to one of Lucky Dog Animal Rescue's rural shelter partners. That shelter partner reached out to Lucky Dog, and Meatball is now safe, getting lifesaving heartworm treatment

Timely treatment decreases the likelihood of life-long heart and lung damage caused by heartworm disease. The American Heartworm Society recommends an evidence-based treatment protocol often considered the safest and most successful. However, the treatment is difficult to administer in shelters due to the prolonged length of time in treatment and exercise restriction (120+ days) and the cost and logistics of administering three doses of the adulticide medication melarsomine. Many shelters have developed abbreviated heartworm treatment protocols which have not been rigorously tested in prospective controlled clinical trials.

The logistics and cost of heartworm treatment present multiple challenges for shelters. Prolonged in-shelter heartworm treatment in accordance with the American Heartworm Society protocol is impractical for many shelters where space and staffing are in short supply. Some shelters allow heartworm-positive dogs to be adopted with outpatient treatment instructions or a private veterinary clinic referral. Other shelters euthanize heartworm-positive dogs.

Can a new condensed heartworm treatment plan measure up to traditional protocols?

Our research team developed a prospective clinical trial comparing the safety and efficacy of two treatment protocols conducted over a shorter time frame than traditional protocols. The two-year study, “Comparative Efficacy of Heartworm (Dirofilaria immitis) Treatment Procedures with Shortened Time Frames in Infected Shelter Dogs,“ is made possible by a grant from PetSmart Charities, which funds research to increase access to veterinary care. In developing the protocol, the researchers kept some key goals in mind:

Match the safety of traditional protocols
Achieve high treatment success
Minimize the number of medical treatments for staff to carry out
Decrease the length of time to complete the treatment protocol
Contain treatment costs as much as possible

Under-resourced shelters in the southern states often struggle to find positive outcomes for heartworm-positive dogs. Dogs naturally infected with heartworms are transferred to the Lucky Dog Animal Rescue South Carolina Rescue Campus where they are spayed or neutered, vaccinated, treated for any illnesses or injuries, and then begin heartworm treatment.

Sign on dog kennel for exercise restriction

Condensing the Treatment Timeline

Long heartworm treatment protocols can contribute to shelter crowding and distress in dogs that must be isolated from other dogs, cannot join playgroups, and are restricted to short leash walks for weeks to months at a time. More efficient protocols would make heartworm treatment of more dogs possible.

Dogs are randomly assigned to a heartworm treatment protocol. Both protocols include the same medications but with different timing and frequency of the melarsomine adulticide injections. During treatment, dogs receiving two doses have one month of limited exercise whereas dogs receiving three doses have two months of limited exercise.

The dogs are monitored at the Lucky Dog for the duration of heartworm treatment procedure, after which they are available for adoption in the Northern Virginia-Eastern Maryland-DC area. Adopters agree to take their dogs to a testing site six months after the last melarsomine injection to determine if treatment was successful. If the test is still positive it is repeated at nine months, at which time another positive test would be considered a treatment failure.

“Two-dose” heartworm treatment protocol

The “two-dose” protocol includes melarsomine injections two days in a row, heartworm preventive (ProHeart 12), antibiotic (doxycycline), and corticosteroid (prednisone) followed by a month of limited exercise.

“Three-dose” heartworm treatment protocol

The “three-dose” protocol includes a single melarsomine injection, heartworm preventive (ProHeart 12), antibiotic (doxycycline), and corticosteroid (prednisone) followed by a month of limited exercise. Then two more melarsomine injections are administered two days in a row followed by another month of limited exercise.

Meet ThE “Lucky Dogs”

Heartworm Disease Resources

Did you adopt a Lucky Dog from the heartworm treatment study?

Not only did you take home a terrific new companion, but your dog plays a crucial role in the search for a streamlined heartworm treatment that can save more dogs in shelters. Your Lucky Dog has completed their heartworm treatment before adoption. The next step is a blood test six months after heartworm treatment to ensure its success. We have arranged multiple testing sites in the Northern Virginia-Eastern Maryland- DC area. You will receive the results of the tests and follow-up instructions a few days later.

Our study coordinator will be in touch a few weeks before the test is due to arrange an appointment at a convenient testing site. If you have any questions about the study, contact us for more information at HeartwormStudy@LuckyDogAnimalRescue.org.