Red Bank Veterinary Hospital reports two PET/CT cases that drove opposite clinical decisionsTwo-dose heartworm protocol achieved 95.3 percent efficacy in 168-dog shelter trialCareCredit embeds financing eligibility into Clarus PIMS to cut checkout frictionRelief veterinarians now represent one in ten private practice DVMsSingle hydrogel injection linked to 12-month pain reduction in 18-dog elbow OA studyThree JAK inhibitors and two monoclonal antibodies now approved for canine atopic dermatitisAnti-IL-23 biologic hit positive results in a 19-dog IBD pilot trialNew veterinary graduates have clinical foundations but lack the volume fluency practices expectRed Bank Veterinary Hospital reports two PET/CT cases that drove opposite clinical decisionsTwo-dose heartworm protocol achieved 95.3 percent efficacy in 168-dog shelter trialCareCredit embeds financing eligibility into Clarus PIMS to cut checkout frictionRelief veterinarians now represent one in ten private practice DVMsSingle hydrogel injection linked to 12-month pain reduction in 18-dog elbow OA studyThree JAK inhibitors and two monoclonal antibodies now approved for canine atopic dermatitisAnti-IL-23 biologic hit positive results in a 19-dog IBD pilot trialNew veterinary graduates have clinical foundations but lack the volume fluency practices expect
The Exam RoomBy The VeterinaryPracticeNow Desk3 min readOctober 28, 2026
A two-dose melarsomine protocol achieved 95.3 percent efficacy in clearing heartworm in shelter dogs with Class 1 or 2 disease, compared with 98.8 percent for the standard three-dose approach, according to a randomized clinical trial published in the Journal of the American Veterinary Medical Association.
The 168-dog trial and what it measured
The study enrolled "168 dogs with Class 1 or 2 heartworm disease" and ran from April 2024 to December 2025, according to the JAVMA report. Dogs in the two-dose group "received melarsomine injections on consecutive days 14 and 15, while the three-dose group received injections on days 14, 44, and 45," the study reported. Both groups received doxycycline, moxidectin, and prednisone, and both underwent four weeks of exercise restriction following treatment.
All 168 dogs survived treatment. The JAVMA study reported that complications were uncommon, with seven dogs needing chest radiographs with or without further treatment, though none needed intensive management.
The trial was conducted by "Lucky Dog Animal Rescue, the University of Florida Shelter Medicine Program, Toronto Humane Society, and PetSmart Charities," according to the publication. "The authors concluded that the compressed two-dose protocol, when" paired with doxycycline, moxidectin, and prednisone, was both safe and effective.
The efficacy difference and the shelter calculus it changes
The two-dose protocol gave up efficacy compared with the three-dose approach, 95.3 percent versus 98.8 percent, but shortened the treatment timeline. For a shelter managing overcrowding and a fixed budget, that compression matters more than the margin does. A dog that clears treatment faster opens a kennel slot earlier, which means the facility can treat more heartworm-positive intakes with the same staff and space.
The study limited enrollment to Class 1 and 2 disease. Class 3 or 4 presentations were not tested, and the authors did not evaluate the protocol in those cases.
What the trial controlled that private practice may not
The trial controlled exercise restriction in a shelter environment, where compliance is managed by staff rather than negotiated with an owner. In private practice, a client who takes the dog home on day 16 may not enforce strict rest the way a shelter kennel does, and that gap could change the complication rate. The study did not measure post-treatment outcomes in a home environment.
The trial also did not track long-term reinfection risk or whether dogs remained on preventive after treatment. A dog that clears treatment but reinfects six months later because the owner skipped preventive is a treatment success in this trial and a practice failure in the medical record.
We're hearing interest from shelters that see the compressed timeline as a way to increase throughput without adding kennel space or staff hours. The safety profile between protocols was equivalent when paired with doxycycline and moxidectin, so the risk is not in the drug but in the compliance piece, whether the facility or the client can enforce strict rest.
For practices that work with shelter intakes or see heartworm-positive strays, this gives a defensible shorter protocol for uncomplicated Class 1-2 cases, provided strict rest can be enforced. For owner-DVMs, shelters in the referral network may start sending more heartworm cases if treatment throughput increases. That could mean more post-treatment recheck revenue if they send follow-up out, or more competition if they build treatment capacity in-house and keep the rechecks.
The compressed protocol does not replace clinical judgment on which cases can tolerate it. A Class 2 dog with exercise intolerance or respiratory signs may still warrant the three-dose approach even if the shelter's budget prefers the two-dose timeline. The efficacy difference is small in a controlled trial, and whether it stays small in practice depends on the case being treated and the environment the dog goes home to.
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