Monoclonal antibodies show promise as canine parvovirus treatment

Managing a canine parvovirus case can be time consuming and stressful for hospital staff members, not to mention the patient and owner. However, recent advances in monoclonal antibody (mAb) therapy promise to make these cases significantly less challenging, says Dr. Chris George, medical affairs specialist at Elanco Animal Health.

Reducing hospital stays for canine parvovirus patients by even a day is good for everyone. "Anything we can do to speed recovery and get these dogs back home quicker helps reduce the emotional burden on staff and supports hospital flow," says Dr. Chris George, medical affairs specialist at Elanco Animal Health.

"This is the first time in 50-plus years of treating parvo (symptoms) that we have something that treats parvo. We're targeting the virus and not just another symptom," Dr. George said during an Elanco-sponsored July 19 presentation at the AVMA Convention 2025 and 40th World Veterinary Association Congress in Washington, D.C. "The earlier you can treat these dogs, the better, because you're going to prevent damage from that virus, you're stopping it right there in its tracks."

Smart weapons

Dr. George reviewed the growing body of research showing the efficacy of Elanco's Canine Parvovirus Monoclonal Antibody (CPMA) treatment, which has been conditionally approved by the U.S. Department of Agriculture (USDA) for treatment of canine parvovirus.

State laws and regulations vary regarding the use of a conditionally approved animal drug, according to Dr. Beth Thompson, president of the National Assembly of State Animal Health Officials. Some states require a review before a conditionally approved drug can be used, while others have no such regulations.

In practice, the CPMA is administered as a single intravenous injection alongside standard supportive care. Monoclonal antibodies support the immune system by acting as a kind of smart weapon designed to specifically target the virus and help natural antibodies neutralize it.

Dr. George summarized an Elanco-funded challenge study conducted under USDA guidance and published in the April 2024 issue of JAVMA. In that trial, 28 8-week-old puppies were intranasally challenged with CPV-2b. All dogs shed parvovirus by Day 4 and then received either CPMA or a placebo without any additional therapies.

"There was a 0% mortality rate in treated dogs," Dr. George said, adding that secondary outcomes favored the treatment group, with faster resolution of inappetence, vomiting, and lethargy, and reduced fecal viral shedding later in the first week.

Additionally, Dr. George highlighted early data from a shelter cohort in Ohio using CPMA as an adjunct to established protocols. In that retrospective comparison, published this past April in the Journal of Shelter Medicine and Community Animal Health, the median length of hospitalization decreased from four days to two after CPMA was added to care pathways, and time to serial negative antigen tests also shortened, particularly among less-ill dogs. While overall survival was similar between groups, he said, the operational and welfare impacts of fewer days in isolation were meaningful for teams and patients.

Thanks to canine mAb therapy, "I truly believe that parvo is not a referral-only disease. You can treat parvo in general practice; you can do it in a shelter. All you really need are a few supplies, a little bit of time, and we can have a very positive outcome for the vast majority of our parvo cases," Dr. George said.

Safety findings to date also have been favorable, he noted, citing a prospective field safety study in 147 client-owned dogs. No hypersensitivity or anaphylactic reactions were reported.

The most common adverse events were mild injection-site reactions in approximately 4% of dogs, with transient gastrointestinal signs in a smaller fraction. These data are consistent with publicly available summaries of field safety under USDA oversight.

Dr. George also addressed labeling age limits and practical use in young patients. "CPMA is labeled for treatment of dogs 8 weeks of age or older," he said, noting that the efficacy study enrolled that age group, while the safety dataset included puppies as young as 6 weeks. He acknowledged that use below 6 weeks would be extralabel and said clinical data are lacking in that population.

Added protection

In late June, the USDA granted an additional on-label indication for passive immunity to prevent parvovirus in exposed puppies. Dr. George described the addition as significant for shelters and other high-risk environments where parvovirus can spread: "With both treatment and prevention options now available for puppies exposed to the virus, we have powerful tools to intervene earlier and more effectively."

For prophylaxis, Dr. George described a lower subcutaneous dose intended to provide rapid passive immunity in puppies with known exposure, such as litters or shelter intakes. He cautioned that, as with maternal antibodies, passive antibodies can interfere with active immunization.

"Think of CPMA as giving them another dose of maternal antibodies and resetting the vaccine clock," he said.

Dogs that receive CPMA for treatment of confirmed infection should have routine core vaccinations restarted after recovery, consistent with established schedules, according to Dr. George. Further, dogs that receive CPMA for prophylaxis should have their vaccine series extended, with a booster given at least 17 weeks after CPMA to ensure an appropriate serologic response.

He referenced data showing that most puppies developed protective titers when a modified live parvovirus dose was administered around 15 weeks after CPMA, with more than 90% achieving an adequate response by week 18.

Overall, Dr. George sees CPMA as part of a broader therapeutic evolution rather than as a standalone solution.

"I do not recommend CPMA as a monotherapy for all of your parvo patients," he said, noting that many clinical presentations require fluids, antiemetics, analgesia, early enteral nutrition, and antibiotics when indicated.

He also pointed to adjunctive measures, including oral recuperation fluids rich in prebiotics and amino acids along with fecal microbiota transplantation, that have been associated with faster return of appetite or shorter hospital stays in small studies without clear mortality effects. The goal of any treatment plan, according to Dr. George, should be to combine targeted antiviral therapy with supportive care to shorten morbidity, reduce isolation days, and lower the labor burden on staff without compromising outcomes.

Moreover, shortening hospitalization by even one to two days can relieve pressure on isolation wards, reduce staff stress, and help puppies reenter critical socialization windows sooner.

"Anything we can do to speed recovery and get these dogs back home quicker helps reduce the emotional burden on staff and supports hospital flow," Dr. George said.