Ceva Animal Health is urging veterinarians and dog owners to add the topical parasiticide Vectra 3D to heartworm drug regimens as an additional layer of protection.
The Double Defense campaign, unveiled last week at the WVC conference in Las Vegas, reminds practitioners and clients that heartworm preventives are extremely effective—perhaps 99.99 percent—but that mosquitoes, when given enough chances, can capitalize on slim opportunities and infect a dog.
“After fighting heartworm the same way for decades, it’s time for a new approach,” said John McCall, professor emeritus of infectious diseases at the University of Georgia College of Veterinary Medicine.
A study conducted by McCall, MS, Ph.D., found that Vectra 3D (dinotefuran/pyriproxyfen/permethrin) was at least 95 percent effective in repelling and killing mosquitoes for 28 days. The monthly spot-on is labeled for use on dogs to fight fleas, ticks and mosquitoes.
C. Thomas Nelson, DVM, who co-authored the American Heartworm Society’s heartworm guidelines, noted that macrocyclic lactones used to prevent heartworms in dogs are virtually 100 percent effective.
“Virtually … doesn’t mean completely,” Dr. Nelson said.
“You can’t stop it all,” he added. “Something is going to get through.”
The efficacy of heartworm preventives also is threatened by resistance issues. In addition, the Companion Animal Parasite Council discovered a 166 percent increase in positive heartworm cases from 2013 to 2015.
“Macrocyclic lactone preventives have been used very successfully now for the past two to three decades,” McCall said. “They’re very reliable and very safe, very effective, very convenient to administer. But we also realize that during the past few years there is emerging resistance to these preventives.
“Unfortunately we don’t know to what extent that resistance is spreading. But we know it’s inevitable, it’s happening and it will spread.”
McCall’s study also discovered that Vectra 3D was 100 percent effective in blocking the transmission of microfilariae from dogs to mosquitoes.
Targeting the vector—the mosquito—is nothing new in the fight against heartworms.
“Forty years ago mosquito control was a big part of guidelines because we didn’t have the drugs we have nowadays,” Nelson said. “[The guidelines still] talk about the importance of protecting the pet against exposure—bring them in at night, using fly traps, mosquito traps.”
Ceva’s technical services director, Elizabeth Hodgkins, DVM, JD, warned pet owners not to use Vectra 3D on cats. The drug is not approved for feline use, but Ceva does offer a different preventive, Vectra, as a flea killer for cats.
One way to spread the protection, she said, is to bring Vectra 3D-using dogs closer to cats.
“I would tell my clients if I was still in practice: If you have a cat, use a preventive, and if you don’t have a dog, get one,” she said. “Pal ’em up as much as you can, seriously.”
Even one additionally protected dog can scatter the mosquito defense to other animals, McCall said.
“If you have one animal treated, it [can] kill all the mosquitoes around that animal,” he said. “You exponentially reduce the number of mosquitoes in that area for a long period of time.”
While other veterinary drugs are sold as mosquito fighters, McCall’s study looked only at Vectra 3D.
“The product has already been shown to be very effective as a repellent and an insecticide,” he said. “We know that these products are not all equal, so don’t assume that every product you see on the market is going to have that same level of activity.”