Reaction to recalled heartworm medication linked to 600 dog deaths among possible causes
A drug linked to the deaths of dogs across the country may have killed a rare red wolf that federal wildlife managers were counting on to help save the endangered species.
One of just a few hundred red wolves in the world, the young adult female died at a Charleston nature preserve last month after the members of the U.S. Fish and Wildlife Service injected it with a heartworm-prevention drug that since has been recalled.
A Clemson University autopsy report released last week did not pinpoint a reason for the death, but the report said the wolf might have died from heat stroke or a reaction to the heartworm medicine, ProHeart6.
The U.S. Food and Drug Administration on Sept. 3 recalled ProHeart6 after receiving more than 5,000 reports of side effects in pets, including bleeding, vomiting and death. The agency’s recall, citing reports of “unexplained” adverse reactions to the drug, urged veterinarians not to use the medicine for dogs until further study is completed.
Fort Dodge Animal Health, which produced the drug, was unable to assess whether ProHeart6 could have killed the wolf, but the company maintains few dogs have bad reactions to the medicine. Wolves and dogs are closely related biologically.
Nonetheless, biologists at the Cape Romain National Wildlife Refuge, where the wolf died, will stop using the drug on wolves, refuge manager Matt Connolly said. Connolly said he was unaware of concerns about ProHeart6 before the wolf received a shot. The wolf died Aug. 25, more than a week before the recall.
“We didn’t find out it had been recalled until after,” Connolly said of ProHeart6.
ProHeart6 prevents heartworm in canines for up to six months. Since receiving federal approval in 2001, it has been touted as an easier way for pet owners to protect their animals from heartworms because only two shots are needed each year, as opposed to monthly medication.
That’s why the Fish and Wildlife Service injected a family of wolves last month in preparation for their release into the wilds of Bull Island at the Cape Romain refuge.
But hours after injecting the wolves with ProHeart6, U.S. Fish and Wildlife Service biologists found the female dead in her pen. That left two pups without a mother and the male without a mate.
Federal biologists had planned to release the wolf family from a temporary holding pen as part of a program to help the species rebound. The remaining wolves have not been released, but federal officials expect they will be.
The federal red wolf program is important, biologists say, because the shy animal is one of the world’s most endangered species, numbering no more than 300. Red wolves are Southern cousins of gray wolves found in the West but are smaller, with a reddish tinge to legs, heads and ears. Red wolves almost became extinct in the early 1900s because of hunting and habitat loss.
For more than 15 years, the government has released mating pairs of red wolves at Bull Island to raise pups in the wild. The program has allowed young wolves to learn survival skills before being transferred to the government’s main red wolf recovery site, a wildlife refuge in northeastern North Carolina.
In recent years, however, the Fish and Wildlife Service had trouble getting wolves to mate at Bull Island, so officials were excited when the young female produced pups this spring.
Clemson’s autopsy report says that while there was not conclusive evidence of the cause of death, a reaction to the drug “cannot be excluded from consideration in this case.” The report goes on to say the “significance of the treatment must be evaluated.”
The report, however, also said heat stroke could have killed the red wolf. The animal struggled and panted heavily after wildlife managers captured it in a pen. After the injection, it lay on the ground for up to 45 minutes before a veterinarian injected it with the stimulant epinephrine to revive the animal. Later in the day, the animal was found dead.
Clemson University animal pathologist Pam Parnell declined to discuss the autopsy she conducted.
Bud Fazio, the wildlife service’s red wolf recovery coordinator, could not say this week how many wolves have been injected with ProHeart6 at zoos andrefuges across the country, or how the agency would proceed in those areas.
Connolly said other red wolves, including the female wolf’s mate and two pups, had been injected at Cape Romain without any adverse reactions. The refuge also has several animals it keeps in captivity.
The FDA had given signals for two years that the medicine posed hazards to some animals, records show. A July 22, 2002, letter from the manufacturer to veterinarians said a new warning label would be added to ProHeart6 about adverse reactions. One concern was cardiac arrest.
Up to 600 dogs treated with ProHeart6 have died, the FDA said last week.
Rami Cobb, a veterinarian with Fort Dodge Animal Health, said she did not know how the drug could have affected a wild animal, such as a red wolf.
“I am no expert on wolves,” she said, “but I am really grieved to hear we have lost any animal, especially an endangered species.”
Reach Fretwell at (803) 771-8537 or firstname.lastname@example.org.