In the light of recent reports that a medication used for the treatment of heartworm in dogs is in short supply after the manufacturer stopped production this month, Central Veterinary Associates is urging its clients and the public to take preventative measures for their pets.
Earlier this month, Merial, a producer of animal health products based in Duluth, Georgia, stated that there has been a shortage of melarsomine ― the active ingredient in immiticide, the only FDA-approved medication for the treatment of canine heartworm disease. The shortage is expected to last indefinitely.
Merial has notified veterinarians of the shortage earlier this month. The company is working with the FDA to find a new supplier, but said that could take weeks or months. Any requests for immiticide must be made directly to the company by the pet’s veterinarian.
Heartworm disease occurs when adult female heartworms release their young (called microfilaria) into an animal’s bloodstream. The mosquito becomes infected with the young heartworm while taking blood meal from the infected animal. The microfilaria then matures to the infective larval stage within the mosquito. After that, the mosquito bites another animal and the larvae enter through the bite wound. It takes a little over six months for the larvae to mature into adult worms. In dogs, the worms may live up to seven years and grow as long as 12 inches.
Dogs who may have been recently infected may exhibit no signs of the disease, while heavily infected dogs may eventually show clinical signs, including a mild, persistent cough, reluctance to move or exercise, fatigue after only moderate exercise, reduced appetite and weight loss.
To check your pet for heartworm, bring it to a veterinarian who will test the animal before being prescribed a heartworm preventive. These preventives may include the form of a pill (ivermectin or milbemycin oxime), a topical liquid that can be applied onto the pet by the owner (selamectin or moxidectin) or an injectable (ProHeart 6), which is only used for dogs. For a dog, a test might be as simple as a blood test. The FDA emphasizes that these are preventive measures and are not to be considered as a replacement for treatment.
Heartworm disease is very deadly for all types of pets — dogs, cats and ferrets. With the treatment of heartworm disease now out of production, there may not be a cure for quite some time, making routine prevention the only “cure” for now or off-label medications, which are not as safe or effective.