Heartworm disease is a potentially life-threatening infection currently affecting at least one million pets in the United States. Despite the availability of safe, convenient, and effective prevention, heartworm disease is more widespread than ever, and is now endemic in all 48 continental states.
Learn how to protect your pet from this unrelenting threat. Here are seven fast facts every pet owner should know about heartworm disease and prevention in pets.
#1: Heartworm disease is transmitted to pets by mosquitoes
When mosquitoes bite and feed on a dog, cat, or wild mammal infected with heartworm disease, they ingest the larval stage of Dirofilaria immitis—a blood-borne parasite. Once inside the mosquito, Dirofilaria immitis progress to their infective stage. When the mosquito takes their next blood meal from your pet, the infective larvae are transferred through the bite wound to your pet. The larvae then move through the tissues and slowly migrate toward their final destination—your pet’s lungs and heart—where they mature into adult worms over the next six months, with females reaching up to 14 inches long.
#2: Heartworm disease is deadly but preventable in pets
Once an adult infection is established, the worms severely damage the heart and major lung vessels by creating intense inflammatory reactions and altering normal function. These changes to vessel and heart chamber walls, as well as the worms themselves, over time create resistance to normal blood flow and heart muscle contraction, ultimately leading to deadly consequences, including:
- Congestive heart failure — As the heart muscle weakens, fluid backs up into the lungs and abdomen.
- Caval syndrome — This condition, which is also known as cardiovascular collapse, occurs when the worms form a blockage in the heart. Death may be rapid, especially if the blockage happens during exercise.
- Worm embolism — Worms or worm segments may form a blockage in the major vessels and obstruct blood flow.
- Sudden death — Cats may experience a fatal reaction to immature worms in their respiratory system.
These emergencies are easily avoidable with consistent year-round heartworm prevention dosing and yearly screening tests at Harbor Pines Veterinary Center. Heartworm prevention is available as 6- or 12-month injections for dogs, and once-monthly chews or liquid applications for dogs and cats. When given as directed, veterinarian-prescribed heartworm prevention has an almost 100% efficacy rate—however, only a single missed dose allows heartworm disease to take hold, so vigilance is required.
#3: Heartworm disease may go unnoticed until your pet is in late illness stages
Early stage heartworm disease is almost impossible to identify. Dogs may experience mild signs, while cats may have no visible signs during the entire infection. Signs for either species can seem vague and non-specific to many owners, but should always be investigated by a veterinarian. Early signs in dogs may include:
- Persistent cough
- Reluctance to exercise
- Fatigue after mild exercise
- Weight loss or changes in appetite
Because cats experience heartworm disease differently, their clinical signs are more misleading—and may not be apparent at all.
#4: Cats can get heartworm disease, but differently
Unlike dogs, cats are not natural heartworm disease hosts, so the heartworm life cycle is not assured. Cats can rid their body of circulating immature heartworms (i.e., microfilariae), so despite an infective mosquito’s bite, true infection and disease may not occur. However, if a few microfilariae escape the cat’s defenses and mature to adulthood, the cat will experience heartworm disease.
Clinical signs in cats are often nonspecific, or can mimic respiratory disease, making diagnosis a challenge. Signs may include:
- Cough or wheezing
- Increased respiratory rate
- Weight loss
Many cats show no signs at all or, because of a sudden obstruction in their heart or lungs, the first sign may be sudden death.
#5 Heartworm disease treatment is available only for dogs
If your dog tests heartworm disease-positive, treatment is available—but does come at a cost. Canine heartworm treatment is expensive, the recovery process is lengthy, requiring four to six months of strict crate rest, and serious side effects can occur as the worms die off.
Unfortunately, no safe treatment is available for cats, although medical management can help keep your cat comfortable for as long as possible. With dedicated veterinary-supervised care, cats can outlive their heartworms, which only live about two to three years in cats.
#6: Prevention is the safest and most affordable option for your pet
Without a doubt, heartworm prevention prescribed by your pet’s veterinarian is the best way to ensure their protection against this devastating disease—and for cats, the only way. Prevention is available in monthly oral or topical treatment for dogs and cats, and 6- or 12-month injections for dogs. With so many products on the market, you can easily feel overwhelmed, but our veterinarian can make specific recommendations that will suit your pet’s age, breed, and individual preferences.
#7: Year-round dosing and annual testing are essential for pets
Heartworms don’t take a winter vacation, so while you may see fewer mosquitoes during the cooler months, year-round dosing is necessary to prevent a surprise infection. Annual heartworm screening tests at your pet’s yearly visit can help us identify early disease or—ideally—ensure your prevention plan is working.
Help us break the hold of heartworm disease on pets—call Harbor Pines Veterinary Center to schedule your pet’s heartworm screening test, or to discuss preventive options for your pet.