Heartworm disease can be a daunting topic for pet owners, with a myriad of misconceptions floating around. Let’s dive into the facts and debunk some of the most prevalent myths surrounding this serious condition.
Myth 1: Dogs Contract Heartworm Directly from Infected Dogs
Contrary to popular belief, heartworms are not transmitted directly from dog to dog. Instead, they are carried by mosquitos in their microfilarial stage. These microscopic parasites require a two-week maturation period inside a mosquito before they can infect a new host. Thus, a dog cannot catch heartworm from another dog.
Myth 2: Heartworm is Exclusive to the Southern United States
While it’s true that the Southeastern U.S. sees higher infection rates, heartworm has been detected in dogs across all 50 states. Climate change and increased mosquito activity due to urban development have spread the risk nationwide. Additionally, the relocation of pets from high-infection areas has inadvertently introduced heartworm to regions with lower infection rates. The disease has also been observed in Mexico, South America, Western Europe, and Asia.
Myth 3: A Negative Heartworm Test Ensures Freedom from Infection
Heartworm blood tests detect proteins from adult female worms, which take about seven months to mature from the initial infection. This means that for the first seven months post-infection, a blood test will not show a positive result, even if the dog is infected. It’s crucial to retest dogs that initially test negative after seven months of prevention to rule out a prior infection.
Myth 4: Missing a Month of Prevention is Harmless
Monthly heartworm preventatives are designed to eliminate young microfilariae in the blood, but only if administered consistently. Missing a dose allows the parasites to mature into a stage that the medication can no longer affect. It’s vital to resume prevention as soon as possible if a dose is missed, as even a single lapse can leave your dog vulnerable.
Myth 5: Heartworm Preventatives are Toxic to Dogs
Preventatives contain medications that are toxic to the development of heartworm larvae but are used in doses 200 to 1,000 times less than those that would harm a dog. Some Collie-related breeds may have a lower tolerance to certain drugs, but even in these cases, the doses in preventatives are safe. Genetic testing can help assess risk for individual dogs, and alternative preventatives are available for higher-risk breeds.
Myth 6: Heartworm Preventatives Only Protect Against Heartworms
Many heartworm preventatives also offer protection against some intestinal worms, providing the added benefit of deworming and maintaining a healthy gastrointestinal tract in dogs.
Myth 7: Dogs Always Show Symptoms with Heartworm Infection
Dogs can remain asymptomatic for months following a heartworm infection. As the parasites damage the arteries leading from the heart to the lungs, it takes time for these issues to manifest as symptoms. Advanced heartworm disease can lead to heart enlargement, failure, or a severe heart condition called caval syndrome, which can be fatal. Symptoms may include coughing, lethargy, and exercise intolerance.
Myth 8: Higher Doses of Preventative Medication Treat Heartworm
Preventative medications are not a treatment for heartworm; they are designed to stop the development of larvae. Treating heartworm requires a four-month regimen involving several drugs administered at specific intervals. During part of this treatment, dogs must be kept inactive due to the cardiovascular risks associated with dying worms. Severe infections may necessitate immediate surgery.
Myth 9: Heartworm Treatment Undoes the Damage Caused by the Parasites
While treatment can eliminate the worms and clear the infection, it does not reverse the damage they caused to the blood vessels. Most dogs recover well, but arterial tissue damage may persist even years after the infection has been resolved.