Taking steps to protect your pet from heartworm disease is important, because these parasites cause significant damage to your pet’s heart and lungs, with potential life-threatening consequences. Our team at Wales Animal Clinic wants to help by providing tips to protect your pet from these dangerous parasites.
#1: Know how heartworms are transmitted in pets
Heartworms are parasites transmitted by mosquitoes that can mature to adulthood, mate, and produce offspring (i.e., microfilariae) in many animals, including dogs, coyotes, foxes, and racoons. When a mosquito feeds from an infected dog or wild canid, they ingest the microfilariae, which then mature inside the insect over a few weeks, to a stage that can be transmitted to other pets and animals. At this stage, they travel to the mosquito’s mouth and are deposited in the insect’s saliva on the next pet or animal that the mosquito bites. The microfilariae then enter the host animal—which could be your pet—through the mosquito’s bite wound, causing infection.
#2: Know heartworm disease dangers for pets
Heartworms affect dogs and cats differently, since dogs are considered natural hosts and cats are atypical hosts.
- Dogs — The young heartworms travel to the dog’s heart and pulmonary vasculature where they attach and grow to around 12 inches long. The worms’ presence causes inflammation in the vessels supplying the lungs, and scarring and fibrosis in the tissue, which results in difficulty for the heart to pump blood through the high-resistance area. Eventually, the heart cannot effectively pump blood throughout the body, causing heart failure. Dogs can harbor numerous heartworms in their heart, and a large enough number can cause blockage of blood flow inside the heart. This condition (i.e., caval syndrome) can be fatal for affected dogs if the worms aren’t promptly surgically removed.
- Cats — Since cats are atypical heartworm hosts, their immune system reacts strongly to the parasites’ presence. When the young heartworms reach the cat’s pulmonary vasculature, the cat’s immune system mounts a massive inflammatory response in the vessels and adjacent lung tissue, causing significant respiratory distress. This condition is called heartworm associated respiratory disease (HARD). In addition, if one or two worms reach adulthood, their presence can cause blockage in the cat’s small heart, resulting in collapse or sudden death. Clot formation is another possible complication that can cause sudden paralysis in one or both of the cat’s hind limbs if the clot becomes stuck in the aorta where the vessel branches to perfuse the limbs.
#3: Know heartworm disease signs in pets
Pets don’t typically exhibit signs in heartworm disease initial stages, but as their condition progresses, signs may include:
- Dogs — Signs in heartworm-infected dogs include a mild persistent cough, lethargy, exercise intolerance, excessive panting, and fluid accumulation in the chest and abdomen. In severe cases, dogs may collapse or die suddenly. Active dogs, those harboring numerous worms, and dogs affected by other health issues typically show more pronounced signs.
- Cats — The massive inflammatory response in the lungs causes signs including wheezing, increased respiratory rate and effort, panting, and difficulty breathing. Other potential signs include collapse, and paralysis in one or both hind limbs. Sudden death may also occur.
#4: Know how heartworm disease is diagnosed in pets
Pets should be tested for heartworm disease once a year to ensure they have not been exposed. Diagnostic tests include:
- Microfilariae test — In some cases, microfilariae can be detected on a direct blood smear, but subtle infections are often missed. Difil and Knott’s tests are methods to concentrate the microfilariae in the blood, but these methods don’t detect infections if no microfilariae are circulating.
- Antigen test — Antigen tests are most commonly used as a screening test for dogs. This extremely sensitive test detects adult female heartworms.
- Antibody test — Antibody tests are important when diagnosing cats. They detect the pet’s immune response to the heartworms, and can detect infection sooner than antigen tests.
- X-ray and ultrasound — Imaging modalities may be needed to definitively diagnose heartworm disease, especially in cats.
#5: Know that heartworm disease in pets can be difficult to treat
As we have explained, many pets show no disease signs in the initial stages, and your pet’s heart and lungs may be significantly damaged before diagnosis is made. This can make treatment difficult.
- Dogs — Infected dogs typically have multiple stages of heartworms throughout their body, and killing these parasites too quickly can cause life-threatening inflammation and potential heart blockage. The first step is to restrict the dog’s activity, because exercise can increase damage to their heart and lungs. Their condition will then need stabilizing, to ensure they are as healthy as possible before treatment is started. Treatment involves administration of a series of injections to kill the different stages of heartworms, and typically takes at least two months.
- Cats — No treatment for heartworms is approved for cats, and disease management is focused on controlling the inflammation caused by the parasites.
#6: Know that preventing heartworm disease in pets is the best approach
Providing year-round heartworm prevention is the best way to protect your pet from these dangerous parasites. Numerous application forms are available to make administration convenient for your lifestyle, and many products also contain protection against other parasites, such as fleas, ticks, and intestinal parasites.
- Oral medications — Chewable tablets that should be given once a month are available.
- Topical medications — Spot-on applications that should be applied once a month also are available.
- Injectable medications — Injections can be given once a year or once every six months, but must be administered by a veterinary professional.
Providing year-round heartworm prevention and having your pet tested once a year is the best way to protect them from heartworm disease. If your pet is due for a heartworm test, contact our team at Wales Animal Clinic to schedule an appointment.