Heartworms are present in all 50 states, but are more prevalent in some areas than in others, such as here in Virginia. The condition is easily preventable, still, heartworms affect many pets each year. Our Columbia Pike Animal Hospital team doesn’t want your pet to be a heartworm disease victim, so we provide nine heart-stopping facts about these invasive parasites.

#1: Mosquitoes transmit heartworms to pets

The mosquito population continues to rise in Virginia, and peak season is from April to late fall. These pesky critters transmit heartworms and also play a role in their development. When a mosquito bites an infected heartworm host (i.e., a dog or wild canid), they ingest baby heartworms (i.e., microfilariae). While in the mosquito, the young parasites mature to an infective stage over two to three weeks. During their next meal, an infected mosquito can then pass along the infection to a vulnerable pet.  The parasites develop in your furry pal’s body tissues for three to four days before migrating to their final destination—your pet’s heart and lungs. The worms make themselves at home and can grow to about 12 inches over the next six months. When they are fully mature, the worms mate and produce offspring that a passing mosquito can ingest, further spreading the infection.

#2: Numerous pets are infected with heartworms every year

According to the Companion Animal Parasite Council (CAPC), approximately 300,000 U.S. dogs are infected with heartworms every year. Numbers aren’t as accurate for cats, because they aren’t routinely tested. However, studies have demonstrated that up to 15% of cats in certain locations are exposed to heartworms each year.

#3: Heartworms affect dogs and cats differently

As their name implies, heartworms damage an infected animal’s heart. In dogs, who are natural heartworm parasite hosts, the disease mostly causes vascular inflammation, eventually leading to congestive heart failure (CHF). In some cases, the high worm load—up to 100 worms—causes a blockage within the heart (i.e., caval syndrome). 

Cats are atypical heartworm hosts, and the condition affects them differently than it does dogs. A cat’s immune system reacts strongly to baby heartworms, and clears out most of them, preventing the worms from maturing to adulthood. However, when the young parasites reach a cat’s lung tissue and vasculature, an extreme immune response causes severe lung inflammation that results in heartworm-association respiratory disease (HARD). While few worms mature to adulthood within your feline friend’s vasculature, only one or two adult worms can damage their tiny heart.

#4: Heartworm-positive pets often do not exhibit signs

Most pets in the early heartworm disease stage don’t exhibit signs, and in some cases, the first sign is sudden collapse or death. Cats and dogs exhibit different heartworm disease signs:

  • Cats — Feline heartworm disease is mostly a respiratory condition, often mimicking feline asthma. Signs include wheezing, panting, increased respiration rate, difficulty breathing, and vomiting. 
  • Dogs — Canine heartworm disease signs include lethargy, cough, exercise intolerance, decreased appetite, and weight loss. When CHF develops, abdominal fluid accumulates, causing a pot-bellied appearance.

#5: Indoor-only pets can also contract heartworm disease

While pets who spend a lot of time outdoors have a higher heartworm disease risk, indoor pets are also susceptible. Mosquitoes can easily enter your home through open windows and doors, torn screens, and vents. One bite from an infected mosquito can cause heartworm disease, putting your pet’s life at risk.

#6: Diagnosing heartworms in pets can be challenging

Most heartworm tests are unable to detect the parasites until six months after infection. Therefore, the parasites are fully established by the time your pet tests positive. In addition, false-negative results can occur, delaying treatment, making prevention extremely important to your pet’s protection.

#7: Heartworm treatment is risky for dogs

For a dog’s heartworm treatment to be effective, the medications must kill the parasites at every life stage. As the parasites die, they can cause anaphylactic reactions or life-threatening blood clots. Canine heartworm treatment includes:

  • Activity restriction — Exercise can worsen heartworms’ damage, and you must keep your pet in a crate or a cage to keep them quiet throughout the months of treatment.
  • Stabilization — Our Columbia Pike Animal Hospital team must first stabilize your pet’s condition to ensure they are healthy enough to start the worm kill off.
  • Killing the microfilariae — Our team prescribes medications to kill the microfilariae.
  • Antibiotics — Heartworms live in close concert with the bacterium Wolbachia, which can exacerbate inflammation. We prescribe antibiotics to kill this pathogen.
  • Killing the adult worms — To kill the adult worms, we must administer intramuscular injections deep in a dog’s lower back muscles. Doses are administered in stages to help reduce the side-effect risk.
  • Steroids — In some cases, we administer steroids to help control a dog’s  inflammatory response.

#8: No treatment is available for cats

No approved treatment is available for cats. Feline heartworm treatment relies on supportive care in hopes that the cat will outlive the adult worms in their heart, making prevention the only option for protecting your cat from contracting heartworm disease.

#9: Preventing heartworm disease in pets is simple

Preventing heartworm disease is simple and much cheaper than treating an infected pet. Pets should receive a heartworm prevention product year-round, because an unseasonably mild winter day can lead to mosquito activity, putting your pet at risk. Many preventives protect your pet from other parasites such as ticks, fleas, and intestinal worms, in addition to heartworm. These medications’ many options make protecting your pet from heartworms convenient:

  • Spot-on treatments — You can apply a spot-on treatment to the back of your pet’s neck once a month.
  • Chewables — Some products are available as a yummy treat that you should give to your pet once a month.
  • Injectables — If you don’t want to administer your pet’s preventive on a monthly basis, our team can administer an injection every 6 to 12 months.

Protect your pet from contracting heartworm disease by ensuring they receive preventive medications. To discuss the best option for your pet’s heartworm preventive, or to schedule your furry pal’s annual heartworm test, contact our Columbia Pike Animal Hospital team.