Every time you visit the veterinarian, you’re bombarded with recommendations to protect your pet from parasites. With multiple parasites plaguing pets, keeping them straight and understanding the true risks can be difficult. April is Heartworm Awareness Month, and the Village Veterinary Hospital team is sharing our heartworm knowledge to help pet owners better understand this major pet health risk. Here are the facts.

#1: Mosquitoes spread heartworms

The same lovely creatures that create itchy bites and spread human diseases, such as malaria and West Nile virus, also transmit heartworm infection to pets. Mosquitoes pick up the immature heartworm larvae when they bite other infected animals, which serve as disease reservoirs. Pet dogs or wildlife, including wolves, coyotes, or foxes, can serve as reservoirs. Once inside the mosquito, the heartworm larvae mature into an infective stage after 10 to 14 days, and then are transmitted to another pet that the mosquito bites.

#2: Heartworm has been found in all 50 states

In decades past, heartworm was a problem in warm, humid areas, and seldom occurred in arid desert states. Now, however, pets are frequently transported across the country by rescue groups, mosquito species are expanding their ranges, and heartworm is a problem in all 50 states. The Southern coastal states still have the highest incidence, but all pets across the country are at risk.

#3: Heartworms cause serious heart and lung damage

Once inside a pet, heartworms mature, grow up to a foot long, and travel slowly to the heart and lungs, where they cause inflammation and damage inside major blood vessels, or the heart and lungs themselves. Dogs can host anywhere from 30 to 100 or more worms, and more worms equate to more damage. Cats are not ideal hosts and can carry only one or two worms but, unfortunately, lower worm burdens do not equal less damage.

#4: Infected pets don’t show signs until significant damage has already occurred

Initial infection is nearly impossible to detect because the worms can take months or years to mature to adulthood and reproduce, which is when signs appear, and significant damage has already occurred by that time. Signs in dogs may include:

  • Exercise intolerance
  • Coughing
  • Poor appetite
  • Weight loss
  • Heart failure

Signs in cats are similar, but usually their lungs are affected most significantly. Signs may include:

  • Coughing, wheezing, or breathing difficulties
  • Weight loss
  • Vomiting
  • Poor appetite
  • Difficult walking, weakness, or fainting
  • Sudden collapse or death

Close-up of several long, thin parasitic worms on a metallic surface. Intertwined, with one prominently curved in the foreground showing reddish areas, these are the kind of parasites that would concern any vigilant veterinarian.

#5: Heartworm prevention protects pets from infection

Monthly heartworm preventives are recommended for all pets, including indoor cats, who can be exposed to indoor mosquitoes. A heartworm preventive contains a low dose of a prescription deworming medication that kills immature heartworms, but cannot kill the adults. However, a prevention product administered topically or orally monthly continuously kills the larvae, which cannot cause heartworm disease if they do not mature into adults.

#6: Lapses in heartworm prevention leave pets vulnerable

Any lapse in prevention can lead to heartworm infection, as heartworm larvae that were transmitted to your pet in the previous few weeks can mature past the stage in which they are easily killed. Because heartworm prevention works this way, and because mosquito activity is difficult to predict, prevention should be given year-round with no breaks.

#7: Heartworm preventives also control intestinal parasites

Pets should also receive heartworm preventives year-round because the drugs used in these medications kill other worm types. So, monthly heartworm prevention also serves as a monthly intestinal deworming treatment, and destroys parasites that could harm pets and human family members.

#8: Infected cats cannot be safely treated

Prevention is the only way to protect cats from heartworm disease. Unfortunately, the drugs used in dogs are not safe for cats with confirmed heartworm infections, and no safe treatment exists for cats. Instead, infected cats must be closely monitored and treated supportively until they clear the worm infection, or the worms die naturally. Sadly, infected cats often die suddenly.

#9: Heartworm treatment for dogs is painful, stressful, and expensive

Infected dogs can be treated, but could still suffer long-term complications if their infection was severe. Those treated in early infection stages typically do well, but the treatment itself is risky. Dogs first must be on a months-long prevention regimen to kill larvae, and then are given a painful injection series, all while confined to strict cage rest. They also require antibiotics and steroids during treatment to reduce toxic reactions from the dying worms.

#10: Routine heartworm testing is recommended for all dogs

All dogs, including those on a year-round prevention, need a blood heartworm antigen test each year to ensure their preventive is working and that no worms slipped in while their preventive was accidentally missed. Dogs and cats should also be tested before starting a new prevention regimen.

Now that you know the facts, you can feel confident discussing heartworm disease and prevention with our Village Veterinary Hospital team. Call us to schedule your pet’s next wellness visit and heartworm test, or for help selecting and starting a new heartworm prevention regimen.