Florida does not get any winter respite from pests like mosquitoes, fleas, and ticks. This means your four-legged friend is at risk year-round for contracting serious diseases—including some that can cause your pet irreversible damage. Many myths surround heartworm disease, so our Boca Midtowne Animal Hospital team is answering your most common questions about this deadly condition. 

Question: How do pets get heartworm disease?

Answer: Heartworm disease is transmitted via an infected mosquito’s bite. A single bite can infect an animal with heartworm microfilariae (i.e., larvae), which then take about six months to mature into approximately foot-long adults that set up shop in your pet’s heart, lungs, and surrounding blood vessels. 

Q: Are cats safe from heartworm disease?

A: Heartworm disease is commonly considered a canine condition, but can affect any mammal, including humans. However, heartworms prefer canine hosts and thrive best in domestic and wild dogs, but do infect cats on occasion. Because dogs are the preferred hosts, they can be infected with hundreds of worms, whereas cats are usually infected with only two or three worms.

Q: What are heartworm disease signs in dogs?

A: Heartworm disease signs in dogs can develop slowly over months to years. Initially, you may notice that your dog has a mild, persistent cough, followed by exercise intolerance, increased coughing and excessive fatigue after exercise, and decreased appetite and weight loss as the disease progresses. In the advanced disease stages, your dog’s abdomen may become swollen with fluid, which indicates they have developed congestive heart failure.

Q: What are heartworm disease signs in cats?

A: Cats, as always, are their own unique creatures, and their heartworm disease signs differ from signs in dogs. Cats typically develop heartworm associated respiratory disease (HARD) that looks like asthma. Other heartworm disease signs in cats include:

  • Coughing
  • Wheezing
  • Appetite and weight loss
  • Vomiting
  • Incoordination
  • Seizures

Unfortunately, the first—and only—sign that a cat has heartworm disease often is sudden death.


Q: How is heartworm disease diagnosed in pets?
A: Heartworm disease is typically diagnosed through routine blood work that often combines testing for other parasitic and viral diseases, as well. This test reveals a great deal of information about your pet’s disease status, but is limited on heartworms, and will give a false negative result if the pet has too few heartworms, a male-only heartworm population, or heartworms that have not reached adulthood.

Because of in-house testing’s limitations, an additional blood sample is sent to an outside laboratory to confirm heartworm presence.

Q: How is heartworm disease treated in pets?
A: Heartworm disease treatment is difficult and costly—unlike simply administering heartworm preventives. Your dog with heartworm disease will require a month-long series of painful injections administered deep into the lumbar muscles to kill the adult worms, followed by a six- to eight-week recovery period, during which your dog must be kept calm and completely exercise restricted. Exercise restriction is critical to prevent an anaphylactic reaction to the dying worms, and to avoid vascular clots of worms.

No treatment for heartworm disease is available for cats, who can only be administered supportive care until—hopefully—they outlive the adult heartworms without suffering too much pain or complications.

Q: How can I protect my pet from heartworm disease?
A: Heartworm disease is a deadly, but easily preventable, condition. Preventives are available in several forms (e.g., chewable tablets, topical skin products), which make administration simple. Depending on your pet’s needs, their heartworm prevention product can be combined with flea, tick, and intestinal parasite preventives. Plus, a ProHeart 12 injection will protect your dog against heartworm disease for a full 12 months.

The most important protection for your pet against heartworm disease is ensuring they receive their prevention product on time, every time. A lapse in a preventive dose can result in disease.

Q: Can I make environmental modifications to reduce mosquito populations?

A: You can reduce your pet’s mosquito exposure and reduce their disease risk with these environmental modifications:

  • Dump standing water — Female mosquitoes lay their eggs in stagnant water, so ensure buckets are emptied, gutters are kept free of debris, flower pots drain, and birdbath water is refreshed regularly.
  • Check window screens — Mosquitoes can easily slip through tiny holes in window screens, so either keep windows shut or ensure screens are free from holes and tears.
  • Take care of your lawn — Mosquitoes like to rest in cool, damp, and dark areas, so keep grass cut short and trees and shrubs trimmed.
  • Treat pools and ponds — Apply a larvicide product to your pond to eradicate mosquitoes, and ensure your pet stays out of the pond. Cover your pool at night to prevent mosquitoes from laying eggs, and run the filter regularly.

We hope you feel more confident about protecting your pet from heartworm disease, but if you have more questions, or would like advice on the heartworm preventive best for your pet, do not hesitate to contact our Boca Midtowne Animal Hospital team. We will happily schedule their wellness screening and discuss heartworm testing and preventive options.