How Much Do You Know About Heartworms?

Laurie Anne Walden, DVM

April is Heartworm Awareness Month. How much do you know about this infection? Check out the questions, then scroll down for the answers.

1. How are heartworms transmitted?
   a. By mosquitoes
   b. By eating raw meat
   c. Through the feces of infected animals
   d. By vampires

2. About how many dogs tested positive for heartworm in North Carolina in 2017?
   a. 90
   b. 900
   c. 9000
   d. 90,000

3. Adult heartworms grow to what length in a dog’s heart?
   a. 3 inches
   b. 6 inches
   c. 9 inches
   d. 12 inches

4. In addition to dogs, which animals can get heartworms?
   a. Cats
   b. Ferrets
   c. Both
   d. Neither

5. True or false: Dogs should receive heartworm preventives through the winter.
   a. True
   b. False

6. You forgot your dog’s monthly heartworm pill and now it’s a month overdue. What should you do?
   a. Have your dog tested for heartworms before giving the pill.
   b. Give your dog the pill now.
   c. Give your dog a double dose.
   d. Panic.

7. True or false: Heartworm preventives sold over the counter at pet stores work just as well as the prescription versions.
   a. True
   b. False
   c. Unfair trick question

8. Which state is free of heartworms?
   a. Maine
   b. Alaska
   c. Wisconsin
   d. None of the above

Answers
1. a. By mosquitoes
Mosquitoes pick up tiny heartworm larvae, called microfilariae, when they take a blood meal from an animal infected with adult heartworms. When the mosquito bites another animal, it injects these larvae into the new host. The larvae mature into adult heartworms in the new host in about 6 months.

2. c. 9000
According to the Companion Animal Parasite Council, 9457 dogs tested positive for heartworms in 2017 in North Carolina. This number has been increasing each year. To see more parasite statistics, see the Parasite Prevalence Maps on the Pets & Parasites website.

3. d. 12 inches
Adult heartworms grow about 12 inches long in dogs. Infected dogs typically have 14 to 20 of these foot-long worms in their heart and lungs.

4. c. Both
Both cats and ferrets get heartworm disease. In cats, heartworms do not grow as large as they do in dogs and are usually fewer in number. However, heartworm infection can be devastating in cats, potentially causing severe respiratory disease or sudden death. In ferrets, even a single worm can cause serious illness because ferrets’ hearts are so small. Medical options for heartworm removal (like those used in dogs) cannot be used in cats and ferrets. Heartworm preventives are available for cats and ferrets.

5. a. True
For best protection, the American Heartworm Society recommends year-round heartworm prevention for all dogs, not just for dogs in southern states. Also, think of this: for several days this past February, the temperature in Charlotte was 75°F or higher. Do you want to risk your pet’s health by guessing what the mosquitoes here consider “winter”?

6. b. Give your dog the pill now.
But do not give a double dose! Have your dog tested 6 months after missing a pill. The test detects adult heartworms, not larvae, so the test result will not be positive until the larvae have had time to mature.

7. b or c. False; unfair trick question
All heartworm preventives approved by the Food and Drug Administration for use in dogs and cats are available only by prescription. Deworming medications that are available over the counter (without a prescription) either don’t prevent heartworms or are not approved by the Food and Drug Administration for use in dogs and cats.

8. d. None of the above
Heartworms have been diagnosed in all 50 states.
 
For more information, see the American Heartworm Society website.

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