April is Heartworm Awareness Month

What is heartworm disease?

•  This is a serious and potentially fatal disease in our dogs and cats. It is spread by mosquitoes and leads to foot long worms (heartworms) living in the heart, lungs and blood vessels of the affected pet.
• This causes severe lung disease, heart failure and can lead to damage of other internal organs.

Who is affected?

• Dogs: Canines are the natural host for heartworms. This means that they live, mate, and produce offspring within the canine’s heart/lungs. Year round heartworm prevention is key to preventing the spread of this disease and to protecting your family pets!
• Cats: Most heartworms in cats do not make it to adulthood. A cat heart is so small that typically only 1-3 worms would be able to live in it. Cats usually have the larval form of heartworm disease that leads to complications from Heartworm Associated Respiratory Disease (HARD). Year round heartworm prevention will prevent this complication in your cats!
• Ferrets: Their infections are a combination of what we see in cats and dogs, but it is much harder to diagnose and there is no treatment like there is for dogs. Year round prevention is recommended for all ferrets.

Heartworm Life Cycle:

• Adult heartworms within the canine species reproduce and form babies called microfilaria. These microfilaria circulate in the bloodstream.
• Mosquitoes are a pivotal part of the life cycle. A mosquito needs to bite an infected canine and pick up the microfilaria from the bloodstream. The microfilaria then develop into the infective larva within the mosquito.
• When a mosquito bites another animal, they then deposit the infective larva into the tissue of the new animal. These larva then take 6-7 months to develop into the adult heartworms and travel through the animal’s tissue to the heart/lungs where they will live.
• Adult heartworms can live for 5-7 years in the heart/lungs producing new microfilaria to infect even more mosquitos and perpetuate the life cycle. During this time, they can do a lot of damage to the structure and functionality of the heart and lungs.

Symptoms of Heartworm Disease:

• Early in the infection, most animals do not show any signs of infection. This is why yearly heartworm testing is so important. We can often detect a heartworm infection BEFORE the pet develops clinical signs.
• Later in the disease process, we can see clinical signs like a persistent cough, decreased energy/exercise intolerance, decreased appetite and/or weight loss.
• As the disease progresses, we can see heart failure sometimes with fluid build up in the abdomen.
• Dogs with large worm burdens can develop a life threatening condition called Caval Syndrome. This is when the large number of worms block the blood flow to the heart or lungs. This leads to a sudden onset of labored/difficult breathing, pale gums, and dark to coffee colored urine. Emergency surgery to remove the worms from the heart/lungs is needed or these animals will not survive.

How severe is heartworm disease in our area?

• While this incident map is from 2019, not much has improved in the years since this. The Houston area reports a large number of new heartworm infections EVERY year.
• The most important thing you can do for your pets is to keep them on heartworm prevention YEAR ROUND and perform a yearly heartworm test to ensure your prevention is working properly and to guarantee support from the manufacturer of the prevention in the rare case something goes wrong.

Heartworm Testing

• Dogs and cats should be tested once a year for heartworm disease, even if your pet is consistently on heartworm prevention. Annual testing allows us to ensure that the prevention is doing its job and most manufacturers will cover most (if not all) of the cost of heartworm treatment if their product fails as long as you have annual heartworm tests performed.
• Puppies:
  • Start on heartworm prevention at 8 weeks old
  • Heartworm test at 7 months old and then again 7 months later
  • Annually after that
• Adults off of prevention:
  • Heartworm test and start on heartworm prevention immediately
  • Repeat heartworm test again in 7 months
  • Annually after that as long as they are consistent with heartworm prevention
• Adults on prevention:
  • Annually to ensure that the heartworm prevention is doing its job!
• Cats:
  • Annual testing with an antigen and antibody heartworm test. This will detect infections that are larval only without the presence of adult heartworms

How does Heartworm Prevention Work?

• Heartworm prevention kills the larval forms of the heartworm.
• It takes as little as 51 days for the larva to change into the juvenile/immature adult stage which cannot be killed by the prevention.
  • This is why it is so important to give your monthly prevention on time every month or to come back into the clinic on time for your Proheart 12 injections!
  • Just one missed dose can lead to a heartworm infection for your beloved pet

What Happens if My Pet Has Heartworm Disease?

• The first step is to get your pet back on a monthly heartworm prevention and to perform an additional test to confirm that your pet is truly positive for heartworm disease
• Survey chest radiographs (x-rays) and lab work will be recommended to determine the overall health of your pet and to determine if adulticide treatment is safe for them
• You and your vet will discuss the timeline of the adulticide treatment to treat/kill the adult heartworms and prevent further damage to their heart/lungs
• Consistent monthly heartworm prevention is imperative moving forward to prevent reinfection with heartworm disease.

Check out the website for HeartwormSociety.org to find out more information!