heartworm infographic

Heartworm and Your Dog

Heartworm is a scary and potentially fatal disease.  Taking it seriously is vital to your dog’s health.  Just about every pet parent knows that heartworm medications are recommended every month, but not everyone follows this recommendation.  The question is, should you?

Heartworms are transmitted by mosquitos. There are more than 3,000 of species of mosquitos.  Seventy or fewer species can actually transmit the disease and that number goes down to only twenty species in the United States. Some of these include common species such as Aedes, Anopheles, Culex and Mansonia. 

You dog’s risk to heartworm depending largely on where you live geographically and the length of your mosquito season.  Climates that are very warm and get a lot of moisture have higher numbers of heartworm infections than cool and dry climates.

When a mosquito who carries the disease bites an animal, it deposits larvae in saliva on the skin surface. That larvae the beings quickly moving inside of the dog through the bite. Their preferred location inside of the dog is the right ventricle of the heart and the main pulmonary arteries. As the worms mature, which typically takes about 6 months, they can grow up to one foot in length. These worms then mate and microfilariae, which are embryos, are released by the female worms after fertilization. Heartworms can survive for several years inside of a dog.

Heartworm is not contagious, meaning one dog cannot get it from another, but rather if a mosquito bites a dog who has heartworm, it will then carry the disease to the host of its next bloodmeal.

There are certain factors that have changed where we typically see heartworm disease. These include:

  • Global warming and climate change.
  • Dogs who are heartworm carriers moving to areas where heartworm atypical.
  • Dogs traveling to heartworm areas on vacation.
  • Wildlife such as coyotes and foxes living closer to urban areas.
  • Winds carrying mosquitoes to new areas.

While certain regions in the United States certainly have higher occurrence of heartworm, it has been documented in all 50 states and considered epidemic is 48 states. 

The treatment for heartworm is very hard on a dog and is very expensive. Melarsomine dihydrochloride is an arsenic containing drug that is injected deep into the back muscles. Heartworm treatment can have serious side effects that can include blood clots to the lungs.

Prevention is truly the best way to ensure your dog is not a host to heartworm. But the word prevention is a bit misleading. What the drug does is kill off the larvae. It does not kill adult heartworms. Which is why it’s important to have your dog tested for heartworm before starting a prevention drug.  Also, if you have skipped a few months of prevention you should have your dog retested. 

For dogs on year-round prevention, testing is recommended once a year.  Prevention drugs do not stay in your dog’s bloodstream. It works by killing off any larvae that has been in the bloodstream before it reaches a more mature stage. Conventional veterinarians and the American Heartworm Society recommend giving the drug every 30 day on a year-round basis.  Holistic vets may recommend giving a little less frequently. It’s important to talk to your vet and follow their recommendation. 

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