Heartworm Test

Heartworm is spread by mosquitos to dogs and is potentially life-threatening. In the past, it was less of a concern in Atlantic Canada due to our colder temperatures, however, with climate change, we are starting to see heartworm move east.

What are the symptoms of heartworm in a dog?

A dog who is a host or carrier can be completely free of symptoms to show signs of severe illness – coughing, lethargy, collapse & enlarged abdomen from heart failure. Dogs can also die from heartworm disease.

How do dogs get heartworm?

Dogs pick up heartworm from the bite of an infected mosquito. The life cycle is as follows: host dogs have adult heartworms in their right ventricle & pulmonary arteries; fertile adult worms release the first stage microscopic larvae (L) called microfilariae (MF) into the hosts circulation; a mosquito bites the host and ingests MF; MF then undergoes two stages of developments to become third stage (L3) or infective larvae; the mosquito then bites another dog and injects L3 into the skin. Two more developmental stages called moults occur and they then migrate to the right heart and mature into adults. Some MF remain in the blood making the dog a host. The lifecycle takes 7-9 months.

What are the treatment options for heartworms?

Dogs are diagnosed by detecting microfilariae in the blood or detecting antigens associated with heartworm in the blood. Dogs who test positive are treated by injections to kill the adult worms and added treatment is required to kill the MF.

Why is recovery and heartworm treatment challenging?

Heartworm treatment is challenging to the fact that the adult worms remain the heart once killed unless they are removed surgically. Also, underlying heart disease caused by the worms is not curable but needs to be treated for the duration of the dog’s life. Often, dogs will die during treatment.