Heartworm is a parasitic worm called Dirofilaria Immitis that lives in the arteries within the lung and in the right side of the heart. The adult worms can grow quite large and can interfere with blood flow, eventually causing heart failure. Dogs become infected via a mosquito bite (so do not even need to leave the house to become infected!) – once infected, the baby heartworm (microfilariae) mature into full adult worms, before becoming ready to infect the next animal the mosquito bites.
The dog is the most common host for this parasite but other animals can more rarely be affected, e.g. cat, fox, ferret.
In the early stages of infection there may be no symptoms, but as time progresses and with heavy worm burdens, the pet may show coughing, and reduced capacity to exercise and eventually can be fatal. Diagnosis of heartworm infection is usually based on a blood test.
Testing a pet may be necessary if they are showing symptoms, or more often if they have missed one or more doses of their preventative medication.
Treating cases of heartworm is expensive and risky to the pet and involves some very strong medication and sometimes even surgery. Certainly prevention is much better than treatment. Medications that can be used include:
- Monthly tablets (note: not all “all-wormers” actually prevent heartworm)
- Certain monthly “spot-on” treatments
- Annual heartworm injection given by your vet (may be better for those pets whose owners sometimes forget the monthly dose).
If you think you may have missed or been late with a heartworm preventative, please contact your vet who will decide if your pet needs to get a blood test prior to restarting treatment.
Written by Dr Naomi Morgan
Posted on 29 October 2018
Last updated on 11 December 2019
Tagged with: heartworm