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Canine Heartworm

Your dog may often be exposed to and infected by many different parasites. eg fleas, worms.
One of the more serious parasites is Heartworm which can cause sever debilitation and eventually death. The Heartworm (Dirofilaria immitus) is spread from dog to dog by mosquitoes. A mosquito will pick up a stage of the heartworm (microfilaria) when it feeds on an infected dog. This microfilaria is passed on to the next dog the mosquito bites as a heartworm larvae. Over a period of 6-9 months this larvae migrate to the blood vessels between the heart & lungs and mature to become an adult heartworm. Some can be up to 30cm long when mature

These worms then cause damage to the blood vessels and upset the normal dynamics of blood flow between the heart and lungs (pulmonary circulation). This can lead to heart failure and eventually, and often slowly, death. 
Note: It is important to note that heartworm cannot be spread from dog to dog directly, it requires a mosquito to carry the infection

Clinical Signs of Heartworm Infection:

The clinical signs are related to the damage done to the blood vessels near the lungs and the heart failure caused by the heartworm:
  • Coughing
  • Tiredness
  • Weight Loss
  • Reduced ability to exercise
  • Poor Coat
  • Pot Belly
  • Weakness


Treatment often requires a stay in a vet surgery for several days. Drugs are given to kill the adult heartworm. This can often lead to more problems including blood clots and sever inflammatory reactions round the dead worms. Drugs can be given to try to counteract these problems. This, of course, can all be quite expensive. 
It may be several weeks before you dog has recovered from he treatment, however the damage done by the heartworms is generally permanent. There may even be situations where it is decided that the treatment is more risky to your dog's health than leaving the heartworms there.

Heartworm Prevention

Prevention of heartworm infection is the best option. This involves monthly medication and should begin at around 6 weeks of age and be given for life. Options for heartworm prevention:
  • Heartgard PLUS Chews - meaty treats given each month for the control of heartworm, hookworm and round worm
  • Interceptor Flavour Tabs - a flavoured tablet given each month. Will also control some other types of worms
  • Proheart Tablets - an economical, plain, once-a-month table for the prevention of heartworm
  • Sentinel Spectrum Flavour Tabs - a flavoured tablet given each month. Will also control intestinal worms and provides flea control
  • Canimax - a tablet given once every six weeks for the prevention of heartworm and control of some other types of worms 
  • Revolution - applied to the skin on the back of the neck once each month for the control of heartworm and fleas in dogs
  • Advocate - applied to the skin once each month for the control of fleas, heartworm and intestinal worms in dogs.
  • Valuheart - an economical Australian made ivermectin-based (same as Heartgard) monthly heartworm tablet
See the range of Heartworm preventatives available at VetStop here

If your dog is older than 6 months and has not been on heartworm prevention it is advisable that you consult with your Vet become commencing any prevention.
If there has been a period of time where you have not given heartworm prevention then you should also contact your Vet before re-commencing the prevention.