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Heartworm Disease and Prevention


Heartworm disease is a serious and potentially fatal infection involving a parasitic worm, Dirofilaria immitis.

  • Heartworm is spread by infected mosquitoes, which inject a heartworm larvae into a dog when they bite.
  • After the dog has become infected, the heartworm larvae travel through the blood system, eventually developing into an adult worm in the heart and lungs, causing extensive inflammation and damage.
  • Heartworm causes significant damage to the cardiovascular system, and can cause life threatening heart failure.
  • Common signs of heartworm disease include coughing, tiredness and difficulty breathing.
  • Heartworm is regularly diagnosed in unprotected dogs in Hong Kong, and all dogs should take heartworm prevention medicine.
  • Proheart SR-12 is the best prevention for heartworm. It is an injection that is usually given at the same time as the annual G6 vaccination (above), and will prevent heartworm for one year.
  • Heartworm can also be prevented by using monthly tablets such as Heartgard or medication applied to the skin such as Revolution.
  • Puppies should start taking a heartworm preventative medication before they are 6 months old, and preventative medication should be continued for life.
  • Heartworm is extremely rare in cats and preventative medication is normally not required.