Heartworm is a parasite that lives in the heart and blood vessels. The larvae of this parasite is transmitted by mosquito bites which enter the bloodstream of the dog. Eventually the larvae develop into new worms that find their way into the heart.

Signs of an infected dog:

• Coughing
• Lethargy
• Loss of appetite
• Poor breathing
• Listlessness
• Fainting

Annual blood tests should be done to test if your dog is positive for heartworm, especially in areas were mosquito infestation is common.

There is a vaccine against heartworm but before administering the vaccine the test must be conducted. If the test is positive for heartworm, vaccinating your dog can be fatal. The worms infested in the heart and bloodstream will die and clog the flow of the blood, leading to death. Vaccination should only be given if the dog is negative for heartworm.

Another way to prevent heartworm is by giving your dog medication monthly, which comes in a pill or chewable form. This medication is much safer, however it is more costly.

Vaccinations are administered annually, however it is rarely done in Japan compared to the US and the UK due to the dangers it may present.