Heartworm is an important disease of dogs in Laos. Here the incidence of Heartworm is high due to the presence of already infected dogs and availability of the disease transmitter, the mosquito, all year round. 

How is it spread?

The mosquito sucks blood from an affected dog, thus ingesting the microfilaria (baby worms)

Within the mosquito these microfilaria change into infective larvae

The mosquito then infects a healthy dog when feeding

These larvae develop into adult worms which migrate to the heart and large blood vessels

The adult female worms will start producing more microfilaria and allow the cycle to repeat

 What are the Signs of Disease?

The first symptoms of disease include coughing, breathing difficulty, weakness and exercise intolerance. As the number of adult heartworms increase they interfere with the normal functioning of the heart. Consequently congestive heart failure and death can occur.

 How is it Diagnosed?

A sample of blood is taken and tested for adult heartworm. If your pet has tested positive to Heartworm you will need to discuss treatment options with the veterinary surgeon.

 How can it be Prevented?

Heartworm is easier to prevent that cure. There are two choices:

  • Giving heartworm prevention tablets EVERY month. Ideally all puppies should start tablets from 3 months of age (at the time of their 2nd vaccination) and continue for the rest of their lives. No test is required if started at this age. Remember to weight your dog regularly to ensure correct dosing.
  • PROHEART injection. This is given yearly in dogs over 9 months of age. It can be given to dogs between 3-9 months of age but doesn’t last a full year in these cases – the veterinarian will be able to advise you on this.

If a dog has not started heart worm prevention by 6 months of age a Heartworm test will be required. If you forget to give the prevention tablets or the injection is overdue, discuss with the veterinarian for advice regarding need for a blood test.

 How to Treat?

Treatment is expensive and can be risky. Prevention is much better, cheaper and kinder to your dog. A positive test can mean either INFECTION (the worms are present but not yet causing clinical signs) or DISEASE (symptoms of coughing, exercise intolerance, weakness or breathing difficulty may be evident).


  • The disease is staged by the veterinarian and a treatment plan is devised. Generally, treatment involves a strong chemical (IMMITICIDE) being injected into the lumbar muscles of the dog, 2 injections, 24 hours apart. Your dog will have to be hospitalized for treatment as we need to monitor the dog for any possible reaction to the drug or to the dying worms.

  • The vet may or may not prescribe other supportive drugs before and after these injections.

Post Treatment Care/Plan:

  • After you collect your dog from the clinic, it is important that it receives absolute rest i.e. NO EXERCISE and NO PLAYING for several weeks after treatment. If you allow your dog to be active then the heart will beat faster causing dead worms to create blockages in blood vessels, kidneys or other organs. REST IS ESSENTIAL

  • One month after treatment you will need to visit the clinic for one further injection and to start preventative medicine to stop re-infection. Six months after treatment we need to repeat the heartworm test to ensure the infection has been cleared.

Call 021 316 410
Or 020 7714 1144

Email: info@theanimaldoctors.org

Opening hours: 9am - 8pm (7 days)
24/7 Emergency and Critical Care

Address: Tha Deua, Km 3 between RMA and Rashmi Hotel

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