Heartworm infection is common in Nevada County and is a real danger for dogs and cats in this area.  Infection occurs following a mosquito bite.  The bite transfers the larval heartworm which then migrates through the dog’s body, eventually ending in the heart after about 6 months.  Once in the heart the larva finishes its growth and develops into a mature worm that then begins to reproduce.  The microfilaria offspring of the worms are then transferred to feeding mosquitoes continuing the life cycle.  One reason heartworms are so common in our area is the very high incidence of infection in our resident coyote population.

Prevention of this disease is easy and should be year round.  Many prescriptions are effective, including Heartgard and Interceptor available from our hospital.  These medications are given once monthly and are very safe.  They only prevent the developing worms however, and are not effective in killing the adult worms once infection has taken hold.  These drugs can safely be given to heartworm positive dogs, contrary to previously available preventions.

We perform annual screening for heartworms with a simple blood test.  If a dog becomes positive, treatment is possible but can be expensive and is sometimes dangerous.  Signs of heartworm infection include tiredness, cough, vomiting and loss of appetite.  Severe cases can result in abdominal bloating, hemorrhage in the lungs and death.  Early treatment is always best and provides the best prognosis.  If your dog tests positive we will recommend testing to confirm the infection and provide the safest treatment.  These include chest X Rays and blood and urine testing.

Treatment consists of several injections given in the hospital that will eliminate the adult worms in your dog’s heart.  We follow the treatment with a period of rest, usually 30 days, to allow the dying worms to be absorbed harmlessly.  High blood pressure and a rapid heart rate could cause the worms to travel into other areas of the body and cause harm or even death.  Watch closely for increasing cough, lethargy, loss of appetite or other unusual symptoms and notify us immediately.

Usually heartworm prevention is begun again (or continued) soon after treatment.  A follow-up heartworm test should be completed in 4 months to monitor success.  A very small number of dogs can remain infected after treatment and may need further care.
It is not uncommon for an owner to forget to give their pet its heartworm prevention for a period of time.  If for two months or less, simply start your pet back on prevention and then let us know at your next visit.  If the gap has been for a longer period, call for advice- most times you can restart the medication immediately, but may need additional heartworm testing.

Cats can get heartworms too.  We recommend monthly prevention either with Revolution (also effective against fleas, intestinal parasites and ear mites), or oral Heartgard or Interceptor.  Infection is less common than with dogs but diagnosis and treatment can be trickier.  Signs include cough and vomiting.  Blood testing or radiographs are available to help with a diagnosis.  Treatment varies but usually consists of management of symptoms instead of cure.  Prevention is therefore important.

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