Heartworms in Dogs

Heartworms infect dogs more often than any other animal.  Heartworms often have no symptoms but over time can do significant damage to your dogs heart even leading to death.  As detection is nearly impossible in the early stages of the worms growth it is important to use preventative medication to avoid heartworm infections.

Heartworms are transmitted from one animal to another via mosquitoes.  First the mosquito bites (sucks blood from) an infected animal thereby ingesting young heartworms and then bites a second animal (your cat for instance) during which silva from the mosquito bearing the young heartworms is secreted.  The young take about 7 months to mature and can grow up to 30 cm in your cats heart.

Some dogs will not show any symptoms at all.  Others might be just little less active than others (this may appear simply to be laziness on the part of yourdog).  If symptoms do develop this does not generally occur until the worms have begun reaching maturity (For example after 7 months of the worms living in them).  The most common signs are coughing and rapid breathing which can also be indicative of some other illness. Other signs may be vomiting and weight loss which may also be indicative of other illnesses.  If untreated heartworms can kill your do.

Blood tests that your veterinarian may perform on your dog to detect heartworms are the heartworm antibody test and the heartworm antigen test. Blood can also be tested for the presence of microfilaria or for their level of eosinophils. One thing to keep in mind is that while these tests are 99% accurate if there are adult female worms in your dog, that these tests often show no results if the worms have not matured yet or if all the worms are male.  Basically this means that a negative test does not mean yourdog does not have worms, it simply means that you dog does not have any detectable adult female heartworms.  Therefore if your dog has been untreated for a long period of time it is important to have a followup visit to retest for worms.

Other test that may be performed are x-ray, angiogram or ultrasound

Before dogs can be treated for heartworks it is very important that the dog be evaluated for heart, liver, and kidney function to assess the risks of treatment.

Adult worms are killed with an arsenic-based compound such as Immiticid.

After treatment, the dog must rest (restricted exercise) for several weeks to give its body time to absorb the dead worms without ill effect. Otherwise, when the dog is under exertion, dead worms may break loose and travel to the lungs, potentially causing respiratory failure and death.

Treatment is not completed until several weeks later when the microfilariae are dealt with in a separate course of treatment.

Surgical removal of the adult heartworms is also a treatment that may be indicated, especially in advanced cases with substantial heart involvement.

Monthly preventative medications which are started at 4-6 weeks of age and annual heartworm testing. We recommend Tri-Heart Plus to help prevent heartworms.