Heartworm in Dogs

Heartworms are the most dangerous worm to affect dogs, however they are preventable.  Adult heartworms will live in the dog's heart and pulmonary arteries, eventually causing heart failure and resulting in death if left untreated.

Heartworm is spread from host to host by mosquitoes.  It is therefore more common in the subtropical and tropical areas, however it can be contracted anywhere that there are mosquitoes.  When an infected mosquito bites a dog it transfers the heartworm larvae to the dog.  Within 2-3 months after infection the heartworm larvae will develop and then travel into the bloodstream to the cardiac or pulmonary arteries where it will stay and develop into an adult.  Within 5-7 months after the initial infection the adult worm can grow to 30cm in length and 1mm in diameter.  Adult worms can mate and then reproduce live young known as microfilariae.  These microfilariae can live in the bloodstream for up to two years until ingested by a mosquito.  They then develop further within the mosquito and then they are able to be transferred onto another dog or host.  

There are usually no signs or symptoms that a dog has been infected with heartworm until the heartworm becomes an adult and grows inside the heart or lungs which can be years after the initial infection.  Even then some dogs may not show any signs of heartworm infection.  The most common symptom of heartworm infection is the development of a cough.  To start with the cough may be mild but as the heartworm infestation continues the cough will become more persistent and severe.  The dog will often show an intolerance to exercise, often coughing, having breathing difficulties and tiring quickly.  As the heartworm disease advances other symptoms may include weight loss, lethargy, fainting, coughing up blood and congestive heart failure.

Heartworm in dogs can be diagnosed by a veterinarian by performing a blood test known as a heartworm antigen test.  X-rays may also be taken to determine the extent of damage caused by the heartworm on the lungs and heart.  To treat heartworm in dogs early detection is crucial.  Treatment is a very long and costly process, often with side effects.  Sometimes treatment is not an option, particularly in advanced cases or if the dog is suffering from other health complications like heart, liver or kidney function problems.  

Thankfully heartworm disease in dogs can be easily prevented.  There are a wide range of heartworm preventatives available including tablets, chewable tablets, soluble tablets, spot-ons and injections.  Preventatives may need to be administered daily, monthly or yearly and are often combined with intestinal worm or flea treatment.  Dogs should be started on a heartworm preventative from 6-8 weeks of age and must be started before six months of age.  If treatment is not started before six months of age a heartworm test may be required.  If a dog is older than six months or their past heartworm prevention history is not known do not just start a heartworm preventative as it can be dangerous in heartworm positive dogs.  Consult your veterinarian who will usually conduct a heartworm test prior to the preventative being started.  

Popular heartworm preventatives include;
*  Dimmitrol Heartworm Tablets which are given daily.
*  Once a month spot-on treatments with combined intestinal worm and flea control like Advocate or Revolution.
*  Monthly Chews with heartworm and intestinal worm prevention like Interceptor Spectrum or Heartgard Plus.
*  Monthly tablets like Milbemax for Dogs or Valuheart
*  Once a year heartworm injection to be administered by a veterinarian.  

No matter what heartworm treatment you use compliance is most important.  It must be administered according to the directions, at the correct dose, at the correct interval and never missing a dose.  If a dose or more than one dose is missed you should consult your veterinarian for advice.  

If you ever have any concerns about you dogs health or think that your dog may be suffering from heartworm disease please contact your veterinarian immediately.

To view to full range of Heartworm Preventatives available at vet-n-pet DIRECT click here