Heartworm is a worm which lives in one of the chambers of the heart and in the large blood vessels supplying the lungs. The worm causes a disease which is slowly progressive. After 2 to 5 years symptoms such as a chronic cough or weight loss develop. At this stage treatment is both dangerous to the dog and very expensive.
Heartworm larvae are injected into the dog by an infected mosquito. The larvae have to survive in an infected mosquito for about twenty days before they are ready to set up infection in a dog. Once the larvae have infected the dog they go through a few more developmental stages (called Molts) before they mature into adult worms living in the heart. These adults produce the next generation of microscopic larvae which live in large numbers in the blood stream, where they can be picked up by another mosquito.
The best time to kill heartworm is when they have been in the dog for at least a week but no longer than a month. This is because they molt during this time and while molting they are extremely susceptible to a few drugs.
To date I have not found heartworm in dogs that have not left Armidale. However it is reported to exist in Ebor, Bundarra, Inverell, Tenterfield, and of course on the coast and out west.
Treatment options for heartworm are as follows:
(1) Heartworm tablets once a month – Sold sometimes combined with other parasite treatments, at greater expense
(2) Heartworm yearly injection – Convenient, and we send reminders for this.
(3) Daily heartworm tablets – Can kill your dog if it already has heartworm, so needs a blood test first.
(4) Spot-on monthly treatments – They also treat fleas and some worms and scabies
(5) Ivomec sheep drench once a month – This product is not registered for dogs and advice must be sought and followed for the correct dose rate. It contains the same drug as in options (1) and (2).