When I first graduated in Sydney in 1981, heartworm was just rasing its ugly head having spread from the more tropical climates of Queensland.
For the next few years, there was a huge increase in the number of cases we were seeing. This was because there was a massive dog population not on any type of prevention. The heartworm carrying mosquitoes had a field day, so to speak.
Graphs from this period show a nearly exponential increase in the number of infected dogs. It was pretty scary for pet owners to say the least.
Slowly, more owners became aware of the problem through education by their veterinarians. The earlier heartworm preventatives came on to the market. The first of such was Dimmitrol (DEC)- a daily tablet.
Since then the exponential curve has dropped off sharply. Today, most dogs are on some form of prevention. The heartworm carrying mosquitoes find it increasingly difficult to find an unprotected dog. As a result, they can neither get infected or pass heartworm onto their next dog.
This is why it is vitally important to maintain prevention. We don't want to go back to the 1980's.
Similar stories about the spread of Heartworm exist for most countries. It is endemic alongside the Mississippi river in the USA.
We are now seeing heartworm in cats. It usually occurs at approx. one tenth the rate for dogs in that area. For example, if the chances of an unprotected dog getting heartworm in your area is 30%, then the chances for a cat are 3%.
We now have some great products on the market for heartworm prevention in both dogs and cats.