How Deadly
is Heartworm?


Sharlene Goodsworth

Canine Holistic Wellness Centre


We’ve all seen the heart in a jar at a vet clinic congested with spaghetti-like heartworms striking the very fear with the intended message - don’t let this, become your dog!  An easy and graphic promotional tool for vets to sell heartworm medications that you’d be quick to accept without question especially after reading the attached slogan “one single bite from a mosquito can kill your dog of heartworm”.  
If it only takes one bite, then why are local National Parks and Wildlife Service (NPWS) needing to use the 1080 baits in the local national parks to keep control of the fox / wild dog populations? If heartworm disease is so prevalent on the Coast why aren’t the fox / wild dog populations being decimated by heartworm?  
So let’s put heartworm under the microscope and see what really is going on here on the Central Coast. It’s not quite what you’ve been lead to believe… Is heartworm really a threat to our dog’s health?

Firstly we need to understand the complexities of the life cycle of the heartworm to fully gauge just how difficult it is to end up with an active heartworm infection. It takes a long-drawn-out period of time, developing through many stages of its life cycle to infect a dog and more importantly many environmental conditions need to align to make infecting a dog even occur. 


FACT: we need to understand that not any old mosquito can spread heartworm.  It has to be a certain species of mosquito and only females at that, which will act as an airborne incubator.  Without this proper female species of mosquito, your dog can’t get heartworm – Period!


FACT: if the temperature is below 15 degrees Celsius the Microfilariae is deactivated in the mosquito and it can not incubate. Hence why transmission is impossible in colder weather – Period!


FACT: Puppies can’t “catch” heartworms from their mothers and dogs can’t “infect” other dogs & humans – Period!
Heartworm Life Cycle Stages:  
Each stage of the Heartworm lifecycle presents a growth from microfilariae stages into larvae stages, juvenile stages and eventually into adults. The chances of larvae getting to adult and having both female and male present to reproduce into full heartworm infection is near impossible and I will explain why...


Stage L1: To begin the life cycle of a heartworm you need to align the right female species specific mosquito and have access to a dog already infected with sexually mature male and female heartworms that have produced baby microfilariae. The heartworm microfilariae MUST BE at the L1 stage of development when the mosquito bites the dog and withdraws blood. Meaning microfilariae need to be circulating in the dogs blood.
Stage L2:  The female mosquito incubates the microfilariae in her system attempting to bring it to L3 stage.  
Stage L3:  It’s crucial through this stage that the temperature remains above 27 degrees Celsius (day and night continuously) for a period of 10-14 days of incubation, for the microfilariae to reach L3 stage, and be ready for transmission. The female mosquito transmits the L3’s to your dog’s skin with a bite via her contaminated saliva. That’s if the female mosquito is still alive by this stage. Once the transmission has taken place into the host dog, it takes approximately a week or two to the L4 stage under the skin at the site of the bite.  
Stage L4: After a couple of weeks camping around the transmission site the microfilariae migrate to the muscles in the chest and abdomen and then takes for 45 -65 days to incubate the final stage of the larvae before they move from the tissue to the blood stream as juveniles. But a dog still isn’t doomed yet!
Stage L5:  As the larvae enters the bloodstream as juveniles. You would need both male and female larvae to develop into heartworm disease. Otherwise, same-sex larvae can never reproduce. The dog can be a carrier of heartworm but never have the heartworm disease.   
Stage J1:   It takes approximately 4 to 5 months for the surviving juveniles to achieve maturity into adults.  We are now looking at a total of 6-7 months post-infection of our species-specific female mosquito from the L3 stage. If a single-sex worm is present they can’t reproduce and cause heartworm disease and will die within 1 to 2 years.
Stage A1:  This is where a dog has both female and male active adult heartworm causing heartworm disease. They start breeding and produce microfilariae to circulate in the blood. However, this stage is still treatable and the success rate is extremely high. 


Only a certain female species-specific mosquito can incubate “heartworm”. 

The temperature has to be above 15 degree Celsius or transmission is halted, so thus limiting it to the warmer months only.
L3 stage of mosquito incubation requires the temperature to be consistently above 27 degree Celsius for almost 2 weeks for the incubation to be successful or it can’t incubate the L3 stage of the microfilariae.


Dogs require duel sex larvae or they can NOT develop heartworm disease.
Dogs can be a carrier of heartworm but not have heartworm disease.
As the late and great Dr Glen Dupree heartworm specialist had always indicated, “I operate under the assumption that all dogs have heartworms. But there is a big difference between having heartworms and heartworm disease and that difference is a healthy immune system”. More on that in a minute!


The most important factor we need to understand why heartworm is not active on the Central Coast is due to environmental conditions. We pulled the stats from temperature averages across the coast and found some interesting facts…
We now know that female species-specific mosquito can’t sustain heartworm incubation of microfilariae which is rendered deactivated in temperatures less than 15 degrees Celsius. According to the above table, we see that is a massive part of the year, ranging from Mid March till Mid November. This means that 8 months of the year the microfilariae become non-active (dormant). Even if we have a plague of mosquitoes due to wet weather, heartworm is not on the menu during this period as the environmental conditions are not right due to the low temperature.
When we view the average high we see the average is around 27-28 degrees Celsius. Now, remember, we need a period of 10-14 days (consecutively day and night) for the temperature to be in excess of 27degree Celsius to successfully incubate the microfilariae to the end of L3 stage. We just don’t offer the right temperatures here on the Central Coast to allow the appropriate female species-specific mosquito to spread heartworm to our dogs. Now we can understand better why the NPWS head out into the local national parks with their 1080 poisons and cull the foxes to reduce numbers.
Some may be thinking that it appears that your pet now has a double type of protection. Firstly, granted from the lower weather temperatures forcing transmission redundant for a solid 8 months of the year and secondly from giving the trusty heartworm preventative medication. Wrong, wrong, wrong!!!
Remember Dr Dupree making this comment earlier… “but there is a big difference between having heartworms and heartworm disease and that difference is a healthy immune system”…
The heartworm preventative medications are some of the most toxic and damaging products on the pet market that we can use as a prevention. Why would we use such harsh and destructive chemicals risking greater disease just to prevent something with such minimal risk, especially now you understand what it takes and knowing the Central Coast just doesn’t offer the right breeding conditions?
Holistic vet Dr Jeffrey Levy says; “I’ve treated many dogs for heartworm. The only dogs that developed symptoms of heart failure were those that were being vaccinated yearly, eating commercial dog food and getting suppressive drug treatment for other symptoms, such as itchy skin problems. I concluded from this it is not the heartworm that caused disease, but the other factors that damaged the dogs’ health to the point where they could no longer compensate for an otherwise tolerable parasite load. It is not really that different from the common intestinal roundworms, in that most dogs do not show any symptoms. Only a dog whose health is compromised is unable to tolerate a few worms. Furthermore, a truly healthy dog would not be susceptible to either type of worm in the first place.”
“Disease is not caused by viruses or by bacteria or by heartworm bearing mosquitoes. Disease comes from within, and one aspect of disease can be susceptibility to various pathogens. So the best thing to do is to address those susceptibilities on the deepest possible level so that the pathogens will no longer be a threat. Most importantly, don’t buy into fear.”
But we are buying into fear. We fear our dogs will get one mosquito bite and die because we never knew just how difficult it was to contract heartworm disease. So, therefore, we pump these HEAVY preventatives into our dogs which in turn are only making them more susceptible to the risk of disease on all levels by greatly weakening their immune systems. We can’t stress enough that your dog requires a strong immune system to live a vibrant and healthy lifestyle. Here at the Canine Holistic Wellness Centre, we can independently test and help you navigate the complexities of improving your pets immune system. We specialise in minimising risk and identifying intolerances causing high risk to your pet’s health.   
How can we ever believe that by continually bombarding our pets with copious amounts of pesticides and chemicals that this is going to keep them healthy and free of disease? Where did we go so wrong to believe this is good medicine? There are better ways to deal with potential threats such as heartworm and the care and prevention of it!
Canine Holistic Wellness Centre 4324-9992