Heartworms, Should you be Scared?
April 10, 2021

Heartworms, Should you be Scared?

Image courtesy of  http://www.montereycountymosquito.com/

Heart-worms, what’s the deal with these nightmarish creatures and should you be scared for your pet’s safety. The short answer is yes, yes, yes and yes. With a small amount of prevention you can avoid a lot of suffering for both you and ultimately your dogs.

After going through the seemingly eternal process of getting rid of heart worms in our very own dog Dagny, our beloved Border Collie Mix, (standard treatment is about 4 months total) I thought it might be appropriate to answer some basics on the topic so that you might avoid the pitfalls that myself and so many others have succumbed to. Please keep in mind the following information is for education only, we are not vets and therefore would encourage you to seek out advice from professionals regarding your pets health before starting any treatment protocol.

How do dogs contract Heart-worms? Mosquito bites

How are the heart-worms transmitted? They can only and I repeat only be transmitted through the bite of a mosquito. There are over 70 types of mosquitos that can transmit the disease and it only takes one bite. There is unfortunately no way to tell if the dog has been infected at this stage. So use the damn preventatives. More about this later.

Once the dog has been infected, it typically takes about 7 months for the immature larvae/worms to move from the site of the bite to the pulmonary artery, heart, lungs, or other vessels where they will camp out and start to reproduce after they have developed into adults. The adult worms can get up to 16” long and typically live from 5-7 years. They look a lot like a bundle of spaghetti. Look up some pics if you never want to eat again. The babies are called microfilariae(MF). These little friends of no one are what the vet will test for to see if the adults are breeding.
If the MF’s are discovered in the blood work, an x-ray will typically follow in an attempt to class the disease. Here are the 4 stages of Heart-worm.

Stage 1- This stage is often difficult to diagnose. Most dogs will present with no symptoms. There won’t be any abnormal behavior to alert you that there is an issue. Many times the blood test will come back negative as the adults have not started to breed yet. Survival rates are extremely high when treated during stage 1.

Stage 2 - Stage 2 is when symptoms begin to express themselves. Coughing and lethargy are the hallmarks of stage 2. The disease can typically be detected at this point and treatment is usually very successful with no long term damage.

Stage 3 - Stage 3 basically doubles down on stage 2. Dogs tend to cough a lot more. They are extremely tired after exercise and may choose not to exercise at all. They typically have trouble breathing and might even cough up blood. The adult worms will probably show up on the x-ray as well as any changes to the heart, lungs or wherever else the worms are present. Treatment at this stage becomes much more dangerous. The adult worms can be killed fairly easily but may form clots upon their(worms) death as they circulate around the dogs body. The parasites can also release a harmful bacteria which is hopefully controlled through the administration of an antibiotic. Most dogs can still make a full recovery from this stage.

Stage 4 - Stage 4 or caval syndrome is a dire situation that can only be cured with surgery. This stage is categorized by a major escalation of the previous symptoms and there will be obvious changes on the x-ray. The right side of the heart is often filled with so many worms that regular heart function is almost impossible. The dog has only days to live at this point. Surgery can go quite well in some cases, and not so well in others. There is no documented survival rate that is consistent. The more worms that can be removed the better the outcome. Dogs can and often do recover from this level of the disease.

What does the treatment protocol entail? Treatment for heart-worms begins with assessing the situation. If you suspect possible worms then get to your vet as soon as possible. Remember if the dog is showing symptoms, it has been infected for at least 6-7 months and needs to be treated immediately. Bloodwork will happen first, then X-rays if the bloodwork is positive. If the dog has microfilariae, then an antigen test for the adults also must be done. At this point the disease will be staged and the full on treatment will begin.
The infected dog (after having exercise reduced to almost nothing) will typically be given a powerful antibiotic (doxycycline) and an anti heart-worm medication like Heart-guard (ivermectin). The antibiotic prevents the bacteria carried by the worms from infecting the entire system. The Heartguard will then kill most or all the microfilariae (baby worm larvae). Once these drugs have been administered, the dog is given an opportunity to stabilize until the the adult worm killing drug melarsomine is injected on two different occasions usually separated by a month. Total treatment time is usually 4 months. The reduction of exercise is the most important thing you can do while dealing with this affliction. As the worms die and decompose, they can become clots that travel to the lungs, heart, brain and the vital organs of the infected dog. If the dog is highly active, there is a much higher probability of a clot forming and ending up somewhere that it becomes harmful or fatal. Please do not let them exercise at all during this period of time. Make sure they have plenty of toys to keep them busy while they are being crated and only allow them to walk to go to the bathroom. The restriction is probably the hardest part as the animal obviously doesn’t understand what is happening and you have to watch them not understand the process. Use the preventatives, don’t let this happen to your dogs!

Keep a few more things in mind.

Heart-worms have now been discovered in all 50 states. You animals are not safe from these things unless you live 5 degrees from the North or South Poles. And even then who knows for sure.

You are safe as a human being, for the most part. Although human transmission is possible the worms have a very hard time establishing themselves in a human environment.

The life cycle of the worm is very important. They need 2 weeks above 57 degrees to mature in the mosquito host. If the temperature falls below that threshold the cycle starts all over again. Larval stages 1-3 happen in the mosquito and then 4-5 happen in the animal.

It is possible to see worms in the poop of your dog, this is an obvious sign of an infestation. They are not necessarily heart worms. Hook worms, round worms, tape worms and whip worms could also be the culprits. Any of these would necessitate an obvious immediate trip to the vet.

Do I have to treat year round or is seasonal treatment acceptable? Most of us do not like incorporating any kind of chemical in the lifestyle of our pets unless it is absolutely necessary. If you live in the Northern Tier of the USA, it is certainly cold enough to keep the larval development at bay until the spring and summer months arrive. We (Northeastern PA) treat seasonally with the first application falling in early spring and continuing through at least the first hard freeze. If you are in the Southern Tier, you will be treating year round for the best possible coverage for your animals.

Can my felines get heart-worms? The short answer is yes, cats are also susceptible to heart-worms. They are not the typical host so the worms usually do not grow into adults. There is a preventative treatment for cats as well but nothing to treat the adult worms. A little prevention will go a long way. Many of the same symptoms that present in the canine world also present in felines.

The untreated heart-worm infestation is a potentially fatal problem for both dogs and cats. There are however preventative treatments that are both economically friendly and very effective at preventing the disease. Please make sure that as we move into the heat of spring, your animals are protected with both heart-worm treatments and some type of flea and tick prevention as well.