Heartworms

Since its discovery in 1856, dog heartworm has been one of the most widespread diseases in the United States. Heartworms usually live in the dog's heart, blood vessels, and sometimes lungs. One of the biggest problems with heartworms is that they can hinder the function of the dog's heart. Heartworms may present problems such as weight loss, chronic coughing, vision problems, shortness of breath, and worse, chronic heart failure, blockages of the blood vessels, and even death.

What are some of the early signs/symptoms of dog Heartworm? Since signs and symptoms of heartworms can vary greatly from one dog to the next, it is best to take your pet to a veterinarian for a certain diagnosis. You need to know that in most instances, a dog will not show visible signs of the disease until it has advanced to the point that it can't be cured. Early detection is the key when it comes to heartworm treatment to give your dog the best chances of recovery.

Here is a list of some of the most common symptoms a dog with heartworms may exhibit. If you notice any of these in your dog, get him to your vet as soon as possible. - decreased stamina, or tiring out prematurely - has trouble breathing/gasping for breath - chronic cough that persists more than a few days - if it is a working dog, he/she can't hunt/work as well as usual, and/or collapses from being exhausted - seems like dog has trouble seeing, has convulsions or jaundice - dog becomes emaciated (very thin), this usually comes shortly before death

How do dogs get Heartworms? 

Heartworm is spread by certain breeds of mosquitoes (not all breeds of mosquitoes are able to transmit heartworm). Dogs can’t “catch" heartworm from other dogs. So if there are mosquitoes in every state, why don’t all states have Heartworm? There are very specific conditions that must be met to for Heartworm to be transmitted.

An adult female heartworm must infect and thrive in a dog, fox, coyote, etc to produce microscopic baby worms that circulate in the bloodstream. Adult heartworms can only survive in their host for 3-5 years and multiple generations within one host are not possible because baby heartworms require female mosquitoes as intermediaries to complete their lifecycle. 

A mosquito must then draw blood from an animal that has not only been infected but specifically has had Heartworm long enough to develop mature female adults that have produced babies.

Then, the heartworm babies must be in the L1 stage of development at the time of the bite. 

According to Merck Vet Manual and a study funded by Merial done by the University of Pennsylvania, baby heartworms develop and mature into “infective stage" larvae over a period of 10 to 14 days (only if temperatures remain around 80*F and the humidity is 80%.  It is longer the lower the temperature and humidity) but ONLY if the climate conditions maintain above 57*F for a minimum of 2 weeks.  If, at ANY time, the temperature drops below 57*F the maturation cycle ceases entirely and development cannot occur.  Additionally, the lower the temperature, the longer maturation takes.  Therefore, if the temperature is 60*F it could take as long as 2 months for the larvae to incubate in the gut of the mosquito then migrate to the salivary glands and be transmitted to a new host. Additionally, The Washington State University vet school reports that laboratory study show that maturation of the worms requires “the equivalent of a steady 24-hour daily temperature in excess of 64*F for approximately one month."  Jerold Theis, DVM PhD notes that “if the mean monthly temperature is only a few degrees above 57*F it can take so many days for infective larvae to develop that the likelihood of the female mosquito living that long is remote." http://www.merckvetmanual.com/mvm/circulatory_system/heartworm_disease/overview_of_heartworm_disease.html?qt=heartworm&alt=sh

The baby heartworms must be at the L3 stage of maturation at the time of the bite.  At any other stage will not of migrated into the mosquitoes saliva yet.

The infected mosquito must bite a new susceptible host to transmit the maturing heartworm.  As stated above, for transmission to occur the bite must occur AFTER the incubation period in the mosquito and BEFORE the temperature or humidity drop low enough to kill the developing larvae.  If this occurs, the infective larvae are deposited onto the surface of the animal’s skin and enter the new host through the mosquito’s bite wound. Because the larvae are not injected directly into the bloodstream the body has the opportunity to rid themselves of the heartworm before it can infect them.  A healthy immune system includes a proper pH of the skin, proper mucous production and multiple other forms of defense against external invaders, specifically in the case that the skin is broken/punctured.

Once inside a new host, it takes approximately 6 months for the larvae to mature into adult heartworms after migrating through the muscles of the chest and abdomen. Due to the time required for Heartworm to mature there is ample time for prevention and regulation through veterinary testing and regular holistic treatments.  The adult heartworms are only capable of reproducing if male and female babies were both present at the time of the original bite. Should they be able to reproduce and make babies, the babies will all die unless a mosquito carrying L3’s intervenes.

Unless the host is bit by another mosquito all the adult worms and babies will die off. If the outside temperature maintains at above 57*F (even at night) for over a month, and you live in a humid climate that is full of mosquitoes, and there are many untreated dogs in the area, and your pet has a compromised immune system, all other conditions are just perfect your pet might get heartworm and the cycle will continue. Obviously in most areas the climate doesn’t maintain consistently high enough temperatures for this cycle to occur for the majority of the year and therefore, preventative treatments of any kind are only necessary in the warmest months or in travel to hot and humid places.

In the event that this is the case, year round holistic treatment is recommended.  In the event that holistic treatment is not available prescription treatment may be necessary.  In all other climates, holistic treatment (see below) is recommended 2-6 days a week only during stints of above average heat.

How can I treat my dog for heartworms?

If you catch it early, heartworms may be treated by various chemicals. This type of treatment is risky, as the same chemicals used to kill heartworms is toxic to dogs. The chemicals are usually given in low doses over several weeks. If all heartworms were killed at once, they would end up in the lungs of the dog, most likely killing the dog. It is important that only a licensed veterinarian treat the dog with chemicals due to these risk factors. Besides the lethal chemicals, there is also a surgical option for removing the heartworms. Only your vet can determine if there is a need for invasive surgery, or if another option would be best for your dog. There are also medications that you can give your dog to treat/prevent an infestation of heartworms. These pills, or chewable tablets, are made to kill the heartworms already inside your dog before they can grow into healthy adult worms.

Do not depend on this medicine alone to keep your free from heartworms though. He/she can still develop heartworms during mosquito season, as mosquitoes are constantly looking for food sources. It is important for you to watch your dog closely during this time so you can catch the signs/symptoms early. Even though they can be beneficial, heartworm medications can still have drawbacks. For example, if your dog is already infested with heartworms, the medicine will not get rid of all the parasites. If you suspect your dog has a severe infestation, take him/her to your vet as soon as possible, as they can collect blood samples for testing and prescribe the correct medicine for your dog.

How Can I Prevent Dog Heartworms?

As you know, mosquitoes are the ones responsible for giving your dog heartworms. If you live in an area that is prone to mosquitoes, try to keep your dog from being bitten in the first place. You may move your dog into a screened-in porch, keep your yard clean and grasses cut short, get rid of standing water in the yard, and use insect repellent sprays or dust on your pet. Ask your vet to prescribe any medicines he sees fit for your pet. You can also take your dog to the vet for regular blood testing to ensure he doesn't have heartworms. You must take great care in protecting your dog from this dangerous threat as symptoms of this parasitic infestation are not readily visible most of the time. Most vets agree that you and your pet will be better off getting an annual check-up verses only going to the vet once your dog shows symptoms of a disease.

How are Heartworms treated?  What is the best medicine to use?

Heartworm medicines are available in a huge range and to select the best preventive medicine, ask your vet to prescribe one. Most heartworm medicines are monthly.  There are two ways of dealing with this....either year round, or during summer months.  Ask your vet what area you are in and what he recommends.  For lower Michigan May-October may be sufficient, if further south it will increase to year round.

In winter,  you don’t have to worry about heartworms and may stop giving your dog heartworm-prevention drugs.  Also they may not be needed if you live pretty far north - it's a minor problem in most of Canada or Alaska for example.  But say your dog, despite your best efforts (or he's a rescue, or whatever reason) has now gotten Heartworm.  How is it cured?

Drug Injections

Heartworms in dogs are commonly treated by injecting a series of drugs into the bloodstream of the dog to kill the adult worms. Regular treatments are done to monitor the intensity of infection or harm caused to the dog’s body. Heartworm removal is very dangerous and a do with compromised health may not survive the injections.

After initial injections, the recovery period is approximately 4 to 6 weeks or longer. During the recovery phase, regular preventives are given to the affected dog to stop the reproduction of microfiliaria and formation of more baby worms. Few dogs also need to take additional antibiotics or other medicines to fight the heartworms.

After 6 months of the first heartworm treatment, the vet runs all the diagnostic tests again to know if the dog is safely out of the danger zone and that all the heartworms are dead by now. If heartworms are still diagnosed, the treatment procedure begins all over again. It is extremely dangerous as the worms are dying off because the dog's body must reabsorb and get rid of the worms - taxing his circulatory, respiratory and immune systems.

Surgical treatment

In extreme cases of heartworm disease spreading in dogs, surgery is done to extract all the worms from a dog’s body.  This would be the equivalent of open heart surgery.

Arsenic-based Medicines

The infected dogs are commonly given an arsenic-based drug. But, the side-effects are inflammation due to excessive killing of heartworms and sometimes respiratory failure. Survival during such treatments is difficult for dogs. That’s why it’s advised to prevent the disease rather than to treat it later on. Prevention is better than cure!

The Best Preventive Medicines for Heartworm In Dogs

It’s imperative that we prevent it instead of treating it when it’s too late. There are homeopathic or natural treatments for heartworm and for its prevention but there’s no 100% guarantee of being cured. The medicinal treatment has proved its worth and effectiveness during past years.

You may be curious about the active ingredients in the medicine and about the type of medicine that you may use to prevent the disease. There are three types of medicines: chewing pills that are to be given on monthly or seasonal basis, topical medicines that are applied to the skin for prevention if your dog hates pills and injections that are administered in severe conditions or when the two other options have been ruled out by your vet.  We provide links to most of these products in the sidebar and below.

HEARTGARD and Heartgard Plus are popular heartworm preventives. The two major ingredients of the chewable pill are: Pyrantel pamoate and Ivermectin. Basic Heartgard is for heartworm, and the plus protects against additional parasites.  This is an oral medicine for dogs and cats.It comes in chewable and non-chewable forms. The chewable tablet is loved by a large population of dogs due to its beefy flavor. HeartGard Plus can treat roundworms, hookworms and a few other parasites.

TRI-HEART -  is another commonly medicine prescribed by vets for prevention against heartworms. Tri-heart is  a generic substitute for HeartGard Plus. The two major ingredients of the chewable pill are: Pyrantel pamoate and Ivermectin. Additionally, Tri-heart protects your dog against hookworms, whipworms, and roundworms.  Tri-Heart claims it is safe and effective for all dog breeds. It is devoid of ivermectin which has harmful side-effects in susceptible dogs (see below).

REVOLUTION - Revolution is a safe and simple monthly topical medication used to protect your dog or cat from heartworms, fleas, and ear mites. Revolution is also used on dogs for the treatment or prevention of fleas, the American Dog Tick, ear mites, and canine sarcoptic mange. When used on cats it is also used to treat or prevent fleas, ear mites, hookworms, and roundworms. Revolution requires a prescription from your veterinarian.

K9-ADVANTIX - Topical prevention and treatment 5-way protection Waterproof, remains effective after exposure to rain or sunlight Easy to apply topical solution. Topical solutions repel the mosquitos and are waterproof.  They kill fleas, ticks and mosquitoes on dogs through contact, so they don’t have to bite your dog to die. 

INTERCEPTOR - Buy Interceptor for Dogs Interceptor is an excellent heartwormer. The oral treatment controls and prevents heartworm disease in dogs. The chewable treats also prevent adult hookworms and eliminate whipworm and roundworm infection in dogs and puppies. The monthly oral medication kills immature form of the heartworm and protects dogs from dangerous heartworm infection. Suitable for dogs and puppies over 4 weeks of age weighing more than 2 pounds, Interceptor should be given monthly. The oral heartwormer is safe to use in pregnant and nursing dogs.

ADVANTAGE and Advantage Multi, also known as Advocate  kills and controls fleas, heartworms, gastrointestinal worms (hookworm, roundworm and whipworm), sarcoptic mange, demodicosis, and ear mite infestation in canines. This topical solution is easy to apply and on adult canines and puppies older than 7 weeks of age. This powerful parasitic preventive works against internal and external pests for a   month after which it must be reapplied. Using Advantage multi ensures safety from the unhealthy infestations irrespective of the dog’s breed.

PROHEART - is an injectable version of heartworm preventatives given by your vet for those who cannot give their dog a monthly chewable. The major ingredient of ProHeart is Moxidectin, which treats heartworms as well as hookworms. Injectables are never the best choice because of the possibility of side-effects like allergic reactions. In old dogs, injectables like ProHeart are too risky.

The effectiveness of these drugs hasn’t shown a significant difference between them. These drugs provide a protection against heartworms at around 100%.

Are There Any Risks of Medicinal Prevention of Heartworms?

Drugs for pets never come without side-effects.  There are risks, in terms of the dosage and regularity of medicines. The milder side-effects that have been identified in dogs include loss of appetite, nausea, and vomiting. However, some more serious adverse reactions have also been administered in dogs who were taking heartworm medicines. One of the reasons that I do NOT recommend TRIFEXIS.  I have heard of too many dogs that died or had seizures from that particular medication. Other serious side effects  include tremors, seizures, shocks, lung failure,  coma and even death. But, such reactions are mostly associated with over-dose of heartworm medicines.

Despite the list of top-rated and highly effective drugs listed for heartworm, talk with your veterinarian about your concerns and ability to stick to a schedule.  A genetic sensitivity to ivermectin can be seen in several breeds, but is more often seen in the following breeds:

• Collie
• Old English sheepdog
• Shetland sheepdog (Sheltie)
• Australian shepherd
• German shepherd
• Longhaired whippet
• Silken windhound
• Border collie
• Dogs of mixed breeds that include herding breeds

This genetic sensitivity is due to a mutation in what is called the MDR1 gene. This mutant gene may make the dog more sensitive to several other medications as well. Not all individual dogs in the breeds listed above carry the mutant gene. The only way to know if an individual dog has the mutant MDR1 gene is through testing. 

If your dog has ivermectin toxicity, you may see any of the following symptoms:

• Lethargy
• Depression
• Drooling
• Vomiting
• Dilated pupils
• Loss of appetite
• Disorientation
• Tremors/Seizures
• Blindness
• Trouble standing
• Slow heartbeat
• Difficulty breathing
• Coma

Ivermectin toxicity cannot be reversed. If the drug was given within the past 4 – 6 hours, your veterinarian may induce vomiting and/or give your dog activated charcoal to help minimize the amount of ivermectin that is absorbed.

Additionally, your veterinarian may perform the following tests:

• Chemistry tests to evaluate kidney, liver, and pancreatic function, as well as sugar levels
• A complete blood count to rule out blood-related conditions
• Electrolyte tests to ensure your dog isn’t dehydrated or suffering from an electrolyte imbalance

Your veterinarian will work to keep your pet comfortable and will treat any symptoms that develop. Treatment will depend on the symptoms and may include giving your dog fluids directly into a vein (intravenously), nutritional support (possibly with a feeding tube), placing your dog on a ventilator, maintaining your dog’s body temperature, or administering medication to control seizures.

When given a proper dose, parasite preventives are safe for most dogs and it is very important to protect your dog from deadly parasites, such as heartworms. To prevent toxicity, always follow the recommended dose for all medications. If you have one of the breeds that is more susceptible to ivermectin toxicity, please speak to your veterinarian about the risks and benefits of ivermectin - there are alternatives.