HEARTWORM FACTS – Prevalence, Medication and Alternative Treatment

“To judge by your local veterinarian's stern insistence on regular heartworm pills for your dog, you'd think we're in the midst of a brutal epidemic, leaving piles of the dead in its wake. I think there's an epidemic, too, but of a different sort: of disease-causing toxicity instilled in our pets by heartworm preventative pills.” – The Nature of Animal Healing by Dr. Martin Goldstein, DVM

How is Heartworm spread? 

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.

First, 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. 

Second, a mosquito must 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.

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

Fourth, 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

Fifth, 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.

Sixth, 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.

Seventh, 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.

Eighth, 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.

Prevalence – How likely is your furry friend to get Heartworm?

States most likely to have HeartwormFlorida, Louisiana, Mississippi, Alabama, Georgia, Texas, South Carolina, North Carolina, Tennessee, Arkansas, Oklahoma, Montana and Puerto Rico

States with Moderate likelihood to heave Heartworm – New Mexico, Arizona, California, Utah, Kansas, Colorado, Nevada, Illinois, Indiana, Kentucky, Ohio, Virginia, Delaware, Washington D.C., Maryland, Wyoming, Michigan, Rhode Island, Connecticut, Massachusetts, New Hampshire, Vermont, Maine, Hawaii and Alaska.

States with Low chances of getting Heartworm: Oregon, Washington, Idaho, Montana, Nebraska, South Dakota, North Dakota, Iowa, Minnesota West Virginia, Wisconsin, Pennsylvania, New York, New Jersey.

Ok so how likely is “likely” to get it?  What are the real numbers?

In 2011 out of 4,784,707 dogs tested 56,781 were positive, that’s 1.18%

In 2012 out of 4,234,777 dogs tested 47,846 were positive, that’s 1.12%

In 2013 out of 5,704,699 dogs tested 69,293 were positive, that’s 1.21%

In 2014 out of 7,179,225 dogs tested 90,470 were positive, that’s 1.26%

In 2015 out of 8,993,885 dogs tested 115,016 were positive, that’s 1.27%

In 2016 out of 7,607,987 dogs tested 101,098 were positive, that’s 1.32%

As you can see the overall chance that your pet will get Heartworm, the nationwide average (which includes high and low prevalence states) is 1.23%.


As you can see from data posted by the AHA (American Heartworm Society) on HeartwormSociety.org Heartworm outbreaks are rarely severe in the same places every year (which the exception of the Mississippi river and southern Louisiana).  Therefore, some years a specific city may be high incident and the very next year it may be moderate or low incident.


Data taken from https://www.heartwormsociety.org/pet-owner-resources/incidence-maps

Data from the NOAA (National Centers for Environmental Information) gives great insight into why this is.  Climate averages and ranges are responsible for Heartworms ability to proliferate in an area.  As you read above, the conditions must be warm and lasting for Heartworm to be spread.  National Temperature and Precipitation maps show the following data:

2011 ranked “Above Average” in temperature for the year, with Texas and parts of the Northeast being Much Above Average.

2012 ranked “Record Warmest” in temperature for the year.

2013 ranked “Above Normal” in temperature for the year.

2014 ranked “Above Normal” in temperature for the year.

2015 ranked “Much Above Average” in temperature for the year

2016 ranked “Much Above Average” in temperature for the year

Data taken from http://www.ncdc.noaa.gov/temp-and-precip/us-maps/ytd/201607?products[]=nationaltavgrank&products[]=regionaltavgrank&products[]=statewidetavgrank&products[]=divisionaltavgrank#us-maps-select

So if my state doesn’t climate conditions for Heartworm, why does it sometimes have Heartworm cases? 

Natural disasters are the primary cause of this.  Most pets that are infected with Heartworm are homeless for some period.  Therefore, they often are often also dealing with other immune compromising issues such as poor diet, mange, group diseases and infection. Natural disasters cause animals in shelters to get dispersed to shelters in other states.  If an animal is infected with Heartworm in another state then tests positive for it in your state, your state is listed as Heartworm positive. Therefore, states with amazing shelters and no Heartworm will increase the statistical values of heartworm in your state, even if your state doesn’t have conditions under which heartworm can spread.

Viewing www.Fema.Gov/Disasters/Grid/Year is a great way to get an idea of when and where natural disasters have occurred and where shelter dogs may be moving out and dispersed into shelters in other states.

Can other species, besides dogs, get Heartworm?

Yes.  Cats, Wolves, Coyotes, Foxes, Ferrets, Sea Lions, African Leopards, Beavers, Reptiles and Humans can get heartworm.  However, the definitive host is the dog.  The CDC tracks Heartworm cases in domestic animals (Dogs and Cats) and posts results on the CAPC (Companion Animal Parasite Counsel) site.  There have been Zero cases of Heartworm in cats in the United States since prior to 2011 (data is not available for viewing prior to 2011). https://www.capcvet.org/parasite-prevalence-maps/

Prevention and Treatment Options –

Dr. Martin Goldstein, DVM states, “Only a small percentage of dogs who get heartworm die from it, especially if they're routinely tested twice yearly for early detection. Even in untreated dogs, after a period of uncomfortable symptoms, the adult worms die.” He states that his early career he treated hundreds of heartworm cases and only saw 3 deaths, the last one in 1979. He also notes, “After two decades of pervasive administration of heartworm pills in the U.S., the chances of your dog contracting heartworm in most parts of this country even a first time are slimmer still.” However, with the increase in medication used on pets, in particular heartworm medication, the incidence of cancer, seizures, immune mediated hemolytic anemia and other diseases are skyrocketing.  Many of these diseases are specifically stated on the Heartworm medication product inserts as side effects to the medication.

Rules to keep in regards to treatments:

  • Research any products active ingredients before administering it
  • Never give meds or other treatments without first identifying if they may negatively interact with other products you are giving your pet.
  • Learn what symptoms might alert you to a reaction to a product given
  • When giving allopathic treatments, know that a prescription is required to use them but their use is not mandatory under any circumstances
  • Always check the product for age range allowances
  • Studies with ivermectin indicate that dogs with white feet/toes are more sensitive to the effects of ivermectin.  The rule of thumb is “WHITE FEET, DON’T TREAT.” http://www.cliniciansbrief.com/sites/default/files/attachments/Ivermectin%20Toxicosis.pdf
  • Dr. Martin Goldstein, DVM states, “The most common form of heartworm prevention is a monthly pill, Ivermectin, taken just before and during mosquito season. (Many veterinarians recommend giving it year-round, even in areas of the country that experience winter.) Some brands also contain other toxins to kill intestinal parasites. The other approach to treatment is with a daily dose of the drug diethylcarbamazine, starting several weeks before mosquito season. The drugs called for in either course of treatment are, simply put, poisons. Unfortunately, while they kill off microfilaria, they have the toxic effects of poisons, and can be especially damaging to the liver. But I have seen one obvious, immediate effect of these once-a-month preventatives in case after case: when you give a dog that pill, over the next few days, wherever he urinates outside, his urine burns the grass. Permanently! In some cases, you can't grow grass there until you change the soil. What, I wonder, can it be doing internally to your dog in that time?”   
  • All dogs should be tested twice a year for heartworm. In high prevalence areas doses of black walnut given two to three times a week are effective. Dr. Martin Goldstein, DVM states that he has “actually reversed clinical heartworm with it. (For a thirty-pound dog, one capsule three times weekly during mosquito season in areas that have reported any incidence of heartworm.)” -The Nature of Animal Healing by Martin Goldstein Copyright©

2000 by Martin Goldstein. http://www.bluerosecavaliers.com/#!heartworm/c1i8x

Allopathic Treatments

HEARTGARD and TriHeartPlus (Ivermectin)

Product insert: http://www.heartgard.com/Style%20Library/docs/Dog_information.pdf :

  • These medications are for eliminating the TISSUE stage of heartworm larvae and are specifically listed as not being beneficial treatment for any other stage.
  • The insert also states that the medication should be used, “during the period of the year when mosquitoes, potentially carrying infective heartworm larvae, are active.”  Nowhere does it state that it should be given at any other time.
  • The insert states that “all dogs should be tested for existing heartworm infection before starting treatment with Heartgard Plus which is not effective against adult D.immitis (mature heartworm)….While some microfilariae may be killed by the ivermectin in HEARTGARD Plus at the recommended dose level, HEARTGARD Plus is not effective for microfilariae (baby heartworm) clearance.”
  • Side Effects listed on product insert: A mild hypersensitivity-type reaction, transient diarrhea, depression/lethargy, vomiting, anorexia, diarrhea, mydriasis (pupil dilation), ataxia staggering (loss of full control of body movements), convulsions (seizures) and hypersalivation, vomiting or diarrhea, tremors, drooling, paresis (partial paralysis caused by nerve damage or disease), recumbency (leaning, resting, reclining), excitability, stupor, coma and death.  Dr. Adesola Odunayo, DVM, MS, DACVECC and Dr. Marie E. Kerl, DVM, MPH, DACVECC & DACVIM state that Heartworm medication such as Ivermectin can cause neurologic signs in dogs (such as Seizures), bradycardia, absence of menace response, respiratory depression, elevated liver enzymes and thyroid problems. Immune Mediated Hemolytic Anemia, urinary bleeding, permanent lawn staining/death and Cancers also have also been associated with heartworm medication.
  • Dr. Martin Goldstein, DVM states, “Additionally, heartworm medication is a common cause of your pets urine burning your lawn. Overuse of insecticides for flea and heartworm control are believed, by most holistic veterinarians, to contribute to the increasing prevalence of cancer and chronic disease in our companion animals.”


INTERCEPTOR (milbemycin oxime) reports the above reactions plus weakness.  

Sentinel (milbemycin oxime) reports vomiting, depression/lethargy, pruritus, urticaria, diarrhea, anorexia, skin congestion, ataxia, convulsions, hypersalivation and weakness.

REVOLUTION® (selamectin), Topical Parasiticide for Dogs and Cats: pre-approval reactions of vomiting, loose stool or diarrhea with or without blood, anorexia, lethargy, salivation, tachypnea, and muscle tremors. Post-approval experience included the above plus pruritis, urticaria, erythema, ataxia, fever, and rare reports of death and seizures in dogs. 

Proheart 6 :  severe allergic reactions (anaphylaxis): facial swelling, itching, difficulty breathing, collapse;  lethargy (sluggishness); not eating or losing interest in food; any change in activity level; seizures; vomiting and/or diarrhea (with and without blood); weight loss; pale gums, increased thirst or urination, weakness, bleeding, bruising; rare instances of death. This product was voluntarily withdrawn from the market in 2004 because of deaths but has been reintroduced.

Some of this information is provided by http://www.acreaturecomfort.com/heartworminfo.htm


Like prescription medications, herbal preventatives make animals less appealing to mosquitoes, only they do it using herbs instead of pesticides/insecticides. NEITHER method kills adult heartworms, which is why regular testing for heartworm is absolutely necessary regardless of what method you choose for prevention.

Side Effects and Risks - As with all herbal remedies and treatments, including prescriptions, the healthier the animal overall, the more responsive your pet will be to the treatment. Providing your companion with the best diet along with proper supplements for optimal health will go a long way to preventing disease and making them less appealing and susceptible to parasites. For information on the diagnosis of heartworm disease, see Diagnosis of Heartworm Disease by Wendy C. Brooks DVM, DABVP on the Veterinary Partner website.

Azmira Giardia and Parasitic – this herbal extract supplement contains all-natural ingredients to help defend your pet’s body against a wide range of worms, amoebas, and parasites, including heartworm.  Provides an excellent compound containing bitter principles, which activate digestion secretions and blood cleansing. Can be used safely to clean out the colon, even with IBS, when parasites are the suspected trigger. This extract can also be used internally, as well as topically, to address parasitic fungal and yeast growth.

Ingredients: Proprietary blend of Wormwood, Quassia Bark, Black Walnut Hulls, Neem Leaves, Bilva Herb, Embelia Ribes, Eclipta Alba, Phyllanthus Amarus, Gentian Root, Ginger Root, Grain alcohol and Spring Water.

Directions: - Give daily 6 days a week for 6 weeks. – Take the 7th week off – Repeat this cycle for 6 months – After 6 months, take a month off – After the month off, begin the cycle again if needed. – Give 1 drop per 5 pounds of body weight per dose. Can be doubled initially to build up therapeutic properties or needed for acute situations. – Give orally, mixing extract in a small amount of warm water or food. Repeat dose up to 3-4 times per day in between meals, for optimum results.

For additional product questions call 520-886-1727 or 520-293-6639 or email productsupport@azmira.com

Long Term Prevention

This article was written in 2016.  As climates increase or decrease the prevalence of Heartworm will also fluctuate.  Using the resources provided in this document will allow you to continue to track the climate changes and other new developments in your area.  If there are natural disasters in high temperature/humidity areas of the United States, many of their infected shelter pets are likely to move into your state.  If enough infected pets moved into the state at once and the weather happened to be abnormally hot and humid the incidence of heartworm in your state may increase.   If your state has excessively high heat and humidity on a given year, the chance of heartworm may increase from 1.17% to 1.25%. You can easily track these factors yourself to determine the necessity of prophylactic treatment and testing.