Heartworm: Risks in Nova Scotia

Insect vector diseases are nasty organisms carried inside ticks or mosquitos and passed on to our pets or us through a bite.  You will hear most about heartworm and Lyme here in Nova Scotia.  Your decisions on how to deal with the potential dangers to your pets should be based on an understanding of the actual risk of acquiring the disease.

Heartworm is a nasty parasite that in adult form likes to live in the heart and associated large vessels of dogs and less frequently, cats. It is passed to an animal when a mosquito carrying  a 3rd larval stage of heartworm takes a blood meal.   The mosquito originally becomes infected feeding on a heartworm positive animal with stage 1 larva in the blood.  You may think that heartworm would be a big player here with our mosquito populations, but what happens between Stage 1 larva and stage 3 is temperature dependent.  The mosquito must incubate the stage 1 larva at a CONSTANT temperature of about 25 C for 10-14 days at 80% humidity to develop to the infective stage.  This is improbable though not impossible in our climate.

One potential route for heartworm to make in roads here is via infected dogs that are imported from heartworm endemic areas providing a pool of first stage larvae for our mosquitos.  At Full Circle Veterinary Alternatives, we are currently working with an owner to treat a rescued heartworm positive dog.  On average, we are asked about this two to three times a year.  Despite the movement of dogs from one geographic area to another, for the disease to take hold we still need an environment that can sustain the heat and humidity.

The American Heartworm Society discusses the possible development of infected mosquitos in urban microenvironments for instance around industrial heat sources, damp area, or standing water in direct sunshine. In the future we may see homegrown heart worm. Periodic heartworm testing can be done on dogs so that we discover that trend before many dogs become ill.

Techniques to reduce exposure to mosquito borne diseases range from insect repellents made from essential oils and herbals to monthly topical or oral pesticides and/or drugs that will kill any Stage 3 and 4 larva circulating in your pets blood stream. Some classically trained homeopaths will advocate using heartworm nosodes as preventatives; however, these have never been tested and Dr. Don Hamilton in his book Homeopathic Care for Cats and Dogs admits that there are cases where nosodes did not protect.

In Nova Scotia, judicious testing for heartworm can be done to ensure that your dog has not inadvertently met an infected mosquito from travels out of Nova Scotia or from a local geographic hot spot.  Testing is usually done 6 months after exposure to mosquitos and identifies antigen to heartworm or directly visualizes the 4th larval stage called a microfilaria.

Talk to us about your options for reducing drug use.  Heartworm preventatives are unlikely to be needed if your dog stays in Nova Scotia; however, travellers may want to use preventatives while away or on your return.  At Full Circle, we offer testing for heart worm both for travelling pets and as a periodic screening test.

For more information on the number of cases of heartworm and other insect borne disease, visit the heart worm incidence site maps available online.

http://www.petdiseasereport.com/content/prevmap.aspx?currentprev=LS

References:

https://www.virbacvet.com/practice_resources_assets/ahs-canine-guidelines-virbac.pdf

https://www.heartwormsociety.org

Hamilton, Donald  Homeopathic Care for Cats and Dogs

 

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