Heartworm Disease in Dogs

There is a common misconception that once the weather starts to cool down, heartworm prevention is no longer necessary. The trouble with that line of thinking is that it only takes one infected mosquito to render that assumption dangerous. Smaller species of mosquitoes can travel one to three miles from their breeding grounds, and larger species that are common in the Midwest can travel up to seven miles in search of a blood meal. The threat doesn’t even have to be in your immediate backyard to be present.

There are 25 different species of mosquito that can carry heartworm, and they are active at different times of the day and year so the risk is present year-round, not just when mosquitoes are most active. With the relocation of pets from heartworm infected areas to other parts of the country due to natural disasters, heartworm infection is becoming more prevalent everywhere. It was already found in all 50 states, but the incidence of infection continues to rise. The American Heartworm Society conducted a survey of veterinary practices in 2016, and in that study, 21.7 percent of veterinary practices reported seeing more heartworm positive cases in 2016 than in 2013, just three years earlier. The increase in prevalence is due in part to gaps in prevention administration and emergence of heartworms that are resistant to current preventive medications. Currently, six strains of heartworm that are resistant to current prevention methods have been identified. New protocols recommend combining repellant strategies and preventive medications to combat these issues.

Mosquito-repellant strategies help prevent heartworm transmission on two fronts: they help prevent mosquitoes from picking up the infective microfilarae from infected animals as well as terminating any mosquitoes that are able to feed on an infected animal before they can develop infective larvae (the stage that would be able to infect other animals), and they help prevent mosquitoes from biting heartworm-free animals and transmitting infection to them. In fact, in studies where both heartworm prevention and mosquito repellant treatments were utilized, it was found that the overall antifeeding effect of the repellant was 98.5 percent. Blocking transmission of heartworm infection from a heartworm-positive pet is shown to be possible by these results.

Multimodal approaches to prevent infection are nothing new in human medicine and are commonly prescribed to prevent the infection by and spread of such diseases as malaria. These double-up efforts provide an additional layer of prevention that can help combat issues such as resistance to medications used to prevent heartworm infection taking hold once it is introduced into a pet’s body by preventing the introduction of the infectious agents in the first place.

In addition to these strategies, you can help prevent the spread of mosquitoes by eliminating potential habitats in your backyard. One inch of standing water is all that is needed for mosquitoes to reproduce, and with an emphasis on staying hydrated and our penchant for cooling down with water play, those conditions may readily exist without our even really being aware that they do. Keep windows and doors screened when they are open; correct any landscaping issues that allow water to pool; add bubblers or fountains to decorative ponds to keep the water moving; empty, wash and refill water bowls daily and keep items such as buckets, bird baths and baby pools emptied and turned over when not in use.

If you have any questions about adding a topical mosquito repellant to your pet’s existing heartworm protocol, such as when and how to administer it or the best products to use, or about continuing your pet’s heartworm prevention year-round, please contact our office.