What to Know About Climate Change and Vector-Borne Disease in Pets

Climate change is affecting national patterns of disease in complex ways—and it's becoming an increasingly important concern for pet owners everywhere. This is especially pertinent for the vector-borne diseases carried by mosquitos, ticks, fleas, and other arthropods. The ecology of insect vectors is intimately tied to climate factors and, in turn, influences the seasonality, distribution, and prevalence of vecto- borne diseases in communities around the U.S. Here's how that may affect your patients.

Climate Change and Vector-Borne Diseases

According to the U.S. Global Change Research Program, the warming climate fosters earlier seasonal tick activity, an extended biting season, and a continuing northward expansion of ticks into new areas. This directly increases the risk of exposure to the pathogens ticks carry for both people and animals.

The increasing temperatures that come with climate change can also accelerate the life cycles of vectors and their parasites. This may cause both faster maturation and faster transmission to the next host, increasing risks for infection.

Extreme weather events fueled by climate change—now increasingly common—can also spread pathogens to previously non-endemic areas. For example, canine heartworm disease spread across the continent via dogs evacuated from the southeastern U.S. following Hurricane Katrina in 2005. In that case, displaced dogs were adopted by kind owners across the country that unwittingly became reservoirs of heartworm in previously minimally affected areas.

Impact on Pets and People

Many veterinarians have reported an increase in heartworm and Lyme disease in recent years. This means veterinarians have to educate themselves on vectors and vector-borne diseases that they might not have diagnosed 10 or 20 years ago, so they can pass along that information to their clients, and also highlights the need for comprehensive vector-borne disease screening as part of routine preventative care.

At the top of the list are tick-borne diseases and heartworm. Experts agree that Ixodes species ticks are moving into colder areas as a result of a warming climate. Their seasonal activity is growing longer, too, in already endemic areas. Other ticks also take advantage of the milder winters seen in a changing climate. Based on recent studies, the Mayo Clinic warns that the range of Amblyomma americanum, the tick vector of certain types of ehrlichiosis in dogs and cytauxzoonosis in cats, is likely expanding rapidly as a result of a warming climate.

When it comes to mosquito-borne diseases, heartworm is the major concern in dogs and cats (although arboviruses like the West Nile virus have been occasionally reported as a cause of illness in pets). The changes in habitat availability and reproductive rates wrought by rising temperatures, changing precipitation patterns, and extreme weather events will influence the distribution and prevalence of heartworm disease in the U.S.

  Let's set the vector straight. Read our e-book on vector-borne diseases.

In the southern U.S., it's particularly important to be aware of the potential for previously non-endemic vector-borne diseases to cross into the country and become endemic. This has already been happening with Chagas disease in Texas, where Texas A&M University reports local transmission. Leishmaniasis, another disease usually confined outside the U.S. by the range of its sand-fly vectors, may also have the potential to expand into the country as temperatures warm, so it's vital to closely monitor for cases that could indicate autochthonous spread, meaning transmission that is happening in new locations, not contracted elsewhere during travel.

Communication and Education

Changing communication is key to getting your clients on board with the emerging threat of vector-borne diseases and truly understanding the potential risks. This starts at your practice.

  • Conversation: Instead of asking whether a pet is indoor or outdoor, ask how much time and under what circumstances a pet spends time outdoors. Or, when recommending flea, tick, and heartworm preventives, ask clients when they last gave their preventives rather than simply if they use them at all.
  • Social media: Don't forget to use social media to educate pet owners about vector-borne disease, too, as it's one of your most powerful communication tools.
  • Resources: You can make use of the many available resources online. The American Animal Hospital Association provides tips on discussing the impacts of climate change with your clients, including making them aware of new diseases emerging over time. The Cary Institute also provides links to media reports on the role of climate change in vector-borne disease spread that may help educate and inform.

Other resources can tell you and your clients what ticks are being found in your area. The University of Rhode Island runs TickEncounter, which reports tick sightings and offers strategies to avoid them. TickReport by the University of Massachusetts Amherst also provides tick identification and testing for pathogens, as well as information on the tick-borne disease surveillance they've done since 2006. And the Companion Animal Parasite Council (CAPC) provides prevalence maps provides multiple views of the United States (and Canada) on heartworm, tick-borne disease agents, intestinal parasites, and viral diseases.

By increasing everyone's awareness of climate change and vector-borne diseases in the area, you can provide the best protection and treatment for both your patients and clients.

Preparing for a Warming World

While there are some studies indicating what may happen in the future with vector-borne diseases of companion animals, like Lyme and heartworm disease, the future is still uncertain regarding new spillovers or vector-borne diseases that may emerge in pets as climate change continues to progress. How veterinarians respond to climate change and vector borne diseases will ultimately determine how much pets—and people—are in danger in a warming world. Taking steps now may indeed make a difference.

Erin Lashnits

Dr. Lashnits is a clinical assistant professor in small-animal internal medicine at the University of Wisconsin School of Veterinary Medicine. She received her MS in biology from Stanford University, DVM from Cornell University, and PhD in comparative biomedical sciences from North Carolina State University. She spent a few years in general practice and emergency medicine before completing her internal medicine residency at NC State University. Dr. Lashnits’s current research focuses on the epidemiology of zoonotic vector-borne diseases and other infectious diseases affecting underserved veterinary populations in a One Health context. The views and opinions in this piece are the author's own and do not necessarily reflect the views of either The Vetiverse or IDEXX.

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