Does Climate Change Impact Flea and Tick Populations?

By Geoff Williams

 

Someday, in the not-so far off future, we may be calling flea and tick season flea and tick year.

 

Climate change gets a lot of press for creating extreme weather and threatening sea coasts with rising tides, but a problem that doesn't often turn up is the risk it creates for the world's pets.

 

The problem? As the climate heats up, it's become less unusual to find record-hot days in traditionally cold months like November and December, which means that ticks and fleas are finding the world a more hospitable place and our dogs, cats and small animals (like rabbits) have better odds of catching diseases spread by fleas and ticks.

 

If you're interested in what's happening as far as climate change and fleas and ticks are concerned, here's what you can expect.

 

Fleas and Ticks Are Expanding Their Territory

 

As temperatures rise, certain areas of the country are becoming more inviting to fleas and ticks. Worldwide climate trends continue to break records, with 2016 being the hottest year ever on record, according to NASA and the National Oceanic and Atmospheric Administration.

 

This might explain why ticks that can spread Lyme disease have been making their way through northern Sweden for the last 30 years. Meanwhile, in the United States, black-legged ticks (which transfer Lyme and other diseases) have approximately doubled in the last two decades. Twenty years ago, you'd never see them, for instance, in Northern Minnesota, and now you do.

 

While climate change appears to be the primary cause for the spread of ticks and fleas, “it could be climate change plus other things,” says Mayla Hsu, PhD., a microbiologist and a science officer for the Global Lyme Alliance.

 

Hsu lists a variety of factors that have been helped spread fleas and ticks along with rising temperatures, including urban sprawl (in which humans and pets move to far-flung areas and possibly bring ticks and fleas with them) and the rise of the deer population and invasive plants (which have given ticks more hosts and ways for them to travel from place to place).

 

As for the continuing urban sprawl, Hsu says that there's been some debate among ecologists that you may be safer from ticks walking your dog in the deep woods rather than on the fringe of a forest.

 

"The thinking is that in the deep forest, you have more animals that can act as hosts, and so that dilutes your risk when you're walking your dog," Hsu says. "And then when you walk along the border zone, like a mix of suburban and forest areas, where there are a lot of trees with ticks but not too many animals, you're more susceptible to being bitten."

 

Climate change appears to be affecting ticks more than fleas, says Thomas J. Daniels, PhD., an associate research scientist at Fordham University's Louis Calder Center Biological Field Station. Fleas aren't as affected by climate change, he says, because they live on their hosts (meaning your pet dog or cat). So, while the world around your pet is changing, your pet's environment remains fairly constant for fleas, Daniels says.

 

"That’s not to say that a warmer planet won’t have some effect on fleas, but it will be more indirect – and unpredictable," Daniels says.

 

An Increase in Flea and Tick-Borne Illnesses

 

Naturally, if flea and tick season – warmer months like summer and fall – lasts longer, the odds increase that your pet could catch a disease. The season is lengthening, Hsu says, adding that, "above 34 degrees, ticks can move around, and you can still get bitten."

 

The types of flea and tick-borne diseases your dog or cat is at risk for include:

  • Rocky Mountain Spotted Fever: one of the better-known tick-borne diseases that can affect dogs and occasionally cats. According to the Centers for Disease Control and Prevention (CDC), there is no vaccine for the disease (which can be treated by oral antibiotics) and it can cause life-threatening conditions in dogs including kidney failure and liver damage.
  • American canine hepatozoonosis: according to the Companion Animal Parasite Council, if your dog were to catch this tick-borne disease, he or she might suffer from a high fever, pain and may lose all interest in eating food.
  • Tularemia: this is a disease that usually is spread from a tick to a cat (although dogs can get it and so can humans), according to the CDC. Cats develop a high fever, nasal issues and sometimes abscesses form around the tick bite.
  • Lyme disease: a potentially fatal disease transmitted through deer ticks that dogs, cats and humans can get. The disease is transmitted after about 48 hours, according to the CDC, and can cause anything from kidney disease or nervous system disorders.
  • Bartonellosis: better known as "cat scratch fever" (although dogs can get it, too), Bartonellosis is a disease spread by fleas. Fortunately, the worst your cat will likely be in for are swollen glands, aching muscles and maybe a fever. You could catch it from your cat, but it is not fatal.

 

Interestingly, some flea and tick diseases may drop if the temperatures keep rising, according to Daniels.

 

"Not all disease agents are likely to move equally well. For instance, predictions are that the agents of anaplasmosis and Powassan fever may not do as well in a warmer climate so we might see infection rates in ticks with those agents actually drop in some areas," he says.

 

Powassan fever isn't believed to be harmful to cats or dogs, but some animals and humans can get it. Your dog, however, can come down with canine anaplasmosis, which is carried by deer ticks and western black-legged ticks, and your dog and cat are also able to get a different type of anaplasmosis carried by the brown dog tick. Symptoms include vomiting and nervous system disorders, but antibiotics can be used to treat it, according to the CDC.

 

Today's flea and tick treatments won't treat tomorrow's flea and ticks, Daniels says. The parasites will adapt to the ingredients in the medications and survive. "This resistance to the active ingredients in the repellents will force manufacturers to find new agents," he says. "It’s the way of the world."

 

Still, fleas and ticks will endanger a lot of pets and people as the planet's climate warms, and Hsu admits that she is concerned: "Ticks are spread, moving and increasing, and we don't have enough awareness of what a problem it can be. We need to be vigilant."

 

That means being militant about using flea and tick medication year-round, especially if you live in a part of the country where winters are mild. It also means taking your dog or cat to the vet for regular check-ups and not hesitating to go when something is amiss. 

 

Want to learn more about fleas, ticks and your pet? Visit our flea and tick survival guide.