Fleas have been around for thousands of years and have been responsible for some of the worst outbreaks of disease the world has ever seen—like the Modern Plague. These tiny, wingless, blood-sucking parasites would jump from dead rats to human hosts and transmit the bacteria, causing massive sickness and death.
Nowadays, fleas prefer our furry friends to humans, and also prefer cats to dogs. Keep this in mind if you live in a multi-pet household, especially with an outdoor cat.
“If there is a flea issue in the household, it’s usually the cat that’s the issue,” Dr. Eckholm explains. “If there are stray or feral cats in the neighborhood, they can be the source of the problem.”
The diseases fleas transmit can be highly contagious: Plague has a high mortality rate if left untreated but there have been fewer than 1000 confirmed cases in the U.S. in more than 100 years. Fortunately, it is treatable in humans with antibiotics, but it’s our responsibility as pet parents to makes sure our dogs are protected, too.
There are four stages in the life cycle of a flea: egg, larva, pupa, and adult. Fleas thrive in warm, humid conditions—long, cold winters are their nemesis. The prevalence of fleas really depends on the climate where you live.
“Any of the milder climates that have shorter winters will have more fleas in their environment,” Dr. Eckholm says. “Places like The South and California are more likely to have pets develop flea allergies than dogs who live in Michigan where the cold, cold winter kills the whole flea population.”
Mainly, fleas exist as eggs and larva, waiting protected in their cocoons for the optimal moments to hatch, which is usually when a dog or cat walks by. Just a single flea can cause problems, at least in flea-allergic dogs. One flea can bite 20 to 40 times per hour!
“It would take a huge number of fleas to cause problems in a dog that is not flea allergic,” Dr. Eckholm clarifies. “And if that’s the case, you are going to be seeing them on your dog.”
The increase of carpeting in homes has made flea problems worse, and infestations have been harder to eradicate. Regular washing of bedding in hot water and vacuuming with a powerful vacuum can help reduce the number of eggs and larvae around the house.
“Vacuuming is one of the most important things you can do,” Dr. Eckholm suggests. “If it gets beyond the point of vacuuming, I suggest calling an exterminator, but that would be extreme. Usually, it’s not filth, it’s just bad luck.”