By Matt Soniak
“For every one flea you see on a dog or cat, there’s nine more out in the environment that you’re not seeing,” says Dr. Craig Prior, medical director of the VCA Murphy Road Animal Hospital in Nashville and president-elect of the Companion Animal Parasite Council.
I wish I’d met Prior a few years ago when I had to deal with many pet parents’ worst enemy. Both my cats got fleas one summer, and I thought the problem had been solved after treating the adult fleas on my feline housemates with a flea bath. I was completely unprepared for the rest of the uninvited guests in the house—the eggs and flea larvae developing out of sight and getting ready to make a meal of my pets (and my legs). Maybe you’ve made that same mistake by treating the adult fleas you can see, while getting caught off-guard by their larvae.
What exactly are flea larvae and how do you control them? Let’s get to know the little buggers.
Fleas have life cycles that are very different from our pets’ and ours. There are four stages in the life cycle of the flea: eggs hatch into larvae, which spin cocoons and develop into pupae and then emerge as adults. Depending on environmental conditions like heat, humidity and the presence or absence of hosts, the cycle can take anywhere from a few weeks to a few months.
Flea larvae hatch from the eggs that adult female fleas lay on their hosts. They don’t stay there, but fall off around the house as the host moves around. The eggs are like “little ping pong balls,” says Prior. “The pet gets up, stretches and shakes, and the eggs just fly off into the environment — typically where that pet is sleeping or has been sleeping.” The eggs wind up in areas where the host spends a lot of time, and it’s here that the larvae hatch and develop.
Larvae hatch from their eggs after two to seven days. Larvae are negative phototaxic, a technical way of saying they move away from light sources. They’ll try to get as far down into cracks and crevices in floorboards and carpets as they can, says Prior.
Larvae feed on “flea dirt.” Once they’re settled away from light, the larvae—which make up about one-third of the flea population in a home—spend one to two weeks developing and feeding on organic debris and flea “dirt,” the dried feces of adult fleas that is basically just dried blood. After that, the larvae will spin cocoons and enter their pupal stage, eventually emerging as adults. Nestled in this protective cocoon, flea pupae can survive for long periods of time, emerging only when triggered by signs of a potential host. It is not uncommon for people to move into a previously occupied house or apartment and find themselves fending off fleas who have laid dormant for months.
Controlling larvae hiding around the house requires tools and techniques different from those used to kill adult fleas. Prior says one of the best things you can do is vacuum thoroughly, using a beater bar attachment to pick up eggs and larvae on floors and pet bedding. One crucial step here is to seal and throw away the vacuum bag or clean out the dirt cup on a bagless vacuum when you’re done, and get the collected eggs and larvae out of the house. “If you don’t, you’ve got a reservoir of infection in that vacuum cleaner bag,” Prior says. After that, there are many flea control products, such as foggers and sprays, that can eliminate the larvae and eggs that vacuuming might have missed. Not all of these products are created equal, and Prior recommends your veterinarian as your best resource for battling fleas. They know you, your pet, your lifestyle and the local environment, and can help you figure out the best and safest products to use in your home. It may take up to two months before you start to see improvement, as pupae already in place continue to emerge as adults.
After removing the adult fleas from your pet and controlling the eggs, larvae and pupae in the house, you also need to prevent reinfestation. This can be difficult because there are so many other flea hosts outside and probably close to your home. In North America, says Prior, coyotes, foxes, bobcats, cattle, skunks, raccoons, possums, rodents, ferrets and other animals are all hosts to the same fleas that plague dogs and cats. Keeping your pets indoors as much as possible is a good start, and you should also work to make the area around your home an uninviting place for wild or stray animals and the fleas they might be carrying.
Remember that flea larvae like dark, protected environments. Keeping attics, crawl spaces and areas underneath decks and porches sealed up can keep animals out and prevent them from contaminating these places with flea eggs. Of course, you can only have so much control over what happens outside. Keeping your pets on lifelong flea control will help kill any fleas that do decide to hop onto your pet.
Image: Nicolas Primola via Shutterstock
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