Blog post Tara Roth, Ph.D.

Flea Circus is No Fun for Pets or People

Most people have had an encounter with a flea at some point – the jumping black specks, the small itchy bumps they leave in their wake, and the general feeling of unease due to having a parasite in your home. However, few people understand the biology of fleas and why they invade our homes in the first place.

While most of us are familiar with the cat and dog fleas that plague our pets and ourselves, only a few species of fleas will bite a range of host species. This is because fleas are nest parasites, which means they live in the nests and homes of their hosts. Because of this, most fleas are “semi-host specific” and are rather choosy about what animals they will feed on. For example, there is a flea that specializes on woodrats (Orchopeas sexdentatus) and one that prefers American pika (Geusibia ashcrafti). While these fleas will take a blood meal from another species, they prefer not to and generally don’t survive well once separated from their preferred host. Large animals that don’t have nests, like deer, don’t usually have fleas at all, or only have fleas they picked up from other species.

Fleas must feed regularly in order to survive, although eggs and pupae can survive up to 12 months in a vacant nest until a new host arrives. This is why a vacant home can suddenly become infested when new residents arrive. When a flea first emerges as an adult, it must find its first blood meal within one week or it will starve to death. After this first blood meal, non-reproducing female and male fleas may survive without feeding up to 4 days but egg-laying adult females will die within 24 hours without a blood meal. This leaves very little time to find a new host if their old host is gone. This makes fleas critical in the transmission of plague: when rodents infected with plague die, their fleas are left without a host and will soon leave the rodent’s burrow in search of a new host – in some cases, a human walking nearby. While plague is rare in the United States (an average of seven cases are reported every year), it is seasonal and outbreaks can be detected in wild rodents from spring to early fall.

Protect yourself from fleas by preventing infestations in your home. Apply flea medication to your pets and keep cats indoors. When hiking or camping, avoid resting or setting up camp near rodent burrows or where there is high rodent activity. If fleas do infest your home, vacuum and wipe surfaces regularly to remove them. Consumer flea control products can be effective but always read the label carefully and follow the directions.

Sometimes flea infestations occur in homes without pets when wildlife make their dens in, under, or around the home. If you have repeated flea infestations despite following the above recommendations, consider contacting a licensed pest control company to help locate the source of the problem.

More information about fleas can be found at the University of California Integrated Pest Management Website.