Flea infestation inside the house from outdoor pets?

A few days ago we discovered fleas in the house, which was likely due to our untreated outdoor (only) cats. It's weird because even though we cleaned the house thoroughly and treated the cats (though not with too much success) we still find about 10-17 daily and we don't EVER let the cats come in. Could it be because the cats often hang around our terrace and we keep bringing the fleas and their eggs in? Or does this suspect a human flea (pulex irritans) infection? I'm curious because if it's just pet fleas then completely treating the cats and cleaning the house a few times should get rid of them, but if it is human ones, then we'd be cleaning it full time.
By the way, we live in a family house in a small town.

What do you think?

When I was in college a room mate liked petting the out door cats. Then another room mate ended up with flea bites. QWith our pets here we use diatomaceous earth all over the place when something goes awry and flee treatment for the furry ones regularly during flee season.  

Hi Mark, welcome to Permies.

I think a likely scenario of how the fleas got in the house is not so much the cats hanging out on the terrace but more likely they hitched a ride inside on humans.

I don't know how to differentiate between flea species and can't offer advice there.

I think Amits suggestion of diatomaceous earth is a good one, and I suggest the same.

That's what I meant, we most likely brought the fleas in that hopped off our cats, and I'm not sure if it's reasonable to get this amount of fleas in just by walking in and out of the house.

Márk Mészáros wrote:That's what I meant, we most likely brought the fleas in that hopped off our cats, and I'm not sure if it's reasonable to get this amount of fleas in just by walking in and out of the house.

I suspect that the number of fleas in the house did not come in on humans one by one, but more likely a few came in and laid eggs that hatched, unfortunately.

As far as I know, animal fleas cant reproduce when feeding on human blood, neither do they spend long enough time on humans to actually mate. Or is that not right?

I'm curious about whether these are likely to be human fleas or not.

I did a little reading on the internets about fleas. Interestingly, nowhere did I find anything saying anything about a male flea being involved in flea reproduction and egg fertility aside from a sentence quoted below that merely says "adult fleas will breed". Maybe there is more information is there, but the 4 or 5 websites I went to made no mention of this. I kept reading the same sentence: "Females lay eggs".

As far as the variety of flea that I think you have, I am going to hazard a guess and say it is cat fleas because 1) you mentioned you have cats and 2) it is the most common species of flea. I did read that cat fleas are not exclusive to biting cats, and will bite other animals to get a meal, including humans.

Here is a handy graphic about the flea life cycle and some information about fleas from petmd.com and I must disclose that I did not cut and paste the information in it's entirety, omitting info about sprays, medications & fumigating or fogging because this is Permies, and there are other ways.

There are four stages in the life cycle of a flea: egg, larva, pupa, and adult. Depending on the environmental temperature and humidity levels, the total life cycle will take anywhere from a couple weeks to many months. Optimal conditions for fleas are between 70-85°F and 70 percent humidity.

Flea Eggs

The beginning of the life cycle occurs when an adult female flea lays eggs following a blood meal from the host (e.g., your pet). Blood is necessary for the adult flea to reproduce. These eggs are small, white objects (slightly smaller than a grain of sand) that are laid in the pet’s fur in bunches of about 20. A single adult female can lay about 40 eggs every day.

The eggs will fall off your pet as s/he moves, allowing them to be disbursed throughout the environment where your pet spends his or her time. Eggs represent about one-half (50 percent) of the entire flea population present in an average home.

Eggs take anywhere from two days to two weeks to develop, hatching when environmental conditions are just right for them. If temperatures are cold and dry, the eggs will take longer; if temperatures are warm and humidity levels are high, the eggs will hatch at a faster rate. Larvae then emerges as the next life stage.

Flea Larvae

The emerging larvae are blind and will avoid being out in the light. They develop over several weeks by eating pre-digested blood (known as flea “dirt”) that adult fleas pass, along with other organic debris in the environment.

In appearance, flea larvae can be up to ¼-inch long and are white (almost see-through) and legless. Larvae make up about 35 percent of the flea population in the average household. If conditions are favorable, the larvae will spin cocoons in about 5-20 days of hatching from their eggs. This leads to the next life stage, called the cocoon or pupae stage.

Flea Pupae

The pupae stage of the flea life cycle accounts for about 10 percent of the flea population in a home. This cocoon stage is the last developmental stage before the adult flea emerges. The cocoon protects the pupae for several days or weeks before the adult flea emerges. If environmental conditions are not right for emergence, the cocoon can protect the developing flea for months, and in some cases, years.

Cocoons have a sticky outer coating that allows them to hide deep in the carpeting and not be easily removed by light vacuuming or sweeping. The cocoon also serves to protect the developing adults from chemicals.

The adult flea will not emerge until the presence of a potential host is made obvious - by vibrations, rising levels of carbon dioxide, and body heat. This may be triggered by your pet walking by, or people moving in the house, alerting the flea to emerge from its cocoon to feed.

Adult Fleas

Once a flea has emerged from the cocoon, it will need to begin feeding from a host within a few hours. Shortly after the first meal, adult fleas will breed and begin laying eggs within a few days. Female fleas are not able to lay eggs until they obtain a blood meal.

New adult fleas have a flat-bodied appearance and are very small and dark in color. Once they have had a chance to feed off your pet, they will become larger and lighter in color, taking on the more recognizable flea shape. Adult fleas account for less than 5 percent of the entire flea population in a home. They spend the majority of their time living on the host while they feed, breed, and lay eggs, and can live anywhere from a couple of weeks to several months on the host animal.

Eliminating Fleas

Use your knowledge of the flea life cycle to eliminate an infestation. Treat the environment properly by vacuuming regularly for several weeks and thoroughly washing bedding and toys in hot soapy water to remove eggs, larvae, and pupae. Remember to seal and remove vacuum bags after a cleaning session. You can even encourage faster emergence of the remaining pupae with a humidifier and an increase in the home temperature.  

I read on fleascience.com about how they breed, but I realized since that it didn't mention that the breeding must take place on a host.
I hope you are right, so once we take care of the cats outside the inside will be easier to handle.

we have inside and outside cats that don't mix .we keep diatomaceous earth outside on porch and were cats hang out and inside .sprinkle around and sweep into cracks. be careful and don't  breath it in.seams to take care of fleas.