Summary
This article covers 15 16 reasons why flea control may fail. Many errors can be avoided by understanding the life cycle, habitat, and behavior of fleas. For example, cocooned adults can enter into a sleep-like state for up to 5 months. This causes control issues, as the life cycle from egg to adult would otherwise complete in 17-26 days.
Details
1. Unrealistic Expectations
Without proper expectations, it can seem like flea control efforts aren’t working. This can lead to confusion, frustration, and abandoning measures that would work if only given more time.
Flea eradication takes patience. No treatment kills fleas instantly or permanently. It may take several hours (up to 36 hrs) for exposed fleas to die. High expectations for flea control products can cause client dissatisfaction. Manufacturer efficacy statements are generally overrated. Thus, it’s not uncommon to see fleas, dead and alive, on treated pets. However, newly acquired fleas shouldn’t survive long enough to lay eggs.
Even after adult fleas are killed on pets, the bulk of the infestation remains. 95-99% the population consists of eggs, larvae, and pupae living in the environment. Infestations usually aren’t detected until many adults are already living on a pet, causing extreme discomfort and noticeable scratching. Or flea populations reach levels where people in the home are getting bites. This means they’ve been reproducing freely for several weeks, and that there will be a large biomass of immature stages hidden in the environment.
New adults will continually emerge from indoor and outdoor reservoirs of immature fleas. For the infestation to end, all of the young stages must mature into adults, emerge, and die. This usually takes around 8 weeks, but can last up to 6 months. During that time, seeing new fleas in the home and on pets is common.
2. Problematic Pupae
Cocooned flea stages make eradication troublesome. When larvae hatch, they actively avoid light, moving deep down into carpets or other substrates. There, they safely grow and pupate. Insecticides have little effect on pupae, because sprays can’t penetrate to the base of carpets. Likewise, vacuuming can’t remove these stages. These fleas need to mature and emerge in order to die.
To make matters worse, cocooned adults can elect not to emerge. Instead, they enter into a quiescent (dormant-like) state for up to 5 months. This significantly increases their longevity, as the life cycle from egg to adult would otherwise complete in 17-26 days. The pre-emerged state is a mechanism that increases the odds of a host being around when the adults finally emerge. The fleas immediately wake up and emerge upon detecting heat and pressure, which indicate that a host is resting on the cocoon. Vacuuming can help simulate these host cues and force earlier emergence.
3. No Integrated Approach
Adult fleas live on pets. Immature stages develop in the pet’s environment. For a control regimen to be effective, both the pets and the environment need to be treated. Attacking fleas at all stages, with variety of control tools, is known as integrated flea control. An integrated approach typically involves pet-owner education, vigilant use of adulticides and insect growth regulators, and regularly doing mechanical control (e.g. vacuuming and laundering). Incomplete approaches to overall flea control is a common problem, especially when pet owners still have the belief that weekly flea shampooing is an adequate flea control method.
See our page on How to get rid of fleas for more information.
4. Stopping Treatment Early
Flea treatments must be administered for the full duration instructed by the product label or veterinarian, even when it looks like the infestation has ended. Not seeing adult fleas for a while doesn’t mean the infestation is over. For months, unseen young stages will continue to mature and emerge as adults. If a new female fleas finds an untreated animal, she’ll take a blood meal, mate, and lay eggs within 1-2 days. Each female produces around 25 eggs a day. Thus, re-infestation can occur quickly.
5. Only Treating When Fleas are Visible
Related to the previous error, some pet-owners only treat pets when fleas are present. The adult fleas die with the first treatment, and so it’s assumed the infestation is over. However, those fleas were actively reproducing. Large numbers of eggs, larvae, and pupae will be growing in the environment. Without continued treatment, re-infestation is assured.
6. Allowing a Lapse in Treatment
Adhering to the schedule labeled on flea control products is crucial. Topical treatments typically need to be re-applied every 30 days. Failure to administer treatment on time will give emerging adults a window of opportunity to jump on pets and reproduce. Even a minor lapse in treatment can make the product appear ineffective.
7. Forgoing Treatment in Winter
The changing of the seasons won’t end an existing flea infestation. Fleas are most prevalent in the summertime. Their development slows down in the cooler months, but it never ceases entirely. Fleas can’t survive in freezing temperatures outdoors. Unfortunately, if a pet is infested, that means much of the flea population is living indoors where it’s warm.
8. Improper Treatment Dosage
Flea medications are specifically formulated for dogs and cats of certain sizes. The full dose of the correct product needs to be administered. If not, the treatment may fail. Sometimes pet-owners will attempt to save money by splitting treatments between multiple pets, or by purchasing products for larger animals than their own. This can lead to under-dosing or over-dosing. Owner concerns about pet toxicity can also lead to under-dosing.
9. Not Treating All Pets
C. felis (cat fleas) can infest cats, dogs, and even ferrets. When fleas are found, all animals in the home should be treated. Owners will sometimes forgo treating pets which show no signs of having fleas. Left untreated, that animal will eventually get infested and become the primary host. The infestation will continue.
10. Neglecting Hot-Spots
Immature fleas aren’t evenly distributed throughout a house or yard. Development can only occur in areas where flea eggs and flea feces have both fallen from infested hosts. Environmental requirements of humidity and temperature further limit viable habitats. Surviving fleas end up concentrated in carpeted rooms where pets frequently rest, groom, and eat. Hot-spots commonly occur around pet bedding, and at the foot of sofas and beds. It’s important to give special attention to identified hot-spots when spraying and vacuuming. Flea control failure often results from ineffectual recognition and treatment of these point sources.
11. Administering Treatments Incorrectly
Pet-owners will sometimes skim over product directions, or neglect them completely. Examples: 1) Flea drops must be applied to the skin of the animal, not the fur. 2) Efficacy is lost if flea drops are administered when the pet is wet (e.g. after shampooing). 3) Oral medications are often directed to be given with food to increase absorption.
12. Excessive Bathing or Swimming
Repeated immersion in water will cause flea drops to lose their efficacy, even those labeled as water resistant. Most flea drops diffuse across skin via the animals’ oils. When pets are frequently bathed or allowed to swim, it can rinse away the oils and insecticide. Immersion in water more than once weekly is not recommended.
Similarly, after floors are treated with a flea spray, wet cleaning should be avoided. Dry vacuuming doesn’t alter the residual activity of insecticides. However, wet cleaning, such as mopping, steam cleaning, and carpet shampooing, will reduce insecticide activity.
13. Re-infestation from External Sources
Flea infestations usually originate outdoors. Flea eggs are deposited in yards when infested wildlife pass through (e.g. opossums, raccoons, foxes, coyotes, and feral cats). The young fleas develop in moist, shaded areas, where they eventually emerge as adults to infest pets. Fleas can also sometimes survive in cars and secondary houses. If these peripheral reservoirs of fleas aren’t dealt with, lasting control will be difficult. It is especially difficult to control fleas in rural areas where pets travel large ranges instead of being fenced in a back yard.
14. Using Unproven Methods
Today, many pet-owners are looking for natural, chemical-free control solutions. These types of methods should be embraced if they’re effective. However, many of these remedies have no record of success. Or they may only kill one life stage (usually adults, which only make up 1-5% of infestations). At their worst, natural solutions promoted as “safe” may actually be more hazardous to pets than synthetic products. One example is citrus oil.
15. Insecticide Resistance? Unlikely
Pet-owners often claim insecticide resistance as the reason for flea control failure. While resistance is possible, there’s no evidence yet of this happening with the modern ingredients used today. In all likelihood, the failure was a result of poor adherence to proven flea control procedures.
16. Poor Sanitary Habits
Flea infestations are more likely to thrive in the absence of sanitary measures. For example, if floors are swept infrequently, if carpeting isn’t vacuumed, or if bedding and blankets are changed infrequently. The infrequent and inefficient cleaning of carpeting can be a major cause of the parasite’s success in homes.
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Will taking my area rugs outside and leaving them for several hours kill flea eggs, larvae and pupae
It depends upon how hot or cold it is outside. And it will probably take longer than a few hours. A few days will be more effective. To increase the heat, it may be a good idea to place the rugs in large black plastic bags and then in direct sunlight.