The cat flea (Figure 1) is the most common external parasite of dogs and cats. These small, hopping insects also bite humans. In addition to the discomfort of bites and the chance of secondary infection by contamination of bite sites, the cat flea is an intermediate host of the dog tapeworm, the most common intestinal flatworm parasite of dogs and cats.
Managing flea infestations and dealing with apparent “control failures” can be frustrating. It often results in a request for a recommendation for “something else to spray” because the product being used is not working. Dr. Michael Dryden (Kansas State University) has worked extensively with flea management. He defines a true control failure “as the persistence of an infestation (house or pet) for more than 60 to 90 days despite the timely application of a flea product on the pet (i.e., every 30 days for a monthly product).”
Are expectations too high?
“I have treated but still find fleas on my pet. “ Some topically applied products do not kill fleas immediately, but the insects usually die within 24-hours. Finding small numbers of fleas on pets that are on a treatment program often means that fleas are continuing to emerge from breeding sites. This is normal. Focus on identifying and cleaning/treating these areas. Fleas also can be picked up from other sources, but more often than not, the source is at home or very close to it.
Are product recommendations being followed?
Apply preventive flea control products at the interval specified on the label. Skipping a treatment or being just a few days late can make a big difference. A female flea begins to lay eggs within 1 to 2 days of getting on a host and soon may lay up to 40 eggs per day. These eggs fall off the host and into the bedding or where pets rest. This keeps chronic infestations going.
Is the product being applied correctly and at the proper dose?
Spot-on products often need to be applied directly to the skin. That means parting the hair so the applicator tip contacts the skin. Do not apply the insecticide to just the hair.
Use an accurate weight for the pet. Ready-to-use doses usually are packaged for different weight ranges. Volumes or individual doses are small, so be sure to dispense all of it onto the pet. Failure to use all of the material may make a big difference in control. Be thorough; treat all pets, even if they don’t seem to have fleas.
Check the label for restrictions on age of pet or species. Some insecticides are labeled for use only on dogs or cats while others may be used on both.
Cats must not be treated with products containing permethrin. Also, cats must not be subjected to secondary permethrin exposure by treated dogs in the household. Mutual grooming or sharing sleeping areas can result in poisoning. Among the symptoms expressed by cats exposed to permethrin: muscle tremors, twitching, and salivation. Take the cat to your veterinarian immediately.
Have off-pet sources been identified and treated?
Adult fleas are the noticeable part of an infestation but represent only a small proportion of the total flea population in an infestation. About 95% of the total flea load is off the pet. Most life stages, such as larvae (Figure 2), are off the pet in bedding or regular sleeping areas. Until this is addressed, flea problems will continue to be chronic and changing products targeted at killing the adults will not give satisfactory results.
If adult flea control efforts on the pets have been “by-the-book,” then make sure to take adequate steps to address breeding sites. Washing bedding in hot soapy water and vacuuming carpets and upholstered furniture where pets lay are important steps in a total flea control program.
Flea Life Stages
Proportional distribution of flea life stages in a typical infestation.
|Flea life stage
|% in that stage||Where they occur|
|Adult (lives about 3 weeks)||5||On pet|
|Pupa (1 to 2 weeks
but can be much longer)
Larva (up to 2 weeks)
|Pet bedding/ sleeping area, carpet, upholstered furniture, occasionally in yard – dog house, resting areas, etc.|
|Egg (3 to 4 days)||50|
Fleas & the Dog Tapeworm
The dog tapeworm is an intestinal flatworm parasite made up of a chain of segments. Mature segments (proglottids), which contain tapeworm eggs, break off and pass out in the feces or crawl out through the anus while infested animal sleeps. Eliminated segments soon dry and break open to release tapeworm eggs. Released eggs must be eaten by flea larvae in order to continue their development. The resulting infected adult flea must be ingested by a dog or cat as it nibbles to relieve the itching from the flea bite.
Products for Flea Treatment
Many different products are available for home treatment. The most effective formulations contain both an adulticide (e.g., permethrin) effective against the biting adult stage, and an insect growth regulator (IGR) necessary to provide long-term suppression of the eggs, larvae, and pupae. Often these products can be identified by the word Plus in the brand name.
Aerosol formulations are easier to apply than liquids. Moreover, aerosol products can be directed under and behind beds, furniture, etc. Be thorough and include all likely areas of flea development. Treat carpets, throw rugs, under and behind beds and furniture, and beneath cushions on which pets sleep, if allowed by the label. Pay particular attention to areas where pets spend time or sleep; this is where most flea eggs, larvae, and pupae will be concentrated. For example, if the family cat sleeps within a closet or hides under the bed, these areas must be treated or the problem will continue. Hardwood and tile floors generally do not require treatment but should be thoroughly vacuumed.
Expect to see some fleas for 2 weeks or longer following treatment. Provided all infested areas were treated initially, these “survivors” are probably newly emerged adults which have not yet contacted the insecticide. Instead of re-treating the premises immediately, continue to vacuum. Vacuuming stimulates pupae to hatch, bringing the newly emerged adults into contact with the insecticide sooner.
Outdoor flea treatment may be needed in some cases. Focus on areas where pets rest, sleep, and run (such as doghouse and kennel areas), under decks, along fences, and next to foundations. It is seldom necessary to treat the entire yard or open areas exposed to full sun.
Flea traps, such as those utilizing a light and glue board to attract and capture adult fleas, can be helpful but will not eliminate a flea infestation unless used in combination with other methods. If adult fleas continue to be seen beyond 2 to 4 weeks, retreatment of the premises (and pet) may be necessary.
By Lee Townsend, Extension Entomologist