Fleas are external parasites that live off the blood of mammals and birds. Like mosquitoes, they are a problem in Davis in large part because of our warm climate. Probably one of the least friendly and one of the more pestilent examples of town wildlife, pet owners should be especially vigilant to control these disease- and parasite-carriers.

An SEM Micrograph of a flea

Some well-known species:

  • Cat Flea (Ctenocephalides felis)
  • Dog Flea (Ctenocephalides canis)
  • Northern Rat Flea (Nosopsyllus fasciatus)
  • Oriental Rat Flea (Xenopsylla cheopis)

Flea saliva can produce an allergic reaction in some people and animals. A raised, itchy bump with a single puncture point in the middle is characteristic of a flea bite. Ironically, it is C. felis or cat fleas that typically plague dogs!


Fleas transmit diseases and parasites such as bubonic plague, typhus, and tapeworm; on top of this, many dogs have flea allergies that can result in dry patches of skin that become hairless from scratching and biting. The bubonic plague disease, caused by the Yersinia pestis bacterium, is most often carried to cats and humans by fleas that have bitten infected rodents such as squirrels and rats. Tapeworm parasites (Dipylidium caninum) are transmitted by fleas that consume tapeworm eggs from an infected mammal host. Tapeworms infecting domesticated mammals include D. caninum which can infect dogs, cats and people; Taenia pisiformis which infects dogs from rabbits; Taenia taeniaeformis which infects cats through rats or mice. Be aware that if your cat is a hunter, s/he is more likely to get tapeworm directly from rodents and should be wormed more frequently. Humans are unlikely to get tapeworm from pets though small children who eat animal feces may have problems.


Fleas are most abundant during warm and moist winters and spring.

Because fleas like to hang out in grass, within carpets and bedding when not feasting on you or some other mammal, it's important to take a multi-pronged approach to control. Infestations must be attacked simultaneously on the indoor environment, outdoor environment, and at the host level. Also be aware that whatever controls you use must target both eggs, larval, and adult stages — many products contain an insect growth regulator that will prevent fleas from procreating. Try to do everything within one- or two-days to ensure that you've attacked all stages of infestation. Repeat treatments may be necessary in cases of extreme infestations or when populations are continually brought back into the household.

Over-the-counter products containing active ingredients such as chlorpyrifos (Dursban) and permethrin have shown good results as well as those containing contact insecticide along with an insect growth regulator such as methoprene (Precor), fenoxycarb and pyriproxyfen (Nylor, Archer). Growth regulators prevent eggs from hatching and larval fleas from pupating into reproducing adults, but do not kill adult fleas. Methoprene will reduce flea populations up to 95% in 14 days while pyriproxyfen, due to its photostability, lasts in carpets for many months. Not all of these may be safe for use on skin (either yours or Fido's), so read the instructions very carefully! Also, be aware that permethrins typically degrade within a day and possibly more quickly when exposed to sunlight — kinda nice, but it can make the job of controlling fleas a perpetual task. Flea traps are also available, which are basically just a piece of really sticky tape. Nice idea, but largely ineffective... some say that for every flea you see, there are twenty others.

Environmental controls can include yard sprays, bug bombs for your living environment, and sprays applied directly to bedding. Blankets or rugs used as bedding for infested hosts should be discarded or laundered in hot, soapy water; carpeted areas and upholstered furniture should be thoroughly vacuumed and the vacuum bag contents discarded. Cleaning carpets with a steam cleaner should kill some of the larval fleas, and remove accumulated organic matter on which flea larvae feed.

Pet owners must control flea populations on their pets as well as in the environment. In Davis, most people opt to treat prophylactically with a prescription medication such as Fipronil/Frontline® or Lufenuron/Program®. Other options for controlling populations on domesticated animals include dips, dusts, flea collars, sprays, shampoos and other topical treatments such as Imidacloprid/Advantage™. Shampoos are essentially contact insecticides, and to be effective these must stay on the animal for at least ten-minutes before rinsing. A fairly effective natural shampoo insecticide is D-limonene, a volatile oil from citrus fruits — these shampoos are good on kittens, puppies and for homes with infants. According to Consumer Reports (August 1991), flea collars aren't effective and are probably a waste of money.

To learn more about infestations in Davis, please visit our Town Wildlife page; check our Dogs page for additional information on the dog's life in Davis.