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May contain: invertebrate, insect, animal, and flea
Plague-infected flea

Fleas are small (1-8mm long), flattened, wingless insects (Order: Siphonaptera). Adult fleas are capable of jumping and have mouthparts adapted for piercing skin and sucking blood. Most fleas are parasites of mammals. Flea larvae resemble small worms and construct silk cocoons that are difficult to see because they are typically covered with debris.   

Life cycle & habitat: 

Fleas LifeCycle by CDC

Fleas undergo a four-stage life cycle that includes egg, larva, pupa and adult stages. Female fleas require a blood meal prior to laying eggs. Eggs are laid on the host animal, and typically drop into the bedding or nest of the host. Larvae then feed on organic material present in the nest/bedding. Once the cocoon is created, flea pupae can survive for several months without feeding.   

Impact on human health: 

  • Flea bites may cause discomfort, and inhalation of flea products (shed skins) may cause an allergic reaction in some people. 
  • Locally, the cat flea (Ctenocephalides felis) is the most important flea pest of humans and many domestic animals (including cats and dogs).
  • Plague can be found in wild rodents (primarily chipmunks and ground squirrels) and their associated fleas in high elevation areas in California. These include foothills, plateaus, mountains and high elevation coastal areas. Although urban rats were historically important in plague transmission, they no longer play an important role in California. For more information visit the CDPH plague page


  • Frequent vacuuming (or steam cleaning) of areas where pets sleep is an effective way to remove flea larvae and their potential food source.
  • There are a wide variety of products available that are designed to combat flea infestations. Some products are applied directly to animals, while others are used on household surfaces. Always read and follow the directions/labels carefully.
  • The District does not have a flea control program, and residents may need to contract with a private pest control company for service.   

What you can do to prevent exposure: 

  • Control fleas on pets and in the home (click here for detailed information on this subject).
  • Discourage rodents from living in and around the home- for more information, visit our Rodent Program page.
  • Avoid contact with sick, dead or wild animals.

Helpful Links

UC IPM Pest Notes: Fleas

  • Flea life cycle
  • Management of fleas (on pets, indoors, outdoors)

CDPH: Plague Page

  • Fact sheets
  • Information about plague in California

CDC: Fleas

  • Flea life cycle (with explanation of graphic)

EPA: “Taking care of fleas and ticks on your pet” Fact Sheet

  • Tips for pet owners
  • Advice for reporting incidents (with flea control products)
Facts About Plague in California


Mullen. G.R. and L.A. Durden. 2009. Medical and Veterinary Entomology, 2nd ed. Academic Press. Burlington, MA.

Rust. M.K. 2010. Pest Notes: Fleas. Davis: Univ. Calif. Agric. Nat. Res. Publ. 7419.

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