Integrated Pest Management

IPM Manual for Structural Pests in British Columbia

Chapter 5: Fleas

Learning Objectives

When you have completed this lesson, you should be able to:

Describe the lifecycle of the cat flea.
Describe a monitoring program to identify areas of flea concentration.
Describe the "pupal window" and why it is a problem in flea control.
List the three objectives of a long-term flea control program.
Describe cleaning methods used to control fleas.
Describe a treatment program to control fleas on pets.
Describe the use of insect growth regulators in flea control.
Describe when to use adulticide sprays for flea control.

Identification

The cat flea, Ctenocephalides felis felis, is the most common flea on pets. They are found on dogs, cats, raccoons and other animals. Fleas are a common and often severe problem in the coastal and lower mainland areas of B.C. They are less of a problem in the interior and northern areas of the province.

Cat fleas go through a life cycle with four stages: egg, larvae, pupa and adult. Adult cat fleas feed on the blood of their host animals. The eggs are laid on the host, but soon fall off. They may land anywhere the animal goes, but most will be where the pet spends the most time. The adult fleas excrete large amounts of partly digested blood, which dries into reddish-black pellets or 'flea dirt'.

Cat flea larvae feed on organic material in the environment and on the 'flea dirt'. The dried blood in the flea dirt contains is essential for development of the larvae. The larvae complete development in 5 to 24 days. They are very susceptible to heat and drying out. They cannot survive for long at temperatures of 35°C or at relative humidities below 50%. Indoors they can live under furniture, behind baseboards, under the edges of carpets or in cracks between boards of hardwood floors. They tend to avoid light and move downwards, whether in a carpet or in turf or leaf litter.

Drawing of cat The pupae are protected inside a silk cocoon, covered with a layer of debris. Under good conditions, the adults begin emerging from the pupae within five days to two weeks. Emergence is often thought to be stimulated by vibrations, such a people or pets walking nearby. It has been shown, however, that pupae can also continue to develop and emerge without this stimulus. Under poor conditions, the fully formed adult flea may emerge from the pupa, but may remain inside the silken cocoon until conditions improve. This pre-emerged adult is a very protected stage of the flea. Cat fleas can remain in this stage, protected from drying out and from the effects of pesticides for several months. Once it has emerged from the cocoon, the adult flea is attracted to pets (and people) by body heat, movement and the carbon dioxide given off during breathing.

Monitoring

Before applying treatments, the pest manager should:

Inspect the premises for conditions that promote the build-up of flea populations and for conditions that should be remedied to aid in long-term control (see Prevention, below).
Interview the clients to determine where the fleas are and how bad the problem is perceived to be. In a home with pets, find out from the homeowners where the pet's resting spots are (indoors and outdoors). This information will help target the flea monitoring program.

A light in the trap attracts fleas, which are caught on a sticky card under the plastic grid.

Action Decisions

Tolerance for fleas varies with the situation. Treatments should be done when the flea populations are at a high enough level to be irritating to the client.

Where pets or their owners are allergic to fleas, there may be no tolerable number of fleas.

Prevention

Clients should be advised about the importance of controlling fleas on pets (for methods, see below), to prevent flea populations from becoming established in the building. Pets can be prevented from picking up fleas by restricting where the animals roam and by fencing out stray animals.

Conditions that allow flea populations to multiply should be corrected. For example, dense vegetation near a pet kennel should be clipped or mowed to eliminate the shady, moist conditions preferred by fleas. Look for difficult to treat places that pets may use, such as under a porch or crawlspace (this may need to be screened off to prevent access).

Because rodents, squirrels and raccoons harbour fleas, anywhere they have access to a building should be screened or blocked. Any other harbourage, such as wood piles, junk or stored materials, should be cleaned up or removed.

Control

To achieve long-term control, the pest management program objectives should include:

eliminating adult fleas,
preventing immature life stages from developing, and
providing a period of continuous control while pupating fleas continue to emerge.

Control programs can fail because most flea pupae and pre-emerged adults (still in cocoons) are not killed by insecticides applied to carpets and other areas. This leaves a "pupal window", which is a problem in a flea control program. It is the 2 to 4 week period after treatments are applied, when adult fleas continue to emerge from pupae that were not affected by the treatment. The pest manager should let clients know that a few late emerging fleas can be expected and that an adulticide (insecticide to control adults fleas) may need to be reapplied in 1 to 2 weeks.

When fleas are reported biting people or pets after homes have been vacant for extended periods, it can be due to the long survival ability of the pre-emerged adults still in cocoons. It can also be due to a new infestation in the house or yard coming from raccoons or stray cats.

In commercial buildings without pets, flea complaints may arise when fleas hitch-hike into the building on people or when the building is unknowingly inhabited by raccoons or other animals. If there are no animals in the building it is unlikely that a flea population is established (in these instances, flea traps and thorough vacuuming will be sufficient to control the infestation).

Cleaning

Thorough cleaning may be sufficient to control of fleas. Steam cleaning carpets and upholstery kills most of the adults, larvae and probably some eggs in the carpet. It will also remove the adult flea excrement that is essential food for the larvae.

After carpet cleaning treatments, the client should thoroughly vacuum floors, baseboards and carpets daily for at least a week to remove remaining eggs and capture newly emerging adults. After vacuuming, the vacuum cleaner bag should be removed and taped shut before disposal to prevent fleas from escaping.

Flea Control on the Pet

Drawing of puppy It is important to make sure that clients know how to control fleas on their pets. This must be done at the same time that treatments are carried out to control fleas in the building and yard. Flea controls for animals include shampoos, sprays, flea combs and an insect growth regulator (lufenuron) that is fed to the animal. If a pet has a large number of fleas, it may be advisable to have the animal taken to a vet for treatment. Clients should be advised that it is also essential to wash or clean the pet's bedding and any throw rugs, kennels, carrier boxes, etc. used by the animal.

Preferred Pest Control Products

Insect growth regulators: Methoprene (Precor®) is effective on flea larvae. It can be applied to carpets and floors (after cleaning) and gives long lasting control of up to 120 days for some formulations. Methoprene treatments alone, or with spot applications of an adulticide, such as pyrethrins, can provide sufficient control in situations where flea populations are small and where the fleas can be effectively controlled on the pets.

A new product, containing the insect growth regulator lufenuron, is now available from veterinarians. This is an oral medication, fed to the animal monthly, to prevent flea eggs from developing. It does not affect adult fleas feeding on the animal.

Pyrethrins: Pyrethrins have a short period of activity, therefore, repeated spot treatments are needed to control the adult fleas that continue to emerge from the pupae. Pyrethrins may be used in conjunction with methoprene, which controls the immature fleas, to give satisfactory control of moderate flea populations.

Biological Control

Insect parasitic nematodes (e.g., Vector®), have recently been registered for control of fleas outdoors. The nematodes are mixed into water and soaked into the turf or soil. They are used to prevent re-infestation of pets by controlling the immature stages living in the yard. They are likely to be of most value when household pets are usually confined to their own yards.

Future Controls

Boric acid dust is registered in the U.S. for use in treating carpets for fleas. A light application of boric acid has been found to be an effective control. While not registered in Canada at this time, it may become available in the future.

Other Pesticides

With the widespread availability of insect growth regulators and pyrethrins, more toxic adulticides are only likely to be required where fleas are causing severe irritation to people or pets. Permethrin (Dragnet® and Prelude™) is the only residual spray registered for flea control indoors. It is necessary to take substantial precautions to minimize exposure of people and pets to this pesticide. Its use inside buildings should be limited to spot applications and crack and crevice treatments.

Evaluation

Fleas can re-infest a building from pets or other animals, therefore continuous monitoring and evaluation of control measures is essential. Flea traps can be used to monitor flea populations where infestations are expected, or have been found in the past.