is currently empty

Information and Advice About Fleas

Fact Sheet: Fleas

Adult fleas are 1 - 8mm long and brownish in colour. The flea's body is laterally compressed (i.e. flat), and covered with backward-directed bristles, they are wingless and have small or no visible eyes. Fleas piercing mouth parts and muscular legs - the hind ones being adapted for jumping - are distinguishing features.

Adult fleas live exclusively as parasites of warm-blooded animals, especially mammals, although birds may also be attacked. While they show a certain degree of host preference, fleas will feed on other animals in the absence of the normal host. In fact, they tend to be more nest-specific than host-specific, for while adult fleas may feed on the blood of a variety of animals, the larvae require more precise conditions which are associated with the habitats and nesting habits of the hosts than the characteristics of their blood.

Cat fleas (Ctenocephalides felis) are responsible for many flea infestations, the remainder being attributable to a variety of bird and animal species. Infestations by Pulex irritans (human fleas) are now uncommon. The significance of Ctenocephalides felis is explained by the increased number of pets being kept and the tendency for their beds to be neglected during cleaning. Wall to wall carpeting also provides a relatively undisturbed environment for the larvae of fleas to develop, whilst the spread of central heating has served to ensure ideal temperature conditions.

Pest Significance

Fleas can be vectors of disease or may transmit parasitic worms. The most serious infection which they can spread is bubonic plague, transmitted to man by rodent fleas (Xenopsylla cheopis) which carry the causative bacillus from infected rats. Rodent fleas may also carry murine typhus and, because of their readiness to attack humans as well as rats, are probably the major flea vector of disease. Dog fleas are an intermediate host of the dog tapeworm, whose vertebrate host is usually the dog but which can sometimes be transmitted to humans.

In Europe, fleas are generally not responsible for the transmission of disease. Nonetheless, fleas are still objectionable because of the bites they inflict and the deep-rooted social stigma attached to humans with flea infestations.

Bites from fleas are identified as a tiny dark red spot, surrounded by a reddened area. The bite persists for one or two days and is intensely irritating. First bites are not generally liable to cause serious reactions, but they may lead to hypersensitivity. Reactions are usually delayed following regular biting over a long period; they then follow a period when reactions are immediate. The cycle then repeats until a state of non-reactivity - immunity to the bite of fleas is achieved.

Life Cycle

The development cycle of fleas from egg to adult is normally completed in four weeks, but at lower temperatures will take much longer.

The eggs of fleas are about 0.5mm long, oval, pearly-white in colour and laid in the fur or feathers of the host of in its nest of bedding. They do not adhere to the host but readily fall from the animal, are shaken or off. The same applies to to the dark coloured faeces of the adult fleas, thus creating the black and white - salt and pepper - effect associated with infestations of fleas. Four to eight eggs are laid after each blood meal and a single female may produce 800-1000 eggs during her lifetime, which may be as long as two years.

The eggs hatch in about one week to give white, threadlike, legless larvae 1.5mm. The larvae of fleas thrive in dark, humid places such as animal bedding and carpet fluff, and feed on organic debris and adult flea excrement. A cat's bedding may support a population of 8,000 immature and 2,000 adult fleas. After 2-3 weeks, by which time they will have moulted twice and be about 5mm long, the fleas larvae spin silken coccoons, incorporating debris, in which to pupate. This is the quiescent phase and the flea may overwinter in this state. The adult flea is stimulated to emerge by the vibrations set up by a passing host. This explains the occasional mass attacks which take place in deserted premises.


In many instances infestations of fleas in well-kept houses can be easily traced to pets. Where this is not the case it is useful to establish the pest species. This will help to identify possible hosts and even the foci of the infestations. Control measures must be directed at the brood as well as the adult fleas.

Hygiene/Management: Regular cleaning will deny the insects their ideal breeding conditions and so make an important contribution towards their control. Infested clothing, beds and bedding should be destroyed by burning or thoroughly cleaned and the same measures employed when dealing with any old bird and animal nests you may find. Accumulations of debris should also be removed from cracks and crevices such as between floorboards, and the whole area thoroughly cleaned.

Insecticidal control: Insecticidal products are available which have been specifically formulated and registered for use on the host animals themselves. Only these products should be applied to animals and care should be taken to follow the manufacturers' instructions. The PCP UK Flea Killer Kit comprises several products which are safe for use in areas frequented by pets, and even on pet bedding, including a specialist Household Flea Spray. The use of a residual insecticide on wider areas may be beneficial. Protector C is a potent insecticide with lasting residual action, deadly to a wide range of insects, but harmless to mammals and humans, and with no staining or smell once dry. Available in 5 litre bottle, for application with hand sprayer, or in a handy 1 Litre Trigger Pack .