The fleas are small, wingless, obligate, blood-feeding insects. Over 95% of flea species are ectoparasites of mammals, while the others are ectoparasites of birds. The order is relatively small with about 2,500 described species, almost all of which are morphologically very similar.
Adult fleas usually live in temporary association with their host; flea morphology, physiology and behaviour are intimately associated with hosts that are only intermittently available, temporary episodes of feeding and the microhabitat of the nest, burrow or dwelling of the host animal. Mammals and birds which do not build nests, or return regularly to specific bedding, lairs or burrows generally do not have fleas. Hence, fleas are common on rodents, bats, carnivores and rabbits and virtually absent on ungulates. Through their close association with the habitations of humans and their companion and domestic animals, a number of species of flea have become distributed worldwide and now proliferate in previously inhospitable habitats.
Many species of flea are able to parasite a range of hosts. This, combined with their mobility, which allows them to move easily between hosts, makes them parasites of considerable medical and veterinary importance and makes them difficult to control. Once on their host, fleas feed daily or every other day. Females require significantly more blood than males. Blood-feeding may have a range of damaging effects on the host animal, causing inflammation, pruritus or anaemia. Fleas may also act as vectors of bacteria, protozoa, viruses and tapeworms. Flease are also important as agents of cutaneous hypersensitivity reactions, particularly in cats and dogs.
Wall, R, Shaw, S.E. & Penaliggon, J. (1997) The prevalence of flea species on cats and dogs in Ireland. Medical & Veterinary Entomology, 11, 404-406.
Wall, R. & Shearer, D. (2001) Veterinary Ectoparasites: Biology, Pathology and Control. 2nd Edition, Blackwells Science Ltd, Oxford.