Flea

Flea
Fleas are insects that belong to the order Siphonaptera which means “wingless siphon”. There are about 2500 species of fleas that belong to 239 genera and only relatively few of them are important to human. Among the medically important species, Xenopsylla cheopsis is probably the most significant species of all, which is vector of plague (Yersinia pestis), flea-borne endemic typhus (Ricckettsia typhi). Adult fleas are very small insects (up to 1/8 inch), so it is difficult to see a number of the characteristics used to describe them. These reddish brown to black, wingless insects are compressed from side to side so that they look like they are walking “on edge.” They have piercing-sucking mouthparts through which they obtain blood meals from their hosts. Flea larvae are tiny (up to 3/16 inch long), hairy, and wormlike with a distinct, brownish head, but no eyes or legs.

Medical Importance

Flea bites usually cause minor itching but may become increasingly irritating to people with sensitive or reactive skin. Some people and pets suffer from flea bite allergic dermatitis, characterized by intense itching, hair loss, reddening of the skin, and secondary infection. Just one bite may initiate an allergic reaction, and itching may persist up to 5 days after the bite. Some people are bothered by the sensation of fleas walking on their skin, but bites are the major nuisance. Bites tend to be concentrated on the lower legs but can also occur on other parts of the body. The bite consists of a small, central red spot surrounded by a red halo, usually without excessive swelling. Murine typhus is caused by Rickettsia typhi which is ingested by the flea with its blood meal. This is a disease of rodents, particularly rats especially Rattus rattus. Infection is caused by infected faeces being rubbed into abrasion or coming into contact with delicate mucous membranes. The rickettsia of murine typhus can pass across the flea ovaries, into eggs then to the larvae.

Biology & Life Cycle

Adult fleas may live up to 6 – 12 months and during which females may lay 300 – 1000 eggs mostly in small batches of about 3 – 25 a day. Eggs hatch within 2 – 14 days. A minute legless larva will emerge and is usually very active. Larva feed on almost any organic debris including host’s faeces, and partly digested blood excreted from the adults. Larval period ranged between 10 – 21 days, but can be as long as 200 days under unfavourable conditions. Pupae go through a developmental period of 7 – 14 days. Adult may remain in cocoon until suitable condition arises. When feeding, fleas eject faeces composed at the first semi-digested blood of the previous meal and then excess blood taken during feeding. Although most species of fleas have one or two favourite species of hosts, they are not entirely host-specific. Example : Ctenocephalides felis (cat flea), C. canis (dog flea), Xenopsylla cheopsis (rat flea) will readily attack man in the absence of their normal hosts.

Control

The best approach to managing fleas is prevention. New, safer, and more effective products aimed at controlling fleas on the pet have made flea management without pesticide sprays feasible in many situations. Management of fleas on the pet must be accompanied by regular, thorough cleaning of pet resting areas indoors and outside. Once fleas infest a home, control will require a vigilant program that includes cleaning and treating infested areas indoors, eliminating fleas on pets, and cleaning up and possibly treating shaded outdoor locations where pets rest. Flea populations can be controlled by preventing the hatching of flea eggs by exposing the fleas to IGR in the host’s blood or in the fur. These IGRs are not insecticidal on the adult fleas. When IGR products are used there may be an occasional need for supplemental insecticidal control of adult fleas that bother the pets or people in the home, usually by use of a flea collar or non-residual spray. Special combs are available that help remove adult fleas from the coat of a shorthaired pet. Removing fleas may provide comfort to the animal and reduce flea breeding. Combing pets at regular intervals is also a good way to monitor the flea population and help you decide when other control measures may be necessary. Thoroughly and regularly clean areas where adult fleas, flea larvae, and flea eggs are found. Vacuum floors, rugs, carpets, upholstered furniture, and crevices around baseboards and cabinets daily or every other day to remove flea eggs, larvae, adults, and food sources. Vacuuming is very effective in picking up adults and stimulating preemerged adults to leave their cocoons. Besides treatment of fleas on the pet, insecticide applications are required indoors and frequently to selected areas outdoors. Treat all perimeter areas of the home and the yard, and especially any kennels or other pet runs. Treatment of the entire yard area may sometimes be necessary, especially where inspection indicates the widely environmental conditions favor flea development.