Description

Fleas in dogs cause itching and hair loss. The most common flea in dogs is the cat flea, Ctenocephalides felis, followed by the dog flea, C. canis.

Morphology and behavior

Fleas are small (1/16 to 1/8-inch (1.5 to 3.3 mm) long), agile, usually dark colored (for example, the reddish-brown of the cat flea), wingless insects with tube-like mouth-parts adapted to feeding on the blood of their hosts. Their legs are long, the hind pair well adapted for jumping (vertically up to seven inches (18 cm); horizontally thirteen inches (33 cm)) - around 200 times their own body length, making the flea one of the best jumpers of all known animals (in comparison to body size), second only to the froghopper. Their bodies are laterally compressed (human anatomical terms), permitting easy movement through the hairs or feathers on the host's body (or in the case of humans, under clothing). The flea body is hard, polished, and covered with many hairs and short spines directed backward, which also assist its movements on the host. The tough body is able to withstand great pressure, likely an adaptation to survive attempts to eliminate them by such as mashing and scratching. Even hard squeezing between the fingers is normally insufficient to kill a flea. It is possible to eliminate them by pressing individual fleas with adhesive tape or softened beeswax (or "cheese" wax) or by rolling a flea briskly between the fingers to disable it then crushing it between the fingernails. Fleas also can be drowned in water and may not survive direct contact with anti-flea pesticides.

Fleas lay tiny white oval shaped eggs better viewed through a loupe. The larva is small, pale, has bristles covering its worm-like body, lacks eyes, and has mouthparts adapted to chewing. The larvae feed on various organic matter, especially the feces of mature fleas. The adult flea's diet consists solely of fresh blood.  In the pupal phase the larva is enclosed in a silken, debris-covered cocoon.

Life cycle and habitat

Fleas are holometabolous insects, going through the four life cycle stages of egg, larva, pupa, and imago (adult). The flea life cycle begins when the female lays after feeding. Adult fleas must feed on blood before they can become capable of reproduction.  Eggs are laid in batches of up to 20 or so, usually on the host itself, which easily roll onto the ground. As such, areas where the host rests and sleeps become one of the primary habitats of eggs and developing fleas. The eggs take around two days to two weeks to hatch.

Flea larvae emerge from the eggs to feed on any available organic material such as dead insects, feces, and vegetable matter. They are blind and avoid sunlight, keeping to dark places like sand, cracks and crevices, and bedding. Given an adequate supply of food, larvae should pupate and weave a silken cocoon within 1–2 weeks after 3 larval stages. After another week or two, the adult flea is fully developed and ready to emerge from the cocoon. They may however remain resting during this period until they receive a signal that a host is near - vibrations (including sound), heat, and carbon dioxide are all stimuli indicating the probable presence of a host.  Fleas are known to overwinter in the larval or pupal stages.

Once the flea reaches adulthood its primary goal is to find blood - adult fleas must feed on blood in order to reproduce.  Adult fleas only have around a week to find food once they emerge, though they can survive two months to a year between meals. A flea population is unevenly distributed, with 50 percent eggs, 35 percent larvae, 10 percent pupae, and 5 percent adults.  Their total life cycle can take as little as two weeks, but may be lengthened to many months if conditions are favorable. Female fleas can lay 500 or more eggs over their life, allowing for phenomenal growth rates.

Adult female rabbit fleas, Spilopsyllus cuniculi, can detect the changing levels of cortisol and corticosterone, hormones in the rabbit's blood that indicate she is getting close to giving birth. This triggers sexual maturity in the fleas and they start producing eggs. As soon as the baby rabbits are born, the fleas make their way down to them and once on board they start feeding, mating, and laying eggs. After 12 days, the adult fleas make their way back to the mother. They complete this mini-migration every time she gives birth.

Fleas and classification

Fleas are related to mecoptera,  winged insects with good eyesight. The flightless boreid (snow scorpionfly) with its rudimentary wings seems to be close to the common ancestor of the 2000 or so known varieties of flea, which split off in many directions around 160 million years ago.  Their evolution continued to produce adaptations for their specialized parasitic niche, such that they now have no wings and their eyes are covered over. The large number of flea species may be attributed to the wide variety of host species they feed on, which provides so many specific ecological niches to adapt to.

Flea systematics are not entirely fixed. While, compared to many other insect groups, fleas have been studied and classified fairly thoroughly, details still remain to be learned about the evolutionary relationships among the different flea lineages.

Flea treatments

For humans

The itching associated with flea bites can be treated with anti-itch creams, usually antihistaminics or hydrocortisone.  Calamine lotion has been shown to be effective for itching.

For pets

Modern flea control is approached using Integrated Pest Management (IPM) protocols at the host (pet) level. IPM is achieved by targeting fleas during at least two separate life stages, with at least two separate molecules. This is typically achieved using an adulticide to kill adult fleas and a insect development inhibitor (IDI), like lufenuron, or insect growth regulator (IGR), like methoprene, to prevent development of immature stages. Fleas, their larvae, or their eggs can be controlled with insecticides. Lufenuron is a veterinary preparation (Program) that attacks the larval flea's ability to produce chitin but does not kill fleas. Flea medicines need to be used with care as many, especially the acetylcholinesterase inhibitors, also affect mammals. Popular brands of topicals that do not contain cholinesterase inhibitors include Advantage, Advantix, Frontline and Frontline PLUS. In 2008, three next-generation flea products reached the market: Promeris, Comfortis, and Vectra 3D.

Cedar oil, a non-toxic natural substance, has been proven effective in the eradication of infestations in pets. Cedar oil is being used to treat sand-flea infestation of US Military forces in the Gulf.

Since more than three quarters of a flea's life is spent somewhere other than on the host, it is not adequate to treat only the host mammal for fleas. It is important also to treat the host animal's environment. Thorough vacuuming, washing linens in hot water, and treating all hosts in the immediate environment (the entire household, for example) are essential.

For the home

Combating a flea infestation in the home takes patience as for every flea found on an animal there are many more developing in the home. A spot-on insecticide, such as Advantage, Frontline, or Revolution will kill the fleas on the pet and in turn the pet itself will be a roving flea trap and mop up newly hatched fleas. The environment should be treated with a fogger or spray insecticide containing an insect growth regulator, such as pyriproxyfen or methoprene to kill eggs and pupae, which are quite resistant against insecticides. Frequent vacuuming is also helpful, but the vacuum bag must be disposed of immediately afterwards.

Diatomaceous earth can also be used as a home flea treatment in lieu of acetylcholinesterase inhibitory treatments or insecticides which carry with them a risk of poisoning for both humans and animals. Diatomaceous earth however is dangerous to pets and people when inhaled and is therefore not recommended.

Dried pennyroyal has been suggested as a natural flea control,  but is not recommended in homes with pets due to its high toxicity to mammals.

Borax is sold as a "Natural Laundry Booster" and can also be used as another home treatment for flea infestations. Borax contains boric acid which kills fleas by dehydrating them, but its safety for pets is untested. .

Using dehumidifiers with air conditioning and vacuuming all may interrupt the flea life cycle. Humidity is critical to flea survival. Eggs need relative humidity of at least 70-75 percent to hatch, and larvae need at least 50 percent humidity to survive. In humid areas, about 20 percent of the eggs survive to adulthood; in arid areas, less than five percent complete the cycle.  Fleas thrive at higher temperatures, but need 70° to 90°F(21° to 32°C) to survive. Lower temperatures slow down or completely interrupt the flea life-cycle. A laboratory study done at the University of California showed that vacuuming catches about 96 percent of adult fleas. A combination of controlled humidity, temperature, and vacuuming should eliminate fleas from an environment, and altering even one of these environmental factors may be enough to drastically lower and eliminate an infestation.

Wikipedia and GNU

The content of this entry is from the Wikipedia article "Flea" licensed under the GNU Free Documentation License.