Genus: Pulex irritans (human flea)
There are over 1,600 species and subspecies
of fleas that inhabit the earth’s diverse environment. Many of these fleas are parasites in the
insect order Siphonaptera. Pulex irritans, also called the human flea, is not often seen
in contemporary living quarters, but in the past this flea came in contact with
all classes of people. Human blood is
the preferred food of Pulex irritans, but it will feed on other mammals. Today,
this species is most often found on pigs.
Individuals that work with swine are some of the most likely people to become
infested. In societies where personal hygiene is important, infestations by
human fleas are not as common. Human
fleas were extremely common before the development of modern standards in both
hygiene and laundering. Most fleas,
during that time, were found in a person’s bedding. In an attempt to decrease infestation, the
Chinese placed warmed flea traps made of ivory or bamboo between the sheets
before going to bed at night. During the
Renaissance period, ladies frequently wore fur collars, called cravats, to catch the
pestering fleas. The cravat could then
be removed and shaken out to decrease the chance of coming in contact with any
irritans is mainly a nuisance to humans. The flea's saliva contains enzymes and
histamine-like substances, which may cause an allergic reaction in some of
their victims. These allergic reactions
may involve an intense itching sensation. The parasite can also be a vector of
a variety of diseases. Even though Pulex irritans was not the primary species responsible
for spreading the bubonic plague throughout
Humans, canids, felids, pigs, badgers, and rats may all become infested.
Pulex irritans is found worldwide.
Adults –The adults are approximately 1.5 to 4 mm in length and are laterally flattened. They are dark brown in color, are wingless, and have mouthparts that aid in both the piercing of the skin and sucking of the host’s blood. Neither genal nor pronotal combs are present. The adult flea may have either a curved or rounded head. Only five percent of living fleas are in adult form at any given time. Most fleas are distributed in the egg, larva, or pupa stages.
Eggs – The flea eggs are about 0.5 mm in length. They are oval shaped and pearly white in color. Nonfertile females will produce eggs just as fertile females do, however, the eggs will be nonviable. Eggs are often laid on the body of the host, but since they are not sticky or cemented down, they can fall off in many different places.
Larvae – The larvae are approximately 6 mm in length. They are maggot-like, creamy/yellow in color, and have thirteen segments with bristles on each segment. The larva resembles a small legless caterpillar. The larvae will feed on a variety of debris, including dried excrement, dried blood, dead mites, dried bits of skin, and other organic remains. In some cases, the successful metamorphosis of a few species of flea larvae depends on the presence of fecal matter from the parent flea. In order to provide nutrition for the larvae during development, the parent flea will consume large amounts of blood. During this larval development period the parent flea consumes a great deal of blood (up to thirty times its own weight). The intake of blood will be used to produce a large quantity of feces to feed the larvae.
Pupae – The pupa, with a loosely woven debris-collecting cocoon, is approximately 4 x 2 mm. After undergoing three separate molts, the larvae will begin to spin silk cocoons. After days, weeks, or even months, the pupae will emerge from the cocoons as adults. If conditions are unfavorable, a cocooned flea can remain dormant for up to a year, waiting for the proper prey to become available.
Life cycle (stages)
Eggs may be either laid in the host's place of rest, often called environmental hot spots, or directly on the host. If the eggs are laid on the host, they will easily fall off due to their lack of stickiness. Larvae will hatch from the eggs and begin to feed. The larvae may remain in this stage for up to two hundred days. The pupae are the most tolerant and can last in this form anywhere from ten days to fifty weeks. The time span is dependant on various environmental conditions. The pre-emergent adults (pupae) may be stimulated to emerge by heat, carbon dioxide, or movement (both human and/or pet activity). If these specific stimuli are absent, the emergence of the flea will be delayed. The life span of adult fleas can range from only a few weeks to over an entire year.
Site of infestation
Pulex irritans will attach to and begin feeding on the skin.
Pulex irritans can lead to restlessness, and both irritation and scratching of the skin. Pulex irritans is also a vector of Yersinia pestis (plague).
Diagnosis of Pulex irritans is accomplished by finding the fleas on the host.
All animals in the household, especially cats and dogs, should be treated for Pulex irritans. In addition to flea removal, anti-inflammatory agents, and antibiotics for secondary pyoderma should be used. The environment should also be treated. Due to the development of new flea-control products, this is not always necessary except with cases of heavy infestations. Carpets should be shampooed and vacuum frequently. After vacuuming, the vacuum bag should be disposed of immediately. Room foggers may also be used in the house. The bedding or “environmental hot spot” should be washed in hot water, dusted, and sprayed, or have half a No Pest R Strip placed on the underside of the pet’s housing quarters. In the case of heavy infestations, a professional exterminator should be contacted. Pigs should be treated with pyrethroids or organophosphates and pet rats should have a No Pest R Strip placed above their cage.
Other control measures
Remember to treat both the environment and the host.
Public health significance
Pulex irritans can become a human parasite.