|female (left) male (right)|
The human flea, Pulex irritans, is a cosmopolitan flea species that has, in spite of the common name, a wide host spectrum. It is one of six species in the genus Pulex; the other five are all confined to the Nearctic and Neotropical regions. The species is thought to have originated in South America, where its original host may have been the guinea pig or peccary.
Morphology and behavior
Pulex irritans is a holometabolous insect. This insect has a four-part life cycle consisting of eggs, larvae, pupae, and adults. Eggs are shed by the female in the environment and hatch into larvae in about 3-4 days. Larvae feed on organic debris in the environment. Larvae eventually form pupae, which are in cocoons that are often covered with debris from the environment (sand, pebbles, etc). The larval and pupal stages are completed in about 3-4 weeks when the adults hatch from pupae. When the adults hatch, they must seek out a warm-blooded host for blood meals.
The flea eggs are about 0.5 mm in length. They are oval shaped and pearly white in color. Eggs are often laid on the body of the host, but they often fall off in many different places. The larvae are approximately 6 mm in length. They are creamy white or yellow in color. Larvae have thirteen segments with bristles on each segment. The larvae will feed on a variety of organic debris. The pupa are approximately 4 x 2 mm. After undergoing three separate molts the larvae will emerge as adults. If conditions are unfavorable, a cocooned flea can remain dormant for up to a year in the pupal phase. 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 piercing-sucking mouthparts that aid in feeding on the host’s blood. Both genal and pronotal combs are absent and the adult flea has a rounded head. Most fleas are distributed in the egg, larva, or pupa stages.
Relationship with host
Direct effects of bites
Fleas are a pest species to their hosts, causing an itching sensation that results in discomfort and leads to scratching in the vicinity of the bite. Flea bites generally cause the skin to raise, swell and itch. The bite site has a single puncture point in the center. Bites often appear in clusters or small rows and can remain inflamed for up to several weeks.
This species bites many species of mammals and birds, including domesticated ones. It has been found on dogs and wild canids, monkeys in captivity, opossums, domestic cats, wild felids in captivity, chickens, black rats and Norwegian rats, wild rodents, pigs, free-tailed bats, and other species. It can also be an intermediate host for the cestode Dipylidium caninum.
Fleas can spread rapidly and move between areas to include eyebrows, eyelashes, and pubic regions.
Hair loss as a result of itching is common, especially in wild and domestic animals. Anemia is also possible in extreme cases of high-volume infestations.
Plague is a disease that affects humans and other mammals. It is caused by the bacterium, Yersinia pestis. The human flea is capable of being a carrier of the plague bacterium. Plague is infamous for killing millions of people in Europe during the Middle Ages. Without prompt treatment, the disease can cause serious illness or death. Today, human plague infections continue to occur in the western United States, but significantly more cases occur in parts of Africa and Asia.
There are three forms of plague that can be transmitted to humans: bubonic plague, septicemic plague, and pneumonic plague. Bubonic plague causes patients to develop sudden onset of fever, headache, chills, and weakness and one or more swollen, tender and painful lymph nodes (called buboes). This form usually results from the bite of an infected flea. The bacteria multiply in the lymph node closest to where the bacteria entered the human body. If the patient is not treated with the appropriate antibiotics, the bacteria can spread to other parts of the body. When symptomatic of septicemic plague, patients develop fever, chills, extreme weakness, abdominal pain, shock, and possibly bleeding into the skin and other organs. Skin and other tissues may turn black and die, especially on fingers, toes, and the nose. Septicemic plague can occur as the first symptom of plague, or may develop from untreated bubonic plague. Pneumonic plague results in patients developing fever, headache, weakness, and a rapidly developing pneumonia with shortness of breath, chest pain, cough, and sometimes bloody or watery mucous. Pneumonic plague may develop from inhaling infectious droplets or may develop from untreated bubonic or septicemic plague after the bacteria spread to the lungs. The pneumonia may cause respiratory failure and shock. Pneumonic plague is the most serious form of the disease and is the only form of plague that can be spread from person to person (by infectious droplets).
Treatment of plague
Plague is a very serious illness, but is treatable with commonly available antibiotics. The earlier a patient seeks medical care and receives treatment that is appropriate for plague, the better their chances are of a full recovery.
People in close contact with very sick pneumonic plague patients may be evaluated and possibly placed under observation. Preventive antibiotic therapy lmay also be given, depending on the type and timing of personal contact.
Treatment and prevention
Common treatments include body shaving and medicated shampoos and combing. When preventing fleas, it is important to treat both the host and the environment. Household pets should be treated to prevent being infested. Carpets, and other floor surfaces, should be shampooed and vacuumed regularly to prevent fleas. When dealing with an infestation, bedding and clothing that may have been exposed should be washed thoroughly in hot water and kept away from other materials that have not been exposed. In extreme cases, extermination by a professional is necessary.
- Michael F. Whiting, Alison S. Whiting, Michael W. Hastriter & Katharina Dittmar (2008). "A molecular phylogeny of fleas (Insecta: Siphonaptera): origins and host associations" (PDF). Cladistics 24 (5): 1–31. doi:10.1111/j.1096-0031.2008.00211.x.
- Paul C. Buckland & Jon P. Sadler (1989). "A biogeography of the human flea, Pulex irritans L. (Siphonaptera: Pulicidae)". Journal of Biogeography 16 (2): 115–120. doi:10.2307/2845085. JSTOR 2845085.