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PubMed1984

[Pediculus humanus capitis: a municipal antiparasite campaign among school children].

The results of a prevalence survey of lice and a control program in the primary schools of a city in the Barcelona metropolitan area (Spain) are presented. Crude prevalence was 6.10%, standard deviation 2.66. In another survey three months later, prevalence was 1.92%. Differences among school grades had fallen. Higher infestation levels were found between third and sixth grades.

Child↗
PubMed1995

A resistance of head lice (Pediculus capitis) to permethrin in Czech Republic.

An outbreak of pediculosis at primary schools was recorded in the Czech Republic in 1992. Almost 20% of children in some schools were infested. This outbreak can be attributed to the resistance of head lice to permethrin, which has not been mentioned in literature yet. The resistance factors established in three towns range between 2 and 385 and between 5 and 557 for LC50 and LC90 values, respectively. This resistance has developed after exclusive use of pyrethroids lotion and shampoo in the Czech Republic since 1978, and it was accompanied by a cross-resistance to d-phenothrin and bioalethrin. But the susceptibility of head lice to malathion and pirimiphos-methyl in 1992 was very similar to that found in 1981. The lotion containing 0.3% of malathion (Diffusil H92 M) has been fully effective against the resistant lice. When introduced into the practice, it quickly reduced the infestation of children in primary schools. The other lotion and shampoo containing 0.3% and 0.7% of pirimiphos-methyl respectively were found to be effective as well.

Adolescent↗
PubMedDate not supplied

[The taxonomy of human head and body lice].

The paper considers the systematic points and nomenclature of the genus Pediculus lice. On the basis of some biological and environmental features, it provides evidence for species-specific independence of head and body lice. The morphological identity and reproductive insulating property allow one to subsume them under the heading of double species. In accordance with the International Code of Zoological Nomenclature, the names of Pediculus humanus L., 1758, and Pediculus corporis De Geer, 1778, are proposed for head and body lice, respectively.

Animals↗
PubMedDate not supplied

[Tests for evaluating the effectiveness of pediculicides: importance and limitations].

The obligation to prove pediculicides efficacy is relatively recent. Two tests are required by the authorities to obtain registration. In vitro test (with Pediculus humanus humanus) is the first step to evaluate the efficacy of new molecules. It must be followed by bio-clinical tests (with infested children by Pediculus humanus capitis). For those tests the authors advise to respect the "three units rule": unit of time (no more than 2 days for the test), unit of place (same environment) and unit of action (only one team to apply and evaluate products). This type of tests is possible only in countries with high infestation (at least 60% of prevalence). A third test is consequently advised, the ex vivo test using Pediculus humanus capitis obtained from infested children in France. This test can be useful also to re-evaluate current products in the light of increased resistance or decreased sensitivity of the lice. Finally some other tests can be advised to prove some other activities like remanence or repellent properties or to estimated lice resistance.

Evaluation Studies as Topic↗
PubMed2004

Pediculosis.

The 3 major lice that infest humans are Pediculus humanus capitis (head louse), Pthirus pubis (crab louse), and Pediculus humanus humanus (body louse). Patients with louse infestation present with scalp pruritus, excoriations, cervical lymphadenopathy, and conjunctivitis. A hypersensitivity rash, or pediculid, may mimic a viral exanthem. Head lice infestation crosses all economic and social boundaries, whereas body lice infestation preferentially affects the homeless and displaced. Body lice are major vectors of diseases such as typhus, trench fever, and relapsing fever. Pubic lice infestation often is acquired as a sexually transmitted disease and may be a marker to screen for other sexually transmitted diseases. Treatment of louse infestation can be challenging. Mechanical measures, such as combing, are helpful as adjunctive measures, but most studies suggest they are not as effective as chemical agents. Resistance to chemical agents is a growing problem. Major types of resistance include knock-down resistance, glutathione-S-transferase-based resistance, and monooxygenase-based resistance. Research is needed to identify new effective treatments.

Animals↗
PubMed2007

Evolutionary relationships of "Candidatus Riesia spp.," endosymbiotic enterobacteriaceae living within hematophagous primate lice.

The primary endosymbiotic bacteria from three species of parasitic primate lice were characterized molecularly. We have confirmed the characterization of the primary endosymbiont (P-endosymbiont) of the human head/body louse Pediculus humanus and provide new characterizations of the P-endosymbionts from Pediculus schaeffi from chimpanzees and Pthirus pubis, the pubic louse of humans. The endosymbionts show an average percent sequence divergence of 11 to 15% from the most closely related known bacterium "Candidatus Arsenophonus insecticola." We propose that two additional species be added to the genus "Candidatus Riesia." The new species proposed within "Candidatus Riesia" have sequence divergences of 3.4% and 10 to 12% based on uncorrected pairwise differences. Our Bayesian analysis shows that the branching pattern for the primary endosymbionts was the same as that for their louse hosts, suggesting a long coevolutionary history between primate lice and their primary endosymbionts. We used a calibration of 5.6 million years to date the divergence between endosymbionts from human and chimpanzee lice and estimated an evolutionary rate of nucleotide substitution of 0.67% per million years, which is 15 to 30 times faster than previous estimates calculated for Buchnera, the primary endosymbiont in aphids. Given the evidence for cospeciation with primate lice and the evidence for fast evolutionary rates, this lineage of endosymbiotic bacteria can be evaluated as a fast-evolving marker of both louse and primate evolutionary histories.

Animals↗
PubMed2006

Permethrin-resistant head lice (Anoplura: Pediculidae) in Argentina are susceptible to spinosad.

The insecticidal activity of spinosad was evaluated against susceptible and permethrin-resistant human lice. In a permethrin-susceptible strain of the body louse, Pediculus humanus humanus L. (Anoplura: Pediculidae), the toxicity of spinosad was similar to that established for permethrin, with an LD50 value of 1.2 ng/insect and 2.4 ng/insect, respectively. Topical application of spinosad to populations of permethrin-resistant head louse, Pediculus humanus capitis De Geer (Anoplura: Pediculidae), showed that susceptibility to spinosad was independent of resistance to permethrin. The effectiveness of spinosad against human lice and the low mammalian toxicity reported in the literature suggest that spinosad could be useful for the management of permethrin-resistant human lice.

Animals↗
PubMed2006

[Pediatric head lice: taxonomy, incidence, resistance, delousing].

Based on the current knowledge, head louse (Pediculus capitis) and body louse (Pediculus humanus) are two different species that infest specific parts of the human body and do not interbreed in vivo. In 1991-2002, 6 257 cases of pediculosis were reported in the Czech Republic while 3 138 000 pediculicide packagings, i.e. about 500 times as many as the number of cases, were marketed. Between October 2004 and February 2005, a total of 531 children aged between 6 and 15 years from 16 selected schools in the Zlín and Olomouc regions were screened by dry hair combing. Living lice were detected in 14.1% of the enrolled children and dead nits alone were observed in other 9.8% of the subjects. In vitro tests revealed that the collected head lice were highly resistant to malathion, the active ingredient of Diffusil H 92 M. The number of reported cases of pediculosis roughly doubled in 2005.

Adolescent↗
PubMed1995

[The epidemiological significance of human lice in relation to the characteristics of their parasitism].

Epidemiological significance of clothes and head louse is determined first of all by the type of "parasite-host" connection. Clothes louse has an immediate contact with man only during bloodsucking, it dwells in clothes, consumes big portions of blood and has great productivity. Temperature factor is very important for Pediculus corporis. If the man's temperature is growing the louse will abandon him. The comparison of various literature data and proper author's information has shown that Pediculus capitis didn't play a significant role in epidemic typhoid malady taking into account the modern level of the affection of population with head lice. The author describes the peculiarities of morphology, biology, population dynamics, parasitology and epidemiology of P. capitis and P. corporis.

Animals↗
PubMed2003

An experimental model of human body louse infection with Rickettsia typhi.

Murine (endemic) typhus caused by Rickettsia typhi, one of the most widely distributed arthropod-borne diseases, is transmitted to humans mainly by the oriental rat flea. The human body louse, Pediculus humanus corporis, has been suspected to have a role in the transmission of R. typhi to humans. To evaluate the potential role of Pediculus humanus corporis as a vector of murine typhus, we used R. typhi in an experimental model of human body louse infection previously used with R. prowazekii. A rabbit was made bacteremic by inoculating it with 2 x 10(6) plaque-forming units of R. typhi; it remained bacteremic for at least 59 hours. Two hundred body lice infected by feeding on the bacteremic rabbit were compared to 200 uninfected control lice. Each louse population was fed once a day on the abdomen of a seronegative rabbit. On day 8 post-infection, as a result of disruption of the gut cells and leakage of the blood meal into the hemolymph, four infected lice became bright red and died within four hours. The life span of infected lice was 20 days less than that of the controls. Infected lice did not transmit R. typhi to their progeny (eggs and larvae) as demonstrated by PCR amplification and cell culture. With an immunofluorescence assay, R. typhi was detected in feces from day 7 post-infection, and the organism remained viable in feces for up to 80 days as demonstrated by cell culture. From the 21st day post-infection, the rabbit used to feed the R. typhi-infected lice developed an immunoglobulin response with a titer of 1:50 increasing to 1:200 at the 42nd day post-infection. It showed no clinical signs of infection. The rabbit that was used to feed uninfected lice remained seronegative. Although body lice are not clearly identified vectors of R. typhi, it seems that under certain circumstances they could transmit R. typhi.

Animals↗