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Results for “Pediculus”

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At least 307 records · Page 17Linked to original sources
PubMed1983

Feeding strategy and the mechanics of blood sucking in insects.

As a means of exploring foraging strategies of blood-feeding insects, we studied the mechanics of blood feeding. We develop a mechanistic model for the dynamics of non-Newtonian fluid flow to describe the feeding process for blood feeders. Using available feeding and morphological data, we examine the relationship of feeding time to proboscis design, and consider optimal foraging strategies for blood feeders. Because of the flow rates typical of many blood feeders, the non-Newtonian nature of blood is of little importance for flow dynamics. Observed feeding times and flow rates do not necessarily reflect the energy requirements for feeding. The radius of the food canal is the major morphological determinant of flow dynamics. Feeding time is a monotonically increasing function of blood hematocrit. There is an optimal blood hematocrit of 0.3 which maximizes the rate of total protein intake for blood feeders, regardless of the energy output or proboscis design. This hematocrit level is typical of humans with blood parasite infections. In contrast, the rate of red blood cell intake is maximized at a hematocrit of 0.4. We argue that the existence of such optima may be a general consequence of the mechanics of feeding on nutrients dissolved or suspended in a fluid medium. Results are discussed in relation to foraging strategy, proboscis design, and the coevolution among host, vector, and parasite in blood feeding insects.

Aedes↗
PubMed1991

Clinical observations related to head lice infestation.

Living lice and eggs were found in 19% of 2643 children examined in Israel. Boys and girls were equally infested. Bite reactions, pruritus, excoriations, lymphadenopathy, and conjunctivitis were the most common signs and symptoms. Bite reactions, pruritus, excoriations, and conjunctivitis were found more frequently in infested children than in noninfested children. Lymphadenopathy, eczema, influenza, herpes, crusts behind ears, blepharitis, seborrhea, psoriasis, erythema, vitiligo, secondary infections, and scars were equally common in both groups. The sequence of the skin reactions of a volunteer to continuous exposure to lice bites was as follow: phase I, no clinical symptoms; phase II, papules accompanied by pruritus of medium intensity; phase III, wheal formation immediately after the bite, followed by a delayed papular reaction and intense itching; phase IV, papular reaction with diminished reactivity of the skin and mild pruritus. Healed bite reactions reappeared when other parts of the skin were again exposed to the lice.

Animals↗
PubMedDate not supplied

Ectoparasitic sexually transmitted diseases: scabies and pediculosis.

Scabies and pediculosis are diagnosed on an almost daily basis in many dermatology offices. Whether the patient seeks medical attention because of the often unbearable itch of scabies or because of the fear of lice infestations, the physician should be on the lookout for these ectoparasitic infestations. Secondary bacterial infection, resistance to medication, and the risk of spread of the infestations to family members and other close contacts may complicate the problem. Patients frequently have to battle the myths, prejudices, and even shame that are associated with such infestations.

Animals↗
PubMed2005

Head lice: scientific assessment of the nit sheath with clinical ramifications and therapeutic options.

Head lice, like many insects, produce a protective coating for their newly laid eggs that is essential to the survival of the species. Knowledge of the composition of the sheath, which is the glue by which the egg is attached to human hair, and the nit laying process could lead to production of agents that could be used to attack louse infestations by interfering with the normally protected environment of nymph development within the egg. The physical removal of nits has become an important part of treatment of head louse infestations given the "no-nit" policy in schools. Biochemical analysis has revealed that the nit sheath of the head louse is composed of 4 bands of protein, possibly cross-linked to aliphatic components with a tertiary structure of beta sheeting. Nature has protected the louse by making the nit sheath similar in composition to the hair; thereby, agents designed to unravel the nit sheath may also damage human hair. Possible targets to destroy the nit sheath include proteases, denaturants, beta sheet breaker proteins, and small protein inhibitors of sheath formation. Better understanding of insect glues may allow us to develop compounds so that the liquid secretions of the collateral glands of the female louse, which becomes the nit sheath, do not solidify by oxidation when placed with the louse egg onto human hair. Knowledge of insect behavior, such as oviposition, may also suggest methods for repelling female lice from laying eggs onto hair. Alternatively, agents that coat the nits and restrict the oxygen transfer to the developing larvae may prove beneficial.

Animals↗
PubMed2005

Nit picking.

Explore the source record for details and available documents.

Animals↗
PubMed2006

Fomite transmission in head lice.

Control of various infestations requires an accurate understanding of transmission. After thousands of years of lice infestation, scientific documentation of indirect contact transmission has been substantiated. Lice can be transferred in the egg, instar, and adult stages. Lice have now been shown in the laboratory to be readily dislodged by air movements such as blow-drying one's hair, combing, and toweling. Moreover, passive transfer to adjoining fabric is also frequently observed. Louse transmission by fomites occurs more frequently than has been commonly believed. Close proximity suffices to increase the likeliness of a new infestation. Thus louse control measures should take account of fomite transmission and include screening of all individuals within an infested person's immediate circle of contact, laundering of everything within the infested individuals' bed or quarantining of such material for 10 days, thorough vacuuming of floors, carpets, upholstery, with a standard vacuum cleaner.

Animals↗
PubMed2005

Exclusion of ill children from child-care centers in Israel.

The aim of the study was to examine criteria for ill children in child-care centers. A questionnaire on practices of exclusion/return of children according to specific signs and symptoms was mailed to the directors of care centers in central Israel. Thirty-six of the 60 questionnaires (60%) were returned by mail and the reminded were completed in personal visits to the CCCs achieving a response rate of 100%. About half (51.7%) used "common sense" and "personal feelings" to exclude children and to allow their return, and 29 (48.3%) used the guidelines of the Ministries of Education and Health or other authorities. The percentage of centers excluding children by signs/symptoms was as follows: high fever (>38 degrees C), 100%; low-grade fever, 76.7%; asthma exacerbation, 80.0%; heavy cough, 75.0%; eye discharge or conjunctivitis, 83.3%; diarrhea and vomiting more than twice per day, 100%; rash, 72.3%; otalgia, 46.7%; and infected skin lesion, 66.7%. Only four centers excluded children with head lice. Most centers required a physician's note on return of a child after high fever (76.7%), eye discharge or conjunctivitis (48.3%), and from 75 to 80%, respectively, for frequent vomiting and bloody or mucinous diarrhea. The results show that exclusion practices among child-care centers (CCCs) vary widely, suggesting the need for the establishment of a uniform exclusion and return policy in Israel, with distribution of clear, up-to-date guidelines on the prevention and control of communicable diseases to all day-care centers. In a simple way, this study identified attitudes concerning the exclusion/return of sick children in CCCs and was useful for the discussion of the related policy with CCCs responsible and national health and educational authorities.

Absenteeism↗
PubMedDate not supplied

Pediculosis capitis.

Pediculosis capitis is a worldwide public health concern. Infestation occurs most commonly in children, with a peak incidence between 5 to 11 years of age. The condition is more common in girls and less common in Black children. Direct head-to-head contact is the most common mode of transmission. Pruritus is the most common symptom of infestation. The gold standard for diagnosing pediculosis capitis is finding a live louse or nymph in the scalp or viable egg in the scalp hair. Pediculicides are the most effective treatment. All household members and close contacts should be examined and treated concurrently if infested. The child should be allowed to return to school or to a child care facility after proper treatment. The child should be discouraged from close, direct head contact with others or from sharing items that have come in contact with the hair.

Animals↗
PubMed2001

Mutualists and parasites: how to paint yourself into a (metabolic) corner.

Eukaryotes have developed an elaborate series of interactions with bacteria that enter their bodies and/or cells. Genome evolution of symbiotic and parasitic bacteria multiplying inside eukaryotic cells results in both convergent and divergent changes. The genome sequences of the symbiotic bacteria of aphids, Buchnera aphidicola, and the parasitic bacteria of body louse and humans, Rickettsia prowazekii, provide insights into these processes. Convergent genome characteristics include reduction in genome sizes and lowered G+C content values. Divergent evolution was recorded for amino acid and cell wall biosynthetic genes. The presence of pseudogenes in both genomes provides examples of recent gene inactivation events and offers clues to the process of genome deterioration and host-cell adaptation.

Adaptation, Physiological↗
PubMed2000

Comparison of wet combing with malathion for treatment of head lice in the UK: a pragmatic randomised controlled trial.

BACKGROUND: Concern about the effectiveness and toxicity of insecticide lotions has led to promotion of mechanical methods to remove head lice. We compared the effectiveness of "bug-busting" (wet combing with a fine-toothed comb) and malathion lotion. METHODS: We screened 4037 schoolchildren in two counties in Wales, UK (intermediate resistance to malathion). Of 167 found to have head lice, 81 (aged 3-14 years) were eligible to participate in a randomised controlled trial that compared mechanical removal of lice by a commercial kit every 3-4 days for 2 weeks with two applications of 0.5% malathion lotion 7 days apart; parents carried out both treatments. The outcome measure was the presence of live lice 7 days after the end of treatment. Analyses were by intention to treat. FINDINGS: 74 children completed the study and 72 were included in the analysis. The cure rate was 38% (12 of 32) for bug-busting and 78% (31 of 40) for malathion. Children assigned bug-busting were 2.8 (95% CI 1.5-5.2) times more likely than those assigned malathion to have lice at the end of treatment (p=0.0006). INTERPRETATION: Malathion lotion was twice as effective as bug-busting, even in an area with intermediate resistance. Policies advocating bug-busting as first-line treatment for head lice in the general population are inappropriate. Assessment of the outcome of treatment 1-2 weeks after completion is essential for successful management. Only about 50% of participants complied fully with treatment, so future trials should be pragmatic in design, avoid false incentives, and study representative samples of children.

Adolescent↗