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Maria Ines Picollo - One of the best experts on this subject based on the ideXlab platform.
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Mouthpart sensory structures of the human head louse Pediculus Humanus Capitis
Arthropod structure & development, 2020Co-Authors: Isabel Ortega-insaurralde, Maria Ines Picollo, Romina B. BarrozoAbstract:Abstract Head lice are exclusive human parasitic blood-sucking insects. Distributed worldwide among school-age children, this parasitosis generates scalp irritation and sometimes social prejudice. Understanding how head lice detect and perceive their human hosts is crucial to control transmission. Here, we describe the sensory structures present on the mouthparts of Pediculus Humanus Capitis and their possible contribution to the feeding decision-making process. On the anterior zone of the clypeus around the haustellum two morphological types of sensilla, invariable in location and number, were identified: fourteen short clypeus bristles (SCB) and six long clypeus bristles (LCB). During feeding these structures contact the host skin but not its blood. Located antero-dorsally on the everted haustellum and between the epipharyngeal teeth, a third sensillar type was identified: about four short peg epipharyngeal (SPE) sensilla. These structures are bathed with the incoming blood, when head lice feed, so may have a gustatory role. In behavioural experiments antennectomy of lice did not interfere with feeding behaviour, suggesting that the sensory structures on the mouthparts could be involved in host assessment.
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the sensory machinery of the head louse Pediculus Humanus Capitis from the antennae to the brain
Frontiers in Physiology, 2019Co-Authors: Isabel Ortega Insaurralde, Sebastian Minoli, Ariel Ceferino Toloza, Maria Ines Picollo, Romina B. BarrozoAbstract:: Insect antennae are sophisticated sensory organs, usually covered with sensory structures responsible for the detection of relevant signals of different modalities coming from the environment. Despite the relevance of the head louse Pediculus Humanus Capitis as a human parasite, the role of its antennal sensory system in the highly dependent relation established with their hosts has been barely studied. In this work, we present a functional description of the antennae of these hematophagous insects by applying different approaches, including scanning electron microscopy (SEM), anterograde antennal fluorescent backfills, and behavioral experiments with intact or differentially antennectomized lice. Results constitute a first approach to identify and describe the head louse antennal sensilla and to determine the role of the antenna in host recognition. SEM images allowed us to identify a total of 35-40 sensilla belonging to seven different morphological types that according to their external architecture are candidates to bear mechano-, thermo-, hygro-, or chemo-receptor functions. The anterograde backfills revealed a direct neural pathway to the ipsilateral antennal lobe, which includes 8-10 glomerular-like diffuse structures. In the two-choice behavioral experiments, intact lice chose scalp chemicals and warm surfaces (i.e., 32°C) and avoided wet substrates. Behavioral preferences disappeared after ablation of the different flagellomeres of their antenna, allowing us to discuss about the location and function of the different identified sensilla. This is the first study that integrates morphological and behavioral aspects of the sensory machinery of head lice involved in host perception.
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response of Pediculus Humanus Capitis phthiraptera pediculidae to volatiles of whole and individual components of the human scalp
Journal of Medical Entomology, 2018Co-Authors: F G Galassi, Ariel Ceferino Toloza, Maria Ines Picollo, Georgina Fronza, Paola GonzalezaudinoAbstract:The head louse Pediculus Humanus Capitis (De Geer) (Phthiraptera: Pediculidae) is a cosmopolitan human ectoparasite causing pediculosis, one of the most common arthropod parasitic conditions of humans. The mechanisms and/or chemicals involved in host environment recognition by head lice are still unknown. In this study, we evaluated the response of head lice to volatiles that emanate from the human scalp. In addition, we identified the volatile components of the odor and evaluated the attractive or repellent activity of their pure main components. The volatiles were collected by means of Solid Phase microextraction and the extract obtained was chemically analyzed by gas chromatograph-mass spectrometer. Twenty-four volatile were identified in the human scalp odor, with the main compounds being the following: nonanal, sulcatone, geranylacetone, and palmitic acid. Head lice were highly attracted by the blend human scalp volatiles, as well as by the individual major components. A significant finding of our study was to demonstrate that nonanal activity depends on the mass of the compound as it is repellent at high concentrations and an attractant at low concentrations. The results of this study indicate that head lice may use chemical signals in addition to other mechanisms to remain on the host.
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Effect of Environmental Conditions and Toxic Compounds on the Locomotor Activity of Pediculus Humanus Capitis (Phthiraptera: Pediculidae)
Journal of medical entomology, 2015Co-Authors: Isabel Ortega-insaurralde, Ariel Ceferino Toloza, Paola Gonzalez Audino, G. Mougabure Cueto, A. Alvarez-costa, Gonzalo Roca-acevedo, Maria Ines PicolloAbstract:In this work, we evaluated the effect of environmental variables such as temperature, humidity, and light on the locomotor activity of Pediculus Humanus Capitis. In addition, we used selected conditions of temperature, humidity, and light to study the effects of cypermethrin and N,N-diethyl-3-methylbenzamide (DEET) on the locomotor activity of head lice. Head lice increased their locomotor activity in an arena at 30°C compared with activity at 20°C. When we tested the influence of the humidity level, the locomotor activity of head lice showed no significant differences related to humidity level, both at 30°C and 20°C. Concerning light influence, we observed that the higher the intensity of light, the slower the movement of head lice. We also demonstrated that sublethal doses of toxics may alter locomotor activity in adults of head lice. Sublethal doses of cypermethrin induced hyperactivated responses in adult head lice. Sublethal doses of DEET evocated hypoactivated responses in head lice. The observation of stereotyped behavior in head lice elicited by toxic compounds proved that measuring locomotor activity in an experimental set-up where environmental conditions are controlled would be appropriate to evaluate compounds of biological importance, such as molecules involved in the host-parasite interaction and intraspecific relationships.
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Toloza et al. Bioactivity of Argentinean essential oils against permethrinresistant head lice, Pediculus Humanus Capitis
2013Co-Authors: Ariel Ceferino Toloza, Julio A. Zygadlo, O Biurrun, Alicia Rotman, Maria Ines PicolloAbstract:Infestation with the head louse, Pediculus Humanus Capitis De Geer (Phthiraptera: Pediculidae), is one of the most common parasitic infestation of humans worldwide. Traditionally, the main treatment for control of head lice is chemical control that is based in a wide variety of neurotoxic synthetic insecticides. The repeated overuse of these products has resulted in the selection of resistant populations of head lice. Thus, plant-derived insecticides, such as the essential oils seem to be good viable alternatives as some have low toxicity to mammals and are biodegradable. We determined the insecticidal activity of 25 essential oils belonging to several botanical families present in Argentina against permethrin-resistant head lice. Significant differences in fumigant activity against head lice were found among the essential oils from the native and exotic plant species. The most effective essential oils were Cinnamomum porphyrium, followed by Aloysia citriodora (chemotype 2) and Myrcianthes pseudomato, with KT50 values of 1.12, 3.02 and 4.09; respectively. The results indicate that these essential oils are effective and could be incorporated into pediculicide formulations to control head lice infestations once proper formulation an
Ariel Ceferino Toloza - One of the best experts on this subject based on the ideXlab platform.
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the sensory machinery of the head louse Pediculus Humanus Capitis from the antennae to the brain
Frontiers in Physiology, 2019Co-Authors: Isabel Ortega Insaurralde, Sebastian Minoli, Ariel Ceferino Toloza, Maria Ines Picollo, Romina B. BarrozoAbstract:: Insect antennae are sophisticated sensory organs, usually covered with sensory structures responsible for the detection of relevant signals of different modalities coming from the environment. Despite the relevance of the head louse Pediculus Humanus Capitis as a human parasite, the role of its antennal sensory system in the highly dependent relation established with their hosts has been barely studied. In this work, we present a functional description of the antennae of these hematophagous insects by applying different approaches, including scanning electron microscopy (SEM), anterograde antennal fluorescent backfills, and behavioral experiments with intact or differentially antennectomized lice. Results constitute a first approach to identify and describe the head louse antennal sensilla and to determine the role of the antenna in host recognition. SEM images allowed us to identify a total of 35-40 sensilla belonging to seven different morphological types that according to their external architecture are candidates to bear mechano-, thermo-, hygro-, or chemo-receptor functions. The anterograde backfills revealed a direct neural pathway to the ipsilateral antennal lobe, which includes 8-10 glomerular-like diffuse structures. In the two-choice behavioral experiments, intact lice chose scalp chemicals and warm surfaces (i.e., 32°C) and avoided wet substrates. Behavioral preferences disappeared after ablation of the different flagellomeres of their antenna, allowing us to discuss about the location and function of the different identified sensilla. This is the first study that integrates morphological and behavioral aspects of the sensory machinery of head lice involved in host perception.
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response of Pediculus Humanus Capitis phthiraptera pediculidae to volatiles of whole and individual components of the human scalp
Journal of Medical Entomology, 2018Co-Authors: F G Galassi, Ariel Ceferino Toloza, Maria Ines Picollo, Georgina Fronza, Paola GonzalezaudinoAbstract:The head louse Pediculus Humanus Capitis (De Geer) (Phthiraptera: Pediculidae) is a cosmopolitan human ectoparasite causing pediculosis, one of the most common arthropod parasitic conditions of humans. The mechanisms and/or chemicals involved in host environment recognition by head lice are still unknown. In this study, we evaluated the response of head lice to volatiles that emanate from the human scalp. In addition, we identified the volatile components of the odor and evaluated the attractive or repellent activity of their pure main components. The volatiles were collected by means of Solid Phase microextraction and the extract obtained was chemically analyzed by gas chromatograph-mass spectrometer. Twenty-four volatile were identified in the human scalp odor, with the main compounds being the following: nonanal, sulcatone, geranylacetone, and palmitic acid. Head lice were highly attracted by the blend human scalp volatiles, as well as by the individual major components. A significant finding of our study was to demonstrate that nonanal activity depends on the mass of the compound as it is repellent at high concentrations and an attractant at low concentrations. The results of this study indicate that head lice may use chemical signals in addition to other mechanisms to remain on the host.
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Effect of Environmental Conditions and Toxic Compounds on the Locomotor Activity of Pediculus Humanus Capitis (Phthiraptera: Pediculidae)
Journal of medical entomology, 2015Co-Authors: Isabel Ortega-insaurralde, Ariel Ceferino Toloza, Paola Gonzalez Audino, G. Mougabure Cueto, A. Alvarez-costa, Gonzalo Roca-acevedo, Maria Ines PicolloAbstract:In this work, we evaluated the effect of environmental variables such as temperature, humidity, and light on the locomotor activity of Pediculus Humanus Capitis. In addition, we used selected conditions of temperature, humidity, and light to study the effects of cypermethrin and N,N-diethyl-3-methylbenzamide (DEET) on the locomotor activity of head lice. Head lice increased their locomotor activity in an arena at 30°C compared with activity at 20°C. When we tested the influence of the humidity level, the locomotor activity of head lice showed no significant differences related to humidity level, both at 30°C and 20°C. Concerning light influence, we observed that the higher the intensity of light, the slower the movement of head lice. We also demonstrated that sublethal doses of toxics may alter locomotor activity in adults of head lice. Sublethal doses of cypermethrin induced hyperactivated responses in adult head lice. Sublethal doses of DEET evocated hypoactivated responses in head lice. The observation of stereotyped behavior in head lice elicited by toxic compounds proved that measuring locomotor activity in an experimental set-up where environmental conditions are controlled would be appropriate to evaluate compounds of biological importance, such as molecules involved in the host-parasite interaction and intraspecific relationships.
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Toloza et al. Bioactivity of Argentinean essential oils against permethrinresistant head lice, Pediculus Humanus Capitis
2013Co-Authors: Ariel Ceferino Toloza, Julio A. Zygadlo, O Biurrun, Alicia Rotman, Maria Ines PicolloAbstract:Infestation with the head louse, Pediculus Humanus Capitis De Geer (Phthiraptera: Pediculidae), is one of the most common parasitic infestation of humans worldwide. Traditionally, the main treatment for control of head lice is chemical control that is based in a wide variety of neurotoxic synthetic insecticides. The repeated overuse of these products has resulted in the selection of resistant populations of head lice. Thus, plant-derived insecticides, such as the essential oils seem to be good viable alternatives as some have low toxicity to mammals and are biodegradable. We determined the insecticidal activity of 25 essential oils belonging to several botanical families present in Argentina against permethrin-resistant head lice. Significant differences in fumigant activity against head lice were found among the essential oils from the native and exotic plant species. The most effective essential oils were Cinnamomum porphyrium, followed by Aloysia citriodora (chemotype 2) and Myrcianthes pseudomato, with KT50 values of 1.12, 3.02 and 4.09; respectively. The results indicate that these essential oils are effective and could be incorporated into pediculicide formulations to control head lice infestations once proper formulation an
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eucalyptus essential oil toxicity against permethrin resistant Pediculus Humanus Capitis phthiraptera pediculidae
Parasitology Research, 2010Co-Authors: Ariel Ceferino Toloza, Hector Masuh, Alejandro Lucia, Eduardo Zerba, Maria Ines PicolloAbstract:During the past decades, chemical control against the head louse Pediculus Humanus Capitis De Geer has been based in the application of products containing permethrin. The repetitive overuse of pediculicides has resulted in the development of high levels of resistance to one or more of these products worldwide. Essential oils obtained from aromatic plants like Eucalyptus are good and safe alternatives due to their low toxicity to mammals and easy biodegradability. In the present study, we reported the chemical composition of Eucalyptus dunnii and Eucalyptus gunni, and the fumigant activity of five Eucalyptus essential oils and their main compounds against permethrin-resistant head lice from Argentina. The most effective essential oils were Eucalyptus sideroxylon, Eucalyptus globulus ssp globulus, and Eucalyptus globulus ssp maidenii, with knockdown time 50% (KT50) values of 24.75, 27.73, and 31.39 min. A linear regression analysis between percentage of 1,8-Cineole and KT50 values of the essential oils showed a significant correlation at a p < 0.01. Since Eucalyptus essential oils showed to be effective against head lice and are classified as safer compounds, they can be employed into pediculicide formulations.
Eduardo Zerba - One of the best experts on this subject based on the ideXlab platform.
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eucalyptus essential oil toxicity against permethrin resistant Pediculus Humanus Capitis phthiraptera pediculidae
Parasitology Research, 2010Co-Authors: Ariel Ceferino Toloza, Hector Masuh, Alejandro Lucia, Eduardo Zerba, Maria Ines PicolloAbstract:During the past decades, chemical control against the head louse Pediculus Humanus Capitis De Geer has been based in the application of products containing permethrin. The repetitive overuse of pediculicides has resulted in the development of high levels of resistance to one or more of these products worldwide. Essential oils obtained from aromatic plants like Eucalyptus are good and safe alternatives due to their low toxicity to mammals and easy biodegradability. In the present study, we reported the chemical composition of Eucalyptus dunnii and Eucalyptus gunni, and the fumigant activity of five Eucalyptus essential oils and their main compounds against permethrin-resistant head lice from Argentina. The most effective essential oils were Eucalyptus sideroxylon, Eucalyptus globulus ssp globulus, and Eucalyptus globulus ssp maidenii, with knockdown time 50% (KT50) values of 24.75, 27.73, and 31.39 min. A linear regression analysis between percentage of 1,8-Cineole and KT50 values of the essential oils showed a significant correlation at a p < 0.01. Since Eucalyptus essential oils showed to be effective against head lice and are classified as safer compounds, they can be employed into pediculicide formulations.
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Evidence of Pyrethroid Resistance in Eggs of Pediculus Humanus Capitis (Phthiraptera: Pediculidae) from Argentina
Journal of Medical Entomology, 2008Co-Authors: Gastón Mougabure Cueto, Eduardo Zerba, Maria Ines PicolloAbstract:Insecticide resistance in Pediculus Humanus Capitis De Geer 1778 (Phthiraptera: Pediculidae) from different countries has been well documented in the last years. Otherwise, little research has been reported about insecticide resistance in insect embryos and none in human louse embryos. In this work, we studied insecticide resistance in eggs of three head lice populations whose pyrethroid resistance was shown in adults and nymphs compared with a susceptible laboratory body louse strain. All head louse populations showed high permethrin resistance in eggs. Levels of permethrin resistance (LCRs) assessed in eggs by immersion technique were higher than those previously reported for the corresponding populations of adults by topical application. Comparison of LCR values for different populations showed that there was a direct relationship between the resistance levels assessed in eggs and those in adults. All permethrin-resistant eggs showed high resistance to d-phenothrin and dichloro-diphenyl-trichloroethane (DDT) and low resistance to carbaryl, which is in common with the resistance profile established for adults and nymphs. The results concerning the high resistance to pyrethroid (permethrin and d-phenothrin) and the cross-resistance to DDT and carbaryl detected in head louse eggs and adults suggested similar resistance mechanisms in eggs and adults of head louse populations from adults.
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Effectiveness of lotions based on essential oils from aromatic plants against permethrin resistant Pediculus Humanus Capitis
Archives of Dermatological Research, 2007Co-Authors: Paola Gonzalez Audino, Eduardo Zerba, Claudia Vassena, Maria Ines PicolloAbstract:In Argentina, field populations of the head louse Pediculus Humanus Capitis De Geer (Phthiraptera: Pediculidae) have developed resistance to permethrin and other pyrethroids. Thus, the aim of this work was the development of a lotion containing essential oils from plants and an alcoholic coadjuvant to improve biological effect. Ethanol + isopropanol (1 + 1 in volume) 50% in water and ethanol 96% were taken as bases for preparation of experimental lotions containing essential oils from plants. We found that experimental lotions containing lavender, peppermint and eucalyptus oils in a 5% composition and the combination of eucalyptus and peppermint in a total concentration of 10%, dissolved in 50% ethanol + isopropanol (1 + 1) in water, showed the best knockdown effect. On the other side, lotion containing peppermint oil and eucalyptus oil (1 + 1) 10%, dissolved in ethanol 96%, showed to be as effective as the best commercial lotion now available in Argentina. Furthermore, addition of 1-dodecanol in all cases increased the effectiveness of all the experimental lotions. This difference is significantly important for 1-dodecanol concentration of 10%, reaching a toxic activity compared to the best commercial lotion available in the market.
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fumigant and repellent properties of essential oils and component compounds against permethrin resistant Pediculus Humanus Capitis anoplura pediculidae from argentina
Journal of Medical Entomology, 2006Co-Authors: Ariel Ceferino Toloza, Gastón Mougabure Cueto, Eduardo Zerba, Julio A. Zygadlo, Fernando Biurrun, Maria Ines PicolloAbstract:The repeated use of permethrin and other insecticides for the control of head lice, Pediculus Humanus Capitis De Geer (Anoplura: Pediculidae), during past decades has resulted in the development of marked levels of resistance. Thus, new alternative insecticides are needed for the control of head lice. We studied the fumigant and repellent properties of essential oils from 16 native and exotic plants in Argentina, and 21 chemical components against permethrin-resistant head lice from Argentina. With a direct vapor-exposure bioassay, the most effective oil was from the native Myrcianthes cisplatensis Cambess (Myrtaceae) with a time to 50% knockdown (KT50) of 1.3 min, followed by exotic species, Eucalyptus cinerea F.V. Muell., Eucalyptus viminalis Labill., and Eucalyptus saligna Smith. with KT50 values of 12.0, 14.9, and 17.4 min, respectively. The most effective components were 1,8-cineole and anisole, with KT50 values of 11.1 and 12.7 min, respectively. Regression analysis of KT50 values and vapor pressures and water-partition coefficients for the essential oil components revealed that the most effective fumigants were among the more volatile components. Repellency assays indicated that the essential oil from Mentha pulegium L. and its benzyl alcohol component were the most effective repellents, having repellency indices of 75.5 and 57.8%, respectively. Thus, some Argentinean plants contain essential oils and components that function as fumigants or as repellents and thereby show potential for development of new control products for head lice.
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The fumigant and repellent activity of aliphatic lactones against Pediculus Humanus Capitis (Anoplura: Pediculidae)
Memorias do Instituto Oswaldo Cruz, 2006Co-Authors: Ariel Ceferino Toloza, Eduardo Zerba, G. Mougabure Cueto, Julio A. Zygadlo, Silvina Mabel Faillaci, Maria Ines PicolloAbstract:New alternative insecticides are necessary for the chemical control of head lice. In this study the fumigant knockdown time 50% (KT50) and repellency index (RI) of three aliphatic lactones was compared with two essential oils and DDVP, against permethrin-resistance Pediculus Humanus Capitis from Argentina. In the fumigant assay, none of the lactones were effective compared to the highest activity of eucalyptus (KT50 15.53 m). In the repellency test, the three lactones were equally or more effective (RI ranging from 60.50 to 76.68) than the positive control (piperonal). These lactones are promising as head lice repellents.
El-sayed H. Shaurub - One of the best experts on this subject based on the ideXlab platform.
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Genetic diversity of the human head lice, Pediculus Humanus Capitis, among primary school girls in Saudi Arabia, with reference to their prevalence
Parasitology Research, 2017Co-Authors: Sarah A. Al-shahrani, Reem A. Alajmi, Tahany H. Ayaad, Mohammed A. Al-shahrani, El-sayed H. ShaurubAbstract:The present work aimed at investigating the genetic diversity of the head louse Pediculus Humanus Capitis ( P. Humanus Capitis ) among infested primary school girls at Bisha governorate, Saudi Arabia, based on the sequence of mitochondrial cytochrome b (mt cyt b) gene of 121 P. Humanus Capitis adults. Additionally, the prevalence of pediculosis Capitis was surveyed. The results of sequencing were compared with the sequence of human head lice that are genotyped previously. Phylogenetic tree analysis showed the presence of 100% identity ( n = 26) of louse specimens with clade A (prevalent worldwide) of the GenBank data base. Louse individuals ( n = 50) showed 99.8% similarity with the same clade A reference having a single base pair difference. Also, a number of 22 louse individuals revealed 99.8% identity with clade B reference (prevalent in North and Central Americas, Europe, and Australia) with individual diversity in two base pairs. Moreover, 14 louse individual sequences revealed 99.4% identity with three base pair differences. It was concluded that moderate pediculosis (~13%) prevailed among the female students of the primary schools. It was age-and hair texture (straight or curly)-dependent. P. Humanus Capitis prevalence diversity is of clades A and B genotyping.
Mehmet Karakus - One of the best experts on this subject based on the ideXlab platform.
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detection of permethrin resistance and phylogenetic clustering of turkish head lice Pediculus Humanus Capitis de geer 1767 populations
Acta Tropica, 2020Co-Authors: Mehmet Karakus, Tugce Atici, şemsi Nur Karabela, Orhan Baylan, Mehmet Emin Limoncu, I C BalciogluAbstract:Abstract Head lice infestation caused by Pediculus Humanus Capitis De Geer, 1767 is one of the most common public health problems. The relationship between humans and head lice dates back millions of years ago that differentiated into different phylogenetic clades. Treatment of head lice infestation usually based on insecticide-based products, which promotes the resistance in the head lice populations. In the present study, we aimed to screen the presence of permethrin resistance among collected P. h. Capitis specimens in Turkey. Three mutation sites (T917I, L920F, and M815I) were screened using real-time PCR and resistance was identified by melt analysis. Of the studied specimens, resistance allele frequency (RAF) was found 0.98 for T917I, 0.99 for L920F, and 1.00 for M815I. The phylogenetic study revealed that Clade A and Clade B are present and overlap in Turkey. The present study is first to screen the resistance among Turkish head lice specimens. To not stimulate the pyrethroids resistance in head lice populations, early detection of resistance is crucial and will help the health professionals to choose suitable formula in the treatment. We suggest that the resistance status needs to be screened in randomly selected populations before any treatment application is given.
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treatment of head lice Pediculus Humanus Capitis infestation is regular combing alone with a special detection comb effective at all levels
Parasitology Research, 2015Co-Authors: Ozgur Kurt, Suha K Arserim, Mehmet Karakus, Cuneyt I Balcioglu, Emin M Limoncu, Nogay Girginkardesler, Serhan Gorgun, Tuba Oyur, Didem Duzyol, Aysegul Aksoy GokmenAbstract:Head lice infestation (HLI) caused by Pediculus Humanus Capitis has been a public health problem worldwide. Specially designed combs are used to identify head lice, while anti-lice products are applied on the scalp for treatment. In the present study, we aimed to test whether combing only by precision detection comb (PDC) or metal pin comb (MPC) could be effective alternatives to the use of anti-lice products in children. A total of 560 children from two rural schools in Turkey were screened. In the PDC trial, children were combed every second day for 14 days, while in the MPC trial, combing was performed once in every four days for 15 days. Children were divided into two groups (dry combing and wet combing) for both trials and results were compared. The results showed no significant differences between dry and wet combing strategies for both combs for the removal of head lice (p > 0.05). The number of adult head lice declined significantly on each subsequent combing day in both approaches, except on day 15 in the MPC trial. In the end, no louse was found in 54.1 and 48.9 % of children in the PDC and MPC trials, respectively. Since family members of infested children were not available, they were not checked for HLI. Four times combing within 2 weeks with MPC combs was found effective for both treatment of low HLI and prevention of heavy HLI. In conclusion, regular combing by special combs decreases HLI level in children and is safely applicable as long-term treatment.