Abstract:Background: The human head louse, Pediculus humanus capitis, is a cosmopolitan blood-sucking ectoparasite affecting mostly schoolchildren in both developed and developing countries. In Honduras, chemical pediculicides are the first line of treatment, with permethrin as their main active ingredient. Despite the extended use of these products, there is currently no research investigating insecticide resistance in Honduran head lice. In head lice, the most common mechanism is knockdown resistance (kdr), which is … Show more
“…Having excess of homozygotes is an indicator of inbreeding or in fixation of mutant alleles. On the contrary, the first study of pyrethroid resistance in head lice from Honduras by Larkin et al [ 20 ] using RFLP techniques have demonstrated that the majorities of head lice had excess of heterozygotes of kdr -type mutations which indicates the active selective pressure among head lice.…”
Section: Discussionmentioning
confidence: 99%
“…The knockdown resistance (kdr), due to the three-point mutation (amino acid substitutions on the M815I, T917I, and L920F) can be identified on the α-subunit of voltage sensitive sodium channel (VSSC) gene [15][16][17]. Several reports suggested that M815I and L920F mutations reduce susceptibility to permethrin [18][19][20], whereas for the T917I mutation, whenever present, whether in alone or combination with L920F mutation, the mutation plays an important role in permethrin resistance and can be used as a molecular biomarker for head lice permethrin or pyrethroid resistance [21,22].…”
Section: Introductionmentioning
confidence: 99%
“…Molecular analysis is one of the most popular techniques used to determine the pyrethroid resistance in insects [19]. Different molecular techniques have been practiced to identify the head lice carrying resistance including quantitative multiplex sequencing [21,23], melting curve analysis genotyping coupled with quantitative PCR fluorescent resonance energy transfer technology (FRET) [24,25], real-time PCR amplification of specific allele (rtPASA), serial invasive signal amplification reaction (SISAR) [11], and restriction fragment length polymorphism (RFLP) [20,[26][27][28][29].…”
Human head lice are blood-sucking insects causing an infestation in humans called pediculosis capitis. The infestation is more prevalent in the school-aged population. Scalp itching, a common presenting symptom, results in scratching and sleep disturbance. The condition can lead to social stigmatization which can lead to loss of self-esteem. Currently, the mainstay of treatment for pediculosis is chemical insecticides such as permethrin. The extended use of permethrin worldwide leads to growing pediculicide resistance. The aim of this study is to demonstrate the presence of the knockdown resistance (kdr) mutation in head lice populations from six different localities of Thailand. A total of 260 head lice samples in this study were collected from 15 provinces in the 6 regions of Thailand. Polymerase chain reaction (PCR) was used to amplify the α subunit of voltage-sensitive sodium channel (VSSC) gene, kdr mutation (C→T substitution). Restriction fragment length polymorphism (RFLP) patterns and sequencing were used to identify the kdr T917I mutation and demonstrated three genotypic forms including homozygous susceptible (SS), heterozygous genotype (RS), and homozygous resistant (RR). Of 260 samples from this study, 156 (60.00%) were SS, 58 (22.31%) were RS, and 46 (17.69%) were RR. The overall frequency of the kdr T917I mutation was 0.31. Genotypes frequencies determination using the exact test of Hardy-Weinberg equilibrium found that northern, central, northeastern, southern, and western region of Thailand differed from expectation. The five aforementioned localities had positive inbreeding coefficient value (Fis > 0) which indicated an excess of homozygotes. The nucleotide and amino acid sequences of RS and RR showed T917I and L920F point mutations. In conclusion, this is the first study detecting permethrin resistance among human head lice from Thailand. PCR-RFLP is an easy technique to demonstrate the kdr mutation in head louse. The data obtained from this study would increase awareness of increasing of the kdr mutation in head louse in Thailand.
“…Having excess of homozygotes is an indicator of inbreeding or in fixation of mutant alleles. On the contrary, the first study of pyrethroid resistance in head lice from Honduras by Larkin et al [ 20 ] using RFLP techniques have demonstrated that the majorities of head lice had excess of heterozygotes of kdr -type mutations which indicates the active selective pressure among head lice.…”
Section: Discussionmentioning
confidence: 99%
“…The knockdown resistance (kdr), due to the three-point mutation (amino acid substitutions on the M815I, T917I, and L920F) can be identified on the α-subunit of voltage sensitive sodium channel (VSSC) gene [15][16][17]. Several reports suggested that M815I and L920F mutations reduce susceptibility to permethrin [18][19][20], whereas for the T917I mutation, whenever present, whether in alone or combination with L920F mutation, the mutation plays an important role in permethrin resistance and can be used as a molecular biomarker for head lice permethrin or pyrethroid resistance [21,22].…”
Section: Introductionmentioning
confidence: 99%
“…Molecular analysis is one of the most popular techniques used to determine the pyrethroid resistance in insects [19]. Different molecular techniques have been practiced to identify the head lice carrying resistance including quantitative multiplex sequencing [21,23], melting curve analysis genotyping coupled with quantitative PCR fluorescent resonance energy transfer technology (FRET) [24,25], real-time PCR amplification of specific allele (rtPASA), serial invasive signal amplification reaction (SISAR) [11], and restriction fragment length polymorphism (RFLP) [20,[26][27][28][29].…”
Human head lice are blood-sucking insects causing an infestation in humans called pediculosis capitis. The infestation is more prevalent in the school-aged population. Scalp itching, a common presenting symptom, results in scratching and sleep disturbance. The condition can lead to social stigmatization which can lead to loss of self-esteem. Currently, the mainstay of treatment for pediculosis is chemical insecticides such as permethrin. The extended use of permethrin worldwide leads to growing pediculicide resistance. The aim of this study is to demonstrate the presence of the knockdown resistance (kdr) mutation in head lice populations from six different localities of Thailand. A total of 260 head lice samples in this study were collected from 15 provinces in the 6 regions of Thailand. Polymerase chain reaction (PCR) was used to amplify the α subunit of voltage-sensitive sodium channel (VSSC) gene, kdr mutation (C→T substitution). Restriction fragment length polymorphism (RFLP) patterns and sequencing were used to identify the kdr T917I mutation and demonstrated three genotypic forms including homozygous susceptible (SS), heterozygous genotype (RS), and homozygous resistant (RR). Of 260 samples from this study, 156 (60.00%) were SS, 58 (22.31%) were RS, and 46 (17.69%) were RR. The overall frequency of the kdr T917I mutation was 0.31. Genotypes frequencies determination using the exact test of Hardy-Weinberg equilibrium found that northern, central, northeastern, southern, and western region of Thailand differed from expectation. The five aforementioned localities had positive inbreeding coefficient value (Fis > 0) which indicated an excess of homozygotes. The nucleotide and amino acid sequences of RS and RR showed T917I and L920F point mutations. In conclusion, this is the first study detecting permethrin resistance among human head lice from Thailand. PCR-RFLP is an easy technique to demonstrate the kdr mutation in head louse. The data obtained from this study would increase awareness of increasing of the kdr mutation in head louse in Thailand.
Urbanization, pollution and the modification of natural landscapes are characteristics of modern society, where the change in human relations with the environment and the impact on biodiversity are environmental determinants that affect the health-disease relationship. The skin is an organ that has a strong interface with the environment and, therefore, the prevalence patterns of dermatoses may reflect these environmental changes. In this article, aspects related to deforestation, fires, urbanization, large-scale agriculture, extensive livestock farming, pollution and climatic changes are discussed regarding their influence on the epidemiology of skin diseases. It is important that dermatologists be aware of their social responsibility in order to promote sustainable practices in their community, in addition to identifying the impacts of environmental imbalances on different dermatoses, which is essential for the prevention and treatment of these diseases.
“…Regarding primary school children in Thailand, kdr T9171 and L920F point mutations were discovered in permethrin-resistant head lice [ 13 ]. In Honduras [ 14 ], Chile [ 15 ], and Madagascar [ 16 ], the T917I kd r allele was found in head lice resistant to pyrethroid insecticides. However, in Senegal, it has been reported that the presence of a point mutation of GluCI is associated with ivermectin-resistant head lice [ 17 ].…”
Background and Aim: Pediculus humanus capitis, the human head louse, remains a global health problem. This study evaluated the resistance of head lice to permethrin and 6-paradol mediated by in vitro detoxification enzyme activity experiments and to describe physical changes in the lice using scanning electron microscopy (SEM).
Materials and Methods: The adult stages of P. h. capitis were collected from patients exposed to 1% permethrin and three different concentrations of 6-paradol (0.00005%, 0.0001%, and 0.00015%) using a filter paper diffusion bioassay. Healthy P. h. capitis adults served as the control. The in vitro bioassays were conducted after 10, 20, 30, and 60 min of exposure. The activities of acetylcholinesterase (AChE), glutathione S-transferase (GST), and oxidase were analyzed. Physical changes in the lice were analyzed using SEM.
Results: Permethrin and 6-paradol exhibited low toxicity against the lice. At 60 min, 1% permethrin had killed 36.7% of the lice present, while 6-paradol had killed 66.7-86.7%. Permethrin induced significantly elevated AChE, GST, and oxidase activity; 6-paradol also caused significantly elevated AChE, GST, and oxidase activity. Permethrin did not cause any ultrastructural morphological changes on the lice, while 6-paradol severely damaged the head, thorax, respiratory spiracles, and abdomen of the dead lice.
Conclusion: This in vitro experimental of P. h. capitis is the first study to report P. h. capitis in East Jakarta shows complete resistance to permethrin and 6-paradol, and to describe the associated increase in AChE, GST, and oxidase activity. It was observed that 6-paradol severely damaged the head, thorax, respiratory spiracles, and abdomen of the dead lice.
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