The association between knockdown resistance and treatment outcome of 1% permethrin lotion in head lice infestations in Nonthaburi province, Thailand.

Head lice infestations significantly impact schoolchildren, with permethrin being the primary treatment. The escalation in the prevalence of the knockdown resistance (kdr) mutation, potentially affecting treatment efficacy, is highly concerning. This study examined head lice infestation prevalence, the efficacy of 1% permethrin lotion, kdr mutation frequency, and the association between kdr genotype and permethrin treatment outcomes in schoolchildren in Nonthaburi province, Thailand. Participants and lice samples were collected from six primary schools using cluster sampling. Clinical outcomes and adverse events were assessed on days 7 and 14 post-treatment. Kdr mutations (T917I) in head lice samples were analyzed using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. Head lice infestation prevalence was 6.1%, with a kdr mutation frequency of 63.2% and a permethrin cure rate of approximately 50%. Multivariate regression analysis revealed the association between kdr genotype and clinical response to permethrin treatment (Odds Ratio (OR) = 13.15, p = 0.005). The presence of resistance genes hinders the cure rate (presence 35.9% versus absence 85.7%). These findings highlight the importance of the kdr genotype in predicting permethrin treatment responses in head lice infestations. Furthermore, in regions with documented reduced permethrin efficacy and a high prevalence of kdr mutations, alternative non-pyrethroid-based pediculicides should be considered. This research could help improve the control of head lice infestations, especially in problematic areas of Thailand.

Microsporidia, a Highly Adaptive Organism and Its Host Expansion to Humans.

Emerging infectious disease has become the center of attention since the outbreak of COVID-19. For the coronavirus, bats are suspected to be the origin of the pandemic. Consequently, the spotlight has fallen on zoonotic diseases, and the focus now expands to organisms other than viruses. Microsporidia is a single-cell organism that can infect a wide range of hosts such as insects, mammals, and humans. Its pathogenicity differs among species, and host immunological status plays an important role in infectivity and disease severity. Disseminated disease from microsporidiosis can be fatal, especially among patients with a defective immune system. Recently, there were two Trachipleistophora hominis, a microsporidia species which can survive in insects, case reports in Thailand, one patient had disseminated microsporidiosis. This review gathered data of disseminated microsporidiosis and T. hominis infections in humans covering the biological and clinical aspects. There was a total of 22 cases of disseminated microsporidiosis reports worldwide. Ten microsporidia species were identified. Maximum likelihood tree results showed some possible correlations with zoonotic transmissions. For T. hominis, there are currently eight case reports in humans, seven of which had Human Immunodeficiency Virus (HIV) infection. It is observed that risks are higher for the immunocompromised to acquire such infections, however, future studies should look into the entire life cycle, to identify the route of transmission and establish preventive measures, especially among the high-risk groups.

Molecular analysis of mitochrondrial cytb of Pediculus humanus capitis in Thailand revealed potential historical connection with South Asia.

BACKGROUND: Pediculus humanus capitis or head louse is an obligate ectoparasite and its infestation remains a major public health issue worldwide. Molecular analysis divides head lice into six clades and intra-clade genetic differences have been identified. Several hypotheses have been formulated to elucidate the discrepancies of the variety of head lice among different regions of the world. It is currently concluded that head lice distribution might be associated with human migration history. This study aims to investigate genetic data of human head lice in Thailand. We believe that the analysis could help establish the correlation between local and global head lice populations. METHOD: We investigated mitochondrial cytochrome b (cytb) gene of the collected 214 head lice to evaluate genetic diversity from 15 provinces among 6 regions of Thailand. The head lice genes were added to the global pool for the phylogenetic tree, Bayesian tree, Skyline plot, and median joining network construction. The biodiversity, neutrality tests, and population genetic differentiation among the 6 Thailand geographic regions were analyzed by DNAsp version 6. RESULTS: The phylogenetic tree analysis of 214 collected head lice are of clade A and clade C accounting for roughly 65% and 35% respectively. The Bayesian tree revealed a correlation of clade diversification and ancient human dispersal timeline. In Thailand, clade A is widespread in the country. Clade C is confined to only the Central, Southern, and Northeastern regions. We identified 50 novel haplotypes. Statistical analysis showed congruent results between genetic differentiation and population migration especially with South Asia. CONCLUSIONS: Pediculosis remains problematic among children in the rural areas in Thailand. Cytb gene analysis of human head lice illustrated clade distribution and intra-clade diversity of different areas. Our study reported novel haplotypes of head lice in Thailand. Moreover, the statistic calculation provided a better understanding of their relationship with human, as an obligate human parasite and might help provide a better insight into the history of human population migration. Determination of the correlation between phylogenetic data and pediculicide resistance gene as well as residing bacteria are of interest for future studies.

Case Report: First Report of Disseminated Trachipleistophora hominis Infection in an AIDS Patient from Thailand.

Microsporidial myositis caused by Trachipleistophora hominis is a life-threatening and emerging microsporidiosis among immunocompromised hosts. This article reports a case of disseminated microsporidiosis caused by T. hominis in southern Thailand. The patient had HIV and presented at the clinic with incapacitating muscle pain. She was diagnosed with disseminated microsporidiosis. Molecular identification revealed the sequence of 18S ribosomal RNA gene involving sequences sharing 99% nucleotide identity with T. hominis from an Australian patient. To our knowledge, this is the first study to report the detection of T. hominis microsporidia in an HIV patient in Thailand.

Presence of the knockdown resistance (kdr) mutations in the head lice (Pediculus humanus capitis) collected from primary school children of Thailand.

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.