Padet Siriyasatien

Insecticide Resistance in Bedbugs in Thailand and Laboratory Evaluation of Insecticides for the Control of Cimex hemipterus and Cimex lectularius (Hemiptera: Cimicidae)

ABSTRACT Bedbugs are found in many countries around the world, and in some regions they are resistant to numerous insecticides. This study surveyed bedbugs in Thailand and determined their resistance to insecticides. The surveys were carried out in six provinces that attract large numbers of foreign tourists: Bangkok, Chonburi, Chiang Mai, Ubon Ratchathani, Phuket, and Krabi. Bedbugs were collected from hotels and colonized in the laboratory to evaluate their resistance to insecticides. Cimex hemipterus (F.) was found in some hotels in Bangkok, Chonburi, Phuket, and Krabi, whereas Cimex lectularius L. was found only in hotels in Chiang Mai. No bedbugs were found in Ubon Ratchathani. The colonized bedbugs showed resistance to groups of insecticides, including organochlorines (dichlorodiphenyl trichloroethane, dieldrin), carbamates (bendiocarb, propoxur), organophosphates (malathion, fenitrothion), and pyrethroids (cyfluthrin, deltamethrin, permethrin, &lgr;-cyhalothrin, etofenprox) in tests using World Health Organization insecticide-impregnated papers. The new insecticides imidacloprid (neonicotinoid group), chlorfenapyr (pyrrole group), and fipronil (phenylpyrazole group) were effective against the bedbugs; however, organophosphate (diazinon), carbamates (fenobucarb, propoxur), and pyrethroids (bifenthrin, cypermethrin, esfenvalerate, etofenprox) were ineffective. Aerosols containing various pyrethroid insecticides with two to four different active ingredients were effective against the bedbugs. The results obtained from this study suggested that both species of bedbugs in Thailand have developed marked resistance to various groups of insecticides, especially those in the pyrethroid group, which are the most common insecticides used for pest control. Therefore, an integrated pest management should be implemented for managing bedbugs in Thailand.

First Isolation of Leishmania from Northern Thailand: Case Report, Identification as Leishmania martiniquensis and Phylogenetic Position within the Leishmania enriettii Complex

Since 1996, there have been several case reports of autochthonous visceral leishmaniasis in Thailand. Here we report a case in a 52-year-old Thai male from northern Thailand, who presented with subacute fever, huge splenomegaly and pancytopenia. Bone marrow aspiration revealed numerous amastigotes within macrophages. Isolation of Leishmania LSCM1 into culture and DNA sequence analysis (ribosomal RNA ITS-1 and large subunit of RNA polymerase II) revealed the parasites to be members of the Leishmania enriettii complex, and apparently identical to L. martiniquensis previously reported from the Caribbean island of Martinique. This is the first report of visceral leishmaniasis caused by L. martiniquensis from the region. Moreover, the majority of parasites previously identified as “L. siamensis” also appear to be L. martiniquensis.

Consecutive cutaneous and visceral leishmaniasis manifestations involving a novel Leishmania species in two HIV patients in Thailand.

Leishmaniasis is an emerging disease in Thailand. Herein, we report on two human immunodeficiency virus (HIV)-infected patients with leishmaniasis who presented with overlapping manifestations between cutaneous and visceral leishmaniasis. Sequencing analysis of the internal transcribed spacer 1 (ITS1) of the ribosomal RNA gene showed that the species was identical to a new species recently described in Thailand. The detection of DNA of this Leishmania species in saliva may have important implications for transmission and epidemiological studies.

Multilocus characterization and phylogenetic analysis of Leishmania siamensis isolated from autochthonous visceral leishmaniasis cases, southern Thailand

BackgroundVisceral leishmaniasis (VL) caused by Leishmania siamensis is an emerging disease continuously reported in six southern provinces of Thailand. To date, the phylogenetic relationships among Leishmania isolates from Thai patients and other Leishmania species are still unclear and the taxonomic diversity needs to be established. In this study, the phylogenetic inference trees were constructed based on four genetic loci (i.e., SSU-rRNA, ITS1, hsp70, and cyt b), using DNA sequences obtained from autochthonous VL patients from southern Thailand and reference sequences of reported Leishmania isolates from other studies deposited in GenBank.ResultsPhylogenetic analyses of hsp70 and cyt b loci supported a clade comprised of L. siamensis isolates, which is independent to the other members in the genus Leishmania. In combination with genetic distance analysis, sequence polymorphisms were observed among L. siamensis isolates and two different lineages could be differentiated, lineages PG and TR. Phylogenetic analysis of the cyt b gene further showed that L. siamensis lineage TR is closely related to L. enrietti, a parasite of guinea pigs.ConclusionThe finding of this study sheds further light on the relationships of L. siamensis, both in intra- and inter-species aspects. This information would be useful for further in-depth studies on the biological properties of this important parasite.

Molecular survey of the head louse Pediculus humanus capitis in Thailand and its potential role for transmitting Acinetobacter spp.

BackgroundHead louse infestation, which is caused by Pediculus humanus capitis, occurs throughout the world. With the advent of molecular techniques, head lice have been classified into three clades. Recent reports have demonstrated that pathogenic organisms could be found in head lice. Head lice and their pathogenic bacteria in Thailand have never been investigated. In this study, we determined the genetic diversity of head lice collected from various areas of Thailand and demonstrated the presence of Acinetobacter spp. in head lice.MethodsTotal DNA was extracted from 275 head louse samples that were collected from several geographic regions of Thailand. PCR was used to amplify the head louse COI gene and for detection of Bartonella spp. and Acinetobacter spp. The amplified PCR amplicons were cloned and sequenced. The DNA sequences were analyzed via the neighbor-joining method using Kimura’s 2-parameter model.ResultsThe phylogenetic tree based on the COI gene revealed that head lice in Thailand are clearly classified into two clades (A and C). Bartonella spp. was not detected in all the samples, whereas Acinetobacter spp. was detected in 10 samples (3.62%), which consisted of A. baumannii (1.45%), A. radioresistens (1.45%), and A. schindleri (0.72%). The relationship of Acinetobacter spp. and the head lice clades showed that Acinetobacter spp. was found in clade A and C.ConclusionsHead lice in Thailand are classified into clade A and B based on the COI gene sequences. Pathogenic Acinetobacter spp. was detected in both clades. The data obtained from the study might assist in the development of effective strategies for head lice control in the future. Detection of pathogenic bacteria in head lice could raise awareness of head lice as a source of nosocomial bacterial infections.

Mitochondrial DNA-based identification of some forensically important blowflies in Thailand.

Accurate identification of insects collected from death scenes provides not only specific developmental data assisting forensic entomologists to determine the postmortem interval more precisely but also other kinds of forensic evidence. However, morphological identification can be complicated due to the similarity among species, especially in the early larval stages. To simplify and make the species identification more practical and reliable, DNA-based identification is preferentially considered. In this study, we demonstrate the application of partial mitochondrial cytochrome oxidase I (COI) and cytochrome oxidase II (COII) sequences for differentiation of forensically important blowflies in Thailand; Chrysomya megacephala, Chrysomya rufifacies and Lucilia cuprina by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The PCR yields a single 1324bp-sized amplicon in all blowfly specimens, followed by direct DNA sequencing. Taq(α)I and VspI predicted from the sequencing data provide different RFLP profiles among these three species. Sequence analysis reveals no significant intraspecific divergence in blowfly specimens captured from different geographical regions in Thailand. Accordingly, neighbor-joining tree using Kimuras 2-parameter model illustrates reciprocal monophyly between species. Thus, these approaches serve as promising tools for molecular identification of these three common forensically important blowfly species in Thailand.

Comparison of PCR methods for detection of Leishmania siamensis infection

BackgroundLeishmania siamensis, a newly identified species, has been reported as a causative agent of leishmaniasis in Thailand. This organism has been identified and genetically characterized using PCR techniques based on several target genes. However, the sensitivities and specificities of these methods for the diagnosis of L. siamensis infection have never been evaluated.MethodsTo evaluate the sensitivities and specificities of PCR methods to detect L. siamensis infection, PCR for different genetic markers, i.e., the small subunit ribosomal RNA region (SSU-rRNA), the internal transcribed spacer 1 region (ITS1), cysteine protease B (cpb), cytochrome b (cyt b), heat shock protein 70 (hsp 70), the spliced leader mini-exon, and the triose-phosphate isomerase (tim) genes were compared.ResultsBoth the ITS1-PCR and the SSU rRNA-PCR could detect promastigote of L. siamensis at concentrations as low as 0.05 parasites/μl or the DNA concentration at 2.3 pg/μl. Though the ITS1-PCR method only recognized 8 samples as positive, all of these could be assessed as true positive according to microscopic diagnosis and/or amplifying the results of the PCR and their sequencing, while other methods also produced false positive results. Compared with the ITS1-PCR method, the PCR amplified SSU-rRNA and cpb gene showed 100% sensitivity for the detection of L. siamensis in clinical specimens. The PCR amplified mini-exon and hsp 70 gene also gave a high sensitivity of 87.5%. In contrast, the PCR methods for cyt b and tim gene showed low sensitivity. The PCR methods for cyt b, mini-exon and tim gene showed 100% specificity compared with the ITS1-PCR.ConclusionAs a result, the ITS1-PCR method is a suitable target for PCR-based detection of L. siamensis infection in clinical specimens due to its high sensitivity and specificity. The results of this study can be used for molecular diagnosis as well as in epidemiological studies of L. siamensis in affected areas.

Analysis of significant factors for dengue fever incidence prediction

BackgroundMany popular dengue forecasting techniques have been used by several researchers to extrapolate dengue incidence rates, including the K-H model, support vector machines (SVM), and artificial neural networks (ANN). The time series analysis methodology, particularly ARIMA and SARIMA, has been increasingly applied to the field of epidemiological research for dengue fever, dengue hemorrhagic fever, and other infectious diseases. The main drawback of these methods is that they do not consider other variables that are associated with the dependent variable. Additionally, new factors correlated to the disease are needed to enhance the prediction accuracy of the model when it is applied to areas of similar climates, where weather factors such as temperature, total rainfall, and humidity are not substantially different. Such drawbacks may consequently lower the predictive power for the outbreak.ResultsThe predictive power of the forecasting model-assessed by Akaike’s information criterion (AIC), Bayesian information criterion (BIC), and the mean absolute percentage error (MAPE)-is improved by including the new parameters for dengue outbreak prediction. This study’s selected model outperforms all three other competing models with the lowest AIC, the lowest BIC, and a small MAPE value. The exclusive use of climate factors from similar locations decreases a model’s prediction power. The multivariate Poisson regression, however, effectively forecasts even when climate variables are slightly different. Female mosquitoes and seasons were strongly correlated with dengue cases. Therefore, the dengue incidence trends provided by this model will assist the optimization of dengue prevention.ConclusionsThe present work demonstrates the important roles of female mosquito infection rates from the previous season and climate factors (represented as seasons) in dengue outbreaks. Incorporating these two factors in the model significantly improves the predictive power of dengue hemorrhagic fever forecasting models, as confirmed by AIC, BIC, and MAPE.

Detection of Leishmania siamensis DNA in Saliva by Polymerase Chain Reaction

Polymerase chain reaction was used to detect Leishmania siamensis DNA from clinical samples collected from six leishmaniasis patients during 2011-2012. The samples used in this study came from bone marrow, blood, buffy coat, saliva, urine, and tissue biopsy specimens. Saliva was a good source for L. siamensis DNA by polymerase chain reaction. L. siamensis DNA was also found in saliva of an asymptomatic case-patient. Levels of L. siamensis DNA in saliva decreased until being undetectable after treatment. These levels could be used as a marker to evaluate efficacy of the treatment. A larger study is needed to evaluate this method as a screening and survey tool to study the silent background of Leishmania infection among the at-risk population.

Disseminated Dermal Leishmaniasis Caused by Leishmania siamensis in a Systemic Steroid Therapy Patient

Leishmania siamensis infection was recently reported from Thailand. Clinical presentation of L. siamensis infections is generally related to human immunodeficiency virus infection. Herein, disseminated dermal L. siamensis infection in a systemic steroid therapy patient from Myanmar is described.