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.
BackgroundLeishmaniasis is a neglected tropical disease that is caused by an obligate intracellular protozoan of the genus Leishmania. Recently, an increasing number of autochthonous leishmaniasis cases caused by L. martiniquensis and the novel species L. siamensis have been described in Thailand, rendering an accurate diagnosis of this disease critical. However, only a few laboratories are capable of diagnosing leishmaniasis in Thailand. To expand leishmaniasis diagnostic capabilities, we developed a simple colorimetric loop-mediated isothermal amplification (LAMP) technique for the direct detection of Leishmania DNA.MethodsLAMP was performed for 75 min using four primers targeting the conserved region of the18S ribosomal RNA gene, and the DNA indicator used was malachite green (MG). To simulate crude samples, cultured promastigotes of L. siamensis were mixed with blood or saliva. Also, clinical samples (blood, saliva, and tissue biopsies) were obtained from patients with cutaneous leishmaniasis (CL) and visceral leishmaniasis (VL). All samples were boiled for 10 min and introduced directly into the LAMP reaction mixture without DNA purification.ResultsThe use of MG resulted in an unambiguous differentiation of positive and negative controls. For L. siamensis, the detection limit was 103 parasites/mL or 2.5 parasites/tube. Saliva, tissue biopsies, and whole blood were indicative of active Leishmania infection, and their direct usages did not adversely affect the detection limit. In addition, this LAMP assay could detect DNA from multiple Leishmania species other than L. siamensis and L. martiniquensis, including L. aethiopica, L. braziliensis, L. donovani and L. tropica.ConclusionsThe simplicity and sensitivity of LAMP in detecting active Leishmania infection could enable the rapid diagnosis of leishmaniasis, thereby facilitating the survey and control of leishmaniasis in Thailand. However, our limited number of samples warranted a further validation with a larger cohort of patients before this assay could be deployed.
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.
Abstract. 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.Leishmaniasis is a neglected tropical diseases caused by an obligate intracellular protozoa belonging to the genus Leishmania. The disease is transmitted to vertebrate hosts by infected female sand flies taking a blood meal.1 Leishmaniasis presents in three clinical forms; visceral, cutaneous, and mucocutaneous.2 Clinical presentation of leishmaniasis depends on the species of Leishmania and the immunity of the host. Detection and species identification of the parasites is essential for prognostic and therapeutic reasons and surveys.
BackgroundThe re-emergence of chikungunya (CHIK) fever in Thailand has been caused by a novel lineage of chikungunya virus (CHIKV) termed the Indian Ocean Lineage (IOL). The Aedes albopictus mosquito is thought to be a primary vector of CHIK fever in Thailand, whereas Ae. aegypti acts as a secondary vector of the virus. The vertical transmission is believed to be a primary means to maintain CHIKV in nature and may be associated with an increased risk of outbreak. Therefore, the goal of this study was to analyze the potential of these two Thai mosquito species to transmit the virus vertically and to determine the number of successive mosquito generations for the virus transmission.MethodsTwo-hundred-and-fifty female Ae. aegypti and Ae. albopictus mosquitoes were artificially fed a mixture of human blood and CHIKV IOL. Mosquito larvae and adults were sampled and screened for CHIKV by one-step qRT-PCR. LLC-MK2 cell line was used to isolate CHIKV in the mosquitoes each generation. The virus isolate was identified by immunocytochemical staining and was confirmed by sequencing. Both mosquito species fed on human blood without CHIKV and uninfected LLC-MK2 cells were used as controls.ResultsAedes aegypti and Ae. albopictus mosquitoes were able to transmit CHIKV vertically to F5 and F6 progenies, respectively. The virus isolated from the two mosquito species caused cytopathic effect in LLC-MK2 cells by 2 days post-infection and immunocytochemical staining showed the reaction between CHIKV IOL antigen and specific monoclonal antibody in the infected cells. DNA sequence confirmed the virus transmitted vertically as CHIKV IOL with E1-A226V mutation. No CHIKV infection was observed in both mosquito species and LLC-MK2 cells from control groups.ConclusionsThe study demonstrated that Ae. aegypti and Ae. albopictus mosquitoes from Thailand are capable of transmitting CHIKV IOL vertically in the laboratory. Our results showed that Ae. albopictus is more susceptible and has a greater ability to transmit the virus vertically than Ae. aegypti. This knowledge would be useful for risk assessments of the maintenance of CHIKV in nature, which is crucial for disease surveillance, vector control and the prevention of potential CHIKV epidemics.
Phlebotomine sand flies are tiny, hairy, blood-sucking nematoceran insects that feed on a wide range of hosts. They are known as a principal vector of parasites, responsible for human and animal leishmaniasis worldwide. In Thailand, human autochthonous leishmaniasis and trypanosomiasis have been reported. However, information on the vectors for Leishmania and Trypanosoma in the country is still limited. Therefore, this study aims to detect Leishmania and Trypanosoma DNA in field-caught sand flies from endemic areas (Songkhla and Phatthalung Provinces) and non-endemic area (Chumphon Province) of leishmaniasis. A total of 439 sand flies (220 females and 219 males) were collected. Head and genitalia dissection of female sandflies were done for morphology identification, and the remaining parts of those sand flies were then used for the detection of Leishmania and Trypanosoma parasites. The DNA was extracted from individual female sand flies. Polymerase chain reaction (PCR) anneal, specific to the ITS1 and SSU rRNA gene regions, was used to detect Leishmania and Trypanosoma DNA, respectively. The positive PCR products were cloned and sequenced. The results showed that the female sand fly species in this study consisted of Sergentomyia khawi (35.9%); Se. anodontis (23.6%); Phlebotomus betisi (18.6%); Ph. kiangsuensis (9.5%); Ph. asperulus (6.4%); Se. barraudi (2.3%); 0.9% of each Se. indica, Ph. stantoni, and Ph. major major; and 0.5% of each Se. sylvatica and Ph. mascomai. The PCR and sequence analysis were able to detect Leishmania and Trypanosoma DNA in sand fly samples, which were identified as L. martiniquensis, 1/220 (0.45%) in Se. khawi, 3/220 (1.36%) of T. noyesi in Se. anodontis, and Ph. asperulus. Fourteen (6.36%) of the unidentified trypanosome species in Se. khawi, Se. indica, Se. anodontis, Ph. asperulus, and Ph. betisi were found in all of the areas of this study. Interestingly, we found a 1/220 (0.45%) co-infection sample of L. martiniquensis and Trypanosoma in Se. khawi from Songkhla Province. These data indicate that several species of sand flies might be potential vectors of Leishmania and Trypanosoma parasites in southern Thailand. However, more extensive study for potential vectors using a larger number of sand flies should be conducted to prove whether these sand flies can be natural vectors of leishmaniasis and trypanosomiasis in both humans and animals. In addition, our study could be useful for the future study of infection prevention, including effective vector control for leishmaniasis and trypanosomiasis in Thailand.
BackgroundIn the past few decades, several researchers have proposed highly accurate prediction models that have typically relied on climate parameters. However, climate factors can be unreliable and can lower the effectiveness of prediction when they are applied in locations where climate factors do not differ significantly. The purpose of this study was to improve a dengue surveillance system in areas with similar climate by exploiting the infection rate in the Aedes aegypti mosquito and using the support vector machine (SVM) technique for forecasting the dengue morbidity rate.Methods and FindingsAreas with high incidence of dengue outbreaks in central Thailand were studied. The proposed framework consisted of the following three major parts: 1) data integration, 2) model construction, and 3) model evaluation. We discovered that the Ae. aegypti female and larvae mosquito infection rates were significantly positively associated with the morbidity rate. Thus, the increasing infection rate of female mosquitoes and larvae led to a higher number of dengue cases, and the prediction performance increased when those predictors were integrated into a predictive model. In this research, we applied the SVM with the radial basis function (RBF) kernel to forecast the high morbidity rate and take precautions to prevent the development of pervasive dengue epidemics. The experimental results showed that the introduced parameters significantly increased the prediction accuracy to 88.37% when used on the test set data, and these parameters led to the highest performance compared to state-of-the-art forecasting models.ConclusionsThe infection rates of the Ae. aegypti female mosquitoes and larvae improved the morbidity rate forecasting efficiency better than the climate parameters used in classical frameworks. We demonstrated that the SVM-R-based model has high generalization performance and obtained the highest prediction performance compared to classical models as measured by the accuracy, sensitivity, specificity, and mean absolute error (MAE).
Several mosquito species have been described as vectors for the Zika virus (ZIKV), such as those in the Aedes , Anopheles , Mansonia and Culex genera. Our previous survey studies were found the ZIKV RNA positive in both male, female and larvae of Culex quinquefasciatus Say and Aedes aegypti (L.) mosquitoes collected from active ZIKV infected patients’ homes in Thailand. Therefore, the aims of this study were to investigate whether ZIKV could be vertically transmitted in Cx . quinquefasciatus , Ae . aegypti and Ae . albopictus . Laboratory and field colonies of these mosquito species were maintained and artificially fed with ZIKV in human blood. Fully engorged mosquitoes (F 0 ) were selected and reared for the vertical transmission study. The subsequent mosquito generations were fed with human blood without the virus. ZIKV in the mosquitoes was detected by hemi-nested RT-PCR and sequencing. C6/36 cells were used to isolate ZIKV from samples that tested positive by hemi-nested RT-PCR. Moreover, ZIKV was identified by immunocytochemical staining 7 days after infection in several organs of infected F 0 females, including the salivary glands, midguts, yoke granules and facet cells of the eye. The localization of the ZIKV antigen was identified by the presence of the specific antibody in the salivary glands, midguts, yoke granules and facet cells. ZIKV was detected in female and male Cx . quinquefasciatus until the F 6 and F 2 generations, respectively. The isolated virus showed cytopathic effects in C6/36 cells by 5 days postinfection. The results suggested that the vertical transmission of ZIKV occurs in Cx . quinquefasciatus in the laboratory. However, we were able to detect the presence of ZIKV in Ae . aegypti in only the F 1 generation in both male and female mosquitoes, and Ae . albopictus mosquitoes were not able to vertically transmit the virus at all. Data obtained from this study could be valuable for developing a better understanding of the role of Cx . quinquefasciatus as a potential vector for ZIKV transmission in Thailand and may be useful in creating more effective mosquito vector control strategies in the future.
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