Effects of physiological conditioning on behavioral avoidance by using a single age group of Aedes aegypti exposed to deltamethrin and DDT

The behavioral and physiological responses of 6-d-old Aedes aegypti (L.) adult females exposed to deltamethrin and DDT were characterized using a free-choice excito-repellency test system. Excluding varying pretest age and carbohydrate availability as possible confounders, insecticide contact (measuring irritancy) and noncontact (measuring repellency) behavioral assays were conducted on two nonbloodfed groups, either unmated or mated (nulliparous), and two blood-fed groups, either parous or newly full-engorged mosquitoes. The degree of escape response to deltamethrin and DDT varied according to the physiological conditioning. Escape rates from contact and noncontact chambers with deltamethrin were more conspicuous in nonbloodfed groups compared with mosquitoes previously bloodfed. There were no significant differences in escape responses between unmated and nulliparous test populations. With DDT, a more pronounced escape response was observed in unmated compared with other physiological conditions. More moderate escape response was seen in nulliparous mosquitoes, and the least was observed in full bloodfed test individuals, regardless of test compound. Ae. aegypti, regardless of pretest conditioning, was completely susceptible to deltamethrin, whereas showing high resistance to DDT. Despite profound differences in resistance, there was no significant difference in avoidance response between chemicals and mosquito conditioning. Moreover, pre- and postbloodmeals were found to influence assay outcome and thus to have relevance on the interpretation of susceptibility and excito-repellency assays.     

A dosimetric comparison of two-phase adaptive intensity-modulated radiotherapy for locally advanced nasopharyngeal cancer

The purpose of this investigation was to evaluate the potential dosimetric benefits of a two-phase adaptive intensity-modulated radiotherapy (IMRT) protocol for patients with locally advanced nasopharyngeal cancer (NPC). A total of 17 patients with locally advanced NPC treated with IMRT had a second computed tomography (CT) scan after 17 fractions in order to apply and continue the treatment with an adapted plan after 20 fractions. To simulate the situation without adaptation, a hybrid plan was generated by applying the optimization parameters of the original treatment plan to the anatomy of the second CT scan. The dose–volume histograms (DVHs) and dose statistics of the hybrid plan and the adapted plan were compared. The mean volume of the ipsilateral and contralateral parotid gland decreased by 6.1 cm³ (30.5%) and 5.4 cm³ (24.3%), respectively. Compared with the hybrid plan, the adapted plan provided a higher dose to the target volumes with better homogeneity, and a lower dose to the organs at risk (OARs). The Dmin of all planning target volumes (PTVs) increased. The Dmax of the spinal cord and brainstem were lower in 94% of the patients (1.6–5.9 Gy, P < 0.001 and 2.1–9.9 Gy, P < 0.001, respectively). The D_mean of the contralateral parotid decreased in 70% of the patients (range, 0.2–4.4 Gy). We could not find a relationship between dose variability and weight loss. Our two-phase adaptive IMRT protocol improves dosimetric results in terms of target volumes and OARs in patients with locally advanced NPC.     

Progress of partial integration of malaria control with other vector borne diseases control in northern Thailand

Thailand partially integrated the malaria program into the provincial and local Public Health system starting in 2003 by adding it to the control of other vector borne diseases and by transferring some activities to the Public Health Department. This study evaluates the results of this transfer on 8 high malaria incidence districts of Mae Hong Son and Chiang Mai Provinces. Indicators were measured for all community hospitals, Vector Borne Disease Control Units, (VBDU), health centers (HC), malaria clinics, and malaria posts in 2003 and 2004 during the first two years of partial integration. The number of Vector Borne Disease Control staff decreased 1.8 - 3%, and their operational budgets decreased 25%. The VBDU staff did all the indoor residual spraying (IRS), insecticide treated net (ITN) work and entomology surveys, they took 80.6% of the blood films, and treated 72% of the patients, while Public Health system did the remainder. The Annual Parasite Incidence (API) (1 - 10/1,000) and IRS coverage (88 - 100%) remained adequate in most areas during the first years after partial integration, but the API increased (to 31.6 - 57.6/1,000) in some populations. The percentage of insecticide treated bed net coverage was adequate in Mae Hong Son (95.4%), but inadequate in Chiang Mai (52.2%). Early diagnosis and prompt treatment (4 - 23 days), hospitals reporting disruption of anti-malarial drugs (3 of 7), and health centers having all needed equipment, training, and drugs for malaria diagnosis (9%) remain inadequate. If the program is allowed to diminish, malaria could spread again among the population. Integration of antimalarial activities into the general Public Health system has only been partially successful. We recommend the integration process and results should be monitored and evaluated to find and mitigate problems as they occur, and modify the integration process if needed.     

Virulent Burkholderia pseudomallei is more efficient than avirulent Burkholderia thailandensis in invasion of and adherence to cultured human epithelial cells

Burkholderia pseudomallei, a causative agent of melioidosis, is a facultative intracellular gram-negative bacillus that is closely related to its avirulent counterpart, Burkholderia thailandensis. However, pathogenic mechanisms and virulence factors of B. pseudomallei remain elusive. In the present study, we compared the invasiveness, adherence, and replication of B. pseudomallei and B. thailandensis in human respiratory epithelial cells A549. Invasion was determined after 4 h of coculturing using antibiotic protection assay. Adherence was demonstrated by coculturing the cells with fluorescein-labeled bacteria for 1 h and the number of positive cells was analyzed by flow cytometry. The results obtained with this in vitro study demonstrated that compared with its avirulent counterpart, B. pseudomallei is significantly more efficient (P<0.01) in invasion, adherence and inducing cellular damage, as represented by plaque formation.     

Human-landing patterns of Anopheles dirus sensu lato (Diptera: Culicidae) in experimental huts treated with DDT or deltamethrin

Anopheles dirus females landing on humans inside experimental huts treated with residual applications of DDT or deltamethrin were observed during the wet season in Pu Teuy Village, Kanchanaburi Province, western Thailand. Two identical experimental huts were constructed in the fashion of typical local rural Thai homes. Pretreatment (baseline) human-landing collections (HLC) in both huts showed an early evening peak of activity between 1900 and 2000 h with no significant difference in numbers of mosquitoes captured between huts over a period of 30 collection nights. During posttreatment HLC, female mosquitoes continued to show greater landing activity inside huts fitted with insecticide-treated panels during the first half of the evening compared with the second half. A greater number (proportion) of An. dirus females landed on humans in the hut treated with deltamethrin compared with DDT. Comparing pre- and posttreatment HLC, the DDT-treated hut showed a 79.4% decline in attempted blood feeding, whereas exposure to deltamethrin resulted in a 56.3% human-landing reduction. An odds ratio was performed to demonstrate the relative probability (risk) of mosquitoes entering and attempting to blood feed in the two treated huts compared with untreated control huts. Mosquitoes were approximately 0.47 times less likely to land on humans inside a DDT-treated hut compared with the deltamethrin-treated hut. Although both chemicals exerted strong excitatory responses, DDT appears to have a more pronounced and significant (P = 0.002) effect on behavior than deltamethrin, resulting in greater movement away from the insecticide source and thus potential reduction of blood-feeding activity.     

Survival outcome of cervical cancer patients treated by image-guided brachytherapy: a ‘real world’ single center experience in Thailand from 2008 to 2018

The objective of our study was to evaluate the survival outcome of cervical cancer patients treated using image-guided brachytherapy (IGBT). From 2008 to 2018, 341 patients with cervical cancer were treated by radical radiotherapy. IGBT (by computed tomography [CT] or transabdominal ultrasound [TAUS]) was used to treat all of these patients. The characteristic data and patient status after treatment were recorded. All data were evaluated for survival outcome analysis. From a total of 341 patients, 295 patients were analyzed and 46 patients were excluded due to data missing in the survival outcomes. At the median follow-up time of 48 months (IQR 30–80 months), The 4-year local control, progression-free survival and overall survival rates were 89.5%, 74.9% and 69.1%, respectively. For overall survival, the size (> 5 cm), pathology (non-SCCA), stage (stage III–IV by FIGO 2009), lymph node (LN) (presented) and overall treatment time (OTT) (> 56 days) showed statistical significance in univariate analysis while non-SCCA pathology, advanced stage, presented LN and longer OTT showed statistical significance in multivariate analysis. In conclusion, our analysis reports a 4-year overall survival rate of 69.1%. Non-SCCA pathology, advanced stage disease, LN presence and longer OTT showed worse prognostic factors in multivariate analysis.     

Evidence of anopheline mosquito resistance to agrochemicals in northern Thailand

The objective of this study was to assess insecticide resistance in anopheline mosquito populations in agroecosystems with high and low insecticide use in a malaria endemic area in Chiang Mai province in northern Thailand. Anopheline mosquitoes were collected in May and June 2004 from two locations with different agricultural insecticide intensity (HIGH and LOW), but similar in vector control strategies. The F1-generation of Anopheles maculatus s.s. and An. sawadwongporni were subjected to diagnostic doses of methyl parathion (MeP) and cypermethrin (Cyp), both commonly used insecticides in fruit orchards in Thailand. An. minimus A from the HIGH location was subjected to diagnostic doses to Cyp. CDC bottle bioassays were used to determine insecticide susceptibility. Time-mortality data were subjected to Probit analyses to estimate lethal time values (LT50 and LT90). Lethal time ratios (LTR) were computed to determine differences in lethal time response between populations from HIGH and LOW locations. The mortality of An. maculatus to MeP was 74% and 92% in the HIGH and LOW locations, respectively. The corresponding figures for An. sawadwongporni were 94% and 99%. There was no indication of resistance to Cyp for all species tested in either location. The LT90 and LT50 values of An. maculatus s.s. subjected to diagnostic doses of MeP were significantly different between locations (p<0.05). Reduced susceptibility to MeP in mosquito populations in the HIGH location is caused by intensive agricultural pest control and not by vector control activities, because organophosphates have never been used for vector control in the area. Our results indicate that there are still susceptible anopheline populations to pyrethroids, which is consistent with other research from the region. Therefore, there is presently no direct threat to vector control. However increased use of pyrethroids in agriculture may cause problems for future vector control.     

Geographical distribution and oncogenic risk association of human papillomavirus type 58 E6 and E7 sequence variations

Human papillomavirus (HPV) 58 accounts for a notable proportion of cervical cancers in East Asia and parts of Latin America, but it is uncommon elsewhere. The reason for such ethnogeographical predilection is unknown. In our study, nucleotide sequences of E6 and E7 genes of 401 HPV58 isolates collected from 15 countries/cities across four continents were examined. Phylogenetic relationship, geographical distribution and risk association of nucleotide sequence variations were analyzed. We found that the E6 genes of HPV58 variants were more conserved than E7. Thus, E6 is a more appropriate target for type‐specific detection, whereas E7 is more appropriate for strain differentiation. The frequency of sequence variation varied geographically. Africa had significantly more isolates with E6‐367A (D86E) but significantly less isolates with E6‐203G, ‐245G, ‐367C (prototype‐like) than other regions (p ≤ 0.003). E7‐632T, ‐760A (T20I, G63S) was more frequently found in Asia, and E7‐793G (T74A) was more frequent in Africa (p < 0.001). Variants with T20I and G63S substitutions at E7 conferred a significantly higher risk for cervical intraepithelial neoplasia grade III and invasive cervical cancer compared to other HPV58 variants (odds ratio = 4.44, p = 0.007). In conclusion, T20I and/or G63S substitution(s) at E7 of HPV58 is/are associated with a higher risk for cervical neoplasia. These substitutions are more commonly found in Asia and the Americas, which may account for the higher disease attribution of HPV58 in these areas.     

A survey of dengue viral infection in Aedes aegypti and Aedes albopictus from re-epidemic areas in the north of Thailand using nucleic acid sequence based amplification assay

Immature stages of Aedes aegypti and Ae. albopictus were collected from 17 dengue re-epidemic areas in Chiang Mai and Lampang Provinces, in the north of Thailand. They were reared to adults and tested for dengue viral RNA by a nucleic acid sequence based amplification assay (NASBA). Of a total of 9,825 Ae. aegypti and 150 Ae. albopictus examined, none of them were found positive for the virus, suggesting that transovarial transmission may be very low in the vector populations and may not play a significant role in the epidemiology of dengue infection in Thailand.