Impact of dengue-preventive behaviors on Aedes immature production in Bang Kachao, Samut Prakan Province, Thailand: a cross-sectional study.

BACKGROUND: Controlling sites where mosquitos breed is a key strategy in breaking the cycle of infectious transmission of the dengue virus. Preventive behaviors, such as covering water containers with lids and adding temephos (commercially named Abate sand) in water containers are needed to reduce and control mosquito breeding sites. This study aimed to investigate the impact of dengue-preventive behaviors on Aedes immature production. METHODS: This cross-sectional study used in-person interviews to record occurrence of dengue-preventive behaviors in Bang Kachao, Samut Prakan Province, Thailand. Larval mosquitos in and around houses were observed and recorded, and covered 208 households. RESULTS: It was found that 50% of these households had containers for drinking water and 94% used water containers. Covering water containers with effective lids showed the best success among dengue-preventive behaviors for reducing Aedes immature production. Adding temephos in water containers also was effective. CONCLUSIONS: Such behaviors substantively affected development of Aedes immatures in and around households.

Solenopsis geminata (tropical fire ant) anaphylaxis among Thai patients: its allergens and specific IgE-reactivity.

BACKGROUND: Specific IgE against Solenopsis invicta (imported fire ant) remains the current diagnostic tool for allergy to ants worldwide. However, S. invicta may not be the only cause of ant anaphylaxis in Thai patients. OBJECTIVE: To characterize ant species causing anaphylaxis in Thai patients and to test allergenic reactivity to whole body extracts (WBE) of S. geminata (tropical fire ants) in patients with evidence of IgE-mediated ant anaphylaxis. METHODS: Thirty-two patients with ant anaphylaxis were identified. The causative ants collected by the patients were subjected to species identification. Twelve patients with ant anaphylaxis and showed positive skin test or serum specific IgE to S. invicta and 14 control subjects were recruited. Whole body extraction from S. geminata was performed for protein characterization using SDS-PAGE and protein staining. IgE-immunoblotting and ELISA-specific IgE binding assays were performed on patients' sera and compared with controls. RESULTS: Of 32 patients with ant anaphylaxis, the most common causative ant identified was S. geminata (37.5%). Western blot analysis of crude S. geminata revealed 13 refined protein components that bound to patients' serum IgE. Three major allergens with molecular masses of 26, 55 and 75 kDa were identified. All 12 patients gave positive results for specific IgE to S. geminata with statistically significant higher absorbance units of 0.390 ± 0.044, compared to healthy control group (0.121 ± 0.010), P < 0.01. CONCLUSIONS: S. geminata is identified as the most common causative ant anaphylaxis in Thai patients. Its WBE comprises of 13 IgE-binding components and 3 major allergens (26, 55 and 75 kDa), which supported possible IgE-mediated mechanism.

IDENTIFICATION OF BAT ECTOPARASITE LEPTOCIMEX INORDINATUS FROM BAT-DWELLING CAVE, KANCHANABURI PROVINCE, THAILAND.

Bat bugs are blood-feeding insects of bats or warm blooded animals and humans. Since 2011, Leptocimex spp (Heteroptera: Cimicidae) has been reported in Thailand. However, microscopic examination of Leptocimex spp is complicated, especially when the entire body of the specimen is not available. To confirm the phenotypic identification of L. inordinatus from a limestone bat cave in Thailand, partial fragments of mitochondrial cytochrome c oxidase subunit 1 (COI) gene and 16S mitochondrial ribosomal DNA were PCR amplified and sequenced, which revealed 97% sequence identity with Cimicidae family members, being most similar to Cacodminae gen. sp. and C. vicinus, both bat bugs. Phylogenetic tree construction showed that L. inordinatus has a separate genetic lineage from that of with human bed bugs (Cimex hemipterus or C. lectularius), swallow bugs and other tick species. The presence of L. inordinatus in a bat-dwelling cave frequented by humans presents a potential public health problem requiring attention in particular regarding the possibility of zoonotic transmission of pathogens.

Ant allergens and hypersensitivity reactions in response to ant stings.

Hypersensitivity reactions caused by ant stings are increasingly recognized as an important cause of death by anaphylaxis. Only some species of ants ( e.g. Solenopsis spp., Myrmecia spp., and Pachycondyla spp.) cause allergic reactions. Ant species are identified by evaluating the morphologic structures of worker ants or by molecular techniques. Ant venom contains substances, including acids and alkaloids, that cause toxic reactions, and those from Solenopsis invicta or the imported fire ant have been widely studied. Piperidine alkaloids and low protein contents can cause local reactions (sterile pustules) and systemic reactions (anaphylaxis). Imported fire ant venoms are cross-reactive; for example, the Sol i 1 allergen from S. invicta has cross-reactivity with yellow jacket phospholipase. The Sol i 3 allergen is a member of the antigen 5 family that has amino acid sequence identity with vespid antigen 5. The clinical presentations of ant hypersensitivity are categorized into immediate and delayed reactions: immediate reactions, such as small local reactions, large local reactions, and systemic reactions, occur within 1-4 hours after the ant stings, whereas delayed reactions, such as serum sickness and vasculitis, usually occur more than 4 hours after the stings. Tools for the diagnosis of ant hypersensitivity are skin testing, serum specific IgE, and sting challenge tests. Management of ant hypersensitivity can be divided into immediate (epinephrine, corticosteroids), symptomatic (antihistamines, bronchodilators), supportive (fluid resuscitation, oxygen therapy), and preventive (re-sting avoidance and immunotherapy) treatments.

Comparison of Two Different Morphological Methods to Study the Pronotum of Cimicidae: Bed Bugs, Bat Bugs, and Swallow Bugs.

An infestation of a Cimicidae (Hemiptera: Cimicidae) member, especially the bed bug, can cause economic loss and impact health. A cost-effective and user-friendly method for identifying the infesting species will help with the early detection and control of infestations. A linear morphometric method is often used, but it requires the examination of many characters and a highly preserved specimen. We conducted a comparative morphometric study of the effectiveness of Cimicidae classification using a single organ, the pronotum, through outline-based and linear morphometric methods. Bat (Stricticimex parvus), human (Cimex hemipterus), and bird (Paracimex sp.) ectoparasites were subject of the study. With both methods, the properties of size and shape were compared and used separately to classify the specimens. Classification analyses of the two methods provided similar results, but more informative variables of size and shape were obtained with the outline-based approach. Size, as analyzed with the outline-based method, could detect sexual dimorphism, and produced better reclassification. The shape variables obtained from the linear measurements were strongly influenced by size variation, much more than the ones obtained from coordinates describing the pronotum contours. Our data suggest that the outline-based approach provides better characterization variables, thus we recommend them for a wider use in other Cimicidae family members.

Competitive suppression between chikungunya and dengue virus in Aedes albopictus c6/36 cell line.

Aedes albopictus C6/36 cell line was used to evaluate dengue virus serotype-3 (DENV-3) and chikungunya virus (CHIKV) co-infection. Virus infection was determined using a one-step duplex reverse transcriptase polymerase chain reaction (D- RT-PCR). D-RT-PCR was positive for both viruses when equal multiplicity of infection (MOI) was utilized. Co-infection with different titers between a higher CHIKV titer (MOI = 1.0) than DENV-3 titer (MOI = 0.1) showed similar results with that of equal titer. However, co-infection with a lower CHIKV titer (MOI = 0.1) than DENV-3 titer (MOI = 1.0) revealed positive results for only dengue virus infection, suggesting DENV competitive suppression of CHIKV. This competitive suppression occurred in mixed-infection samples but not in individually double infection (super infection) samples which produced both dengue and chikungunya virus progenies. Both virus replications depend on the amount of virus titer rather than serial infection. These findings have provided information regarding pathogen-pathogen interaction in host cell, which could be used to predict outbreaks, and to develop virus detection and vector control.

Current Arboviral Threats and Their Potential Vectors in Thailand.

Arthropod-borne viral diseases (arboviruses) are a public-health concern in many regions of the world, including Thailand. This review describes the potential vectors and important human and/or veterinary arboviruses in Thailand. The medically important arboviruses affect humans, while veterinary arboviruses affect livestock and the economy. The main vectors described are mosquitoes, but other arthropods have been reported. Important mosquito-borne arboviruses are transmitted mainly by members of the genus Aedes (e.g., dengue, chikungunya, and Zika virus) and Culex (e.g., Japanese encephalitis, Tembusu and West Nile virus). While mosquitoes are important vectors, arboviruses are transmitted via other vectors, such as sand flies, ticks, cimicids (Family Cimicidae) and Culicoides. Veterinary arboviruses are reported in this review, e.g., duck Tembusu virus (DTMUV), Kaeng Khoi virus (KKV), and African horse sickness virus (AHSV). During arbovirus outbreaks, to target control interventions appropriately, it is critical to identify the vector(s) involved and their ecology. Knowledge of the prevalence of these viruses, and the potential for viral infections to co-circulate in mosquitoes, is also important for outbreak prediction.

The Unequal Taxonomic Signal of Mosquito Wing Cells.

Accurate identification of mosquito species is critically important for monitoring and controlling the impact of human diseases they transmit. Here, we investigate four mosquito species: Aedes aegypti, Ae. albopictus, Ae. scutellaris and Verrallina dux that co-occur in tropical and subtropical regions, and whose morphological similarity challenges their accurate identification, a crucial requirement in entomological surveillance programs. Previous publications reveal a clear taxonomic signal embedded in wing cell landmark configuration, as well as in the external contour of the wings. We explored this signal for internal cells of the wings as well, to determine whether internal cells could uniformly provide the same taxonomic information. For each cell to be tentatively assigned to its respective species, i.e., to measure the amount of its taxonomic information, we used the shape of its contour, rather than its size. We show that (i) the taxonomic signal of wing shape is not uniformly spread among internal cells of the wing, and (ii) the amount of taxonomic information of a given cell depends on the species under comparison. This unequal taxonomic signal of internal cells is not related to size, nor to apparent shape complexity. The strong taxonomic signal of some cells ensures that even partly damaged wings can be used to improve species recognition.

Characterization of chikungunya virus infection of a human keratinocyte cell line: role of mosquito salivary gland protein in suppressing the host immune response.

The chikungunya virus (CHIKV) is a mosquito-borne virus that has recently re-emerged in several countries. On infection, the first vertebrate cells to come into contact with CHIKV are skin cells; mosquitoes inoculate the virus together with salivary gland protein into host skin while probing and feeding on blood. However, there is little known about the susceptibility of human skin cells to CHIKV infection. To clarify this, we investigated the kinetics of CHIKV in the human keratinocyte cell line, HaCaT. CHIKV actively replicated in HaCaT cells, with virus titers in the supernatant increasing to 2.8 × 10(4) plaque-forming units (PFU) ml(-1) 24h post infection. CHIKV infection suppressed production of interleukin-8 (IL-8) in HaCaT cells. The function of IL-8 is to recruit immune cells to virus-infected sites, a process known as chemotaxis. Furthermore, we assessed the role of mosquito salivary gland protein in CHIKV infections by comparing the levels of CHIKV gene expression and chemokine production in HaCaT cells with and without salivary gland extract (SGE). SGE enhanced both the expression of the CHIKV gene and the suppression effect of CHIKV on IL-8 production. Our data suggest that the HaCaT cell line represents an effective tool for investigating the mechanism of CHIKV transmission and spread in skin cells. At the mosquito bite site, CHIKV works together with SGE to ensure the virus replicates in skin cells and escapes the host immune system by suppression of IL-8 production.