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@#Arthropods of medical importance such as mosquitoes, ticks and sandflies are one of the key drivers of arthropod-borne diseases outbreak, posing a great threat to global public health security. For further understanding the transmission mechanisms of arthropod-borne diseases and establishing the prevention and control measures, a series of experiments of arthropods infection need to be carried out under laboratory conditions. Besides the regular biosafety requirements, some specific considerations need to be taken into account when performing arthropod infection and the infected arthropod rearing. Except for the physical containment composed of biosafety facilities, a comprehensive assessment of the biosafety risks during operations and corresponding preventive measures are also critical to eliminate or mitigate the biosafety risks. In this paper, we introduce our practice in handling mosquito infection with Risk Group 2 pathogens in Arthropod Containment Level-2 (ACL-2) laboratory, with an aim to provide a reference for researchers in related fields.
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Background & objectives: Attractive toxic sugar baits (ATSB) is a novel tool which employs mosquito sugar feeding behaviour to kill them. The potential of ATSB against mosquito vectors has been demonstrated in limited scope around the world including Israel, some of the African countries and USA. But their efficacy against mosquito vectors of India is yet to be ascertained. Therefore, current study was planned to evaluate the efficacy of TSB (without attractant) against two important malaria vectors Anopheles culicifacies and An. stephensi along with major dengue vector Aedes aegypti. Methods: TSB solution was prepared by dissolving different concentrations of boric acid in glucose and tested against each of the mosquito species. Another experiment was done by spraying this boric acid sugar solution on to Calendula officinalis plant. It served as a sole source of mosquito feed and mortality of mosquitoes was counted after 24 hours. Results: The TSB resulted in 100% mortality of Ae. aegypti and An. stephensi at 4% concentration of boric acid while in An. culicifacies 100% mortality was achieved at 3% concentration TSB solution. TSB solution with 2% boric acid, resulted in 99.1% mortality in An. culicifacies while ~95 % mortality of An. stephensi and Ae. aegypti. When TSB solution with 2% boric acid was sprayed on plant, ~89-94% mortality was observed in both An. stephensi and An. culicifacies. Interpretation & conclusion: Based on the results, boric acid based toxic sugar bait solution could be a promising tool for vector control. Further studies are needed to find out its toxicity of TSB against non-target organisms and residual efficacy in field trials in different ecotypes.
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Background & objectives: In sterile insect technology (SIT), mating competitiveness is a pre-condition for the reduction of target pest populations and a crucial parameter for judging efficacy. Still, current SIT trials are being hindered by decreased effectiveness due to reduced sexual performance of released males. Here, we explored the possible role of a herbal aphrodisiac in boosting the mating activity of Aedes aegypti. Methods: Males were fed one of two diets in this study: experimental extract of Eurycoma longifolia (MSAs) and sugar only (MSOs). Differences in life span, courtship latency, copulation activity and mating success were examined between the two groups. Results: No deaths occurred among MSA and MSO males. Life span of MSOs was similar to that of MSAs. The courtship latency of MSAs was shorter than that of MSOs (P<0.01). MSAs had greater copulation success than MSOs (P<0.001). In all female treatments, MSAs mated more than MSOs, but the differences in rate were significant only in the highest female density (P<0.05). In MSAs, mating success varied significantly with female density (P<0.01), with the 20-female group (P<0.01) having the lowest rate. Single MSA had better mating success at the two lowest female densities. In MSOs, there were no significant differences in mating success rate between the different female densities. Interpretation & conclusions: Our results suggested that the herbal aphrodisiac, E. longifolia, stimulated the sexual activity of Ae. aegypti and may be useful for improving the mating competitiveness of sterile males, thus improving SIT programmes.
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Objective To investigate the seasonal fluctuations of mosquitoes in Taibai Lake area of Jining City,and evaluate the application effects of two mosquito trapping tools(Gongfu Xiaoshuai mosquito lamp and WJ-C mosquito sampler),so as to provide references for the effective surveillance,prevention and control of local mosquito vectors.Methods The overnight cap-ture of mosquitoes with a man-bait net trap,Gongfu Xiaoshuai mosquito lamp,and WJ-C mosquito sampler was performed to col-lect mosquitoes.The species of adult mosquitoes and seasonal fluctuations were investigated and analyzed.Results A total of 10 914 mosquitoes belonging to 13 species,5 genera were collected with the overnight capture of mosquitoes with the man-bait net trap,and Culex tritaeniorhynchus,Cx.pipiens palllen and Mansonia uniformis were the dominant species,accounting for 77.41％of the total.The proportion of Coquillettidia ochracea increased significantly.All the adult mosquitoes appeared in June,and reached the density peak in July and August.Both of the two surveillance tools showed relatively sensitive capture perfor-mance against mosquitoes.The trapping results of WJ-C mosquito sampler were basically the same as the man-bait trapping meth-od,however,the amount of Mansonia uniformis and Coquillettidia ochracea collected by Gongfu Xiaoshuai mosquito lamp was significantly lower than that of the man-bait trapping method.Conclusions The mosquito species are varied in Taibai Lake area of Jining City.Therefore,monitoring should be strengthened.In addition,the two mosquito trapping tools are sensitive,but they have both advantages and disadvantages,thus we should better pay attention to the consistency of monitoring methods in use.
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Background & objectives: Dengue is an arboviral disease of public health importance in many parts of India and recently many cases have been reported from northeastern India. Aedes mosquitoes, which are the vectors of dengue, are widely prevalent in the region. A study was initiated in Sonitpur district of Assam to understand the spatiotemporal distribution and seasonal prevalence of dengue vectors and to identify the high risk zones. Methods: Ovitrap surveys were conducted in three randomly selected villages under each of the eight public health centres (PHC) in district Sonitpur of Assam, northeastern India during March 2011 - February 2012. Three risk zones (high, medium and low) were identified on the basis of per trap density of Aedes mosquitoes. Meteorological data were collected to study the temporal distribution of dengue vectors. Results: Aedes albopictus (99.3%) was the predominant dengue vector followed by Ae. aegypti (0.7%) recorded in the ovitraps. The highest vector density was observed during the post-monsoon (60.1 ± 18 per trap) while the lowest during the winter (7.6 ± 4.9 per trap) and the season-wise differences in the vector density were significant (p=0.005). Maximum temperature (correlation coefficient, r = 0.45) and minimum temperature (r = 0.408) showed the highest positive correlation with the vector density, whereas the number of rainy days showed high positive correlation (r = 0.185) than the total rainfall (r = 0.117). The high risk zone (Dekhiajuli, Behali, Bihaguri and Gohpur PHC) as indicated by the high larval densities of dengue vectors, 45.3 ± 18, 42.1 ± 22.3, 36.9 ± 29.1, 35.3 ± 22.6 per trap, respectively, was validated by dengue epidemiological data collected during 2012. Interpretation & conclusions: Yearlong monitoring of dengue vectors was done for the first time in this region. Monthly maximum temperature and the number of rainy days could be used for the prediction of larval density of Aedes mosquitoes. The identification high dengue risk zones would help in adopting targeted interventions for disease management in future.
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In an entomological study conducted during monsoon and post- monsoon season in the hilly state of Nagaland, a total number of 58 mosquito species under 11 genera were recorded. Out of these, 21 species viz., Aedes aegypti, Ae. nigrostriatus, Ae. annandalei, Ae. vittatus, Ae.caecus, Ae. vexans, Armigeres kuchingensis, Culex fuscocephala, Cx. pseudovishnui, Cx. murrelli, Cx. brevipalpis, Cx. epidesmus, Cx. minor, Cx. whitmorei, Coquilittidae crassipes, Malaya jacobsoni, Ml. genurostris, Toxorhynchites splendens, Uranotaenia campestris, Mansonia dives and Ma. annulifera were recorded for the first time from this state. Eleven mosquito species recorded earlier were not detected in the present study. Thus, with the addition these 11 species, the total mosquito fauna of the state goes up to 69. All the recognized vectors of malaria in the northeast and the vectors of Japanese encephalitis and dengue are recorded in the present study.
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Objective To establish a simple,convenient,quick and high sensitive method of loop-mediated isothermal amplification (LAMP) for detection of Plasmodium vivax-carrying mosquitoes.Methods The species conservative regions of P.v CSP gene were selected to design 2 pairs of primers which recognized 6 distinct regions.To evaluate the specificity of detection by LAMP,infected Anopheles,An.sinensis (An.s),Plasmodium falciparum (P.f),and healthy human blood DNA were selected as templates.To assess the sensitivity of detection,1.3×10~6,1.3×10~5,1.3×10~4,1.3×10~3,1.3×10~2,1.3×10~1 and 1.3×10~0 copies of P.v CSP plasmid DNA mixed with 1.0 μl An.s DNA were used as the templates of LAMP.The infected An.s DNAs were diluted with negative An.s DNA by 1:2,1:4,1:8,1:16,1:32,1:64,1:128 and 1:256 and then detected by LAMP to show the sensitivity of batch quantity detection.The applied value of this method was evaluated by detecting the same batch of 67 artificial infected An.s mosquitoes,and compared with the detection of microscopic examination and nested PCR in parallel.Results By using LAMP,the detection of infected An.s was positive,while the control samples were all negative.The limits of detection of different proportion dilutions of the mixture of P.v CSP plasmid DNA with An.s DNA were 1.3×10~2 copies.The limits of detection of different proportion dilutions of the mixture of infected An.s DNA with An.s DNA were 1:128.The positive rate of detecting the same batch of 67 artificial infected mosquitoes was 47.76% by LAMP,25.37% by the microscopic examination (X~2 = 7.24,P0.05).Compared with the test of the microscopic examination and then with a statistical analysis,the sensitivity of LAMP was 100%,which agreed well with the sensitivity of nested PCR (100%).Conclusion The method of LAMP is simple,convenient and high sensitive,and it is a potential method for detecting Plasmodium vivax-carrying mosquitoes in the field.
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Detection of Plasmodium sporozoites-carrying mosquitoes is an important indicator in monitoring mosquitoes, evaluating the control of malaria and forecasting the incidence of malaria. Here, we review the detection techniques in Plasmodium sporozoites-carrying mosquitoes and the progress of their applied research, and then briefly discuss the principles of the detection and the prospects for the field.
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Objective To establish a specific, sensitive and simple assay for the detection of Brugia malayi larva in Anopheles sinensis .Methods Using a new DNA purification technique (Microcon 100) and two pairs of oligonucleotide primers (p1, p2 and p3,p4) suitable for detecting B malayi in seven areas in our country, the mosquito vectors infected by B malayi were detected by polymerase chain reaction(PCR).Results This PCR method could amplify separately a 322 basepair(bp) and a 155 bp DNA fragment and detect as few as 1/64 of one L 1 in 1 mosquito,the detectable limit was nearly 4 pg DNA of filarial larvae, and it could also detect 1 infected mosquito with one L 3 of B malayi in pools of up to 200 mosquitoes. In contrast,no such specific 322 bp or 155 bp DNA band was detected in Dilofilaria immitis and normal mosquito.Conclusion This PCR techique established for supervision of mosquito vector in B malayi endemic areas is specific,sensitive,and simple.