Evaluation of the effectiveness of the human-baited double net traps and BG traps compared with the human landing catches for collecting outdoor Aedes albopictus in China.

Dengue fever is one of the biggest threats to public health in China, causing huge disease burden and economic loss. Aedes-mosquito surveillance could be a cornerstone for predicting the risk of Aedes-borne diseases and evaluating the effect of vector management during diseases outbreaks. The human landing catch (HLC) method is regarded as the "gold standard" for catching Aedes mosquitoes, but it potentially exposes field professionals to vectors of known or unknown pathogens. Human-baited double net (HDN) was recommended to replace HLC for emergency monitoring in China when Aedes-borne diseases break out, but it had been reported with low efficiency for capturing Aedes mosquitoes. In this study, we compared HLC with HDN and BG traps for field Aedes albopictus monitoring, with the aim of evaluating the effectiveness of HDN replacing HLC and finding an effective and safe alternative to the HLC for monitoring Aedes albopictus. Six sites in Hangzhou, Shaoxing, and Yiwu, Zhejiang Province, China, were chosen to conduct outdoor HLC, HDN, and BG trap catches from June to October 2021. The tests were performed 3 h apart: 8:30-9:30 AM, 16:30-17:30 PM, and 17:30-18:30 PM. A total of 2330 adult mosquitoes were collected, and Aedes albopictus was the most abundant species in all three catches with 848(98.95%), 559(97.39%) and 867 (96.44%) caught in HLC, HDN and BG traps respectively. Compared to HLC, HDN collected significantly less Ae. albopictus and Ae. albopictus females per trapping period (P < 0.001, P < 0.001), whereas no statistical differences were found between the HLC and BG trap (P = 0.970, P > 0.05). Statistically significant positive spatial correlations for Ae. albopictus sampling was found between HLC and HDN traps (r = 0.543, P < 0.001) and HLC and BG traps (r = 0.658, P < 0.001). In conclusion, both the BG trap and HDN have a significant positive spatial correlation with HLC, making them safer alternatives to HLC for Ae. albopictus monitoring in China. However, with better a sampling efficiency, being less labor intensive, and no human-baited attraction bias, the BG trap could be a better choice than the HDN trap.

Sand Fly (Diptera: Psychodidae: Phlebotominae) Population Dynamics and Natural Leishmania Infections in Attica Region, Greece.

A 2-yr sand fly (Diptera: Psychodidae) seasonality study was performed in Attica Region, Greece, from June 2017 until November 2018, aiming also to detect the presence of Leishmania infection in the collected sand flies. In total, 701 sand flies were collected from urban areas within the Attica Region using BG-Sentinel traps, set weekly in eight fixed sites. Five species were identified morphologically and molecularly, namely Phlebotomus tobbi (Adler and Theodor), which was most the most commonly collected species, followed by P. Neglectus (Tonnoir), P. papatasi (Scopoli), P. simici (Theodor), and Sergentomyia minuta (Rondani). During both survey years sand fly populations peaked in late August to early September. Fifty-nine monospecific pools were examined for Leishmania detection by analyzing the ITS1 nuclear region using both RFLPs and sequencing, seven of which were found positive. Leishmania DNA was identified as L. infantum in six pools (five P. papatasi and one P. tobbi), whereas in one P. papatasi pool Leishmania DNA was identified as L. tropica. This is the first time that L. tropica has been detected in naturally infected sand flies from the Attica Region as well as in central Greece, while previously it has only been detected in sand flies collected from Central Macedonia (Northern Greece).

Comparison of the effectiveness of BG-trap mosquito traps using carbon dioxide versus BG-lure attractants / 中国热带医学

@#Abstract: Objective　To compare the mosquito trapping effect of BG-trap mosquito trap using carbon dioxide versus BG-lure attractant under filed conditions. Methods　In August and September 2020, two areas were set with a distance of 100 m. Two sites were set at each area, and one mosquito trap BG trap was set with a distance of 5 m. Each site was set with different flow of CO2 and different amount of BG-lure attractants. The BG-trap mosquito traps on the same area would exchange positions every other day. The mosquitoes captured by each mosquito trap was collected and classified. and the species, sex and number of mosquitoes captured were recorded and counted. Results　The densities of Aedes albopictus captured by BG+/CO2-and BG-/CO2+were 14 and 31, and that of Culex pipiens pallens were 2 and 16, respectively. The differences were statistically significant (Aedes albopictus, t=-2.675, P<0.05; Culex pipiens pallens, t=-4.873, P<0.05). With BG-lure attractant, the females of Aedes albopictus and Culex pipiens pallens in the CO2+group were 2.6 (25/9.5) and 12.0 (12 /1) times higher than those in the CO2-group, and the differences were statistically significant (female Aedes albopictus, t=-4.119, P<0.01; female Culex pipiens pallens, t=-4.592, P<0.01), suggesting that the most important attractant to female mosquitoes is CO2. With BG-lure attractant, the male Aedes albopictus in the CO2+ group was 3.0 (12/4) times higher than that in the CO2-group, and the difference was statistically significant (male Aedes albopictus, t=-3.284, P<0.01). Without BG-lure attractant, female Aedes albopictus and female Culex pipiens pallens in the CO2 + group were 1.8 (18 / 10) and 15.5 (15.5/1.0) times higher than those in the CO2-group, and the difference was statistically significant (female Aedes albopictus, t=-2.868, P<0.05; female Culex pipiens pallens, t=-5.259, P<0.05). Without BG-lure attractant, the male Aedes albopictus in the CO2+group was 2.0 (9.0/4.5) times higher than that in the CO2-group, with a statistically significant difference (t=-2.508, P<0.05). With CO2, Aedes albopictus and Culex pipiens pallens in the BG + attractant group were 1.4 (43.5/31) and 0.78 (12.5/16.0) times higher than those in the BG-attractant group, and the differences were not statistically significant (Aedes albopictus, t=-0.943, P>0.05 ; Culex pipiens pallens, t=0.709, P>0.05). Without CO2, Aedes albopictus and Culex pipiens pallens in the BG + attractant group were 1.0 (14/14) and 2.0 (2.0/1.0) times higher than those in the BG + attractant group, and the differences were not statistically significant (Aedes albopictus, t=-0.500, P>0.05; Culex pipiens pallens, t=-1.000, P>0.05). Without BG-lure attractant, the densities of female Aedes albopictus captured by adding 0, 1 and 2 parts of dry ice were 10, 17.5 and 18 respectively, and the difference was statistically significant among the three groups (F=3.942, P<0.05). The densities of female Culex pipiens pallens captured were 1, 13 and 18 respectively, and the difference was statistically significant among the three groups (F=13.881, P<0.05). However, there was no significant difference between the capture of female Aedes albopictus and female Culex pipiens pallens by adding 1 part of dry ice and 2 parts of dry ice (female Aedes albopictus, t=0.112, P>0.05; female Culex pipiens pallens, t=-0.540, P>0.05). Without CO2, 10, 10, 9.5 and 1, 1 and 1.5 female Aedes albopictus and Culex pipiens pallens were captured by adding 0, 1 and 2 portions of BG-lure attractants, respectively. There were no significant differences between the three groups (female Aedes albopictus, F=0.120, P>0.05; female Culex pipiens pallens, F=0.477, P>0.05). Conclusions　In the monitoring of BG-trap mosquito trap, the mosquito trapping effect of CO2 is better than that of BG-lure attractant. When the same monitoring effect is obtained, the use of CO2 (100 mL/min) can save the use cost.

Evaluation of the human-baited double net trap and BG trap as an alternative to human landing catches for collecting outdoor Aedes albopictus in China

Objective: Monitoring the density of Aedes(Ae.) albopictus was very important in evaluating the efficiency of vector management, especially when Aedes-borne diseases break, like Dengue fever, Chikungunya fever and Zika. Human landing catch (HLC) is regarded as the “gold standard” for Aedes monitoring, but it is unsafe and unethical since it potentially expose field professionals to a series of pathogens. In this study, we compared HLC with human-baited double net (HDN) and BG trap for field Aedes albopictus monitoring.The study aims to find an effective and safe alternative method to HLC in monitoring Ae. albopictus, especially in emergency monitoring. Methods: Latin square design was used, and three sites in Hangzhou city, Zhejiang province, China, were chosen to conduct outdoor HLC, HDN and BG trap catches in June. The tests were performed at three periods: a morning period (8:30-10:00), an afternoon period (15:00-16:30), and an evening period (16:30-18:00). Then a table with 81 elements was made to compare the efficiency of these three methods. Results: A total of 80, 138 and 78 adult Ae. albopitus was captured by HDN, BG trap and HLC, respectively. Among these three catches, BG trap showed the best efficacy in captured Ae. albopitus adults. The mosquitoes caught by HLC and BG trap were nearly the same at all three time series, but the density of mosquitoes caught by HDN at 16:30-18:00 was 2 times the density at 8:30-10:00 (4.44 vs 2.22 per hour). In this study, significant positive correlation between HLC and BG trap of Aedes albopitus female density was found (r=0.921, P<0.001). However, no statistical significant correlation between HLC and HDN, BG trap and HDN of Ae. albopitus female density was found (r=-0.46, P=0.820; r=0.019, P=0.923, respectively). Besides, the human-bait attraction bias of HLC catches might be more apparent than BG trap and HDN catches. Conclusions: According to our study, with high efficiency, less human-bait attraction bias, and significantly positive correlation with HLC in catching Ae. albopitus females, BG trap could be a sensitive and safer alternative to HLC for outdoor Ae. albopitus monitoring. It also showed strong potential in emergency monitoring when Aedesborne diseases break.