Aedes aegypti (L.) (Diptera: Culicidae) is the primary arboviral vector of yellow fever, dengue fever, chikungunya, and Zika (Smith et al. 2018). Population surveillance of container-inhabiting mosquitoes, specifically Ae. aegypti, is an important priority of Anastasia Mosquito Control District (Dixon et al. 2020). There are several types of adult mosquito traps available commercially for surveillance and control of mosquitoes (Popko & Walton 2016), but most primarily collect either gravid or host-seeking mosquitoes but not both. For example, Reiter et al. (1986) reported on a trap designed for the collection of gravid Culex mosquitoes referred to as the Centers for Disease Control and Prevention (CDC) gravid trap. Later, Mackay et al. (2013) and Barrera et al. (2014a) reported on the development of the CDC's autocidal gravid ovitrap designed to collect container-inhabiting gravid Aedes. Later this trap proved to be a useful method for trapping local populations of Ae. aegypti in Puerto Rico (Barrera et al. 2014b). Eiras et al. (2014) also reported on another gravid trap that was later commercially developed as the Biogents Gravid (BG) Aedes Trap. A smaller economical version, called the BG Bowl Trap, was later developed by the company and marketed primarily for residential use for the control of container Aedes. All these traps use some form of fermented vegetative infusion to lure mosquitoes into them. During Anastasia Mosquito Control District surveillance and control operations, local residents and our mosquito control technicians always have been interested in commercial mosquito traps with multiple functions that could collect host-seeking and gravid mosquitoes simultaneously. Recently, Liu et al. (2019) reported on efforts to increase the collection of host-seeking and gravid Ae. aegypti into the CDC-autocidal gravid ovitrap trap by using a BG lure, whereas Zhu et al. (2019) added a suction fan to this trap for the same purpose. We report here on the continuation of a project to increase the functionality of commercial mosquito traps for simultaneous surveillance and control of host-seeking as well as gravid container-inhabiting Aedes.

Materials and Methods

A CDC gravid trap (John W. Hock, Gainesville, Florida, USA), BG-bowl trap (Biogents AG, Regensburg, Germany), and a modified CDC-autocidal gravid ovitrap trap, as described by Zhu et al. (2019), were used in this study. Each trap contained 200 mL of southern live oak (Quercus virginiana Mill. [Fagaceae]) leaf litter infusion (10 g of leaf litter per liter of reverse osmosis water fermented after 2 wk) plus a proprietary BG lure (Biogents AG, Regensburg, Germany) suspended inside (Fig. 1).

FIELD TEST

All 3 trap types, baited with BG lures, were placed together at 3 different sites in downtown St. Augustine (29.8946889°N, 81.3145194°W), Florida, USA. Specific locations were: South Street, Miruela Street, and Magnolia Street, which were selected based on previous Ae. aegypti larval surveillance (Dixon et al. 2020). Prior to placement, all traps were filled with 200 mL of southern oak leaf litter infusion as mentioned earlier in the semi-field study. A BG Bowl trap modified with a small catch mesh bag was attached to the bottom of the fan inside the trap to collect mosquitoes. All traps were placed in shaded locations 30 m apart, and collections removed at 24, 48, and 72 h post deployment. Batteries were replaced at the time of each mosquito collection. Mosquitoes were identified using the taxonomic key of Darsie and Morris (2003), and gravid status was verified by the presence of eggs in the ovaries after dissection under a stereomicroscope (United Scope LLC, Irvine, California, USA).

Fig. 1.

Mean dissected female mosquitoes with non-gravid and gravid Ae. aegypti collected by 3 modified commercial mosquito traps after release in screened outdoor enclosures.

Mean trap data in the semi-field and field studies were subjected separately to a multivariate ANOVA using JMP statistic software (SAS Institute, Cary, North Carolina, USA). All differences were considered significant at P ≤ 0.05. Due to the small data sets, the Tukey-Kramer HSD test was not performed.

Results

In the semi-field experiments, average numbers of female mosquitoes collected by BG Bowl, autocidal gravid ovitrap, and CDC-gravid traps were 100 ± 15, 65.6 ± 3, and 50 ± 8, respectively. We dissected an average of 96.6 ± 0.6 females caught by BG Bowl, 65.5 ± 0.4 females caught by autocidal gravid ovitrap, and 43 ± 0.3 females caught by the CDC-gravid trap. Averages of 72.7 ± 0.53 females caught by BG Bowl were host-seeking and non-gravid, 60 ± 0.4 females caught by autocidal gravid ovitrap trap were host-seeking and non-gravid, and 33.3 ± 0.2 females caught by CDC-gravid traps were host-seeking and non-gravid. We found a significant difference (F_{2, 6} = 5.58; P = 0.043) between the mean numbers of host-seeking and gravid Ae. aegypti collected by each of the 3 traps in the screened outdoor enclosures; the BG-Bowl trap collected the most. However, there was no difference (F_{2, 6} = 3.22; P = 0.112) between traps when comparing the mean number of gravid mosquitoes collected.

In field trials, a total of 443 adult female mosquitoes were captured, of which 94% were Ae. aegypti, 1% Ae. albopictus (Skuse) (Diptera: Culicidae), and 5% Culex quinquefasciatus Say (Diptera: Culicidae). The overall percentage of Ae. aegypti host-seeking and gravid individuals from all traps was 40% and 60%, respectively. Field collection site significantly influenced (F = 3.93; P = 0.008) the average number of mosquitoes of both physiological groups in traps, with the greatest number obtained from South Street (4.6) compared with the other 2 locations. The BG-bowl trap significantly collected the greater number of mosquitoes than the other 2 traps (F = 13.27; P < 0.0001).

Discussion

Traps combined with attractants have been found to increase the collection of adult mosquitoes (Xue & Smith 2013; Irish et al. 2015, Acevedo et al. 2020). Our study showed that the CDC gravid trap baited with Southern oak leaf infusion and a BG lure collected more Ae. aegypti mosquitoes than Culex, the latter for which it was originally designed in the field. A previous study by Cilek et al. (2017) showed that the BG Aedes trap, CDC-autocidal gravid ovitrap, and CDC gravid trap each baited with Southern oak leaf infusion collected Ae. aegypti, Ae. albopictus, and Cx. quinquefasciatus mosquitoes in northeastern Florida. In that study, the CDC gravid trap collected significantly more gravid Cx. quinquefasciatus mosquitoes than the other 2 trap types. But the CDC-autocidal gravid ovitrap and the BG Aedes trap collected a similar number of gravid Aedes mosquitoes (Cilek et al 2017). Our results also showed that the 3 modified traps collected host-seeking as well as gravid Ae. aegypti in a similar region of northeastern Florida.

In summary, a simple addition to the BG-Bowl trap, baited Southern oak leaf infusion, and BG lure (including a small mesh collection bag), collected significantly more host-seeking and gravid Ae. aegypti in the semi-field and field studies, compared with the other 2 traps in our study. Moreover, we found that the CDC gravid trap similarly modified, collected a greater number of host-seeking and gravid Ae. aegypti compared with the CDC-autocidal gravid ovitrap that added a suction fan. This finding indicates that the modified BG-Bowl trap and CDC gravid trap could be used for the surveillance, and possibly as a control trap tool, for host-seeking and gravid container-inhabiting Aedes.