Assessment of a Novel Adult Mass-Rearing Cage for Aedes albopictus (Skuse) and Anopheles arabiensis (Patton)

Abstract

Successful implementation of the sterile insect technique (SIT) against Aedes albopictus and Anopheles arabiensis relies on a continuous supply of sterile males. To meet this requirement, optimization of the mass-rearing techniques is needed. This study, therefore, aims to assess a new mass-rearing cage (MRC) in terms of egg production efficiency and egg hatch rate (quality). In addition, adult survival was evaluated based on a cage adult-index for Ae. albopictus. Moreover, the cage's suitability for use in mass An. arabiensis egg production was compared to that of the FAO/IAEA Anopheles reference cage. In Ae. albopictus rearing, the new MRC produced 1,112,110 eggs per cage following six blood meals, with minimum loss of eggs in the egging water. Furthermore, the adult index gave a good proxy of daily mortality rates in Ae. albopictus. In An. arabiensis rearing, about 130,000 eggs per egg batch were collected both from the new and the reference MRC. These findings suggest that the new MRC prototype is efficient in terms of egg production and can be used for mass-rearing in SIT programs targeting Ae. albopictus as well as An. arabiensis. The adult index was also positively validated for the detection of unusual mortality rates in Ae. albopictus mass-rearing facilities. Overall, the new MRC has shown several advantages; however, further improvements are necessary to minimize escapes during the egg collection processes.

Keywords: adult index; dengue; egg production; genetic control; insect cage; malaria; plexiglass; sterile insect technique.

Figure 1

The structure of new mass-rearing cage (90 (L) × 90 (H) × 20 (W) cm) with the lower and the upper parts made of 1-cm-thick plates (A); the set-up with netting fixed with Velcro (VELCRO^® Freiberg am Neckar, Germany) (B); egg papers lining the walls of two black containers that can be removed laterally (C).

Figure 2

External view of the new mass-rearing cage prototype (90 (L) × 90 (H) × 20 (W) cm) (A) and the reference Anopheles mass-rearing cage (200 (L) × 100 (H) × 20 (W) cm) structure (B,C). The new mass-rearing cage (D) and the reference Anopheles mass-rearing cage (E) were covered with black cloth to enhance blood feeding.

Figure 3

Aedes albopictus egg production and egg hatch. (A) Mean number of eggs per female according to the week of egg collection. Egg hatch according to the (B) week of egg collection and (C) egg origin. Different letters above the bars indicate significant differences (post hoc Tukey test, p < 0.05). ** indicates a significant difference (likelihood ratio test (LRT), p < 0.01).

Figure 4

Anopheles arabiensis egg production. Mean number of eggs per female Anopheles arabiensis according to the (A) cage type (New, Reference), (B) collected egg batch, and (C) interaction between cage type and egg batch. Different letters above the bars indicate significant differences (post hoc Tukey test, df = 2, p < 0.05). ** indicates a significant difference (p < 0.01, interaction analyzed with Tukey test). NS stands for nonsignificant difference.