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Innovations in mosquito mass-rearing techniques are essential in the quest to develop SIT (sterile insect technique) methods to fight mosquito vectors of disease. This study reports modifications to the Food and Agriculture Organisation/International Atomic Energy Agency (FAO/IAEA) mass-rearing cage (MRC) for mosquitoes to support the behaviour of adult Anopheles arabiensis Patton (Diptera: Culicidae) and to maximize egg production. The effects of an improved sugar-feeding device, and the addition of resting sites and a black cloth shroud to create an artificial horizon (visual contrast of light vs. dark at the edge) were assessed for their effect on adult longevity and egg production. Egg production of adults resulting from larvae reared in individual free-standing trays vs. those reared in the same trays in the FAO/IAEA larval rearing rack was also compared. Finally, the effect of blood feeding and frequency of egg collection from the MRC on average egg production per batch was investigated. Overall, the modifications to the MRC enhanced adult longevity, and the improved cage prototype allowed the collection of more eggs overall from a cohort of adults than was possible using the original and previous cage prototypes. These stepwise improvements are important for the development of economical and logistically efficient mass-rearing systems for the malaria vector An. arabiensis.

Background Anopheles arabiensis is one of the major malaria vectors that put millions of people in endemic countries at risk. Mass-rearing of this mosquito is crucial for strategies that use sterile insect technique to suppress vector populations. The sterile insect technique (SIT) package for this mosquito species is being developed by the Insect Pest Control Subprogramme of the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture. To improve mass-rearing outcomes for An. arabiensis, the question of whether the egg production by females would be affected by the size of the adult holding cages, the source of the blood meal and the total number of pupae that could be loaded into the cages was addressed and finally the impact of adding additional pupae to the cage daily to maintain adult numbers on egg productivity assessed. Methods Mass production cages of two different volumes, two different sources of blood meal (bovine and porcine) and two different population densities (cages originally loaded with either 15,000 or 20,000 pupae) were tested and evaluated on the basis of eggs produced/cage or per female. Males and females pupae with a ratio of 1:1 were added to the cages at day 1 and 2 of pupation. The emerging adults had constant access to 5% sugar solution and blood fed via the Hemotek membrane feeding system. Eggs were collected either twice a week or daily. A generalized linear model was used to identify factors which gave significantly higher egg production. Results Neither cage volume nor blood meal source affected egg production per cage or per female. However, increasing population density to 20,000 pupae had a negative effect on eggs produced per cage and per female. Although high density negatively impacted egg production, adding 1000 daily additional pupae compensating for daily mortality resulted in a substantial increase in egg production. Moreover, in all tests the first and the third egg batches collected were significantly higher than others eggs batches. With the equipment and protocols described here and routinely used at the Insect Pest Control Laboratory (IPCL), it was possible to produce up to 120,000 eggs/cage/day. Conclusion These results demonstrated that 15,000 is the optimal number of pupae to be loaded into the Anopheles Mass production cages. Under this condition, an average of 40 eggs per female was obtained for five gonotrophic cycles. However, an improvement in egg production can be achieved by daily addition, to the original 15,000 pupae, of one thousand pupae a day. Interestingly, feeding females with bovine or porcine blood using both large and small versions of the mass production cage did not affect egg productivity.