Automation for tsetse mass rearing for use in sterile insect technique programmes. Final report of a co-ordinated research project 1995-2001

The rearing of tsetse flies for the sterile insect technique has been a laborious procedure in the past. The purpose of this co-ordinated research project (CRP) 'Automation for tsetse mass rearing for use in sterile insect technique programmes' was to develop appropriate semiautomated procedures to simplify the rearing, reduce the cost and standardize the product. Two main objectives were accomplished. The first was to simplify the handling of adults at emergence. This was achieved by allowing the adults to emerge directly into the production cages. Selection of the appropriate environmental conditions and timing allowed the manipulation of the emergence pattern to achieve the desired ratio of four females to one male with minimal un-emerged females remaining mixed with the male pupae. Tests demonstrated that putting the sexes together at emergence, leaving the males in the production cages, and using a ratio of 4:1 (3:1 for a few species) did not adversely affect pupal production. This has resulted in a standardized system for the self stocking of production cages. The second was to reduce the labour involved in feeding the flies. Three distinct systems were developed and tested in sequence. The first tsetse production unit (TPU 1) was a fully automated system, but the fly survival and fecundity were unacceptably low. From this a simpler TPU 2 was developed and tested, where 63 large cages were held on a frame that could be moved as a single unit to the feeding location. TPU 2 was tested in various locations, and found to satisfy the basic requirements, and the adoption of Plexiglas pupal collection slopes resolved much of the problem due to light distribution. However the cage holding frame was heavy and difficult to position on the feeding frame and the movement disturbed the flies. TPU 2 was superseded by TPU 3, in which the cages remain stationary at all times, and the blood is brought to the flies. The blood feeding system is mounted on rails to make it easier to move, and with a simple locating system it is quick and easy to move the unit to the next set of cages. This system has proved satisfactory for all tsetse species tested, and is being validated for large scale rearing projects in Burkina Faso and Ethiopia. The use of inserts in cages was also investigated, but with mixed results. In initial tests cardboard inserts increased the usable fly density in cages one and a half to two fold, but cardboard is impractical for routine use and subsequent tests with plastic inserts did not achieve such good results. The use of inserts was not continued, but new developments of cage design may enable inserts to be used in the future