When the relevant health and research institutions began to develop the feasibility study, they gave immediate attention to informing people how a successful project would help in eliminating the malaria vector. In addition, it was made clear that other benefits resulting from the research and development would be made available readily and affordably to the stakeholders and the whole country. These include improved malaria diagnostic techniques and laboratory capabilities including equipment and better trained technicians and scientists.
Malaria is a public health problem in Northern State, affecting its economy and development. Although the total population of the state is not large, much money is spent currently on malaria treatment and control. If it is assumed, conservatively, that the above-mentioned 17 hospitals' outpatients represent the state population, elimination of the malaria vector will protect about 186,000 individuals from being infected every year. With limited resources assigned to the programme for continuing surveillance following elimination of the vector, the area could be maintained free of malaria vectors in a sustainable manner. Therefore, the implementation of such a project in an endemic area like Northern State will have a very positive impact on all the stakeholders.
The socio-economic impact of the feasibility study is expected to be great. The current cost of treatment of an uncomplicated malaria case in Sudan averages US$ 12 . More than US$ 2,232,000 is spent annually in Northern State for malaria treatment. In addition, the vector control programme consumes more than 17 tons of insecticides, and the high running cost is about US$ 260,000 per year (E. M. Malik, personal communication). Therefore, a successful feasibility study will have a major economic impact, enhance the development of the area, and minimize harmful effects on human health and the environment by reducing the need for chemical control of the vector.
In spite of these obvious benefits, some aspects of the approach may still be a cause for concern. Some may be concerned about the effects of eradicating the mosquito population on the food chain and on the ecological balance. However, elimination of An. arabiensis is not expected to affect the food chain significantly since the density of the vector in this area is not high, and other species of mosquitoes (which could serve as alternate prey) are abundant. Also, non-target species are not affected because the SIT is species-specific, and this preserves as much as possible the natural ecosystem. It was clearly demonstrated that the abundance of a non-target anopheline species in the Lake Apastapeque releases in El Salvador, Anopheles pseudopunctipennis was not affected by the application of the SIT against the target species Anopheles albimanus .
The release of large numbers of irradiated sterile mosquitoes into the environment may also raise questions among the local population and effective public information programmes will be required. However, it has to be stressed that the released insects are males, which do not transmit any disease, they are not radioactive, and because they are sterile they do not increase the size of the natural population. Therefore, their release is considered to be essentially benign in terms of environmental impact. Removable of females from the release material is a priority for reasons of efficacy and public health and will be accomplished by the use of a genetic sexing strain in the mass rearing facility.
Several biosafety aspects of handling mosquitoes and the irradiation process must be considered. To prevent the escape of reared mosquitoes, appropriate quarantine containment and precautions will be put in place, as described in the Arthropod Containment Guidelines, Arthropod Containment Level 2 . The irradiator is a fully shielded Nordion 220 cobalt-60 Gammacell located in a secure facility at Soba: it is owned by SAEC and operated by well-trained staff who are required to wear personal dosimeters. The specified gamma radiation dose (70 Gy) currently requires one minute exposure. Dosimetry films are also included with the samples to confirm that the proper radiation dose was received by the mosquitoes.
Malaria cases, and the abundance and genotype of released males, will be monitored indirectly by trapping females and assessing their fertility status. There are currently no trapping methods available to directly monitor sterile male abundance. The abundance of target and non-target mosquitoes, and changes in the number of malaria cases in the release area, will be measured. Any unexpected hazards or outcomes will be reported and responses implemented.
Although capacity building is required mainly to cope with the scientific demands of the project, it is also one of the essential administrative considerations. The project is participating significantly in capacity building in the host institutions and at the field site to ensure sustainability, the appropriate scientific conduct of the study, and to function as equal partners in a collaborative project. The extent to which the project contributes to enhancing local health care and increasing the ability to respond to public health needs through training is one of the most important factors being considered during the development phase of the project.