SIT for the Malaria Vector Anopheles arabiensis in Northern State, Sudan: an Historical Review of the Field Site

It is planned to use the sterile insect technique (SIT) as part of an area-wide integrated pest management programme to drive Anopheles arabiensis Patton, the major vector of malaria in Sudan, back from the northern-most edge of its distribution on the Dongola and Abri-Delgo Reaches of the Nile, close to the border with Egypt. The coincidental location of the field site with Upper and Middle Nubia provides a wealth of historical information that can, in lieu of direct data, reveal clues to past changes in vector distribution. Major environmental transitions have occurred across the region since the last glacial maximum, 18 000 years ago: from hyper-arid desert to tropical grassland, then to semi-desert and back to tropical desert today. Large wild animals as diverse as giraffe and hippopotamus emerged and receded. In parallel, human activities and settlement patterns changed markedly with the rise and fall, and rise again, of the Kingdom of Kush during the Kerma and Kushite periods. These factors will have facilitated the spread of mosquito populations and then, by 1500 years ago, contributed to their reduction, or demise. The "saqia" water wheel introduced at the start of medieval times brought an expansion of the human population along the Nile and presumably a gradual resurgence in mosquitoes, which continued with occasional setbacks to the present day. Isolation was almost complete except for limited dispersal downriver via the Abu Hamed Reach. Evidence of malaria in ancient times has been found in Egypt and neighbouring River Nile State, but as yet historical indicators in Northern State are limited to the accounts of foreign visitors and date from 1813. Entomological records are available from about 1908. From these it appears that An. arabiensis is the only anopheline to have been found between the Second and Fifth Cataracts and that it has remained limited to the south of Wadi Halfa over the last century with only intermittent forays into Egypt, where it caused at least two serious malaria outbreaks.

KEYWORDS Anopheles arabiensis, Northern State Sudan, River Nile, mosquito distribution, Gambiae Control Project