Present status of the Old World screwworm, Chrysomya bezziana (Diptera: Calliphoridae), in the Middle Region of Saudi Arabia

Full text: The Old World screwworm Chrysomya bezziana (Diptera: Calliphoridae) was reported in animals from the Middle Region of Saudi Arabia in 1998. Incidences of larval myiasis in sheep and seasonal activity of adult C. bezziana in the Riyadh Region were investigated during the period of Oct. 2001-June 2003. 3,712 sheep were examined and only 73 were found infested with C. bezziana larvae. Among the 73 infested sheep, 44 (60%) were young (less than 6 months old) and 29 (40%) were adults (above 6 months): 48 (66%) were females and 25 (34%) were males; and the mortality rate was 26% (12 young and 7 old sheep died). The infestation rates with C. bezziana were highest during March-May (60%) and Sept-Nov. (31.5%) when the temperature and humidity are optimum. During the hot dry and cold seasons infestation rate were low (5% and 1.5% respectively). During the same period, the seasonal activity of adult C. bezziana was also investigated using sticky traps baited with Swomlure-4. The baited traps were used twice a month. Unfortunately, only 19 adult flies were caught. From these results it is clear that C. bezziana is of no economic importance in the Middle Region of Saudi Arabia because of the long dry hot weather, which is unfavourable for larval development and adult survival. Further studies on the biology, distribution and economic importance of C. bezziana and other fly causing myiasis in Saudi Arabia are required. (author)