Optimisation of Sugar and Blood Feeding Regimen in Anopheles gambiae Mass Production System

Abstract

The sterile insect technique (SIT) is being developed for the control of malaria transmitting mosquitoes. Critical to the success of applying the SIT is the establishment of standardized mass production systems for the target species. As part of efforts to develop standardised mass production systems for malaria vectors, this project sought to optimize adult blood and sugar feeding in a mass production system. Different sugar types (glucose, sucrose and honey) were evaluated at 6 % and 10 % concentrations in water to determine the best sugar diet and concentration for feeding adult An. gambiae. Different blood feeding methods, restrained Guinea pig, anaesthetised Guinea pig and human arm feeding were evaluated. Adult survival, female insemination and egg production were used as criteria to determine optimum sugar and blood feeding. The effect of anaesthetics on blood feeding response and egg production of female An. gambiae was determined by comparing feeding response and egg production of females fed with anaesthetised Guinea pigs as against physically restrained Guinea pigs (Control). The specific effect of different anaesthetic agents on blood feeding response and egg production of female mosquitoes was also determined by comparing the feeding response and egg production of females fed with either Ketamine/Xylazine anaesthetised Guinea pigs or Ketamine/Diazepam anaesthetised Guinea pigs. Effects due to sugar types and concentrations on percentage survival of male and female mosquitoes were observed to be significant at (p < 0.05). Honey at 10 % concentration recorded the highest survival of 84.3 % after 1 week and 12.7 % after 6 weeks whilst glucose and sucrose recorded 81.0 % and 78.0 % respectively after 1 week and 1.3 % for both after 6 weeks. Survival up to 35 and 49 days for males and females respectively occurred only in adults fed with honey. The combined effects of blood feeding methods, anaesthetic types and feeding times on the propensity of female An. gambiae to feed and produce eggs were not significantly different (P > 0.05). However, human arm feeding (HAF) method and Ketamine/Xylazine (KX) anaesthetics fed for 25 minutes recorded higher percentage feeding (76.0 % and 68.0 % respectively) and egg production of 19.0 % and 20.8 % respectively. Anaesthetised Guinea pig feeding (AGF) of adults for 15 minutes followed closely with 60.0 % and 15.1 % blood feeding and egg production respectively whilst restrained Guinea pig feeding (RGF) method and Ketamine/Xylazine (KD) anaesthetic agents recorded the least values. It can be concluded that 10 % honey solution resulted in optimum feeding, survival and female insemination in adult An. gambiae compared to other treatments. Although both human arm feeding and Ketamine/Xylaxine anaesthetised Guinea pig feeding resulted in optimum productivity, anaesthetised Guinea pig feeding of adults for 15 minutes is the ideal feeding method for mass production systems. We recommend that 10 % honey solution, anaesthetised Guinea pig feeding method using 0.05 ml Ketamine/Xylazine anaesthetics and 15 minutes feeding time be employed for adult feeding in mass production of this species.