Non-Destructive near Infrared Spectroscopy for Simultaneous Prediction of Age and Species of Two Major African Malaria Vectors: An. Gambiae and An. Arabiensis

Abstract

Introduction M alaria kills over 600,000 people every year. The disease is transmitted only by female Anopheles mosquitoes that are 10–14 days old, because Plasmodium parasites take a long time to mature inside the mosquito. To stop malaria transmission from mosquitoes to hosts, vector control programmes must therefore reduce the lifespan of mosquitoes to below the parasite incubation period. Assessment of mosquito survival is thus a key determinant of the success or failure of a vector control programme. Species identification in a mosquito population is also crucial because different mosquito species require different interventions. Traditionally, age grading of malaria vectors has mainly relied on laborious and painstaking dissections to determine the reproductive history of mosquitoes. Sibling species identification within the critically important An. gambiae complex group from Africa relies almost exclusively upon standard polymerase chain reaction (PCR) analyses. These protocols are time-consuming and can be costly in a resource-limited area. It is for this reason that, in most cases, only a small sample of the population is tested to estimate species distribution. In the last five years, scientists from Ifakara Health Institute (Tanzania), QIMR Berghofer Medical Research Institute (Australia), United States Department of Agriculture and Centers for Disease Control and Prevention (USA) have been investigating the potential of applying near infrared (NIR) spectroscopy for simultaneous prediction of age and species of two major morphologicallyidentical African malaria vectors (Anopheles gambiae s.s. and Anopheles arabiensis) reared in different environments and preserved using different techniques. For mosquitoes, the NIR spectrum can be instantly collected from the heads and thoraces, and can be analysed for both age and species identification.