The applicability of spectrophotometry for the assessment of blood meal volume inartificially fed Culicoides imicola in South Africa

Abstract

The volume of the blood meal of haematophagous insects will determine the number of infective particles taken up during feeding and may as such denote the minimum dose needed to infect a competent vector. Culicoides midges resort among the smallest of haematophagous vectors and determining and comparing their blood meal volumes may be challenging. Collected Culicoides imicola females were fed on defibrinated bovine blood through a Parafilm® membrane using a Hemotek® system. After feeding, the weight of pools of 10 engorged females was compared to that of 10 unfed females to determine the volume of blood imbibed. After weighing, the pools were homogenized and their absorbance read at 410 nm. Spectrophotometer readings were then converted to blood meal volumes using calibration curves, obtained by the dilution of known volumes of blood used for feeding. Although the mean blood meal volumes determined spectrophotometrically (0.06 μL), differed significantly (P < 0.01) from those obtained by weighing (0.07 μL), the range in blood meal volumes determined spectrophotometrically (0.03–0.08 μL) and by weighing (0.01–0.11 μL) was positively correlated (r = 0.7; P < 0.01). Both methods can be used to determine the blood meal volume.