A semi-automated method for counting fluorescent malaria oocysts increases the throughput of transmission blocking studies

Table 2 Comparison of the transmission blocking potential of two anti-malarials determined by manual and automated counts

Manual count
	Intensity as a % of solvent control (SEM)	Mean prevalence % (SEM)	Reduction in intensity % (SEM)	Reduction in prevalence % (SEM)
DMSO	100 (0)	91.05 (2.95)	0 (0)	0 (0)
DMF	100 (0)	96.90 (0.36)	0 (0)	0 (0)
CH	0 (0)	0 (0)	100 (0)	100 (0)
DHEA-S	82.21 (12.84)	72.78 (11.53)	17.79 (12.84)	10.18 (4.73)
LUM	10.85 (3.35)	69.45 (5.66)	89.15 (3.35)	28.3 (6.01)
Automated count
	Mean oocyst intensity as a % of solvent control (SEM)	Mean prevalence % (SEM)	Reduction in intensity % (SEM)	Reduction in prevalence % (SEM)
DMSO	100 (0)	95.85 (4.87)	0 (0)	0 (0)
DMF	100 (0)	94.60 (1.51)	0 (0)	0 (0)
CH	0.20 (0.13)	5.61 (0.68)	99.80 (0.13)	94.32 (0.62)
DHEA-S	72.59 (3.57)	89.26 (5.25)	27.41 (3.57)	4.37 (4.06)
LUM	15.25 (3.98)	71.95 (8.12)	84.75 (3.98)	24.18 (8.12)

The automated counting macro produced oocyst intensity and prevalence figures closely matching those determined by a manual count. The two anti-malarial compounds and controls were fed to mosquitoes (n = 28-58) in triplicate experiments. 7-9 days after feeding, the midguts were dissected and imaged before being counted both manually and by the counting macro. The mean oocyst intensity is expressed as a percentage of the solvent control, and the reduction in intensity is expressed as 100% minus the mean oocyst intensity. The mean prevalence is expressed as the mean percentage of the number of infected mosquitoes for each replicate, and reduction in prevalence is calculated using the following formula: (individual replicate prevalence/corresponding control prevalence) ×100, then taking the mean of the three replicates and subtracting it from 100%. Calculated standard error of the mean in brackets. By manual count of the parasite-infected midguts, LUM and CH showed a marked inhibition of sporogony. DHEA-S however showed minimal effect on sporogony. The automated count by the macro concurred well and showed no significant deviation from the manually determined counts. The prevalence of infection recorded by the counting macro also closely matched the manually determined values.

ISSN: 1475-2875