MEASUREMENT BY MEMBRANE FEEDING OF REDUCTION IN PLASMODIUM-FALCIPARUMTRANSMISSION INDUCED BY ENDEMIC SERA

The standard laboratory test for reduction in malaria transmission is based on the measurement of oocyst numbers in mosquitoes fed on blood meals containing test and control sera. Interpretation of the results, however, is often hampered by the large variation in numbers of infec ted mosquitoes and oocysts. The objective of this study was to compare 3 measures for the assessment of transmission reduction (so-called R values) and to define the experimental criteria that allow interpretat ion of the results. To determine variability in R values of control se ra, a replicate experiment was performed with 10 non-endemic sera of D utch blood donors. Furthermore, 2 measures for calculation of transmis sion reduction were compared in a triplicate experiment using Plasmodi um falciparum, Anopheles gambiae and malaria endemic sera. Calculation s using the geometric mean of Williams are currently used to identify blocking and non-blocking sera. However, calculations using log-transf ormed data could distinguish more gradual levels of transmission reduc tion activity by endemic sera-i.e. blocking, reducing and non-blocking activity. Grading of transmission reduction activity is important for epidemiological studies on transmission immunity and for validation o f future transmission-blocking vaccines.