The present invention includes a first surface (0) on moving, relates to a system for counting the organisms passing through the second cylindrical surface with a substantially vertical generatrix, in particular, comprising at least one sensitive element (31) and the N thermal radiation detection cells comprise a thermopile (30) (11) creates a field of view (111) extending in one direction, provided with a means (34) which focuses the thermal radiation, the N detection cell (11) are distributed between two curves, the one curve is identical to the base line of the cylindrical surface on which organism crosses, the other curves, at least 5cm length equal to D (42) by the of which apart from the curve, the extension direction of the field of view of each cell, one of the two curves are substantially tangent to systems.