The self-consistency conditions (in the colloidal limit) formulated for the diluted hard convex body systems are used to discuss the third virial coefficient and to propose expressions for the individual contributions to the fourth virial coefficient of hard prolate spherocylinders. The proposed expressions yield values of the third and fourth virial coefficients in a fair agreement with the pseudo-experimental data. The equation of state formulated on the basis of expressions for the first few virial coefficients predicts the compressibility factor in full agreement with simulation data for elongations L* as high as 5. For pure hard spheres, the derived equation of state reduces to the Carnahan- Starling form; for hard sphere mixtures, the EOS differs slightly from the BMCSL expression.