A system for monitoring movement of the free-living second stage juveniles of root-knot nematodes (Meloidogyne spp.) using digital image analysis is described. The method is based on the analysis of video sequences of movement of individual nematodes encumbered with or without Pasteuria penetrans endospores. Software packages were used to grab video images, to process images and to monitor the movement of selected body part positions over time. The nematode centroid point and the nematode rectangular shape area were useful tools to estimate the locomotion. Data showed that a) the normal sinusoidal movement of nematodes is changed when individuals are encumbered with endospores of P. penetrans and b) in all cases a significant greater motility was observed by nematodes without P. penetrans endospores attached. Further, we modelled P. penetrans ‘over-dispersion’ in vitro and in vivo using the Poisson and the Negative Binomial distributions. The negative binomial distribution proved the most appropriate model to fit the observed data sets considering that P. penetrans spores are clumped.