A total of 512 chub (Leuciscus cephalus L.) individuals sampled from four rivers with different pollution levels were examined for Lamproglena pulchella (von Nordmann 1832) prevalence and mean intensity. As a result of the L. pulchella mode of reproduction, the parasite populations showed a significant degree of aggregation. The results, excluding the effect of fish health conditions on the parasite infection, provide evidence of the influence of water quality on parasite prevalence. Parasite density increase in relation to fish length and age suggests a dependence of infection intensity to the exposure time on the fish.