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Amphibian species are known to carry endoparasitic mites. The infestation probability, prevalence, and intensity of mites vary among species and habitats. Mites of the genus Endotrombicula are known to infest African and Malagasy frogs. However, the factors leading to an increase in the probability of mite infestation are unknown. To test for inter- and intraspecific differences in infestation probability and its potential correlation with sex, age, habitat preferences, and/or season within a species-rich West African leaf-litter frog assemblage, we examined more than 6,800 individual frogs for the presence of mites throughout two independent time increments, 1999-2000 and 2016-2017. We found only members of the leaf-litter frog genus Phyrnobatrachus to be infested, while other syntopically occurring genera were not affected. Within Phrynobatrachus, only four out of eight species were infested. Mites prevalence differed between species (highest P. phyllophilus, followed by P. alleni), sex (males higher than females in P. alleni and P. phyllophilus), and age (adults higher than juveniles in P. alleni), as well as season (more mites during wet than dry season in P. phyllophilus). The prevalence of mite infestation did not influence mate choice in P. alleni. Increased humidity showed a clear positive effect on infestation prevalence. We also detected a marked decrease in the prevalence of mites from 1999-2000 to 2016-2017, a period during which climatological changes within the study area have been reported with a tendency toward drier conditions. The decrease in mite infestation prevalence over time might be a signal of increasingly drier conditions.