Abstract The relative importance of both environmental factors and host factors in explaining variation in prevalence and intensity of flea parasitism in small mammal communities is poorly established. We examine these relationships in an East African savanna landscape, considering multiple host levels: across individuals within a population, across populations within species, and across species within a landscape. We sampled fleas from 2672 small mammals of 27 species. This included a total of 8283 fleas, with 5 genera, and 13 species identified. Across individual hosts within a site, both rodent body mass and season affected total intensity of flea infestation, although the explanatory power of these factors was generally modest (<10%). Across host populations in a landscape we found consistently positive effects of host density and negative effects of vegetation cover on the intensity of flea infestation. Other factors explored (host diversity, annual rainfall, anthropogenic disturbance, and soil properties) tended to have lower and less consistent explanatory power. Across host species in the same landscape, we found that host body mass was strongly positively correlated with both prevalence and intensity of flea parasitism. The average robustness of a host species to disturbance was not correlated with flea parasitism. Cumulatively, these results provide insight into the complex roles of both intrinsic (host) and extrinsic (environmental) factors in explaining complex patterns of flea parasitism across a landscape
