Abstract
BackgroundHumans impose a significant pressure on large herbivore populations, such as hippopotami, through hunting, poaching, and habitat destruction. Anthropogenic pressures can also occur indirectly, such as artificial lake creation and the subsequent introduction of invasive species that alter the ecosystem. These events can lead to drastic changes in parasite diversity and transmission, but generally receive little scientific attention.ResultsIn order to document and identify trematode parasites of the common hippopotamus (Hippopotamus amphibius) in artificial water systems of Zimbabwe, we applied an integrative taxonomic approach, combining molecular diagnostics and morphometrics on archived and new samples. In doing so, we provide DNA reference sequences of the hippopotamus liver fluke Fasciola nyanzae, enabling us to construct the first complete Fasciola phylogeny. We describe parasite spillback of F. nyanzae by the invasive freshwater snail Pseudosuccinea columella, as a consequence of a cascade of biological invasions in Lake Kariba, one of the biggest artificial lakes in the world. Additionally, we report an unknown stomach fluke of the hippopotamus transmitted by the non-endemic snail Radix aff. plicatula, an Asian snail species that has not been found in Africa before, and the stomach fluke Carmyerius cruciformis transmitted by the native snail Bulinus truncatus. Finally, Biomphalaria pfeifferi and two Bulinus species were found as new snail hosts for the poorly documented hippopotamus blood fluke Schistosoma edwardiense.ConclusionsOur findings indicate that artificial lakes are breeding grounds for endemic and non-endemic snails that transmit trematode parasites of the common hippopotamus. This has important implications, as existing research links trematode parasite infections combined with other stressors to declining wild herbivore populations. Therefore, we argue that monitoring the anthropogenic impact on parasite transmission should become an integral part of wildlife conservation efforts.Graphical abstract
Highlights
Humans impose a significant pressure on large herbivore populations, such as hippopotami, through hunting, poaching, and habitat destruction
In this study, we report four trematode species that infect the common hippopotamus and show that they are transmitted by six snail species that thrive in Lake Kariba and Mwenje reservoir
Do artificial lakes and biological invasions pose a burden on Hippopotamus amphibius? Considering our findings and the aforementioned burden of trematodes on wildlife populations, we argue that artificial lakes can act as a breeding ground forendemic intermediate snail hosts that transmit hippopotamus infecting parasites, and thereby indirectly affect hippopotamus populations
Summary
Humans impose a significant pressure on large herbivore populations, such as hippopotami, through hunting, poaching, and habitat destruction. Anthropogenic pressures can occur indirectly, such as artificial lake creation and the subsequent introduction of invasive species that alter the ecosystem. These events can lead to drastic changes in parasite diversity and transmission, but generally receive little scientific attention. Besides favoring the colonization and proliferation of endemic snail species, artificial lakes can facilitate the establishment of non-endemic snails that have the potential to drastically alter the dynamics of trematode transmission [5, 18, 19]. Invasive nonendemic snails can affect parasite transmission in three distinct ways: (1) by introducing non-endemic parasites, defined as “spillover”, (2) by successfully transmitting endemic parasites with an overall increased transmission as a result, defined as “spillback”, or (3) by transmitting endemic parasites but with a lower transmission potential, resulting in a “dilution” effect [20,21,22]
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