Botulism in Wild Birds and Changes in Environmental Habitat: A Relationship to be Considered.

Abstract

Simple summaryHuman activities, even those aimed at improving a natural area, can interfere with wildlife and their environment, potentially leading to some changes. In this paper, a botulism outbreak which occurred in waterfowls in a nature reserve after a conservative action is reported. In particular, an artificial pond was created in order to improve the environment of waterfowls, but gray mullets (Mugil cephalus) settled in the pond and proliferated. Fish mortality was observed during summer, leading to an accumulation of decaying organic material, thus creating the optimal conditions for Clostridium botulin growth and toxin production. In the same period, the botulism outbreak with flaccid paralysis and sudden mortality rapidly occurred in waterfowls. The toxin mosaic type C/D was identified as responsible for the disease outbreak. The outbreak rapidly resolved after the removal of the fish carcasses, highlighting the importance of a correct management for any action in natural contexts. In conclusion, before considering any activity in wildlife habitats, it is important to assess first its possible impact on wildlife.Any human activity, even if aimed at the improvement of a natural area, can potentially affect wildlife, leading to possible short-term or long-term changes due to the human–wildlife interaction. In this study, a botulism outbreak which occurred in waterfowl in a nature reserve after a conservative environmental action is reported. More than 180 different species of wild birds, including seventy waterfowl species, live in the area. The wildlife reserve rangers built an artificial pond equipped with draining canals in the wetland in order to improve the environment of waterfowl species and to facilitate their supply of food. Then, presumably due to tidal rides, gray mullets (Mugil cephalus) arrived from the sea and settled in the pond. The number of fishes gradually increased, and several fishes died with a peak of mortality in the summer of 2017, creating a great amount of decaying organic material and the optimal conditions for Clostridium botulinum growth and toxin production. A botulism outbreak then occurred rapidly and was characterised by flaccid paralysis and sudden mortality of the birds. Seven mallard ducks (Anas platyrhynchos), 4 common teals (Anas crecca), 1 garganey (Anas querquedula), 2 wood sandpipers (Tringa glareola), 1 little egret (Egretta garzetta), 1 little grebe (Tachybaptus ruficollis), and 4 Eurasian coots (Fulica atra) were found dead. Interestingly, the toxin identified as responsible for the disease outbreak was the mosaic of type C and D toxins (C/D type). The prompt removal of the fish carcasses led to a rapid resolution of the outbreak of the disease, highlighting the relevance of a correct management for any action in environmental contexts. The conclusion is that any human activity in wildlife habitats should be carefully considered in order to assess the possible impacts and to quickly identify the possible risks of changes in wildlife population.