A review of the factors causing paralysis in wild birds: Implications for the paralytic syndrome observed in the Baltic Sea

We reviewed paralysis in wild birds with a special focus on the Baltic Sea paralytic syndrome recently described by Balk et al. (2009) by assessing multiple causative factors. The review showed that paralysis may occur in various species and that the aetiology can be divided into biotoxins, nutritional deficiencies, environmental contaminants and infectious diseases. The review also showed that the symptoms are influenced by age, sex and species of the affected individual. It seemed that paralysis may be treated or relieved by e.g. thiamine injections or additives. Due to a lack of extensive diagnostic studies, the potentially negative effects of paralysis at the population level of wild birds remain unsolved. We recommend that when investigating paralysis in wild birds, a holistic study approach including multiple factors are undertaken in order to pinpoint cause-and-effect relationships as well as the potential impacts on wild bird populations including those in the Baltic Sea. ► We reviewed the causes of paralysis in wild birds. ► The literature showed that multiple factors may cause avian paralysis. ► These include biotoxins, nutrition, contaminants and infectious diseases. ► Paralysis may be treated or relieved by e.g. thiamine injections or additives. ► We recommend that a holistic study approach is undertaken when investigating paralysis.