Identifying Causative Agents of a Paretic Syndrome in Waterbirds in Southern Portugal
Mena Casero M.V. Turner A.D. Ben-Gigirey B. Alexander R.P. Dean K.J. Hatfield R.G. Maskrey B.H. Mazuet C. Karamendin K. Mateo R.
February 2025Multidisciplinary Digital Publishing Institute (MDPI)
Toxins
2025#17Issue 2
Paretic and paralyzing syndromes affecting wild birds are widely described in the literature, with outbreaks showing an increase in frequency and intensity worldwide during recent years. In the Iberian Peninsula, a paretic clinical picture without known etiology affecting mostly gulls has been reported during the last few decades. This paretic syndrome (PS) affects waterbirds and is characterized by a set of signs of ascendent flaccid paralysis, dyspnea, and diarrhea at different levels of severity. This study presents the first macro-analysis of some potential etiological PS agents in wild birds in southern Portugal. Other possible etiologies of PS related to nutritional deficiencies and environmental pollutants were not studied but are also discussed here. A total of 571 samples, belonging to 377 individuals with (n = 336) and without (n = 41) PS signs, have been tested for seven different toxins groups (botulinum neurotoxin (BoNT), paralytic shellfish toxins (PSTs), domoic acid (DA), anatoxin-a (ATX-a), cylindrospermopsin (CYN), tetrodotoxins (TTXs), and microcystins (MCs)) and three viral infections (gull adenovirus (GA), Newcastle disease virus (NVD), and highly pathogenic avian influenza viruses (HPAIV)). Of all the birds tested for botulinum neurotoxin, those with PS signs were positive (100%) and those without PS signs were negative (0%), confirming an association between PS and botulism. Some samples were positive for PSTs and MCs, but the prevalence in birds with PS signs was not significantly higher (2.5% and 5.3%, respectively) than in birds without signs (5.4% and 5.4%, respectively). Two birds without PS signs were positive for highly pathogenic avian influenza virus. The presence of the rest of the toxins and viruses was negative for all the samples tested. Our results support the relevant contribution of botulinum neurotoxin in the PS outbreaks observed in several species of aquatic birds in the last decades in southern Portugal, suggesting it could be one of the main causes of mortality in waterbirds.
botulism neurotoxin , diagnosis , etiology , paretic syndrome , toxins
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Wildlife Rehabilitation and Research Center of Ria Formosa (RIAS), Rua do Parque Natural da Ria Formosa, Olhão, 8700-194, Portugal
Instituto de Investigación en Recursos Cinegéticos (IREC), Junta de Comunidades de Castilla-La Mancha (JCCM), Consejo Superior de Investigaciones Científicas CSIC, Universidad de Castilla-La Mancha (UCLM), Ronda de Toledo 12, 13005 Ciudad Real, Spain
Centre for Environment Fisheries and Aquaculture Science (Cefas), The Nothe, Barrack Road, Weymouth, DT4 8UB, United Kingdom
Centro Nacional, Instituto Español de Oceanografía (IEO-CSIC), Centro Oceanográfico de Vigo, Vigo, 36390, Spain
Centre National de Référence des Bactéries Anaérobies et Botulisme, Institut Pasteur, Université Paris Cité, F-75015, Paris, France
Scientific and Production Center of Microbiology and Virology, 105 Bogenbay Batyr Street, Almaty, 050010, Kazakhstan
Institute for Environmental Assessment and Water Research (IDAEA-CSIC), Jordi Girona 18, Barcelona, 08034, Spain
Wildlife Rehabilitation and Research Center of Ria Formosa (RIAS)
Instituto de Investigación en Recursos Cinegéticos (IREC)
Centre for Environment Fisheries and Aquaculture Science (Cefas)
Centro Nacional
Centre National de Référence des Bactéries Anaérobies et Botulisme
Scientific and Production Center of Microbiology and Virology
Institute for Environmental Assessment and Water Research (IDAEA-CSIC)
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