Mass Occurrence of Anatoxin-a- and Dihydroanatoxin-a-Producing Tychonema sp. in Mesotrophic Reservoir Mandichosee (River Lech, Germany) as a Cause of Neurotoxicosis in Dogs

Abstract

In August 2019, three dogs died after bathing in or drinking from Mandichosee, a mesotrophic reservoir of the River Lech (Germany). The dogs showed symptoms of neurotoxic poisoning and intoxication with cyanotoxins was considered. Surface blooms were not visible at the time of the incidents. Benthic Tychonema sp., a potential anatoxin-a (ATX)-producing cyanobacterium, was detected in mats growing on the banks, as biofilm on macrophytes and later as aggregations floating on the lake surface. The dogs’ pathological examinations showed lung and liver lesions. ATX and dihydroanatoxin-a (dhATX) were detected by LC-MS/MS in the stomachs of two dogs and reached concentrations of 563 and 1207 µg/L, respectively. Anatoxins (sum of ATX and dhATX, ATXs) concentrations in field samples from Mandichosee ranged from 0.1 µg/L in the open water to 68,000 µg/L in samples containing a large amount of mat material. Other (neuro)toxic substances were not found. A molecular approach was used to detect toxin genes by PCR and to reveal the cyanobacterial community composition by sequencing. Upstream of Mandichosee, random samples were taken from other Lech reservoirs, uncovering Tychonema and ATXs at several sampling sites. Similar recent findings emphasize the importance of focusing on the investigation of benthic toxic cyanobacteria and applying appropriate monitoring strategies in the future.

Self-buckling of filamentous cyanobacteria reveals gliding forces

“…These phototrophic organisms played an important role in the paleoclimate of our planet, having generated the atmospheric oxygen [3,4] on which animal life is based. Today, they are commonly known for their role in giant marine or limnic blooms, which may pose ecological and economical threats [3][4][5][6], but also enable bioreactor applications, for instance as a renewable energy source [3]. Many species from many genera exhibit gliding motility when in contact with solid surfaces or other filaments, but no swimming motion [7].…”

Potentially Toxic Planktic and Benthic Cyanobacteria in Slovenian Freshwater Bodies: Detection by Quantitative PCR

“…Another important finding is the discovery of cyanotoxic potential in biofilm ( Table 4 ). Even though the first observation of potentially toxic cyanobacteria in biofilm samples was reported in 1997 [ 24 ] and cyanotoxins from benthic cyanobacteria are believed to have caused animal death on a few occasions [ 9 , 10 , 11 , 12 , 13 , 24 ], such studies are still scarce. These findings suggest anatoxin-a and microcytins as the prevalent cyanotoxins in cyanobacterial mats.…”

“…The majority of the cyanobacterial qPCR studies are directed at microcystins, while detection of cylindrospermopsins and especially saxitoxins is still relatively rare [ 2 ]. Moreover, most of the studies focus on plankton samples, while cyanobacteria in biofilm are still underrepresented in molecular studies despite increasing evidence of their toxicity with potential acute effects on animals [ 9 , 10 , 11 , 12 , 13 ]. Furthermore, few of these studies include comparison of qPCR method and microscopy [ 2 ].…”

A Summer of Cyanobacterial Blooms in Belgian Waterbodies: Microcystin Quantification and Molecular Characterizations

“…Ingestion of cyanotoxin contaminated water has been shown to be detrimental to human and animal health [8][9][10][11][12][13][14]. Yet in Belgium, no causative link has so far been found between toxic blooms and associated symptoms in humans and animals, such as gastroenteritis, vomiting, liver damage or convulsions [15,16].…”