Spatio-Temporal Monitoring of Benthic Anatoxin-a-Producing Tychonema sp. in the River Lech, Germany

Incidents with toxic benthic cyanobacteria blooms have been increasing recently. In 2019, several dogs were poisoned in the river Lech (Germany) by the benthic anatoxin-a-producing genus Tychonema. To characterize spatial and temporal distribution of potentially toxic Tychonema in this river, a systematic monitoring was carried out in 2020, focusing on the occurrence of the genus, its toxin production and habitat requirements. Tychonema and cyanobacterial community composition in benthic mats and pelagic samples were identified using a combined approach of microscopy and DNA sequencing of the 16S rRNA gene. In addition, anatoxin-a concentrations of selected samples were measured using the ELISA method. The habitat was characterized to assess the ecological requirements and growth conditions of Tychonema. Tychonema mats and anatoxin-a were detected at several sampling sites throughout the entire study period. Toxin concentrations increased with the progression of the vegetation period and with flow direction, reaching values between 0 and 220.5 µg/L. Community composition differed among pelagic and benthic samples, with life zone and substrate condition being the most important factors. The results of this study highlight the importance of monitoring and understanding the factors determining occurrence and toxin production of both pelagic and benthic cyanobacteria due to their relevance for the health of humans and aquatic ecosystems

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

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

Comparison of nine different commercially available molecular assays for detection of SARS-CoV-2 RNA

To face the COVID-19 pandemic, the need for fast and reliable diagnostic assays for the detection of SARS-CoV-2 is immense. We describe our laboratory experiences evaluating nine commercially available real-time RT-PCR assays. We found that assays differed considerably in performance and validation before routine use is mandatory