Widespread anatoxin-a detection in benthic cyanobacterial mats throughout a river network

Benthic algae fuel summer food webs in many sunlit rivers, and are hotspots for primary and secondary production and biogeochemical cycling. Concerningly, riverine benthic algal assemblages can become dominated by toxic cyanobacteria, threatening water quality and public health. In the Eel River in Northern California, over a dozen dog deaths have been attributed to cyanotoxin poisonings since 2000. During the summers of 2013–2015, we documented spatial and temporal patterns of cyanotoxin concentrations in the watershed, showing widespread distribution of anatoxin-a in benthic cyanobacterial mats. Solid phase adsorption toxin tracking (SPATT) samplers were deployed weekly to record dissolved microcystin and anatoxin-a levels at 10 sites throughout the watershed, and 187 Anabaena-dominated or Phormidium-dominated cyanobacterial mat samples were collected from 27 locations to measure intracellular anatoxin-a (ATX) and microcystins (MCY). Anatoxin-a levels were higher than microcystin for both SPATT (mean MCY = 0.8 and ATX = 4.8 ng g resin^-1 day^-1) and cyanobacterial mat samples (mean MCY = 0.074 and ATX = 1.89 μg g^-1 DW). Of the benthic mats sampled, 58.9% had detectable anatoxin-a (max = 70.93 μg g^-1 DW), while 37.6% had detectable microcystins (max = 2.29 μg g^-1 DW). SPATT cyanotoxin levels peaked in mid-summer in warm mainstem reaches of the watershed. This is one of the first documentations of widespread anatoxin-a occurrence in benthic cyanobacterial mats in a North American watershed.

The role of ions, heavy metals, fluoride, and agrochemicals: critical evaluation of potential aetiological factors of chronic kidney disease of multifactorial origin (CKDmfo/CKDu) and recommendations for its eradication

The pollution of water and food through human waste and anthropogenic activities, including industrial waste and agricultural runoff, is a mounting problem worldwide. Water pollution from microbes causes identifiable diarrhoeal illnesses. The consumption of water contaminated with heavy metals, fluoride, and other toxins causes insidious illnesses that lead to protracted, non-communicable diseases and death. Chronic kidney disease of unusual/uncertain/unknown aetiology is one such example, began to manifest in the mid-1960s in several dry-zonal agricultural societies in developing economies that are located around the equator. In Sri Lanka, such a disease is affecting the North Central Province, the rice bowl of the country that first appeared in the mid-1990s. Several potential causes have been postulated, including heavy metals, fluoride, cyanobacterial and algae toxins, agrochemicals, and high salinity and ionicity in water, but no specific source or causative factor has been identified for CKD of multifactorial origin (CKDmfo). Three large studies conducted in the recent past failed to find any of the postulated components (heavy metals, cyanobacterial toxins, fluoride, salinity, or agrochemicals) at levels higher than those deemed safe by the World Health Organization and the US Environmental Protection Agency. At the reported low levels in water and with the heterogeneous geographical distribution, it is unrealistic to expect any of these components individually could cause this disease. However, the additive or synergistic effects of a combination of factors and components, even at lower exposure levels, together with malnutrition and harmful behaviours, and/or a yet-unidentified (or not investigated) toxin, can cause this epidemic. Because the cause is unknown, scientists need to work on broader hypotheses, so that key causative elements are not missed. Taken together the plausibility of multiple factors in the genesis of this disease, the appropriate terminology is CKDmfo, a name that also indicates the need for multi-disciplinary research programs to facilitate identifying the cause(s) and the need for multiple approaches to eradicate it. While some potential causes remain to be investigated, existing data point to polluted water as the main source of this disease. This article evaluates pros and cons of each hypothesis and highlights the importance of among others, providing clean water to all affected and surrounding communities. Available data do not support any of the postulated agents, chemicals, heavy metals, fluoride, salinity/ionicity, or individual agrochemical components, such as phosphate or glyphosate, as causative factors for CKDmfo in Sri Lanka. However, as the CKDmfo name implies, a combination of these factors (or an unknown toxin) together with harmful behaviour and chronic dehydration may cause this disease. Irrespective of the cause, prevention is the only way forward for eradication.

Toxicopathology induced by microcystins and nodularin: a histopathological review

Cyanobacteria are present in all aquatic ecosystems throughout the world. They are able to produce toxic secondary metabolites, and microcystins are those most frequently found. Research has displayed a negative influence of microcystins and closely related nodularin on fish, and various histopathological alterations have been observed in many organs of the exposed fish. The aim of this article is to summarize the present knowledge of the impact of microcystins and nodularin on the histology of fish. The observed negative effects of cyanotoxins indicate that cyanobacteria and their toxins are a relevant medical (due to irritation, acute poisoning, tumor promotion, and carcinogenesis), ecotoxicological, and economic problem that may affect both fish and fish consumers including humans.

Dog poisonings associated with a Microcystis aeruginosa bloom in the Netherlands

In early autumn 2011, three dogs died after they had been exposed to a Microcystis aeruginosa bloom on Lake Amstelmeer, The Netherlands. The cyanobacterial scum from the lake contained up to 5.27 × 10³μg g⁻¹ dry-weight microcystin, the vomit of one of the dogs contained on average 94 µg microcystin g⁻¹ dry-weight. In both cases, microcystin-LR was the most abundant variant. This is the first report of dog deaths associated with a Microcystis bloom and microcystin poisoning in The Netherlands.

Serologic evaluation of human microcystin exposure

Microcystins are among the most commonly detected toxins associated with cyanobacteria blooms worldwide. Two episodes of intravenous microcystin exposures occurred among kidney dialysis patients during 1996 and 2001. Analysis of serum samples collected during these episodes suggests that microcystins are detectable as free and bound forms in human serum. Our goal was to characterize the biochemical evidence for human exposure to microcystins, to identify uncertainties associated with interpretation of these observed results, and to identify research needs. We analyzed serum samples using enzyme-linked immunosorbent assay (ELISA) methods to detect free microcystins, and gas chromatography/mass spectrometry (GC/MS) to detect 2-methyl-3-methoxy-4-phenylbutyric acid (MMPB). MMPB is derived from both free and protein-bound microcystins by chemical oxidation, and it appears to represent total microcystins present in serum. We found evidence of free microcystins in patient serum for more than 50 days after the last documented exposure. Serum concentrations of free microcystins were consistently lower than MMPB quantification of total microcystins: free microcystins as measured by ELISA were only 8-51% of total microcystin concentrations as detected by the GC/MS method. After intravenous exposure episodes, we found evidence of microcystins in human serum in free and protein-bound forms, though the nature of the protein-bound forms is uncertain. Free microcystins appear to be a small but variable subset of total microcystins present in human serum. Research is needed to elucidate the human toxicokinetics of microcystins, in part to determine how observed serum concentrations can be used to estimate previous microcystin exposure.

Microcystin analysis in human sera and liver from human fatalities in Caruaru, Brazil 1996

In 1996, an extensive exposure of Brazilian hemodialysis patients at a dialysis center, using a municipal water supply water contaminated with cyanotoxins, provided the first evidence for acute lethal human poisoning from the cyclic peptide hepatotoxins called microcystins. During this outbreak, 100 of 131 patients developed acute liver failure and 52 of these victims were confirmed to have been exposed to lethal levels of microcystins. Detection and quantitation of microcystins in these biological samples posed some analytical challenges since there were no well-established and routine analytic methods to measure total microcystins in tissue or sera samples. At the time of the 1996 exposure we used analytic methods that combined the use of enzyme linked immunosorbant assay (ELISA), analytical high performance liquid chromatography (HPLC), electrospray ionization ion-trap mass spectroscopy (ES-ITMS) and matrix assisted laser desorption ionization-time of flight spectroscopy (MALDI-TOF). In the intervening years these methods have been improved and others developed that allow a more quantitative and critical analysis of microcystin contaminated tissue and sera. For these reasons, and to see how storage with time might effect the detection and stability of microcystins in these matrices, we reanalyzed selected liver tissues and sera from the Caruaru victims in Brazil. We developed and validated a procedure to measure total microcystins in Caruaru human sera and liver tissue using a combination of ELISA, liquid chromatography and liquid chromatography-mass spectrometry (LC/MS), GC/MS and MS/MS techniques. GC/MS and LC/MS were followed by MS/MS to obtain a fingerprint fragment spectra for the microcystins. The validity of the extraction procedure for free microcystins was confirmed by recovery experiments with blood sera spiked with microcystin-LR. We removed proteins with the Microcon Centrifugal Filter prior to LC/MS and ELISA analysis. A solid phase extraction (SPE) procedure was used for analysis of protein bound microcystins by conversion of ADDA to erythro-2-methyl-3-methoxy-4-phenylbutyric acid (MMPB) combined with GC/MS. We found that the GC/MS method yielded a higher concentration of microcystin than that obtained by ELISA and LC/MS. We hypothesize that this difference is due to better GC/MS detection of the covalently bound form of microcystins in human liver tissue. We also concluded that microcystins are very stable when stored under these conditions for periods of almost 10 years.