Resumen de Proliferación algales tóxicas, mareas rojas y salud: envenenamiento diarreico por moluscos y cáncer colorrectal
Victoria López Rodas, Emilia Maneiro, Juan Martínez, Eduardo Costas Costas
Certain blooms of unicellular microscopic algae that change the colour of the seawater to a reddish tone are called red tides. Hundred kilometres of the sea seem blood during a red tide. In some cases the microalgal species of red tides produce toxins or/and anoxic conditions, causing massive mortalities of marine animals. The proliferation of toxic algae is denominated harmful algal blooms (HAB). The majority of the toxic and red tide species are dinoflagellates, which present fascinating nuclear features (permanently condensed chromosomes organized in stacked rows of parallel nested arches without histones). Considerable time and effort are required to identify a HABs species under light microscopy in monitoring programs. Nowadays, the use of alternative molecular probes (antibodies, lectins, DNA probes) that bind target harmful algae is an increasing procedure in monitoring programs. Toxins produced by harmful species are transferred to food chain and cause numerous human intoxications with different clinical profile such as ciguatera fish poisoning (CFP), paralytic shellfish poisoning (PSP), neurotoxic shellfish poisoning (NSP), diarrhetic shellfish poisoning (DSP), and amnesic shellfish poisoning (ASP). DSP is perhaps the main public health (and economic) problem in Spain and Europe 1. The principal measures to avoid DSP outbreaks are the monitoring of shellfish harvesting areas and toxin analysis. European legislation allows up to 0,16 ìg of DSP toxins per gram of meat. Nowadays, the debate raised by DSP is only as a toxin causing diarrhoea. However, we think that the residual levels of DSP toxins ingested through shellfish consumption could contribute to increase colorectal cancer incidence (CRC). An epidemiological study to correlate dietary customs and tumour incidence shows a statistically significant correlation (p < 0.001) between consumption of molluscs and the incidence of colorectal cancer (coefficient determination = 0.50). An increase of 7 times in shellfish consumption produced duplication in the risk ratio of CRC in the Spanish population. Further analysis is necessary to conclusive association between shellfish consumption and CRC. In a context of global change that favours blooms of toxic microalgae a good approach for public health would be to change legislation to reduce the presence of residual levels of DSP toxins OA in shellfish. This point of view produces a conflict between the economic interests of the sector and public health.
