Low on mussel power

Ecological imbalance in the coastal areas of Kerala has caused food poisoning in people who consumed marine mussel

Published: Wednesday 31 December 1997

disruption of marine ecology is being blamed for cases of food poisoning leading to paralysis in a large number of people in the southern state of Kerala during September and October. More than 1,000 people were hospitalised with symptoms of food poisoning. Many people collapsed, felt dizzy, and their nervous systems were affected after consuming mussel. Mainly centred around the Poovar-Vizhinjam area in the capital Thiruvananthapuram, the news of the poisoning created panic all over the state, affecting the employment of an estimated 30,000 people involved in collecting mussel and clam.

The confusion started with coastal villagers in Poovar-Vizhinjam area complaining of vomiting and symptoms of paralysis. Physicians were initially confused. But the problem was traced to the consumption of mussel. Mussel is widely consumed in Kerala and is found on the rocky coast.Considered a poor man's protein, mussel meat is eaten raw, cooked and with tapioca, a root tuber.

Mussel is known as chippi in south Kerala and Kallummekka in Malabar. But this is also loosely called kakka , a generic name which includes clam. K K Philipose, scientist at the local unit of the Central Marine Fisheries Research Institute ( cmfri ) under the Indian Council of Agricultural Research ( icar ), told Down to Earth that clam is an altogether different organism and is found in the sandy bottom of the backwaters. In Kerala, these largely belong to the Pafia malabarica and Villorita siprinoid , both of which have nothing to do with the poisoning of mussel ( Perna indica ) that grows on rock surfaces and is extracted with knife.

As this was the first time that such incidents were reported from the state, nobody knew of any antidotes available to deal with the problem. It was the due to the timely intervention by C R Soman, a nutritionist who fed the information on the Internet and was flooded with information on shellfish poisoning from all over the world, that the cause of the problem came to light. The local unit of the cmfri immediately started monitoring mussel meat and the reports from the Fishery College, Mangalore, showed very high levels of what are called "saxi toxins". Mussel get these toxins from phytoplankton, unicellular organisms, the numbers of which explode at certain times of the year. Some types of phytoplankton are not poisonous to mussel that eat them. However, they are poisonous to those who consume mussel.

According to Philipose, the sudden explosion in the phytoplankton population is part of the upwelling process on the Kollam-Ratnagiri coast in the peninsular region after the monsoons. According to Soman, this could be due to various reasons such as the flushing of inland water bodies that are increasingly polluted with human waste that is eventually let into the sea during the monsoons. In the case of the Thiruvananthapuram coast, this is quite likely as untreated sewage from the city is discharged into the sea through Parvatiputhanar, a canal on the city outskirts.

Higher loads of nutrients are known to increase the phytoplankton load in water bodies, and this is one reason for the differing degrees of eutrophication (a significant rise in the organic content in a waterbody that leads to the depletion of its oxygen content) in Kerala's backwaters. But this is the first time that cases of food poisoning from mussel meat have been reported in Kerala on such a scale. For the time being, a ban on the extraction and consumption of mussel meat has been imposed on the affected region by the state government.

The Fishery College is the only institute in the area that has advanced equipment necessary for measuring saxi toxins. Recent tests conducted at the college on mussel from Mulloor (an affected area) revealed 243 mouse units per 100 gram of meat (mu/100g, based on laboratory mice). This was as high as 4,240 mu/100g when the sample was first sent. At Kovalam, this was 9,590 mu/100g. The acceptable level of this in the us is 400 mu/100g. However, the European Union stipulates that levels above 200 mu/100g can cause disease (see table: Toxic tales ).

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