Coliform risk assessment through use of the clam Anomalocardia brasiliana as animal sentinel for shellfish harvesting areas in Brazil’s northeast

Abstract

Outbreaks of food-borne diseases related to consumption of contaminated shellfish have been reported in many countries, but not in Brazil, possibly due to deficient reporting. Here we investigated the suitability of the clam Anomalocardia brasiliana as an animal sentinel for coliform monitoring in shellfish harvesting areas of Brazil’s northeast. Samples of shellfish meats (40 clams per sample; n = 8 per collection) were collected at random from April 2009 through March 2010 in the bay area of Mangue Seco (state of Pernambuco). The numbers of thermotolerant coliforms were analyzed through the most probable number technique, and these contamination levels were tentatively correlated with the precipitation recorded on the day of sampling or 24 to 48 h beforehand. A. brasiliana shellfish meats from local retail shops (250 g per sample/ n = 3 per market) sold frozen were also investigated from August 2010 through June 2011. We found that the highest coliform contamination levels were correlated with recent rainfall events, limited to 24 h before sampling. However, irrespective of the rainfall level, the mean contamination above the Brazilian legal threshold of < 3 × 102 MPN/ 100 g for shellfish harvesting areas ranged from 18.7 to 93.7 % of samples analyzed monthly. Additionally, a large number of samples obtained from retail shops were also highly contaminated by coliforms during rainy periods, and therefore were not proper for human consumption. We conclude that A. brasiliana can be successfully used to monitor the contamination levels of coliforms in shellfish harvesting areas in Brazil’s northeast coast.