Studies on heat inactivation of hepatitis A virus with special reference to shellfish: Part 1. Procedures for infection and recovery of virus from laboratory-maintained cockles

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Abstract
The consumption of bi-valve mollusean shellfish has been associated with outbreaks of viral gastroenteritis and hepatitis A. Investigations were undertaken to determine the heat inactivation conditions necessary to render shellfish such as cockles safe for the consumer. Conditions for the laboratory maintenance of live cockles are described. In preliminary experiments either poliovirus (106 TCID50/ml seawater) or hepatitis A virus (HAV) (approx. 104 RFU/ml seawater) was introduced into the shellfish tank. Following 48 h filter feeding, virus was recovered from cockles using an adsorption-elution extraction procedure. Titres of virus recovered ranged from 104 to 105 TCID50/ml of shellfish extract for poliovirus and from 103 to 105 RFU/ml of shellfish extract for HAV. Active ingestion of the virus from the seawater was demonstrated by recovering virus from within cockle guts. To quantify recovered HAV, end-point dilutions and an adaptation of a radioimmunofocus assay (RIFA) were compared. The tests were of similar sensitivity but the RIFA has the advantage of being relatively rapid, shortening the time taken to complete an experiment by as much as 4 weeks.