Occurrence and distribution of Toxoplasma gondii in Eastern oysters harvested in Prince Edward Island.

Principal Investigators: Ruth Cox & Jeff Davidson
Co-investigators: Diana Jaramillo, Spencer Greenwood, & J. McClure

Toxoplasma gondii is a zoonotic protozoan parasite that is found worldwide. It has been shown to bioaccumulate in a number of shellfish species, which can act as sentinels for the detection of the parasite in the marine environment. If these pathogens are not inactivated when they are digested by the shellfish, or when the shellfish is cooked, then they may also present a transmission risk to some consumers. At present, there are limited data available about the prevalence of T. gondii oocysts in shellfish or about the potential for oocyst elimination over time. We propose to evaluate a number of methods of recovery of T. gondii from oyster tissue. We will then establish the prevalence of T. gondii in oysters in waterways of PEI that are relevant to the oyster industry. Finally, we will assess whether or not depuration results in the removal of T. gondii oocysts from oysters over a 2-week period. The aim of this work is to improve methods of detection of T. gondii in shellfish and to provide a novel tool that can be used to screen for T. gondii in oyster populations. We will also determine the prevalence of T. gondii in oysters harvested from relevant waterways.

Objectives:

  1. Evaluate multiple methods of recovery of T. gondii from oyster tissue, according to the standard detection methods for protozoa and the published methods for testing low loads in environmental samples (e.g. water and soil). We will establish which method has the highest sensitivity, particularly when parasite loads are low. This will provide data that can be used to improve detection methods during surveillance of T. gondii in oyster populations.
  2. Establish the prevalence of T. gondii in oysters in waterways of PEI relevant to the oyster industry.
  3. Assess whether depuration results in the reduction or removal of T. gondii oocysts from the oysters over a 2-week period.