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Would you like parasites with that?" - The growing concern about parasites in our foods.

On Friday, October 18, 2013 Dr. Brent Dixon from Health Canada will discuss the growing public health concern in Canada about protozoan parasites, including Cryptosporidium, Giardia, Cyclospora and Toxoplasma, on fresh produce and other foods.  This discussion will include possible sources of food contamination as well as the hurdles faced in the detection and control of these parasites. Here are excerpts from a recent conversation with Dr. Dixon.

Dr. Dixon is Co-founder and Chair of the recently established Food and Environmental Parasitology Network (FEPN) in Canada, which brings together experts from across the country with the major objectives of identifying research gaps in these fields, and initiating collaborative studies. 

He is a recognized expert on foodborne parasitic diseases by the Food and Agriculture Organization of the United Nations (FAO) and by the World Health Organization.  He recently served as Co-Chair of an FAO / WHO Expert Meeting on Foodborne Parasites – Multicriteria Based Ranking for Risk Management.  He also currently serves on two ISO working groups developing standard methods for the detection of foodborne parasites.  

In conversation with Dr. Brent Dixon:

Tell us about your research and its impact.

Bremt DixonMy work involves the development and optimization of methods for the detection, characterization and control of foodborne and zoonotic protozoan parasites of public health concern in Canada, including Cryptosporidium, Giardia, Toxoplasma, and Cyclospora.  In addition, I am involved in on-going surveillance studies along with the Public Health Agency of Canada to determine the prevalence of these pathogens in various retail foods, and in livestock, in Canada, and the potential for human exposure.  I am also looking at shellfish and wildlife (i.e., country foods) as a potential source of transmission in the Canadian Arctic. 

My lab uses PCR-based methods, microscopy and flow cytometry for detection, and DNA-sequence analysis for the molecular characterization of these parasites for the purposes of source tracking and studying transmission patterns.  I have recently reported a relatively high prevalence of parasites in packaged leafy greens.   My colleagues and I at Health Canada have met with representatives of the Canadian fresh produce industry to begin addressing these findings.  I have also reported a very high prevalence of Cryptosporidium and Giardia in livestock in Ontario, with a predominance of zoonotic species and genotypes in dairy cattle in particular, suggesting that these animals could be an important source of transmission to humans.

I reported as well on the potential for zoonotic foodborne transmission of Cryptosporidium and Giardia from seals and shellfish harvested for food in the Arctic.  I recently began testing a variety of retail meats and country foods to determine the prevalence and genotypes of Toxoplasma in Canada.  My research and expertise contribute towards the development of health risk assessments, guidelines and policies aimed at increasing the safety of foods in Canada. 

What are the three take away messages you want the audience to leave with?

  1. Foodborne protozoan parasites are of growing public health concern in Canada due, largely, to global trade in fresh produce, and to poor agricultural practices and poor hygiene in food handlers.
  2. There are many hurdles faced in testing foods for the presence, identification, and viability of contaminating protozoan parasites.  As a result, few surveillance studies have been done so far, and confirmation of the source of illnesses in outbreak investigations is difficult.
  3. There are numerous potential sources of contamination of foods with protozoan parasites including direct contamination from humans and animals and indirect contamination from water.   As such, effective control measures are complex and involve monitoring of watersheds and appropriate treatment of water and wastewater, good agricultural practices, good animal husbandry practices, improved sanitation and hygiene, good consumer practices, etc.       

 What else are you working on / researching?

I’m currently evaluating and developing a number of novel methods for the elution, detection, characterization and control of protozoan parasites from foods.  In collaboration with the National Research Council, we are developing microfluidic chips to separate parasites from food debris and PCR inhibitors.  It is anticipated that this could evolve into a “lab-on-a-chip” technology, whereby it may be possible to simultaneously elute parasites from foods, identify them by PCR, and test their viability.  My lab is also currently screening DNA-aptamers for their effectiveness in targeting the (oo)cyst wall of important food- and waterborne parasites including Cryptosporidium, Toxoplasma and Cyclospora.  Aptamers could be an inexpensive and shelf-stable alternative to labeled monoclonal antibodies for the detection of these pathogens.  In addition, w e’re evaluating the use of a new technology known as imaging cytometry in the detection and viability determination of these parasites.  In terms of control measures, I am looking at the effectiveness of composting manure in reducing the viability of parasite (oo)cysts, as this has major implications in the contamination of fresh produce.  I am also currently evaluating the effectiveness of high pressure processing (HPP) at the production level in reducing the infectivity of protozoan parasites in various types of foods. 

As well I am developing a collaborative research project on the protozoan parasite, Blastocystis, as an emerging zoonotic and food- and waterborne pathogen in Canada.

Learn more      

Presented on October 18, 2013.