Parasitology Laboratory

Research Scientist
Dr. Brent R. Dixon
Bureau of Microbial Hazards, Health Canada
brent.dixon@hc-sc.gc.ca

Research Technical Support: Lorna Parrington, Ryan Boone

Research Activity

The Parasitology Laboratory in the Bureau of Microbial Hazards is involved in the development of novel and effective methods for the detection, molecular characterization, and control of parasites of public health significance in foods, as well as in clinical and environmental samples. Work is also being done on the transmission dynamics of protozoan parasites, including the identification of possible sources of contamination of foods and water. Long-term surveillance studies are underway to determine the prevalence and genotypes of parasites in foods and in the environment.

Current Research Projects

1. Detection of protozoan parasites in foods:
   
   Various methods are being developed and evaluated for the elution, concentration and detection of protozoan parasites, including Cyclospora, Cryptosporidium, and Giardia, in or on fruits, vegetables, and other foods.
2. Methods for the control of parasites in foods:
   
   The efficacy of various control methods such as cooking and freezing, pasteurization, irradiation, brining, and use of disinfectants on the destruction of parasites in foods are being evaluated. Various assays for the determination of viability of protozoan cysts and oocysts are being developed.
3. Transmission dynamics of protozoan parasites:
   
   Investigations involve the detection and molecular characterization of parasites in various foods, faecal samples and other environmental samples. These studies focus on such factors as zoonotic transmission, food handling, and contaminated water.
4. Surveillance studies:
   
   Investigations are underway on the incidence of protozoan parasites in retail foods, water, and animals (e.g., livestock, wildlife, shellfish).

Affiliations

1. Research Scientist (Parasitology), Microbiology Research Division, Bureau of Microbial Hazards, Food Directorate, Health Canada.
2. Section Head, Foodborne Viruses, Parasites and Other Disease Agents, Microbiology Research Division, Bureau of Microbial Hazards, Food Directorate, Health Canada.
3. Co-founder and Chair, Food and Environmental Parasitology Network, a pan-Canadian network of parasitologists based at the Bureau of Microbial Hazards, Food Directorate, Health Canada.
4. Adjunct professor and Graduate Faculty, Department of Health Management, Faculty of Veterinary Medicine, University of Prince Edward Island.
5. Research Associate, Centre for Research on Environmental Microbiology (CREM), Faculty of Medicine, University of Ottawa.
6. Member, American Society of Parasitologists.

Recent Publications

Dixon, B. R., R. Fayer, M. Santin, D. E. Hill, and J. P. Dubey. 2011. Protozoan Parasites, Chapter 24. In Rapid Detection, Characterization and Enumeration of Food-Borne Pathogens. Hoorfar, J. (ed.). ASM Press, Washington, USA (In Press).

Uehlinger, F. D., S. J. Greenwood, R. O'Handley, J. T. McClure, T. Coklin, B. R. Dixon, M. de Boer, H. Zwiers, and H. W. Barkema. Prevalence and genotypes of Giardia duodenalis in dairy and beef cattle in farms around Charlottetown, Prince Edward Island, Canada. Can. Vet. J. (In Press).

Coklin, T., J. M. Farber, L. J. Parrington, C. I. Bin Kingombe, W. H. Ross, and B. R. Dixon. 2011. Immunomagnetic separation significantly improves the sensitivity of the polymerase chain reaction detecting Giardia duodenalis and Cryptosporidium spp. in dairy cattle. J. Vet. Diagn. Invest. 23 (In Press).

Dixon, B., L. Parrington, A. Cook, K. Pintar, F. Pollari, D. Kelton, and J. Farber. 2011. The potential for zoonotic transmission of Giardia duodenalis and Cryptosporidium spp. from beef and dairy cattle in Ontario, Canada. Vet. Parasitol. 175: 20-26.

Levesque, B., C. Barthe, B. R. Dixon, L. J. Parrington, D. Martin, B. Doidge, J.-F. Proulx, and D. Murphy. 2010. Microbiological quality of blue mussels (Mytilus edulis) in Nunavik, Quebec: a pilot study. Can. J. Microbiol. 56: 968-977.

Coklin, T., J. Farber, L. Parrington, Z. Coklin, W. Ross, and B. Dixon. 2010. Temporal changes in the prevalence and shedding patterns of Giardia duodenalis cysts and Cryptosporidium spp. oocysts in dairy calves at an agricultural college in Ontario, Canada. Can. Vet. J. 51: 841-846.

Dixon, B. 2010. The potential for zoonotic transmission of Giardia duodenalis and Cryptosporidium spp. from beef and dairy cattle in Ontario, Canada. Canadian Vet. 5: 15-16.

Dixon, B. R. 2009. The role of livestock in the foodborne transmission of Giardia duodenalis and Cryptosporidium spp. to humans, Chapter 9, pp. 107-122. In Giardia and Cryptosporidium: From Molecules to Disease. Ortega-Pierres, M. G., Cacciò, S., Fayer, R., Mank, T., Smith, H., and Thompson, R. C. A. (eds.). CAB International, Wallingford, U.K.

Dixon, B. 2009. Identification of Giardia and Cryptosporidium in animals and the environment. Canadian Vet. 4: 14-16.

Messier, V., B. Lévesque, J.-F. Proulx, L. Rochette, M. D. Libman, B. J. Ward, B. Serhir, M. Couillard, N. H. Ogden, E. Dewailly, B. Hubert, S. Déry, C. Barthe, D. Murphy, and B. Dixon. 2009. Seroprevalence of Toxoplasma gondii among Nunavik Inuit (Canada). Zoonoses and Public Health 56: 188-197.

Coklin, T., F. Uehlinger, J. Farber, H. Barkema , R. O'Handley, and B. Dixon. 2009. Prevalence and molecular characterization of Cryptosporidium spp. in dairy calves from 11 farms in Prince Edward Island, Canada. Vet. Parasitol. 160: 323-326.

Dixon, B., L. Parrington, M. Parenteau, D. Leclair, M. Santin, and R. Fayer. 2008. Giardia duodenalis and Cryptosporidium spp. in the intestinal contents of ringed seals (Phoca hispida) and bearded seals (Erignathus barbatus) in Nunavik, Quebec, Canada. J. Parasitol. 94: 1161-1163.

Uehlinger, F. D., H. W. Barkema, R. M. O'Handley, M. Parenteau, L. J. Parrington, J. A. VanLeeuwen, and B. R. Dixon. 2008. Comparison of flow cytometry and immunofluorescence microscopy for the detection of Giardia duodenalis in bovine fecal samples. J. Vet. Diagn. Invest. 20: 178-185.

Coklin, T., J. Farber, L. Parrington, and B. Dixon. 2007. Prevalence and molecular characterization of Giardia duodenalis and Cryptosporidium spp. in dairy cattle in Ontario, Canada. Vet. Parasitology 150: 297-305.

Lévesque, B., Lavoie, É., Simard, M., Barthe, C., Dixon, B., Murphy, D., Doidge, B. and J.F. Proulx. 2007. Microbiological quality of blue mussels (Mytilus edulis) in Nunavik (Canada): A pilot study. Proceedings of the 19^th Conference of the International Society for Environmental Epidemiology (ISEE). September 5-9, 2007. Mexico. Salud Publica de Mexico 49: E664.

Uehlinger, F. D., H. W. Barkema, B. R. Dixon, T. Coklin, R. M. O'Handley. 2006. Giardia duodenalis and Cryptosporidium spp. in a veterinary college bovine teaching herd. Vet. Parasitology 142: 231-237.

Santin, M., B. R. Dixon, and R. Fayer. 2005. Genetic characterization of Cryptosporidium isolates from ringed seals (Phoca hispida) in Northern Quebec, Canada. J. Parasitology 91: 712-716.

Dixon, B., J. Bussey, L. Parrington, and M. Parenteau. 2005. Detection of Cyclospora cayetanensis oocysts in human faecal specimens using flow cytometry. J. Clinical Microbiol. 43: 2375-2379.

Hoang, L. M. N., M. Fyfe, C. Ong, J. Harb, S. Champagne, B. Dixon, and J. Isaac-Renton. 2005. Outbreak of cyclosporiasis in British Columbia associated with imported Thai basil. Epidemiol. Infect. 133: 23-27.

Laboratory Methods

Dixon, B. R. 2008. Isolation and identification of Cyclospora cayetanensis oocysts from fresh raspberries. HPFB Laboratory Procedure, Compendium of Methods, OPFLP-5.

Dixon, B. R. 2006. Isolation and identification of anisakid roundworm larvae in fish (Revision). HPFB Laboratory Procedure OPFLP-2, Compendium of Analytical Methods, Volume 5.

Other Related Links

1. Consumer information
2. Public Health Agency of Canada - A-Z Infectious Diseases
3. Centers for Disease Control and Prevention - Parasites A-Z Index