Parasitology Laboratory

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

Research activity

Foodborne transmission of parasites is an important emerging issue in Canada due to a variety of factors including the globalization of the food trade, international travel, the increased number of susceptible individuals, and changes in consumer habits. Foodborne protozoan parasites of particular concern include: Cryptosporidium, Giardia, Cyclospora and Toxoplasma. Many illness outbreaks associated with these pathogens have been reported worldwide, including numerous outbreaks associated with the consumption of imported fresh produce.

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 patterns of parasites, including the identification of possible sources of contamination of foods. Long-term surveillance studies are underway to determine the prevalence of parasites in foods and in the environment. The main objectives of this research and surveillance are to identify and mitigate the risks of infection with foodborne parasites in Canadian consumers.

Current research projects

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, Toxoplasma and Giardia, in food, water and clinical samples.
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.
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.
Surveillance studies
- Investigations are underway on the incidence and characterization of protozoan parasites in retail foods, water, and animals (e.g., livestock, wildlife, fish/shellfish).

Recent publications

Google Scholar Profile

https://scholar.google.ca/citations?hl=en&user=TtAi850AAAAJ

Moakhar, Roozbeh Siavash, Rohan Mahimkar, Arash Khorrami Jahromi, Sahar Sadat Mahshid, Carolina del Real Mata, Yao Lu, Brent Dixon, John Gilleard, Alexandre J. da Silva, Momar Ndao, Sara Mahshid. 2023. Aptamer-based electrochemical microfluidic biosensor for the detection of Cryptosporidium parvum. ACS Sensors. https://doi.org/10.1021/acssensors.2c01349

Merks, Harriet, Ryan Boone, Nicol Janecko, Mythri Viswanathan, Brent R. Dixon. 2023. Foodborne protozoan parasites in fresh mussels and oysters purchased at retail in Canada. International Journal of Food Microbiology 399, 110248, ISSN 0168-1605, https://doi.org/10.1016/j.ijfoodmicro.2023.110248.

Dixon, B. R. 2023. Protozoa: Cryptosporidium spp. In Encyclopedia of Food Safety (FOSA), Vol. 2 (2 ed.). Motarjemi, Y. (ed.). Academic Press, Waltham, MA. Published online early (Oct. 2022): https://www.sciencedirect.com/science/article/pii/B9780128225219000551

Yanta, Christine A., John R. Barta, Antoine Corbeil, Hervé Menan, Karine Thivierge, Robert Needle, Muhammad Morshed, Brent R. Dixon, James D. Wasmuth, and Rebecca A. Guy. 2022. Genotyping Canadian Cyclospora cayetanensis isolates to supplement cyclosporiasis outbreak investigations. Microorganisms (Special issue: Genomic Tools for the Surveillance and Investigation of Foodborne Disease and Enteric Zoonoses). 10(2):447. https://doi.org/10.3390/microorganisms10020447

Yanta, Christine A., Stephen M. J. Pollo, John R. Barta, Sarah J. Reiling, James D. Wasmuth, Brent R. Dixon, and Rebecca A. Guy. 2022. Draft hybrid genome assembly of a Canadian Cyclospora cayetanensis isolate. Microbiology Resource Announcements 11(2): e01072-21 https://doi.org/10.1128/mra.01072-21

Hassan, Eman M., Brent R. Dixon, Syed Sattar, Maria C. DeRosa, Asma Iqbal and Banu Ormeci. 2021. A review of Cryptosporidium spp. and their detection in water. Water Science and Technology 83 (1): 1–25. doi: https://doi.org/10.2166/wst.2020.515.

Dixon, B.R. 2021. Giardia duodenalis in humans and animals – transmission and disease. Res. Vet. Sci. 135: 283-289. ISSN 0034-5288, https://doi.org/10.1016/j.rvsc.2020.09.034.

Reiling, S.J., Merks, H., Zhu, S., Boone, R., Corneau, N., Dixon, B.R. 2021. A cloth-based hybridization array system for rapid detection of the food- and waterborne protozoan parasites Giardia duodenalis, Cryptosporidium spp. and Toxoplasma gondii. Food Waterborne Parasitol. 2021 Aug 11;24:e00130. doi: 10.1016/j.fawpar.2021.e00130. PMID: 34458600; PMCID: PMC8379661.

Eman M. Hassan, Brent R. Dixon, Syed A. Sattar, Andrew Stalker, Banu Örmeci, Maria C. DeRosa. 2021. Highly sensitive magnetic-microparticle-based aptasensor for Cryptosporidium parvum oocyst detection in river water and wastewater: Effect of truncation on aptamer affinity. Talanta 222, 121618, ISSN 0039-9140, https://doi.org/10.1016/j.talanta.2020.121618.

Hutter, Juliana Ayres, Réjean Dion, Alejandra Irace-Cima, Marc Fiset, Rebecca Guy, Brent Dixon, Jeannie Lisette Aguilar, Julien Trépanier and Karine Thivierge. 2020. Cryptosporidium spp.: human incidence, molecular characterization and associated exposures in Québec, Canada (2016-2017). PLoS ONE 15(2): e0228986. https://doi.org/10.1371/journal.pone.0228986.

Pollo, Stephen M.J., Sarah J. Reiling, Janneke Wit, Matthew L. Workentine, Rebecca A. Guy, G. William Batoff, Janet Yee, Brent R. Dixon and James D. Wasmuth. Parasites and Vectors 2020. 13:108. https://doi.org/10.1186/s13071-020-3968-8.

Shapiro, Karen, Lillian Bahia-Oliveira, Brent Dixon, Aurélien Dumètre, Luz A. de Wit, Elizabeth VanWormer and Isabelle Villena. 2019. Environmental transmission of Toxoplasma gondii: Oocysts in water, soil and food. Food Waterborne Parasitol. 15: https://www.sciencedirect.com/science/article/pii/S2405676618300428

Reiling S.J. and Dixon B.R. 2019. Toxoplasma gondii: How an Amazonian parasite became an Inuit health issue. Can. Commun. Dis. Rep. 45(7/8):183–90. https://doi.org/10.14745/ccdr.v45i78a03

Iqbal, Asma, Juewen Liu, Brent Dixon, Bahram Zargar and Syed Sattar. 2019. Development and application of DNA-aptamer-coupled magnetic beads and aptasensors for the detection of Cryptosporidium parvum oocysts in drinking and recreational water resources. Can. J. Microbiol. https://doi.org/10.1139/cjm-2019-0153

Jain, Sona, Zhicheng Huang, Brent Dixon, Syed Sattar, and Juewen Liu. 2019. Cryptosporidium parvum oocyst directed assembly of gold nanoparticles and graphene oxide. Frontiers of Chemical Science and Engineering 13:608-615. https://doi.org/10.1007/s11705-019-1813-4

Maal-Bared, Rasha, Brent Dixon and Diana Axelsson-Olsson. 2019. Fate of internalized Campylobacter jejuni and Mycobacterium avium from encysted and excysted Acanthamoeba polyphaga. Exp. Parasitol. 199: 104-110.

Pollo, Stephen M. J., Sarah J. Reiling, Janneke Wit, Matthew L. Workentine, Rebecca A. Guy, G. William Batoff, Janet Yee, Brent R. Dixon, and James D. Wasmuth. 2019. Nanopore sequencing of Giardia reveals widespread intra-isolate structural variation. bioRxiv 323541; doi: https://doi.org/10.1101/343541 (Unpublished preprint).

Reiling, S.J., L. Measures, S. Feng, R. Boone, H. Merks and B.R. Dixon. 2019. Toxoplasma gondii, Sarcocystis sp., and Neospora caninum in seals from northern and eastern Canada: potential for zoonotic transmission. Food Waterborne Parasitol. https://www.sciencedirect.com/science/article/pii/S2405676619300289

Iqbal, A., N. Janecko, F. Pollari, and B. Dixon. 2018. Prevalence and molecular characterization of Toxoplasma gondii DNA in retail fresh meats in Canada. Food Waterborne Parasitol. 12: 1-9. https://doi.org/10.1016/j.fawpar.2018.e00031

Iqbal, A., L. Measures, S. Lair, and B. Dixon. 2018. Toxoplasma gondii infection in stranded St. Lawrence Estuary beluga (Delphinapterus leucas) in Quebec, Canada. Dis. Aquat. Organ. 130: 165-175 .

Pollo, S.M.J., Reiling, S., Wit, J., Workentine, M., Guy, R., Batoff, G.W., Yee, J., Dixon, B., and Wasmuth, J.D. 2018. MinION re-sequencing of Giardia genomes and de novo assembly of a new Giardia isolate. bioRxiv 343541; doi: https://doi.org/10.1101/343541

Dixon, B. R. 2016. Parasitic illnesses associated with the consumption of fresh produce - an emerging issue in developed countries. Curr. Opin. Food Sci. 8: 104-109.

Dixon, B., B. Mihajlovic, H. Couture, and J. Farber. 2016. Qualitative risk assessment: Cyclospora cayetanensis on fresh raspberries and blackberries imported into Canada. Food Protect. Trends 36: 18-32. [This article was featured on the cover of the journal].

Dixon, B. R. 2016. Emerging markets and parasitic diseases, Chapter 19, pp. 245-258. In One Health Case Studies: Addressing Complex Problems in a Changing World, Cork, S. C., Hall, D. C., and Liljebjelke K. (eds.). 5M Publishing,Sheffield, UK.

Elmore, S. A., K. P. Huyvaert, L. L. Bailey, A. Iqbal, C. Su, B. R. Dixon, R. T. Alisauskas, A. A. Gajadhar, and E. J. Jenkins. 2016. Multi-scale occupancy approach to estimate Toxoplasma gondii prevalence and detection probability in tissues: an application and guide for field sampling. Int. J. Parasitol. 46: 563-570. doi:10.1016/j.ijpara.2016.04.003

Schurer, J., M. Pawlik, A. Huber, B. Elkin, D. Cluff, J. Pongracz, K. Gesy, B. Wagner, B. Dixon, H. Merks, M. Bal, and E. Jenkins. 2016. Intestinal parasites of gray wolves (Canis lupus) in northern and western Canada. Can. J. Zool. 94: 643-650. doi:10.1016/j.ijpara.2016.04.003

Thivierge, K., A. Iqbal, B. Dixon, R. Dion, B. Levesque, P. Cantin, L. Cédilotte, M. Ndao, J.-F. Proulx, and C. P. Yansouni. 2016. Cryptosporidium hominis is a newly recognized pathogen in the Arctic Region of Nunavik, Canada: Molecular characterization of an outbreak. PLoS Negl. Trop. Dis. 10(4): e0004534. doi:10.1371/journal.pntd.0004534

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.

Network

Food and Environmental Parasitology Network (FEPN)

Description

The Food and Environmental Parasitology Network (FEPN) is a network of Canadian researchers, regulators, and public health officials with an active involvement in issues related to food and environmental parasitology. Members of the FEPN represent federal and provincial government, academia, and industry from across Canada.

Scope

The scope of the Network includes foodborne, waterborne, and zoonotic parasites of public health concern in Canada.

Objectives

identify and communicate risks and research/surveillance gaps relevant to the fields
facilitate discussion and collaborative research amongst members and external researchers
provide expert advice and testing in support of outbreak investigations and surveillance studies

Contact information

For further information on the FEPN visit https://www.fepn.ca or contact the FEPN Chair, Dr. Brent Dixon at brent.dixon@hc-sc.gc.ca

Page details

Date modified:: 2011-02-28

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