Molecular epidemiology and risk assessment of human botulism in the Canadian Arctic

• Main Author: Leclair, Daniel
• Format: Thesis
• Language: English
• Published: University of Ottawa (Canada) 2008
• Subjects: Biology; Microbiology; Arctic; Hudson; Hudson Bay; Koksoak River; Nunavik; Ungava Bay; inuit
• Online Access: http://hdl.handle.net/10393/29577; https://doi.org/10.20381/ruor-19813

On a per capita basis, the incidence rate of type E botulism attributable to aged marine mammal meat in Nunavik is very high, with an average rate greater than 3 reported cases per 10,000 population for the period from 1996 to 2004. All cases reported for this period were clustered in Northern villages along the Ungava Bay. A survey for the presence of Clostridium botulinum type E along the coastline of Nunavik indicated a prevalence of spores along the southern coasts of Ungava Bay and Hudson Bay, indicating a possibility of contamination of seal meat from environmental sources during butchering. The highest concentration of spores was found in the Koksoak River (>5400 spores/kg), which flows into southern Ungava Bay. Spores were also found on seal skin and in seal intestinal contents, although at levels lower than found in environmental sources. Contamination of seal meat with C. botulinum type E spores may occur following contact with coastal rocks, tidal water, or shoreline soil, during the butchering process. Genomic analysis of coastal isolates of C. botulinum type E by PFGE indicated a heterogeneous population at the butchering sites, making it difficult to trace contamination sources. Epidemiologically related strains of C. botulinum type E could be identified by PFGE. Several distinct subtypes were involved in botulism incidents originating from Inuit villages of southern Ungava Bay, corroborating the existence of a high genetic diversity of C. botulinum type E in the environment. Some of these subtypes were detected inland and in large rivers flowing into southern Ungava Bay. The temperature used for igunaq preparation was the primary factor influencing the growth and toxigenesis of C. botulinum type E. All igunaq preparations incubated at 4°C were negative for BoNT/E. The use of traditional seal skin pouches or plastic containers did not influence the time to toxicity of seal igunaq preparations aged at abuse temperatures (10 and 20°C), regardless of inoculation dose. Changes in handling of seal meat during butchering to reduce contamination, combined with temperature control of the aging process to 4°C or less, should significantly reduce the risk of botulism from consumption of traditional Inuit foods.