Distribution of Clostridium botulinum Type E Strains in Nunavik, Northern Quebec, Canada

Abstract

The distribution and levels of Clostridium botulinum type E were determined from field sites used by Inuit hunters for butchering seals along the coast of Nunavik. The incidence rates of C. botulinum type E in shoreline soil along the coast were 0, 50, and 87.5% among samples tested for the Hudson Strait, Hudson Bay, and Ungava Bay regions, respectively. Spores were detected in seawater or coastal rock surfaces from 17.6% of butchering sites, almost all of which were located in southern Ungava Bay. Concentrations of C. botulinum type E along the Ungava Bay coast were significantly higher than on the coasts of Hudson Strait and Hudson Bay, with the highest concentrations (270 to 1,800/kg of sample) found near butchering sites located along the mouths of large rivers. The Koksoak River contained high levels of C. botulinum type E, with the highest median concentration (270/kg) found in sediments of the marine portion of the river. C. botulinum type E was found in the intestinal contents (4.4%) and skins (1.4%) of seals. A high genetic biodiversity of C. botulinum type E isolates was observed among the 21 butchering sites and their surroundings along the Nunavik coastline, with 83% of isolates (44/53) yielding distinct pulsed-field gel electrophoresis genotypes. Multiple sources of C. botulinum type E may be involved in the contamination of seal meat during butchering in this region, but the risk of contamination appears to be much higher from environmental sources along the shoreline of southern Ungava Bay and the sediments of the Koksoak River.

Tracking sources ofClostridium botulinumtype E contamination in seal meat

“…Both the skin and the intestines of each harvested seal were also sampled to assess for the presence of endogenous spores, as described previously [9]. In brief, a square metre area was delineated on a large flat rock at the butchering site and swabbed using bacterial sponges.…”

“…Detection of C. botulinum type E spores and/or botulinum toxin in food and environmental samples were performed by enrichment cultivation and mouse bioassay, as previously described [9]. All enrichment broths were incubated at 20°C for 7 days in an anaerobic chamber with an atmosphere of 10% H 2 , 10% CO 2 and 80% N 2 and then assayed for botulinum neurotoxin (BoNT) in a mouse bioassay [9].…”

“…All enrichment broths were incubated at 20°C for 7 days in an anaerobic chamber with an atmosphere of 10% H 2 , 10% CO 2 and 80% N 2 and then assayed for botulinum neurotoxin (BoNT) in a mouse bioassay [9]. All positive shoreline soil or sediment samples were further tested to determine the concentrations of spores using a 5-tube most probable number (MPN) procedure [9] combined with a slot blot immunoassay for type E botulinum toxin [15]. Three 10-fold-decreasing amounts (30 g, 3 g and 0.3 g) and five culture tubes for each amount, for a total of 15 tubes per environmental sample, were cultured in tryptone peptone glucose yeast extract broth.…”

“…Walrus or seal igunaq is usually prepared by ageing meat and blubber (fat attached to the skin), 2–6 weeks in a traditional pouch made from the skin of the harvested animal or within a modern-type container such as a plastic bag, plastic pail, wooden box or galvanised barrel [6]. C. botulinum type E is common in the coastal environment of Alaska [7,8] and Ungava Bay [9], increasing the risk of contamination of marine mammal meat with type E spores during the butchering process.…”

“…Microbial source tracking methods such as pulsed-field gel electrophoresis (PFGE) have been previously used to track environmental sources and to study the genetic diversity of C. botulinum type E [9–11]. The objective of this study was to identify the sources and routes of seal meat contamination with C. botulinum type E spores at the butchering site.…”