Tracking sources of Clostridium botulinum type E contamination in seal meat.

Botulism in Nunavik, Quebec is associated with the consumption of aged marine mammal meat and fat. The objective was to identify meat handling practices presenting a risk of contamination of seal meat with C. botulinum. Potential sources of contamination were assessed through interviews with igunaq producers from five communities of Nunavik. These sources were verified by detection and isolation of C. botulinum from igunaq prepared in the field from seal carcasses. Interviews indicated practices presenting a risk for contamination included: placing meat or fat on coastal rocks, using seawater for rinsing, and ageing meat in inverted seal skin pouches. Although the presence of C. botulinum type E spores was detected in only two of 32 (6.3%) meat or fat samples collected during the butchering process, two of four igunaq preparations from these samples contained type E botulinum toxin. Analysis of C. botulinum type E isolates recovered from these preparations indicated that shoreline soil may be a source of contamination. Seal meat and fat may be contaminated with C. botulinum type E during the butchering process. Measures can be adopted to reduce the risks of contamination in the field and possibly decrease the incidence of type E botulism in Nunavik.

Distribution of Clostridium botulinum type E strains in Nunavik, Northern Quebec, Canada.

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.

A preliminary investigation on the infectivity of Trichinella larvae in traditional preparations of walrus meat.

This study evaluated the infectivity of Trichinella nativa in freshly frozen walrus meat and traditionally aged walrus meat (igunaq) associated with two human outbreaks of trichinellosis in the Canadian Arctic. Trichinella larvae recovered from walrus meat stored at -20 degrees C for up to 20 months remained infective for guinea pigs inoculated with 135 or 716 larval doses. However, none of the 4-5 and 10-month-old igunaq preparations contained infective T. nativa larvae as measured by bioassays using mice and guinea pigs at inoculation doses ranging from 6 to 500 larvae. This indicates that the degradation process that occurred in the field can be sufficient to either kill Trichinella larvae or render them non-infective for mice and guinea pigs. Further research is needed to evaluate the food safety risk of traditional walrus igunaq aged under different field conditions and storage times.

Evaluation of a digestion assay and determination of sample size and tissue for the reliable detection of Trichinella larvae in walrus meat.

A digestion assay was validated for the detection of Trichinella larvae in walrus (Odobenus rosmarus) meat, and appropriate samples for testing were determined using tissues from infected walruses harvested for food. Examination of muscles from 3 walruses showed that the tongue consistently contained approximately 2-6 times more larvae than the pectoral and intercostal muscles. Comparison of numbers of larvae in the root, body, and apex of the tongue from 3 walruses failed to identify a predilection site within the tongue, but the apex was considered an optimal tissue because of the high larval density within the tongue and the ease of collection. All 31 spiked samples weighing 50 g each and containing between 0.1 and 0.4 larvae per gram (lpg) were correctly identified as infected, indicating that the sensitivity of this procedure is adequate for diagnostic use. A sample size of 10 g consistently detected larvae in 2 walrus tongues containing > or = 0.3 lpg (n = 40), and until additional data are available, sample sizes from individual walrus tongues should be a minimum of 10 g. This study provides the preliminary data that were used for the development of a food safety analytical protocol for the detection of Trichinella in walrus meat in arctic communities.