Estimating the burden of illness caused by domestic waterborne Legionnaires' disease in Canada: 2015-2019.

Legionellosis is a disease caused by the bacterium Legionella that most commonly presents as Legionnaires' disease (LD), a severe form of pneumonia. From 2015 to 2019, an average of 438 LD cases per year were reported in Canada. However, it is believed that the actual number of cases is much higher, since LD may be underdiagnosed and underreported. The purpose of this study was to develop an estimate of the true incidence of illnesses, hospitalizations, and deaths associated with LD in Canada. Values were derived using a stochastic model, based on Canadian surveillance data from 2015 to 2019, which were scaled up to account for underdiagnosis and underreporting. Overall, there were an estimated 1,113 (90% CrI: 737-1,730) illnesses, 1,008 (90% CrI: 271-2,244) hospitalizations, and 34 (90% CrI: 4-86) deaths due to domestically acquired waterborne LD annually in Canada from 2015 to 2019. It was further estimated that only 36% of illnesses and 39% of hospitalizations and deaths were captured in surveillance, and that 22% of illnesses were caused by Legionella serogroups and species other than Legionella pneumophila serogroup 1 (non-Lp1). This study highlights the true burden and areas for improvement in Canada's surveillance and detection of LD.

Occurrence of Campylobacter spp. in raw and ready-to-eat foods and in a Canadian food service operation.

The occurrence of Campylobacter spp. in a variety of foods from Ottawa, Ontario, Canada, and raw milk samples from across Canada was determined over a 2-year period. The samples consisted of 55 raw foods (chicken, pork, and beef), 126 raw milk samples from raw milk cheese manufacturers, and 135 ready-to-eat foods (meat products, salads, and raw milk cheeses). Campylobacter jejuni was detected in 4 of the 316 samples analyzed: 1 raw beef liver sample and 3 raw chicken samples. An isolation rate of 9.7% was observed among the raw chicken samples tested. This study also investigated the role of cross-contamination in disseminating Campylobacter from raw poultry within a food service operation specializing in poultry dishes. Accordingly, kitchen surfaces within a restaurant in Ottawa, Ontario, were sampled between March and August 2001. Tests of the sampling method indicated that as few as 100 Campylobacter cells could be detected if sampling was done within 45 min of inoculation; however, Campylobacter spp. were not detected in 125 swabs of surfaces within the kitchens of this food service operation. Despite the reported high prevalence of Campylobacter spp. in raw poultry, this organism was not detected on surfaces within a kitchen of a restaurant specializing in poultry dishes.

Infectious disease outbreaks related to drinking water in Canada, 1974-2001.

BACKGROUND: Recent public attention on drinking water supplies in the aftermath of waterborne infection outbreaks in Walkerton and North Battleford raises questions about safety. We analyzed information on waterborne outbreaks occurring between 1974 and 2001 in order to identify apparent trends, review the current status of monitoring and reporting, and gain a better understanding of the impact of drinking water quality on public health and disease burden. METHODS: Data from outbreak investigations, published and unpublished, were categorized by the type of drinking water provider and were assessed to be definitely, probably or possibly waterborne in nature. RESULTS: The final data set consisted of 288 outbreaks of disease linked to a drinking water source. There were 99 outbreaks in public water systems, 138 outbreaks in semi-public systems and 51 outbreaks in private systems. The main known causative agents of waterborne disease outbreaks were (in descending frequency of occurrence) Giardia, Campylobacter, Cryptosporidium, Norwalk-like viruses, Salmonella and hepatitis A virus. SUMMARY: We found that severe weather, close proximity to animal populations, treatment system malfunctions, poor maintenance and treatment practices were associated with the reported disease outbreaks resulting from drinking water supplies. However, issues related to the accuracy, co-ordination, compatibility and detail of data exist. A systematic and coordinated national surveillance system for comparison purposes, trend identification and policy development is needed so that future waterborne disease outbreaks can be avoided.

Characteristics and frequency of detection of fecal Listeria monocytogenes shed by livestock, wildlife, and humans.

Listeria monocytogenes is a facultative intracellular pathogen that can be carried asymptomatically in various animals and can be shed in feces. We investigated the prevalence and characteristics of L. monocytogenes isolated from livestock, wildlife, and human potential sources of contamination in 2 areas in Ontario, Canada. From February 2003 to November 2005, a total of 268 fecal samples were collected from different animals. Listeria monocytogenes was isolated using selective enrichment, isolation, and confirmation procedures, and 15 samples (6%) yielded to the isolation of 84 confirmed strains. Listeria monocytogenes was isolated from livestock (beef and dairy), wildlife (deer, moose, otter, and raccoon), and human (biosolids and septic) fecal sources. Thirty-two isolates were from serovar 1/2a, 34 from serovar 1/2b, 1 from serovar 3a, and 17 from serovar 4b. Listeria monocytogenes populations were resolved into 13 EcoRI ribotypes, and 18 ApaI and 18 AscI pulsotypes, with Simpson indexes of discrimination of 0.878 and 0.907, respectively. A majority (59%) of L. monocytogenes isolates exhibited potential virulence linked to the production of a functional internalin A, which was supported by higher entry into Caco-2 cells (9.3%) than isolates producing truncated and secreted internalin A (1.3% of entry). Listeria monocytogenes fecal isolates were on average resistant to 6.4 +/- 2.5 antibiotics out of 17 tested, and potentially virulent isolates exhibited an enhanced resistance to kanamycin, gentamicin, streptomycin, and rifampicin. Livestock, wildlife, and human L. monocytogenes fecal communities exhibited overlapping but distinct populations, and some genotypes and phenotypes were similar to those previously described for surface water isolates in the same area.

Distribution and characteristics of Listeria monocytogenes isolates from surface waters of the South Nation River watershed, Ontario, Canada.

Listeria monocytogenes is a facultative intracellular pathogen thought to be widely distributed in the environment. We investigated the prevalence and characteristics of L. monocytogenes isolates from surface waters derived from catchments within the South Nation River watershed (Ontario, Canada). This watershed is dominated by urban and rural development, livestock and crop production, and wildlife habitats. From June to November 2005, a total of 314 surface water samples were collected biweekly from 22 discrete sampling sites characterized by various upstream land uses. Presumptive Listeria spp. were isolated using a selective enrichment and isolation procedure, and 75 L. monocytogenes isolates were identified based on colony morphology, hemolytic activity, and amplification of three pathogenicity genes: iap, inlA, and hlyA. Thirty-two of 314 (10%) surface water samples were positive for the presence of L. monocytogenes, but detection ranged between 0 and 27% depending on the sampling date. Isolates belonging to serovar group 1/2a, 3a (50%) and group 4b, 4d, 4e (32%) were dominant. L. monocytogenes populations were resolved into 13 EcoRI ribotypes and 21 ApaI and 21 AscI pulsotypes. These had Simpson indexes of discrimination of up to 0.885. Lineage I-related isolates were dominant (61%) during the summer, whereas lineage II isolates were dominant (77%) in the fall. Isolates were, on average, resistant to 6.1 +/- 2.1 antibiotics out of 17 tested. Half of the L. monocytogenes isolates exhibited potential virulence linked to the production of a functional internalin A, and some isolates were found to be moderately to highly virulent by in vitro Caco-2 plaque formation assay (up to 28% of entry). There was a statistically significant link between the occurrence of L. monocytogenes and proximity to an upstream dairy farm and degree of cropped land. Our data indicate that L. monocytogenes is widespread in the studied catchments, where it could represent a public health issue related to agricultural land use.

Large-scale comparative genomics meta-analysis of Campylobacter jejuni isolates reveals low level of genome plasticity.

We have used comparative genomic hybridization (CGH) on a full-genome Campylobacter jejuni microarray to examine genome-wide gene conservation patterns among 51 strains isolated from food and clinical sources. These data have been integrated with data from three previous C. jejuni CGH studies to perform a meta-analysis that included 97 strains from the four separate data sets. Although many genes were found to be divergent across multiple strains (n = 350), many genes (n = 249) were uniquely variable in single strains. Thus, the strains in each data set comprise strains with a unique genetic diversity not found in the strains in the other data sets. Despite the large increase in the collective number of variable C. jejuni genes (n = 599) found in the meta-analysis data set, nearly half of these (n = 276) mapped to previously defined variable loci, and it therefore appears that large regions of the C. jejuni genome are genetically stable. A detailed analysis of the microarray data revealed that divergent genes could be differentiated on the basis of the amplitudes of their differential microarray signals. Of 599 variable genes, 122 could be classified as highly divergent on the basis of CGH data. Nearly all highly divergent genes (117 of 122) had divergent neighbors and showed high levels of intraspecies variability. The approach outlined here has enabled us to distinguish global trends of gene conservation in C. jejuni and has enabled us to define this group of genes as a robust set of variable markers that can become the cornerstone of a new generation of genotyping methods that use genome-wide C. jejuni gene variability data.