Public Health Agency of Canada
www.publichealth.gc.ca
C-EnterNet Short Report 2008
Human Case Summary
Table 1: Disease-specific annual incidence rates in Sentinel Site 1 in 2008 compared to 2007, 2006 and historical averages
| 2008 | 2007 | 2006 | Average Incidence Rate (per 100,000 person-years) | |||||
|---|---|---|---|---|---|---|---|---|
| # of Cases | Incidence Rate (per 100,000 person-years) | # of Cases | Incidence Rate (per 100,000 person-years) | # of Cases | Incidence Rate (per 100,000 person-years) | (1990 - 2004)a | ||
| Total | Endemic | 322 | 331 | 285 | ||||
| Travel | 118 | 142 | 131 | |||||
| Outbreak | 33 | 4 | 4 | |||||
| Amoebiasis | Total | 5.98 | 6.44 | 3.66 | 5.35 | |||
| Endemic | 19 | 3.79 | 16 | 3.22 | 12 | 2.44 | ||
| Travel | 11 | 2.19 | 16 | 3.22 | 6 | 1.22 | ||
| Campylobacteriosis | Total | 36.07 | 35.62 | 27.23 | 49.69 | |||
| Endemic | 123 | 24.51 | 131 | 26.36 | 108 | 21.95 | ||
| Travel | 32 | 6.38 | 46 | 9.26 | 26 | 5.28 | ||
| Outbreak | 26 | 5.18 | ||||||
| Cryptosporidiosis | Total | 3.39 | 3.82 | 4.27 | 2.98 | |||
| Endemic | 15 | 2.99 | 12 | 2.41 | 15 | 3.05 | ||
| Travel | 2 | 0.40 | 7 | 1.41 | 6 | 1.22 | ||
| Cyclosporiasis | Total | 0.60 | 0.60 | 0.00 | 0.70 | |||
| Endemic | 1 | 0.20 | 2 | 0.40 | 0 | 0.00 | ||
| Travel | 2 | 0.40 | 1 | 0.20 | 0 | 0.00 | ||
| Giardiasis | Total | 15.94 | 11.27 | 13.61 | 31.87 | |||
| Endemic | 48 | 9.57 | 33 | 6.64 | 35 | 7.11 | ||
| Travel | 32 | 6.38 | 22 | 4.43 | 32 | 6.50 | ||
| Outbreak | 1 | 0.20 | 0 | 0.00 | ||||
| Hepatitis A | Total | 0.40 | 1.41 | 2.44 | 2.72 | |||
| Endemic | 1 | 0.20 | 7 | 1.41 | 4 | 0.81 | ||
| Travel | 1 | 0.20 | 0 | 0.00 | 8 | 1.63 | ||
| Outbreak | ||||||||
| Listeriosis | Total | 1.20 | 0.20 | 0.00 | 0.19 | |||
| Endemic | 3 | 0.60 | 1 | 0.20 | 0 | 0.00 | ||
| Travel | 0 | 0.00 | 0 | 0.00 | 0 | 0.00 | ||
| Outbreak | 3 | 0.60 | ||||||
| Salmonellosis | Total | 22.32 | 26.16 | 22.36 | 25.97 | |||
| Endemic | 82 | 16.34 | 96 | 19.32 | 60 | 12.19 | ||
| Travel | 28 | 5.58 | 33 | 6.64 | 48 | 9.76 | ||
| Outbreak | 2 | 0.40 | 1 | 0.20 | 2 | 0.41 | ||
| Shigellosis | Total | 1.20 | 2.21 | 1.22 | 2.83 | |||
| Endemic | 1 | 0.20 | 2 | 0.40 | 3 | 0.61 | ||
| Travel | 5 | 1.00 | 9 | 1.81 | 3 | 0.61 | ||
| Verotoxigenic E. coli (VTEC) | Total | 2.99 | 3.82 | 7.11 | 5.86 | |||
| Endemic | 14 | 2.79 | 14 | 2.82 | 32 | 6.50 | ||
| Travel | 0 | 0.00 | 3 | 0.60 | 1 | 0.20 | ||
| Outbreak | 1 | 0.20 | 2 | 0.40 | 2 | 0.41 | ||
| Yersiniosis | Total | 1.99 | 4.43 | 3.45 | 3.11 | |||
| Endemic | 7 | 1.39 | 17 | 3.42 | 16 | 3.25 | ||
| Travel | 3 | 0.60 | 5 | 1.01 | 1 | 0.20 | ||
| Cells shaded in yellow represent significant changes from 2006-2007 to 2008 (Fisher's Exact Test P≤ 0.05) a Keegan et. al. 2009. Epidemiology of enteric disease in C-EnterNet's Pilot Site, Waterloo Region, Ontario, 1990-2004. Canadian Journal of Infectious Diseases and Medical Microbiology. In press. |
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Figure 1: Temporal trends of the three most frequent enteric diseases, and total bacterial, viral and parasitic enteric disease from Sentinel Site 1, 1990 to 2008
Note: Total enteric disease includes endemic, travel and outbrake cases.
C-EnterNet’s human enteric samples are collected through the existing passive surveillance system in Ontario. This system has been enhanced by C-EnterNet through the collection of epidemiological and microbiological data for the human cases by using an improved standardized questionnaire for sporadic enteric disease cases and by performing advanced subtyping analyses on human stool samples.
The burden of enteric disease continues to be significant in the Region of Waterloo. It must be noted that under-reporting continues to complicate these measures, not only in Sentinel Site 1 but also across Canada. It has been estimated that for every case of acute gastroenteritis that is counted through public health surveillance, there are 313 cases in the community that go unmeasured1.
In 2008, of the 473 reported cases of 11 bacterial, viral and parasitic enteric diseases in the Region of Waterloo, campylobacteriosis, salmonellosis and giardiasis were most common. Overall, listeriosis increased significantly (p<0.05) in 2008 due to an outbreak and higher numbers of endemic cases reported than in recent years. Overall, both Hepatitis A and VTEC infections decreased significantly (p<0.05) in 2008 compared to 2007 and 2006. Endemic giardiasis increased significantly (p<0.05) in 2008 compared to 2007 and 2006, while endemic yersiniosis decreased significantly (p<0.05). The incidence rate of endemic salmonellosis remains consistently high over the past three years, while the endemic rates of campylobacteriosis and cryptosporidiosis have remained stable.
Travel continues to be a significant factor in the burden of enteric disease. In 2008, 25% of all cases of enteric disease were associated with travel outside of Canada. Travel-acquired campylobacteriosis, giardiasis and salmonellosis showed the highest number of reported cases in 2008. The majority of travel-associated Campylobacter cases had reported travelling to Europe (9/31) and the Americas (7/31). The majority of travel-associated Giardia cases had reported travelling to Asia (14/32) and Africa (10/32), and the majority of travel-associated Salmonella cases had reported travelling to the Americas (15/28). Travel-related cryptosporidiosis decreased slightly since previous years with only 2 cases reported in 2008 with travel to Africa and Asia. There were no travel-associated VTEC infections reported in 2008 compared to previous years, indicating that E. coli O157:H7 appears to be a domestically acquired infection.
In 2008, there was an increase in the number of outbreak-associated enteric disease, with a total of 33 reported cases compared to the previous two years where 4 cases each were reported. The majority of outbreak associated cases (26/33) in 2008 were Campylobacter cases (all cases linked to one event), whereas in previous years, no Campylobacter-associated outbreaks were reported. There were a total of three Listeria associated outbreak cases linked to the Canada-wide outbreak. One listeriosis case linked to an outbreak in Québec was associated with unpasteurized cheese.
Retail Component
Retail meat continues to be an important exposure source for enteric pathogens. Since mid-2005, C-EnterNet has systematically sampled fresh raw pork, chicken and beef from randomly selected grocery stores within the sentinel site on a weekly basis. Retail meat sampling is conducted to understand the risk of pathogen exposure at the consumer level. In 2008, the levels of pathogen contamination on retail raw meat were similar to what was found in both 2006 and 2007 combined with the exception of Yersinia on pork and Campylobacter on chicken. As was the case in 2007, the 2008 prevalence of Yersinia spp. decreased significantly (p<0.05) in pork.
Raw chicken remains the commodity most frequently contaminated with Salmonella and Campylobacter. The prevalence of Campylobacter increased (p<0.05) in 2008 in chicken compared to 2007 and 2006. However, this increase corresponds to the change in the type of chicken breast sampled from skin-on in 2006-2007 to skin-off in 2008 (Cook and Pollari, personal communication). In 2008, as in 2007, the presence of Verotoxogenic E. coli remains low with only two ground beef samples testing positive.
Table 2: Pathogen detection on retail meat in 2006, 2007 and 2008
| 2006 | 2007 | 2008 | |||||||
| Pork (n=140) |
Chicken (n=145) |
Beef (n= 139) |
Pork (n=187) |
Chicken (n=187) |
Beef (n= 187) |
Pork (n=178) |
Chicken (n=185) |
Beef (n=180) |
|
| Campylobacter | 0% | 31% (45) | 0% | 2% (3) | 29% (55) | 1%(1) | 0% | 43% (80) | 1% (2) |
| Salmonella | 3% (4) | 30% (43) | 1%(1) | 3%(6) | 33%(61) | 1%(1) | 1% (1) | 32% (60) | 1% (1) |
| VTEC | 0% | 0% | 0% | 0% | 0% | 1% (2) | 0% | 0% | 1% (2) |
| Yersinia spp | 13% (18) | Not tested | Not tested | 5% (9) | Not tested | Not tested | 3% (6) | Not tested | Not tested |
| Listeria monocytogenes | 9% (12) | 32% (46) | 24% (33) | 12% (22) | 36% (68) | 25% (46) | Not tested | Not tested | Not tested |
| Cells shaded in yellow represent significant changes from 2008 to the combined 2006/2007 years (Fisher’s Exact Test, P ≤ 0.05) Note: 2008 results are preliminary |
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Figure 2: Yearly distribution of pathogen contamination on retail meat, 2006-2008
Agriculture Component
Table 3: Pathogen detection from manure samples in 2006, 2007 and 2008
|
2006 | 2007 | 2008 | |||||||
| Sample Prevalence | Swine (120 samples) |
Dairy (179 samples) |
Swine (120 samples) |
Dairy (112 samples) |
Beef (80 samples) |
Broiler Chickens (36 samples) |
Swine (111 samples) |
Dairy (112 samples) |
Beef (112 samples) |
Broiler Chickens (100 samples) |
| Campylobacter | 13% (15) | 25% (44) | 10% (12) | 21% (23) | 13% (10) | 0% | 68% (76)a | 75% (84)a | 76% (85)a | 10% (10) |
| Salmonella | 28% (33) | 11% (20) | 33% (40) | 13% (14) | 10% (8) | 72% (26) | 28% (31) | 8% (9) | 6% (7) | 62% (62) |
| E. coli 0157:H7 | 0% | 9% (16) | 0% | 5% (6) | 9% (7) | 0% | 1% (1) | 4% (4)b | 13% (14)b | 0%c |
| Yersinia spp | 8% (10) | Not tested | 3% (4) | Not tested | Not tested | Not tested | 4% (4) | Not tested | Not tested | Not tested |
| Listeria monocytogenes | 1% (1) | 8% (15) | Not tested | Not tested | 64% (51) | 3% (1) | Not tested | Not tested | 64% (23)d | 8% (7)e |
Cells shaded in yellow represent significant changes from 2008 to the combined 2006/2007 years (Fisher’s Exact Test, P ≤ 0.05) a Significant increase of Campylobacter in 2008 is most likely due to the implementation of a more sensitive laboratory method |
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Table 4: Pathogen detection at the farm level in 2006, 2007 and 2008
|
2006 | 2007 | 2008 | |||||||
| Farm Prevalence | Swine (30 farms) |
Dairy (45 farms) |
Swine (30 farms) |
Dairy (28 farms) |
Beef (21 farms) |
Broiler Chickens (9 farms) |
Swine (30 farms) |
Dairy (28 farms) |
Beef (28 farms) |
Broiler Chickens (25 farms) |
| Campylobacter | 40% (12) | 60% (27) | 40% (12) | 40% (11) | 33% (7) | 0% | 93% (28)a | 93% (26)a | 96% (27)a | 12% (3) |
| Salmonella | 60% (18) | 22% (10) | 60% (18) | 21% (6) | 14% (3) | 89% (8) | 60% (18) | 18% (5) | 11% (3) | 76% (19) |
| E. coli O157:H7 | 0% | 29% (13) | 0% | 21% (6) | 24% (5) | 0% | 3% (1) | 12% (3)b | 31% (8)b | 0%c |
| Yersinia spp | 30% (9) | Not tested | 13% (4) | Not tested | Not tested | Not tested | 13% (4) | Not tested | Not tested | Not tested |
| Listeria monocytogenes | 3% (1) | 33% (12) | Not tested | Not tested | 90% (19) | 11% (1) | Not tested | Not tested | Not tested | Not tested |
Cells shaded in yellow represent significant changes from 2008 to the combined 2006/2007 years (Fisher’s Exact Test, P ≤ 0.05) a Significant increase of Campylobacter in 2008 is most likely due to the implementation of a more sensitive laboratory method |
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Figure 3: Pathogen detection from manure samples in 2006, 2007 and 2008
Detection of enteric pathogens on farms represents an environmental exposure source. In 2008, all four commodity groups (dairy, beef, swine, and broiler chickens) were sampled. Each month 2-3 farms per commodity are enrolled and visited for a total of approximately 30 farms per commodity per year. The visit involves the administration of a short management survey and sampling of three fresh pooled manure samples from different age groups of animals and one stored manure sample.
Results are presented at the sample level and at the farm level, to account for within-farm similarities. In 2008, the same 30 swine farms were enrolled and sampled as in 2007 and 2006. In contrast, in 2008 13 and 15 of the beef and dairy farms, respectively, had been previously sampled in 2007. Also, the poultry farms sampled in 2008 had not been previously sampled in 2007.
Salmonella was most frequently detected in swine and broiler chickens (at the farm and sample level). Campylobacter was frequently detected (at both the farm and sample level) in swine, dairy and beef farms, and was detected on 3 broiler chicken farms (0 were detected in 2007). The prevalence of Campylobacter increased significantly (p<0.05) in swine, dairy and beef at the farm level in 2008 compared to 2007 and 2006 and is most likely due to the implementation of a more sensitive laboratory methodology at the beginning of 2008, rather than a true prevalence increase. E. coli O157:H7 was detected on both dairy and beef at the farm level, and was detected on 1 swine farm which had not been detected in previous sampling years.
Water Component
Table 5: Pathogen detection in untreated surface water in Sentinel Site 1, 2006-2008
| 2008 | ||||||
| All Sites | A | B | C | D | E | |
| Campylobacter | 24% (24/100) | 24% (5/21) | 24% (5/21) | 28% (5/18) | 41% (9/22) | 0% (0/18) |
| Salmonella | 34% (34/100) | 62% (13/21) | 33% (7/21) | 11% (2/18) | 18% (4/22) | 44% (8/18) |
| E. coli O157:H7 | 1% (1/100) | 0% (0/21) | 5% (1/21) | 0% (0/18) | 0% (0/22) | 0% (0/18) |
| Yersinia spp | 11% (11/100) | 10% (2/21) | 10% (2/21) | 17% (3/18) | 14% (3/22) | 6% (1/18) |
| Cryptosporidiuma | 82% (18/22) | 100% (2/2) | 50% (1/2) | 0% (0/1) | 87% (13/15) | 100% (2/2) |
| Giardiaa | 95% (21/22) | 100% (2/2) | 100% (2/2) | 100% (1/1) | 93% (14/15) | 100% (2/2) |
| 2007 | ||||||
| All Sites | A | B | C | D | E | |
| Campylobacter | 18% (24/134) | 22% (6/27) | 12% (3/26) | 37% (10/27) | 19% (5/27) | 0% (0/27) |
| Salmonella | 10% (13/134) | 4% (1/27) | 7% (2/26) | 7% (2/27) | 4% (1/27) | 26% (7/27) |
| E. coli O157:H7 | 2% (3/134) | 7% (2/27) | 0% (0/26) | 0% (0/27) | 0% (0/27) | 4% (1/27) |
| Yersinia spp | 40% (53/133) | 37% (10/26) | 37% (10/26) | 56% (15/27) | 30% (8/27) | 41% (11/27) |
| Cryptosporidiuma | 88% (35/40) | 100% (3/3) | 100% (3/3) | 67% (2/3) | 85% (22/26) | 100%(5/5) |
| Giardiaa | 100 % (40/40) | 100% (3/3) | 100% (3/3) | 100% (2/2) | 100% (27/27) | 100% (5/5) |
| 2006 | ||||||
| All Sites | A | B | C | D | E | |
| Campylobacter | 9% (13/140) | 18% (5/28) | 4% (1/28) | 14% (4/28) | 11% (3/28) | 0% (0/28) |
| Salmonella | 20% (28/140) | 21% (6/28) | 21% (6/28) | 18% (5/28) | 29% (8/28) | 11% (3/28) |
| E. coli O157:H7 | 1% (1/124) | 0% (0/24) | 0% (0/24) | 4% (1/24) | 0% (0/24) | 0% (0/24) |
| Yersinia spp | 14% (15/105) | 19% (4/21) | 19% (4/21) | 14% (3/21) | 10% (2/21) | 10% (2/21) |
| Cryptosporidiuma | 94% (33/35) | --- | --- | 100% (3/3) | 93% (27/29) | 100% (3/3) |
| Giardiaa | 97% (34/35) | --- | --- | 67% (2/3) | 93% (27/29) | 100% (3/3) |
| Note: Cells shaded in yellow represent significant changes from 2008 to 2006 & 2007 combined (Fisher's Exact Test P≤0.05) | ||||||
| a By microscopy, not culture method | ||||||
Sample Site Legend: B - Conestogo River C - Upper Grand River D - Grand River, near drinking water intake E - Grand River, near one waste water treatment plant effluent |
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Figure 4: Proportion of positive untreated surface water samples tested by culture method in Sentinel Site 1 between 2006 to 2008 for selected enteric pathogens
Since 2005, five sites along the Grand River have been sampled for exposure surveillance within the C-EnterNet sentinel site, to understand the dynamics of pathogen levels in the environment and the transmission of enteric pathogens from both point and non-point sources within the watershed. After three full years of sampling, we have separated the results based on sample collection point. In 2008, only culture-based methods were used for the detection of pathogens in untreated surface water.
The prevalence of Salmonella contamination increased significantly (p<0.05) in 2008 compared to 2007 and 2006, and Campylobacter prevalence showed a significant increase as well, with the highest levels of contamination at site D (near the drinking water intake) in 2008. The prevalence of Yersinia spp. decreased significantly (p<0.05) in 2008 compared to 2007 and 2006 and may be due to changes to laboratory methodology used for Yersinia detection part way through the sampling year.To-date, pathogenic strains of Y. enterocolitica have not been detected in river water. Pathogenic E. coli detection in river samples continues to be low with less than 1% of positive samples in 2008. It is still unclear if this is due to low levels or methodology issues (or a combination of both).
Cryptosporidium and Giardia are consistently being detected at many of the sample locations along the river and thus continue to be an important consideration for water treatment plant operators in the watershed. The prevalence of Giardia contamination in the river has remained fairly stable over the past three years, while the prevalence of Cryptosporidium contamination shows a small decline. Nevertheless, the prevalence for both pathogens remains high in the river.
