C-EnterNet 2007 Annual Report

National Integrated Enteric Pathogen Surveillance Program

8. Parasites

8.1 Giardiasis

In 2007, in Sentinel Site 1, there were 56 reported cases of giardiasis (11.3/100,000 person-years). Of these 56 cases, 22 (39%) were travel-related, one was related to an outbreak, and 33 (59%) were classified as endemic (6.6/100,000 person-years). In comparison, the annual incidence rates for giardiasis in 2006 in Canada and Ontario were 11.1/100,000 and 9.7/100,000, respectively.¹³

Of the endemic cases, ten were female (4.0/100,000) and 23 were male (9.3/100,000), indicating a higher incidence rate among males (Figure 8.1). No cases were reported among individuals in the 15-19 and 20-24 age groups.

FIGURE 8.1: Incidence rates of endemic giardiasis cases by gender and age group in Sentinel Site 1 in 2007

Figure 8.1 - table equivalent

FIGURE 8.2: Monthly distribution of Giardia cases and detection in untreated surface water sampled in Sentinel Site 1 in 2007

Figure 8.2 - table equivalent

The number of cases per month varied from none to five with the most number of cases observed in July and in August (Figure 8.2).

Potential exposure information for the 25 days prior to the onset of illness was available for 25/33 (76%) of the endemic cases (Appendix B). Higher numbers of reported Giardia cases were observed for the following exposures: using a private well, swimming in a pool, eating at a restaurant, eating meat from a butcher shop, eating meat from private kill, shopping at a butcher shop, contact with households pets, living on a farm or in a rural area, visiting a farm animal area (horses), and on-farm exposure to cattle and horses.

TABLE 8.1: Giardia detection and subtyping data from the integrated surveillance activities in Sentinel Site 1 in 2007

	Human	Food Animals (Manure)		Untreated Surface Water
	Endemic Cases	Broiler Chickens	Beef Cattle	Grand River
		9 Farms	21 Farms	5 sample points on Grand River
Microscopic Results
# tested	Unknown	33	76	40
# positive	33	0	52	40 (A, B, C, D, E)
% positive		0%	68%	100%
PCR Results
# tested		33	76
# positive		1	52
% positive		3%	68%
Sequencing Results
# samples with sequencing results	0	1	48	0
Assemblage B		1
Assemblage E			48

Exposure Surveillance

On-Farm

Using microscopy techniques, 68% of the pooled beef manure and 0% of the pooled broiler chicken manure samples, respectively, tested positive for Giardia (Table 8.1). Using PCR methods, 68% and 3% of the pooled beef and pooled broiler chicken manure samples, respectively, were positive for Giardia. Correlations between the microscopy and PCR results were not always observed, although overall proportions were similar for the beef samples. Assemblage E, a non-zoonotic assemblage, was the only assemblage detected in the beef manure. Conversely, the one positive broiler chicken manure sample was identified as Assemblage B, a zoonotic strain.

Water

Giardia was detected in 100% of the untreated surface water samples collected bi-weekly throughout the year in Sentinel Site 1 (Table 8.1), indicating a high prevalence of this potential pathogen. Further molecular subtyping was not performed on these samples. The average concentration of Giardia cysts was highest in the river from October to December (Figure 8.2).

Summary of Giardiasis Results

• Epidemiologically, using a private well, swimming in a pool, eating at a restaurant, eating meat from a butcher shop, eating meat from private kill, shopping at a butcher shop, contact with household pets, living on a farm or in a rural area, visiting a farm animal area (horses), and on-farm exposure to cattle and horses appear to be important risk factors for endemic giardiasis.
• Giardia Assemblage B, which is pathogenic to humans, was only found in one pooled broiler chicken manure sample. Similar molecular subtyping methods on positive human and water samples are needed to inform source attribution estimates. Subtyping of positive water samples commenced in 2008.
• In the sentinel site, Giardia appears to be endemic in untreated surface water.

8.2 Cryptosporidiosis

In 2007, in Sentinel Site 1, there were a total of 19 reported cases of cryptosporidiosis (3.8/100,000 person-years). Of these 19 cases, seven were travel-related and 12 were classified as endemic (2.4/100,000 person-years). In comparison, the annual incidence rates for cryptosporidiosis in 2006 in Canada and Ontario were 2.0/100,000 and 2.5/100,000, respectively.¹⁴ Of the endemic cases, six were female (2.4/100,000) and six were male (2.4/100,000) (Figure 8.3).

FIGURE 8.3: Incidence rates of endemic cryptosporidiosis cases by gender and age group in Sentinel Site 1 in 2007

Figure 8.3 - table equivalent

FIGURE 8.4: Monthly distribution of Cryptosporidium cases and detection in untreated surface water sampled in Sentinel Site 1 in 2007

Figure 8.4 - table equivalent

The onset of the endemic cryptosporidiosis cases occurred in March, July, August, September and November (Figure 8.4).

Potential exposure information for the 12 days prior to the onset of illness was available for 11 of the 12 cases (Appendix B). Higher numbers of reported Cryptosporidium cases were observed for the following exposures: using a private well, swimming, ate meat from a private kill, contact with households pets (dog and reptile), living on a farm or in a rural area, visiting a farm animal area (cat, cattle, horses), and on-farm exposure to pigs.

TABLE 8.2: Cryptosporidium detection and subtyping data from the integrated surveillance activities in Sentinel Site 1 in 2007

	Human	Animals (Manure)		Untreated Surface Water
	Endemic Cases	Broiler Chickens	Beef Cattle	Grand River
		9 Farms	21 Farms	5 sample points on Grand River
Microscopic Results
# tested	Unknown	33	76	40
# positive	12	0	22	35 (A, B, C, D, E)
% positive		0%	29%	88%
PCR Results
# tested		33	76
# positive		0	20
% positive		0%	26%
Sequencing Results
# samples sequenced	0	0	18	26 (multiple genotypes per sample)
C. andersoni a			17	13
C. cervine a				1
C. parvum (bovine genotype) a			1	2
C. hominis a, b				3
C. muskrat genotype I				2
C. muskrat genotype II				1
Other				4

Exposure Surveillance

On-Farm

Using microscopy techniques, 29% and 0% of the pooled beef and broiler chicken manure samples, respectively, tested positive for Cryptosporidium (Table 8.2). Using PCR methods, 26% and 0% of the pooled beef and broiler chicken manure samples, respectively, were positive for Cryptosporidium. C. andersoni was the most common subtype detected in the beef samples, and one sample was positive for the C. parvum bovine genotype.

Water

Cryptosporidium was detected in 88% of untreated surface water samples, indicating a high prevalence of this potential pathogen in the watershed (Table 8.2). Further subtyping determined that C. andersoni was the most common genotype, supporting trends observed in previous sampling years. It should be noted that C. andersoni, while not commonly associated with human infections, has recently been reported in some immunocompetent cases^15 16, suggesting that it may be mildly infectious.

The two most common human pathogenic strains, C. hominis and C. parvum (the bovine genotype), were detected in 5 of the 25 samples tested. More than one genotype was detected in some of the samples. The average concentration of Cryptosporidium oocysts in untreated surface water peaked in December (Figure 8.4).

Summary of Cryptosporidiosis Results

• Epidemiologically, using a private well, swimming, contact with household pets (dog), living on a farm or in a rural area, visiting a farm animal area (cat, cattle, horses), and on-farm exposure to pigs appear to be important risk factors for endemic cryptosporidiosis in Sentinel Site 1.
• In the sentinel site, Cryptosporidium appears to be endemic in untreated surface water. There appears to be no correlation between high levels of Cryptosporidium oocysts in the untreated surface water and human cases (Figure 8.4).
• C. andersoni was the most common subtype identified in beef cattle manure and in untreated surface water.
• C. hominis, which is host-specific to humans, was detected in untreated surface water and this illustrates a human source, although prevalence is low.
• C. parvum, also frequently associated with human infection, was detected in untreated surface water and in pooled beef cattle manure.
• Untreated surface water samples contained other Cryptosporidium sp. strains potentially pathogenic to humans (C. cervine).

8.3 Cyclosporiasis

One travel-related and two endemic cases (0.4/100,000 person-years) were reported in Sentinel Site 1 in 2007, compared to none in 2006.

Cyclosporiasis is not considered to be endemic to Canada. Therefore, active surveillance for Cyclospora was not performed within the food, agricultural and water sources monitored in the C-EnterNet program.

8.4 Amoebiasis

In 2007, in Sentinel Site 1, there were a total of 32 reported cases of amoebiasis (6.4/100,000 person-years). Of these 32 cases, 16 were travel-related and 16 were classified as endemic (3.2/100,000 person-years). Of the endemic cases, seven were female (2.8/100,000) and nine were male (3.6/100,000) (Figure 8.5).

Amoebiasis was removed from national surveillance as of January 2000¹⁷; therefore, comparative incidence data cannot be provided for Canada.

FIGURE 8.5: Incidence rates of endemic amoebiasis cases by gender and age group in Sentinel Site 1 in 2007

Figure 8.5 - table equivalent

Potential exposure information for the seven days prior to the onset of illness was available for 13 of the 16 cases (Appendix B). Higher numbers of reported amoebiasis cases were observed for the following exposures: using municipal water, eating in a restaurant, and visiting a farm animal area (horses).

Entamoeba is a human intestinal pathogen. While not considered a zoonotic agent, Entamoeba has been known to infect dogs. It was not assessed in the various exposure sources (food, agricultural and water) in Sentinel Site 1.

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13 National Notifiable Disease representative (Carole Scott) 2007 [personal communication]. Note: 2006 numbers contain travel and endemic cases and are preliminary and subject to change.

14 National Notifiable Disease representative (Carole Scott) 2007 [personal communication]. Note: 2006 numbers contain travel and endemic cases and are preliminary and subject to change.

15 Leoni F, et al. Genetic analysis of Cryptosporidium from 2414 humans with diarrhoea in England between 1985 and 2000. J Med Micro.2006;55:703-707

16 Morse TD, et al. Incidence of cryptosporidiosis species in paediatric patients in Malawi. Epidemiol Infect. 2007;135:1307-1315

17 Centre for Infectious Disease Prevention and Control, Public Health Agency of Canada, National Notifiable Diseases, 2005. http://dsol-smed.phac-aspc.gc.ca/dsol-smed/ndis/list_e.html