Identifying host sources, human health risk and indicators of Cryptosporidium and Giardia in a Canadian watershed influenced by urban and rural activities.

Cryptosporidium and Giardia were characterized in a watershed in southern Ontario, Canada, over a 2½ year period. River samples were collected every two weeks, primarily near a municipal drinking water treatment plant intake. Cryptosporidium and Giardia were frequently detected with an overall occurrence rate of 88 and 97%, respectively. Giardia concentrations were higher than Cryptosporidium, with median values of 80 cysts 100 L(-1) and 12 oocysts 100 L(-1), respectively. Although pathogens rarely show a significant relationship with fecal or water quality indicators, this study determined that Cryptosporidium, but not Giardia, was significantly correlated with Escherichia coli, turbidity and river flow. There was no correlation between the two types of protozoa, and only Giardia showed a seasonal trend with higher concentrations at cold water temperatures. Cryptosporidium genotyping of all samples found that farm animals and wildlife were an important contributor of oocysts in the watershed, and that Cryptosporidium strains/genotypes of medium to high risk for human infection (C. hominis, C. parvum and C. ubiquitum) were detected in 16% of samples. This study was able to identify Cryptosporidium host sources and human health risk, and to identify differences between Cryptosporidium and Giardia occurrence in the watershed.

Challenges of investigating community outbreaks of cyclosporiasis, British Columbia, Canada.

Investigations of community outbreaks of cyclosporiasis are challenged by case-patients' poor recall of exposure resulting from lags in detection and the stealthy nature of food vehicles. We combined multiple techniques, including early consultation with food regulators, traceback of suspected items, and grocery store loyalty card records, to identify a single vehicle for a cyclosporiasis outbreak in British Columbia, Canada, in 2007.

Cyclospora spp. in herbs and water samples collected from markets and farms in Hanoi, Vietnam.

OBJECTIVE: To determine the prevalence of Cyclospora spp. oocysts in herb and water samples as well as in fecal specimens of clinical cases of diarrhoea in Hanoi, Vietnam. METHOD: From November 2004 to October 2005, water and herb samples collected from markets and farms in Hanoi were examined for the presence of Cyclospora spp. oocysts in concentrated sediments and washings using UV epifluorescence examination of a wet mount. In addition, hospital based surveillance studies were carried out using a structured questionnaire which focused on potential risk factors for cyclosporiasis. Stool specimens were collected from individuals with diarrhoea attending primary healthcare facilities and examined for Cyclospora spp. oocysts by modified acid fast smear and wet mount examination using both light and UV epifluorescence microscopy. RESULTS: Cyclospora spp. were found in 34/288 (11.8%) market water and herb samples, and in 24/287 (8.4%) farm samples. All varieties of herbs sold at the market and grown in farms were contaminated with Cyclospora spp. oocysts. A marked seasonal increase in Cyclospora spp. contamination was observed before the rainy season (39/288) from November to April compared to the rainy season (19/268) from May to October (chi(2) = 7.593, P = 0.006). However, Cyclospora spp. was not found in any stool samples collected in hospital-based surveillance studies. CONCLUSIONS: These results confirm the presence of Cyclospora spp. which varies seasonally in environmental samples (water and herbs collected from farms and markets) within the Hanoi metropolitan area.

Molecular forensic profiling of Cryptosporidium species and genotypes in raw water.

The emerging concept of host specificity of Cryptosporidium spp. was exploited to characterize sources of fecal contamination in a watershed. A method of molecular forensic profiling of Cryptosporidium oocysts on microscope slides prepared from raw water samples processed by U.S. Environmental Protection Agency Method 1623 was developed. The method was based on a repetitive nested PCR-restriction fragment length polymorphism-DNA sequencing approach that permitted the resolution of multiple species/genotypes of Cryptosporidium in a single water sample.

Enzyme immunoassay of Cryptosporidium-specific immunoglobulin G antibodies to assess longitudinal infection trends in six communities in British Columbia, Canada.

A newly developed enzyme-linked immunosorbent assay (ELISA) that detects immunoglobulin G antibodies to the 27-kDa Cryptosporidium parvum sporozoite surface antigen was used to test 4,097 sera collected from pregnant women in 6 communities in British Columbia, Canada, between January 1996, and December 1997. Waterborne outbreaks of cryptosporidiosis occurred in two of the study communities during the period of follow-up, and ELISA seropositivity was high in all six communities during the study period (77% positive to 92% positive). In the community with the largest outbreak, levels of antibody to the 27-kDa antigen increased rapidly and then decayed to background levels within 3-4 months of the peak of the epidemic curve. Trends in serologic reactivity were complex in all communities, and increased antibody levels not related temporally to known waterborne outbreaks were also observed. Serological assays may provide more accurate information regarding community levels of Cryptosporidium infection.

Perspectives on emerging zoonotic disease research and capacity building in Canada.

Zoonoses are fundamental determinants of community health. Preventing, identifying and managing these infections must be a central public health focus. Most current zoonoses research focuses on the interface of the pathogen and the clinically ill person, emphasizing microbial detection, mechanisms of pathogenicity and clinical intervention strategies, rather than examining the causes of emergence, persistence and spread of new zoonoses. There are gaps in the understanding of the animal determinants of emergence and the capacity to train highly qualified individuals; these are major obstacles to preventing new disease threats. The ability to predict the emergence of zoonoses and their resulting public health and societal impacts are hindered when insufficient effort is devoted to understanding zoonotic disease epidemiology, and when zoonoses are not examined in a manner that yields fundamental insight into their origin and spread. Emerging infectious disease research should rest on four pillars: enhanced communications across disciplinary and agency boundaries; the assessment and development of surveillance and disease detection tools; the examination of linkages between animal health determinants of human health outcomes; and finally, cross-disciplinary training and research. A national strategy to predict, prevent and manage emerging diseases must have a prominent and explicit role for veterinary and biological researchers. An integrated health approach would provide decision makers with a firmer foundation from which to build evidence-based disease prevention and control plans that involve complex human/animal/environmental systems, and would serve as the foundation to train and support the new cadre of individuals ultimately needed to maintain and apply research capacity in this area.

Perspectives on emerging zoonotic disease research and capacity building in Canada.

Zoonoses are fundamental determinants of community health. Preventing, identifying and managing these infections must be a central public health focus. Most current zoonoses research focuses on the interface of the pathogen and the clinically ill person, emphasizing microbial detection, mechanisms of pathogenicity and clinical intervention strategies, rather than examining the causes of emergence, persistence and spread of new zoonoses. There are gaps in the understanding of the animal determinants of emergence and the capacity to train highly qualified individuals; these are major obstacles to preventing new disease threats. The ability to predict the emergence of zoonoses and their resulting public health and societal impacts are hindered when insufficient effort is devoted to understanding zoonotic disease epidemiology, and when zoonoses are not examined in a manner that yields fundamental insight into their origin and spread.EMERGING INFECTIOUS DISEASE RESEARCH SHOULD REST ON FOUR PILLARS: enhanced communications across disciplinary and agency boundaries; the assessment and development of surveillance and disease detection tools; the examination of linkages between animal health determinants of human health outcomes; and finally, cross-disciplinary training and research. A national strategy to predict, prevent and manage emerging diseases must have a prominent and explicit role for veterinary and biological researchers. An integrated health approach would provide decision makers with a firmer foundation from which to build evidence-based disease prevention and control plans that involve complex human/animal/environmental systems, and would serve as the foundation to train and support the new cadre of individuals ultimately needed to maintain and apply research capacity in this area.

Novel cryptosporidium genotypes in sporadic cryptosporidiosis cases: first report of human infections with a cervine genotype.

In this study, we genotyped parasites from the fecal specimens of sporadic cryptosporidiosis cases in British Columbia from 1995 to 1999. Genotyping was conducted by polymerase chain amplification of the internal transcribed spacer region, a hypervariable region in the 18S rRNA gene and the Cryptosporidium oocyst wall protein gene. Subsequent analysis was by restriction fragment length polymorphism and DNA sequencing. We identified two new Cryptosporidium genotypes in humans. One of these genotypes has been found recently in deer in New York state. The other genotype has not been identified in humans or animals. These results have important implications for drinking water quality strategies, especially for communities that obtain drinking water supplies from surface sources located in forested regions with deer populations.