This study examined the relationships between potential community-level risk factors and rates of the three most frequently reported enteric infections in the NWT from 1991 through 2008. Significant (p≤0.05) associations seemed to vary by etiology of NGI: campylobacteriosis was primarily associated with cultural and subsistence practices (traditional food consumption, trapping and food price index); giardiasis was mainly associated with health system factors (primary health facility, health expenditure per capita and internal mobility); and salmonellosis was only associated with households in core need (surrogate for socioeconomic status). Campylobacteriosis, giardiasis and salmonellosis are infections that are mainly acquired from the environment, for example, from food, water, and contact with animals or birds; therefore, the significant statistical correlations in the models could be considered as representing indicators of opportunities for exposure rather than direct cause-effect relationships.
Giardiasis was the most commonly reported infection by public health authorities in the NWT. Giardiasis is often contracted through the ingestion of infective cysts found in contaminated water, food, or infected persons by the fecal-oral route. The cysts can be present in contaminated wells and water systems, particularly those sourced from surface water such as fresh water lakes, rivers, and streams . The consumption of raw (untreated) surface water during cultural, economic or recreational activities could be a possible explanation for higher rates of giardiasis with increased internal mobility (population moving between communities). Person-to-person transmission also accounts for many Giardia infections especially in child care settings, in public institutions, or among those residing in areas with poor sanitation and hygiene . Although the role of animals in the transmission of human giardiasis is unclear, about 40% of NWT residents spend time on the land carrying out subsistence activities which can result in increased exposure to pathogenic agents in the physical environment and also in wild animals [8, 12]. Cysts of Giardia spp. have been found in water, sewage and fecal samples of marine mammals harvested for food in the Arctic . In particular, seals have been suggested as one of the reservoirs for giardiasis in the NWT. Although epidemiological studies on human giardiasis have not to our knowledge been conducted in the NWT, 30% of Inuit on Baffin Island (Nunavut) were found to have laboratory-confirmed cases of the infection . Furthermore, several outbreaks in Kodiak and Ketchikan (Alaska) were linked to the consumption of untreated surface water, thought to have been contaminated with cysts from the feces of beaver, hares and other carrier animals .
In our campylobacteriosis model, the statistically significant interaction between traditional foods and trapping suggests that in some instances, at the community level, activities that are thought to enhance exposure may have varying and complex effects on disease rates. We found that when the percentage of community participation in trapping was low, the risk of campylobacteriosis varied little with increasing percentages of traditional food consumption; however, when the percentage of community participation in trapping was higher, the protective effect against campylobacteriosis increased with greater consumption of traditional foods. One explanation for these results may be related to differential reporting between geographic regions. Higher consumption of traditional foods and higher rates of participation in trapping occur most often in more remote communities; however, it is also these communities that are often most disconnected from the reporting network of the surveillance system. Alternatively, it is possible that there is some form of traditional knowledge, genetic adaptation or acquired immunity (reflecting past exposure) that provides some protection to those frequently engaged in both activities. Maintaining a traditional lifestyle and diet are of great importance to the overall health and well-being of Aboriginal peoples ; therefore, targeted community-based collaborative research is required to more fully understand and interpret the complex relationships between these variables.
The combined challenges of storage, preparation, access and availability of traditional foods have caused communities to increase their consumption of retail foods as replacements for traditional foods; however, retail food prices are considerably higher in rural and remote communities compared to urban centers. A number of factors contribute to higher prices including freight charges, store management practices, and the reduced economies of scale for purchasing and retailing in small rural and remote communities [15, 16]. Furthermore, the distance between producer and consumer corresponds to effectively shorter shelf life of perishable foods, raising the likelihood of spoilage and perhaps growth of pathogens (e.g., Salmonella) on fresh foods. Long distance transportation of fresh retail foods requires careful packing, handling, storage and distribution; thus, there are a number of sources from which microbial contamination can be contracted or be exacerbated as the pathogen loads multiply, thereby increasing the risk of illness . In our model, a negative association was found between food prices in communities and risk of campylobacteriosis. Higher prices may affect food choices made by consumers, thereby changing their diet and diet-related health risks . Households may reduce consumption of food items such as meat, dairy, poultry, fruits and vegetables which are more costly and opt for processed and packaged items, which could reduce exposure to pathogens more commonly found in perishable foods . The association between higher food prices and decreased rates of campylobacteriosis may also be due to geographical reporting biases. Economically, traditional foods are still more affordable than retail foods, especially in remote areas ; thus, these communities tend to rely heavily on subsistence activities and may thereby have greater exposure to environmental contaminants and potential health risks [18–20].
Adequate, suitable and affordable housing is an essential component of health and well-being. A large body of scientific evidence demonstrates the association between housing quality and infectious diseases, chronic illnesses, and injuries [21–24]. In the North, the remote location combined with harsh climate creates higher costs and infrastructure needs . Many northern, rural and remote communities face socioeconomic challenges such as relatively low income that can affect their access to adequate, suitable and affordable housing . The 2001 Aboriginal Peoples Survey found that 33% of Aboriginal households are in core need, which is almost double the Canadian rate of 18% . In our model, there was increased risk of infection with Salmonella for communities with higher proportions of households in core need up to 42% after which the rate started to decrease with increasing core need. Features of substandard housing which could facilitate exposure to and spread of Salmonella and other pathogens include poor water supply (quality and quantity) and sanitation (infrastructure) as well as inadequate food storage and preparation, and the intrusion of disease vectors (e.g., insects) [24, 25]. The parabolic effect of households in core need (socioeconomic status) on salmonellosis may reflect complex interrelationships between food consumption patterns, safe food handling behaviors, contact with potential reservoir species of domestic and wild animals and other factors.
Person-to-person spread is not usually considered to be an important means of transmission of non-typhoidal salmonellosis but could be a factor in poor housing. High rates of respiratory illnesses in Aboriginal communities have also been attributed to inadequate and overcrowded housing. Tuberculosis rates in Aboriginal communities are 70 times the Canadian average . Although the mode of transmission of tuberculosis and other respiratory infections differs from those derived from the environment, it does indicate that social determinants of health may play an important role in the communicability of these diseases.
Health care expenditure per capita is a leading indicator of the long-term sustainability of a health care system, with higher per capita costs indicating systems in difficulty . The NWT has the second highest per capita expenditure in Canada as it operates four hospitals, 19 health centers, several nursing stations and a system-sponsored medical travel program for populations less than 50,000 spread across its 33 communities . Between 2000 and 2006, the Canadian Institute for Health Information (CIHI) estimated that territorial government health care expenditures increased by 53% from $158 million to $242 million . In our model, we observed that increases in health care expenditure were inversely related with Giardia rates. Increases in health care expenditure, in combination with existing health programs, may improve access, quality of care and services thereby reducing giardiasis and other disease burden in the territory; however, hypothesis-driven studies are necessary to better understand this association.
Our model also revealed a higher rate of reported giardiasis in communities where the primary health facility was a health center rather than a full-service hospital. Hospitals are located in Fort Smith, Hay River, Inuvik and Yellowknife whereas the other 29 communities are only serviced by health centers or remote nursing stations. Residents of these 29 communities are often unable to visit hospitals because of distance and/or reduced accessibility caused by geographic barriers or severe weather conditions . Residents have reported that medical transfers to hospitals can be isolating and demoralizing experiences because of cultural and language barriers as well as separation from their families and communities . As most cases of NGI are acute, self-limited and do not require hospitalization, they are more likely to be reported to health facilities in close proximity to the community. Giardiasis is largely a waterborne illness and therefore, it is also possible that the “communities with health center” variable is a surrogate for more rural and remote locations where the consumption of untreated surface water occurs more frequently than in urban centers where treated water supplies are readily available .
In summary, the linkage of the NWT Communicable Disease Registry and the NWT Community Survey provided a means of identifying potential community-level risk factors for NGI in the territory. Certain factors were associated with the increased likelihood of campylobacteriosis, giardiasis, and salmonellosis; however, these results should be interpreted with caution. There were several variables in the unconditional analysis that were associated with disease rates that were not included in the final model since they became insignificant in the presence of other factors. These variables should be considered potentially important as some associations may have been underestimated or undetected because of low statistical power. Given the interrelated nature of health determinants, it is also possible that risk factors in the final model were intervening variables (intermediate in the causal process between exposure and outcome) falsely decreasing the effect and significance of variables that were excluded from the model. We cannot rule out the role that geography might play in unbalanced disease diagnosis or reporting impacted by a complex mix of health care-seeking behaviors, access to health services, availability of diagnostic tests, and reporting practices by health professionals and laboratories. The rates of infections reported in this study are likely underestimates of the true incidence of diseases and therefore, should be interpreted as reporting rates rather than as incidence rates . Currently, the disease data that are available are not sufficient nor appropriate to address underdiagnosis or underreporting in the NWT; however, geographically identified case–control studies, sentinel surveillance, community-based programs and knowledge, attitude and practice surveys, could be used to identify and quantify these biases (if any exist) in the future. There were also many factors that could not be evaluated because of the limited suite of epidemiological information that accompanies the notification. Furthermore, it was not possible to take person-level risk factors into account. Analytical studies, particularly cohort and case–control studies would be required to assess the role of person-level factors, such as age and sex, as well as person and household-level exposure to various foods, water and other environmental factors. Additionally, since this is an ecological study, drawing inferences at the person level is inappropriate and may lead to biased interpretation.