Pathogen Survival Trajectories: An Eco-Environmental Approach to the Modeling of Human Campylobacteriosis Ecology
Skelly, Chris, Weinstein, Phil, Environmental Health Perspectives
Campylobacteriosis, like many human diseases, has its own ecology in which the propagation of human infection and disease depends on pathogen survival and finding new hosts in order to replicate and sustain the pathogen population. The complexity of this process, a process common to other enteric pathogens, has hampered control efforts. Many unknowns remain, resulting in a poorly understood disease ecology. To provide structure to these unknowns and help direct further research and intervention, we propose an eco-environmental modeling approach for campylobacteriosis. This modeling approach follows the pathogen population as it moves through the environments that define the physical structure of its ecology. In this paper, we term the ecologic processes and environments through which these populations move "pathogen survival trajectories." Although such a modeling approach could have veterinary applications, our emphasis is on human campylobacteriosis and focuses on human exposures to Campylobacter through feces, food, and aquatic environments. The pathogen survival trajectories that lead to human exposure include ecologic filters that limit population size, e.g., cooking food to kill Campylobacter. Environmental factors that influence the size of the pathogen reservoirs include temperature, nutrient availability, and moisture availability during the period of time the pathogen population is moving through the environment between infected and susceptible hosts. We anticipate that the modeling approach proposed here will work symbiotically with traditional epidemiologic and microbiologic research to help guide and evaluate the acquisition of new knowledge about the ecology, eventual intervention, and control of campylobacteriosis. Key words: aquatic environments, Campylobacter, campylobacteriosis, disease ecology, eco-environmental modeling, ecologic filters, feces, pathogen survival. Environ Health Perspect 111:19-28 (2003). [Online 7 November 2002] doi: 10.1289/ehp.5312 available via http://dx.doi.org/
Campylobacteriosis has been the most common enteric disease in New Zealand since at least the early 1990s (1), with national notification rates currently exceeding 230 cases per 100,000 persons and regional notification rates exceeding 300 per 100,000 (2). In the United States, the Campylobacter spp. pathogens are responsible for the highest incidence of disease of any of the enteric pathogens under surveillance, with between 17 and 25 cases per 100,000 persons across FoodNet sentinel sites from 1996 to 2000 (3). California is the FoodNet site with the highest incidence of campylobacteriosis, with between 30 and 60 cases per 100,000 persons over the same period (3). However, these are probably conservative estimates of disease incidence, as enteric disease surveillance is known to underestimate incidence considerably (4). Despite its widespread incidence, the ecology of campylobacteriosis remains elusive, and suitable ecologic or environmental transport models have yet to be developed. In this review we attempt to lay a foundation for the eco-environmental modeling of human campylobacteriosis.
An eco-environmental model of human disease is an attempt to describe both the ecology (dynamics of the disease, including pathogen filters) and environments (including structure and vectors) through which pathogens must traverse to obtain new hosts. A system, as in the usage "ecosystem" has been defined in the biologic and climatologic literatures as interlinked flows of energy, momentum, and matter (5,6). However, within the public health literature, the term "ecology" is used in different ways, most notably in the context of ecologic analysis, which describes an aggregated scale of analysis, usually in terms of geographically defined human populations (7,8). Other researchers apply the terms "ecology" and "ecosystem" to the construction of conceptual models of the interdependency between human disease and the natural environment (9,10). …