Environmental Engineering Reference
In-Depth Information
The ways in which changes in the rates of ecosystem processes, such as nutrient cycling,
nitrogen deposition, and primary production, might affect the zoonoses such as Lyme dis-
ease are unknown. Nitrogen or carbon dioxide “fertilization” of forest trees might influ-
ence the timing or magnitude of acorn masting, with potentially strong effects on Lyme
disease risk. Climate warming might also stimulate acorn production and affect tick and
host populations, although in ways that are difficult to predict. Warmer winters are likely
to reduce winter mortality rates of ticks, and warmer summers might both increase sum-
mer mortality rates of ticks and change the seasonal timing of their host-seeking activity in
ways that would affect Lyme disease risk.
Effects of winter and summer temperatures, as well as those of both the amount and
pattern of precipitation, on tick population dynamics are poorly understood (
Harvell et al.
2002
). Pursuit of the effects of ecosystem processes and global climate change on zoonotic
diseases represents a new research frontier.
New zoonotic diseases continue to emerge at a high rate, and old ones reemerge or invade
new areas. An ecosystem approach to understanding the causes of emergence and possible
preventive measures would include the following strategic elements. Interdisciplinary teams
of researchers who specialize in pathogens, vectors, vertebrate hosts, population dynamics,
community interactions, landscape ecology, and sociology of human interactions with eco-
logical systems should be assembled. Research teams should explicitly incorporate spatial
patterns and processes affecting disease, from the local scale of pathogen transmission events
from one vector or host to another, to the important landscape features (e.g., edges, fragmen-
tation, patch and matrix composition) influencing population dynamics of hosts and vectors,
to regional land use and climatic characteristics that affect entire assemblages and vital rates.
Temporal dynamics, from the effects of seasonal phenology of vector-pathogen-host
interactions to multiannual fluctuations in vector or host populations, must also be consid-
ered. The networks of taxa under study need to be expanded to include species other than
the pathogen, vector, and primary host. For instance, dilution hosts—those that act as a
“sink” for pathogen infections—often play crucial roles in disease dynamics, as do the spe-
cies that act to regulate populations of important reservoir hosts. Research strategies that
include such elements are likely to identify subtle but powerful factors affecting disease
dynamics that might be amenable to intervention for the benefit of public health.
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