Infectious Diseases Across
the LTER
ASM Workshop Summary
Organizer: Mike Antolin
For the purposes of this workshop, infectious disease were defined as those caused by both microparasites (bacteria, viruses, protista, prions) and macroparasites (e.g. nematodes and trematodes). This is not meant to be a comprehensive list, but is meant to cover the diversity of disease causing agents that affect both plants and animals. Disease is defined as morbidity and mortality of the host organisms.
The workshop included five research presentations by Mike Antolin (SGS: plague in rodents in Colorado), Bob Parmenter (SEV: hanta virus, plague, bartonellosis in rodents in New Mexico), Pieter Johnson (NTL: microparasitic diseases of amphibians, protozoan disease of cladocera), the team of Amanda Wrona and Michael Sheppard (GCE: microsporidian disease of blue crabs, other crustaceans), and Karen Garrett (KNZ: communities of plant pathogens in tallgrass prairie). Other sites represented were JRN, LUQ, and VCR.
Discussion was focused around the following questions:
1) Which diseases
have emerged or have been introduced into their sites?
We distinguished emerging diseases, which are endemic to the area but become prevalent when ecological conditions change transmission pathways (e.g. Lyme disease, dengue fever, hanta virus, Piet Johnson’s talk), from newly introduced diseases (e.g. plague, West Nile, microsporidian disease of crabs, chestnut blight, Dutch elm disease). Further, this area will have overlap with the general issues of invasive organisms, but the hope is that we may be able to develop models of infectious disease based on the first principles of disease transmission.
Although eight LTER sites were represented, a more complete inventory of research in infectious diseases is bound to reveal more studies being conducted.
2) What long-term
data are available through the LTER to help initiate more detailed
epidemiological modeling?
LTER sites will likely have long term monitoring of populations of animals and plants (especially plants) that could provide information of the distribution of organisms that would act as definitive hosts, reservoirs that lead to spill-over to other hosts, or vectors of infectious disease. Understanding of the life cycle of a parasite or disease presents a challenge for most disease studies, but is critical for understanding of transmission rates. Additional factors that need careful elucidation are host and vector densities, which influence contact and transmission rates, and the movement of hosts and vectors through the environment.
Additional LTER resources identified in discussion included:
- Long term climatic data, basic ecosystem measurements (e.g. NPP).
- Geographic/biogeographic data
- Storage of specimens from long-term studies that could provide critical historical information on disease prevalence.
- An evolutionary perspective that is distinctly different than that of the field of medical epidemiology
3) Which
epidemiological models best describe the influence of infectious diseases on
ecosystem processes?
Ecological epidemiologists have developed a rich variety of disease transmission models that quite successfully predict population processes related to infectious disease. Recently, this has included development of spatially-explicit models of disease transmission. The same kinds of analyses on an ecosystem level are much less developed, but the best possibilities lie in spatially-explicit simulations and estimation based on either cellular automata or GIS generated risk surfaces.
4) What tools are
available for creating analytical and predictive models of disease spread and
persistence?
This discussion mainly focused on what is limiting infectious disease research in the LTER. In terms of data, critical measurements beyond general surveys of plants and animals include measuring disease prevalence, host density, and mortality/morbidity caused by disease. Modern techniques based on PCR and serology (antibody) assays have improved our ability to detect disease beyond that afforded by direct counts. Besides population-based disease analyses, the group noted that an additional focus of infectious disease research in the LTER should examine how diseases could influence ecosystem processes (e.g. plant disease may affect NPP).
Additional
limitations and research issues that were noted:
Long term data needed for disease modeling may not be in a useful format (e.g. GIS), and creating these kinds of data requires a considerable up-front investment of time.
For diseases that directly affect humans, epidemiological data may be protected by privacy issues, so it will be critical to forge good relationships with local, state and federal health departments and possibly develop protocols for obtaining additional data from these sources.
Because diseases will not respect the boundaries of LTER sites, it will also be necessary to develop links with resource managers through other agencies (e.g. state wildlife biologists, federal Forest Service or Fish and Wildlife Service biologists).
Most epidemiological models are retrospective (e.g. trace-back to the index case), but predictive models are needed. In the case of the LTER, we are seeing that some disease dynamics are driven by large-scale climatic events (e.g. El Niño) in addition to local epidemiology.
In many cases, taxonomic expertise is lacking for proper identification of host species, but especially for identifying disease causing agents. Again, this implies that LTER will have to forge closer ties to organizations like museums or the CDC (for example).
Action Items:
- We will initiate a web site, either through the LTER network office or on one of our own servers to facilitate the inventory and reporting of infectious diseases on the LTER. Participants at the workshop will constitute a charter working group.
At a minimum, the web site should develop an inventory of ongoing studies, develop a list of cross-site possibilities (e.g. plague is a natural for SEV, SGS, and JRN, the blue crab disease could go across GCE and VCR), and explore how to make infectious disease issues more visible for the K-12 work of the LTER.
- We will organize a workshop to examine the issues of how to make data useable for infectious disease modeling, and a generalized framework for modeling infectious disease. Funding for this workshop could come through LTER or directly from NSF.
List of Participants
(not complete):
Mike Antolin (SGS)
Bob Parmenter (SEV)
Alan Covich (LUQ)
John Porter (VCR)
Pieter Johnson (NTL)
Amanda Wrona (GCE)
Michael Sheppard (GCE)
Karen Garrett (KNZ)
Dan Tripp (SGS)
Lisa Savage (SGS)
John Moore (SGS)
Laurel hartley (SGS)
Jen Baker (JRN)
Dara Parker (JRN)
Andrea Campanella (JRN)
Dylan George