Modeling Routes of Chronic Wasting Disease Transmission: Environmental Prion Persistence Promotes Deer Population Decline and Extinction
Emily S. Almberg1,2*, Paul C. Cross1, Christopher J. Johnson3, Dennis M. Heisey3, Bryan J. Richards4
1 Northern Rocky Mountain Science Center, United States Geological Survey, Bozeman, Montana, United States of America, 2 The Huck Institutes of the Life Sciences, Pennsylvania State University, University Park, Pennsylvania, United States of America, 3 Prion Research Laboratory, National Wildlife Health Center, United States Geological Survey, Madison, Wisconsin, United States of America, 4 National Wildlife Health Center, United States Geological Survey, Madison, Wisconsin, United States of America
Chronic wasting disease (CWD) is a fatal disease of deer, elk, and moose transmitted through direct, animal-to-animal contact, and indirectly, via environmental contamination. Considerable attention has been paid to modeling direct transmission, but despite the fact that CWD prions can remain infectious in the environment for years, relatively little information exists about the potential effects of indirect transmission on CWD dynamics. In the present study, we use simulation models to demonstrate how indirect transmission and the duration of environmental prion persistence may affect epidemics of CWD and populations of North American deer. Existing data from Colorado, Wyoming, and Wisconsin's CWD epidemics were used to define plausible short-term outcomes and associated parameter spaces. Resulting long-term outcomes range from relatively low disease prevalence and limited host-population decline to host-population collapse and extinction. Our models suggest that disease prevalence and the severity of population decline is driven by the duration that prions remain infectious in the environment. Despite relatively low epidemic growth rates, the basic reproductive number, R0, may be much larger than expected under the direct-transmission paradigm because the infectious period can vastly exceed the host's life span. High prion persistence is expected to lead to an increasing environmental pool of prions during the early phases (i.e. approximately during the first 50 years) of the epidemic. As a consequence, over this period of time, disease dynamics will become more heavily influenced by indirect transmission, which may explain some of the observed regional differences in age and sex-specific disease patterns. This suggests management interventions, such as culling or vaccination, will become increasingly less effective as CWD epidemics progress.
Citation: Almberg ES, Cross PC, Johnson CJ, Heisey DM, Richards BJ (2011) Modeling Routes of Chronic Wasting Disease Transmission: Environmental Prion Persistence Promotes Deer Population Decline and Extinction. PLoS ONE 6(5): e19896. doi:10.1371/journal.pone.0019896
Editor: Andrew Yates, Albert Einstein College of Medicine, United States of America
Received: November 10, 2010; Accepted: April 19, 2011; Published: May 13, 2011
This is an open-access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.
Funding: This work was funded by the U.S. Geological Survey. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
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SEE ALSO ;
Mother to Offspring Transmission of Chronic Wasting Disease
Candace K. Mathiason; Amy Nalls; Kelly Anderson; Jeanette Hayes-Klug; Jenny G. Powers; Nicholas J. Haley; Edward A. Hoover Colorado State University, Fort Collins, CO, USA
We have developed a new cervid model in small Asian muntjac deer (Muntiacus reevesi) to study potential modes of vertical transmission of chronic wasting disease (CWD) from mother to offspring. Eight of eight (8/8) muntjac doe orally infected with CWD tested PrPCWD lymphoid positive by 4 months post infection. Ten fawns were born to these CWD-infected doe— 4 of the fawns were viable, 5 were non-viable, and 1 was a first trimester fetus harvested from a CWD-infected doe euthanized at end-stage disease. The viable fawns have been monitored for CWD infection by immunohistochemistry and sPMCA performed on serial tonsil and rectal lymphoid tissue biopsies. PrPCWD has been detected in one fawn by IHC as early as 40 days of age. Moreover, sPMCA performed on rectal lymphoid tissue has yielded positive results on another fawn at 10 days of age. In addition, sPMCA assays have demonstrated amplifiable prions in fetal placental or spleen tissue of 3 non-viable fawns and mammary tissue of the dams. Additional pregnancy related fluids and tissues from the doe as well as tissue from the nonviable fawns are currently being probed for the presence of CWD. In summary, we have employed the muntjac deer model, to demonstrate for the first time the transmission of CWD from mother to offspring. These studies provide the foundation to investigate the mechanisms and pathways of maternal prion transfer.
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All Other Emerging and Zoonotic Infectious Diseases CDC's FY 2012 request of $52,658,000 for all other emerging and zoonotic infectious disease activities is a decrease of $13,607,000 below the FY 2010 level,
which includes the elimination of Prion activities ($5,473,000),
a reduction for other cross-cutting infectious disease activities, and administrative savings. These funds support a range of critical emerging and zoonotic infectious disease programs such Lyme Disease, Chronic Fatigue Syndrome, and Special Pathogens, as well as other activities described below.
not good news, but something most of us all have predicted. they have floundered to long $$$