Dr. Paul Auerbach is the world's leading outdoor health expert. His blog offers tips on outdoor safety and advice on how to handle wilderness emergencies.See all posts »
The Spread of Plague in Prairie Dog Towns
A news report in the summer of 2010 announced that a group of anthropologists had solved the “long-standing mystery” of how it might be that the plague pathogen, Yersinia pestis, persisted in the prairie dog population after a wipeout of the prairie dog town(s) caused by the disease. Prior to this announcement and publication of a paper entitled “Plague outbreaks in prairie dog populations explained by percolation thresholds of alternate host abundance” in the Proceedings of the National Academy of Science (PNAS August 10, 2010 vol 107 no. 32 14247-14250, available at http://www.pnas.org/content/107/32/1427.full), it was already known that plague would decimate prairie dog populations, that the disease was spread by fleas, and that the pattern of re-colonization (of prairie dog towns) followed by devastation could occur over many years.
The authors of the PNAS article used a computer to simulate plague dynamics in a large black-tailed prairie dog town. The simulation showed that plague could persist in the prairie dog population if it was carried by the grasshopper mouse Onychomys leucogaster, which would be an alternate host for the infective fleas. These mice are tenacious critters that sometimes feed on prairie dog carcasses. If the prairie dog died of plague, then it is likely that the mice would acquire its fleas and begin to move the disease through the prairie dog population at an accelerated pace.
I don’t agree with a comment written by the news reporter, which states, “The idea that plague could be facilitated by grasshopper mice was first proposed by Salkeld (first author on the PNAS article) and co-author Paul Stapp of California State University-Fullerton.” In doing a Google search to gather information for this post, one of the first articles I discovered was “A review of flea collection records from Onychomys leucogaster with observations on the role of grasshopper mice in the epizoology of wild rodent plague” (Great Basin Naturalist 48: 83-95, 1988) by Rex E. Thomas. In the abstract of that article, the author stated:
The range of this mouse overlaps much of the distribution of plague, Yersinia pestis, in the western United States, and nearly one-half of the flea species collected from O. leucogaster are known to be of importance in the epizoology of plague. This article discusses the importance of the association of fleas with a hospitable secondary host in the maintenance and transmission of wild rodent plague.
It seems to me that Thomas nailed it back in 1988; this article is not cited in the PNAS article, which is perhaps a fault of the policy of scientific journals limiting the number of reference citations allowed. The contribution of the information from the PNAS article would therefore not be origination of the notion that grasshopper mice are the likely carriers of infective fleas, but rather an important simulation ‘proof’ that grasshopper mice can effectively spread the disease within prairie dog populations and account for its interval recrudescence.
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