, Volume 166, Issue 4, pp 1029–1041 | Cite as

Individual and combined effects of multiple pathogens on Pacific treefrogs

  • John M. Romansic
  • Pieter T. J. Johnson
  • Catherine L. Searle
  • James E. Johnson
  • Tate S. Tunstall
  • Barbara A. Han
  • Jason R. Rohr
  • Andrew R. Blaustein
Community ecology - Original Paper


In nature, individual hosts often encounter multiple pathogens simultaneously, which can lead to additive, antagonistic, or synergistic effects on hosts. Synergistic effects on infection prevalence or severity could greatly affect host populations. However, ecologists and managers often overlook the influence of pathogen combinations on hosts. This is especially true in amphibian conservation, even though multiple pathogens coexist within amphibian populations, and several pathogens have been implicated in amphibian population declines and extinctions. Using an amphibian host, Pseudacris regilla (Pacific treefrog), we experimentally investigated interactive effects among three pathogens: the trematode Ribeiroia sp. (hereafter, Ribeiroia), the fungus Batrachochytrium dendrobatidis (hereafter, BD), and the water mold Achlya flagellata. We detected no effects of A. flagellata, but did find effects of Ribeiroia and BD that varied depending on context. Low doses of Ribeiroia caused relatively few malformations, while higher Ribeiroia doses caused numerous deformities dominated by missing and reduced limbs and limb elements. Exposure to low doses of BD accelerated larval host development, despite there being no detectable BD infections, while exposure to higher BD doses caused infection but did not alter developmental rate. Hosts exposed to both Ribeiroia and BD exhibited the highest mortality, although overall evidence of interactive effects of multiple pathogens was limited. We suggest further research on the influence of multi-pathogen assemblages on amphibians, particularly under a variety of ecological conditions and with a wider diversity of hosts and pathogens.


Coinfection Concomitant infections Polyparasitism Emerging infectious disease Amphibian decline 



We thank J. Longcore for supplying BD isolates, J. Spatafora, C. Briggs, and the UC Berkeley Museum of Vertebrate Zoology for use of laboratory facilities, and A. Congelosi, N. Donn, M. Jones-Romansic, B. Fann, P. Michel, T. Pham, M. Saxon, K. Tonsfeld, and L. Vinueza for assistance. J.M.R. was supported by a United States Environmental Protection Agency Science to Achieve Results Fellowship (FP-91640201-0). Additional funding was provided by grants from The National Science Foundation (NSF) Integrated Research Challenges in Environmental Biology Program (DEB0213851 and IBN9977063) to A.R.B. and NSF (DEB-0809487), United States Department of Agriculture (NRI 2008-00622 and 2008-01785), and United States Environmental Protection Agency Science to Achieve Results (R833835) grants to J.R.R. P.T.J.J. was supported by a fellowship from the David and Lucile Packard Foundation and a grant from NSF (DEB-0841758). These experiments comply with the current laws of the United States and with Oregon State University animal care regulations. Animals were collected according to Oregon Department of Fish and Wildlife regulations.

Supplementary material

442_2011_1932_MOESM1_ESM.doc (104 kb)
Supplementary material 1 (DOC 104 kb)


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Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  • John M. Romansic
    • 1
  • Pieter T. J. Johnson
    • 2
  • Catherine L. Searle
    • 1
  • James E. Johnson
    • 3
  • Tate S. Tunstall
    • 4
  • Barbara A. Han
    • 5
  • Jason R. Rohr
    • 6
  • Andrew R. Blaustein
    • 1
  1. 1.Department of ZoologyOregon State UniversityCorvallisUSA
  2. 2.Department of Ecology and Evolutionary BiologyUniversity of ColoradoBoulderUSA
  3. 3.Department of Biological SciencesCentral Washington UniversityEllensburgUSA
  4. 4.Department of Ecology, Evolution and Marine BiologyUniversity of California, Santa BarbaraSanta BarbaraUSA
  5. 5.Odum School of EcologyUniversity of GeorgiaAthensUSA
  6. 6.Department of Integrative BiologyUniversity of South FloridaTampaUSA

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