Aquatic Parasite Observatory


The goal of the Aquatic Parasite Observatory is to improve our understanding of parasites from aquatic wildlife and the diseases they sometimes cause. To this end, we examine aquatic animals collected from a wide range of locations across the United States and document infections by macroparasites. Collections are performed both by our own field crews, which focus on sites in California and Colorado, and by outside collaborators such as the US Fish and Wildlife Service, which have submitted animals from National Wildlife Refuges across the country. Parasites are quantified and identified using morphological and molecular techniques. Since 1999, we have surveyed nearly 500 wetlands in 43 US states and examined over 23,000 amphibians, 80,000 snails, 1,000 fish, and 80 birds for parasitic infections.


Increased research into aquatic parasites was prompted initially by growing concern over amphibian deformities and declines in the late 1990s. After Congress allocated research funding to study amphibians in 1999, the US Fish and Wildlife Service initiated a scientific investigation into the problem of abnormal amphibians. The parasitological component of this effort was led by Dr. Daniel Sutherland, a parasitologist with the University of Wisconsin. After Dr. Sutherland’s death in 2006, Dr. Pieter Johnson, who had been a collaborator on the project, continued the work and expanded the Aquatic Parasite Observatory to include aquatic host groups beyond amphibians (snails, water birds, and fishes).

Using APO

The Amphibian Parasite Observatory is an online resource available for anyone interested in the parasites of aquatic wildlife. The information is organized to allow users to browse by parasite group or by host species. Links will guide you to individual parasite pages that contain detailed information on parasite taxonomy, morphological descriptions, life cycles, APO host accounts, images and more. All host and parasite records included here stem from direct observations by APO researchers, although in the future we plan to also incorporate literature accounts. We further aim to make the database interactively searchable in future updates.

You can visit our Background page for a brief introduction to the fascinating world of parasites.


  • Director: Dr. Pieter Johnson (e-mail)
  • Research Associates:
  • Homepage:Johnson Laboratory - University of Colorado
  • Phone: (303) 492-5623
    Fax: (303) 492-8699
  • Mailing Address:
    University of Colorado Boulder
    1900 Pleasant Street
    Ramaley Biology N122, CB334
    Boulder, CO, 80309-0334, USA


The Aquatic Parasite Observatory has been made possible by work supported by the National Science Foundation and the United States Fish and Wildlife Service. Any opinions, findings, and conclusions or recommendations expressed on this website are those of the author(s) and do not necessarily reflect the views of NSF or USFWS.

  • © 2013 Aquatic Parasite Observatory
  • University of Colorado Boulder