My research niche melds fish pathology with diagnostics in aquaculture and uses pathology to investigate human impacts on native aquatic environments. I additionally enjoy all sorts of collaborations in domestic diagnostic veterinary pathology such as infectious disease, oncology, and radiology.
Wastewater treatment plant effluent can be much warmer than the surface water it is discharged into and can create gradients of thermal stress for aquatic animals, especially in winter months. In partnership with Colorado Parks and Wildlife and the CSU Cooperative Fish and Wildlife Research unit we have studied the effect of thermal influences on Johnny Darter reproduction above and below WWTP.
Many wild caught Johnny Darters have pericarditis, and some have trematode parasites in the pericardial sac. The natural parasite assemblages of Johnny Darters have not been well described, nor have cases of natural pericarditis been well described in fish, so this an exciting opportunity to identify and fully characterize parasites and associated disease.
Wastewater treatment plants discharge a mix of drugs and pollutants that can impact the physiology of aquatic organisms. In partnership with CPW, a study of zebrafish and fathead minnow larvae exposed to antilipidemics showed dose responsive mortality and numerous deleterious effects. This project precisely demonstrates the connections of human, environmental, and animal health (One Health).
Iron-oxidizing bacteria (FeOB) colonized a groundwater well at a CPW trout hatchery and were associated with severe proliferative branchitis and high morbidity and mortality. This is the first report of morbidity and mortality in fish associated with FeOB. Further work includes speciation of the specific bacteria involved and genetic analysis for potential virulence factors.
The Greenback native trout is Colorado’s state fish. This subspecies was thought to be extinct in the 1930s but an isolated population was found in the wild in 1957 and the fish population has been grown through breeding programs. Morbidity and mortality are issues in the culture setting, and we are investigating the cause of severe vasculitis that was identified in 3-month-old moribund fish.
Epizootic of Clinostomum marginatum (Trematoda: Clinostomidae) in Ambystoma tigrinum from Colorado, USA: Investigation through Genomics, Histopathology, and Noninvasive Imagery.
Calhoun DM, Groves J, Schaffer PA, Achatz TJ, Greiman SE, Johnson PTJ. J Wildl Dis. 2025 Mar 20. doi: 10.7589/JWD-D-24-00068. Online ahead of print.PMID: 40107297
Environmental risk factors for UV-induced cutaneous neoplasia in horses: A GIS approach.
Ramirez M, Duncan C, Schaffer PA, Wobeser B, Magzamen S. Can Vet J. 2023 Oct;64(10):971-975. PMID: 37780476
Elevated Winter Stream Temperatures below Wastewater Treatment Plants Shift Reproductive Development of Female Johnny Darter Etheostoma nigrum: A Field and Histologic Approach.
Adams CM, Winkelman DL, Schaffer PA, Villeneuve DL, Cavallin JE, Ellman M, Rodriguez KS, Fitzpatrick RM. Fishes. 2022 Nov 29;7(6):1-22. doi: 10.3390/fishes7060361. PMID: 36761383
Diagnostic imaging and histopathologic features of rounded atelectasis in four cats and one dog: A descriptive case series study.
Fukuda S, Reetz JA, Hamamoto K, Griffin L, Schaffer PA. Vet Radiol Ultrasound. 2023 May;64(3):411-419. doi: 10.1111/vru.13206. Epub 2022 Dec 18. PMID: 36529901
Optimization Of Fecal Flotations In Marine Parasitology And Determination Of The Specific Gravity Of Helminth Eggs In Pinnipeds.
Rodgers JS, Schaffer PA, Field CL, Ballweber LR, McGrew AK. J Zoo Wildl Med. 2021 Sep;52(3):949-955. doi: 10.1638/2020-0155. PMID: 34687511
