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Susan Knowles

Susan Knowles is a Wildlife Veterinary Pathologist at the National Wildlife Health Center.

She earned a Doctorate of Veterinary Medicine from the Virginia-Maryland Regional College of Veterinary Medicine and completed a residency in veterinary pathology and earned a Doctorate in Veterinary Pathology from the University of Georgia. She is a Diplomate of the American College of Veterinary Pathologists. She joined the Center in 2013 and her interests include wildlife, aquatic, invertebrate and toxicologic pathology, and pathogen discovery. Before joining the Center, she gained a variety of experience in and around her native Maryland, performing research on shortnose sturgeon, serving as a Veterinary Officer in the United States Public Health Service stationed at the National Institutes of Health, and working as a Natural Resources Biologist for the Maryland Department of Natural Resources where she was a member of the Fish and Wildlife Health Program and served as the Marine Mammal and Sea Turtle Stranding Coordinator for the state.

Professional Experience

  • 2013 – Present Wildlife Veterinary Pathologist, U.S. Geological Survey, National Wildlife Health Center, Madison, WI

  • 2006 – 2013 Resident of Anatomic and Aquatic Pathology and Graduate Assistant, Department of Veterinary Pathology, University of Georgia, Athens, GA

  • 2003 – 2003 Veterinary Officer, Junior COSTEP, United States Public Health Service, Rockville, MD stationed at NIH, Diagnostic and Research Services Branch, Veterinary Pathology, Bethesda, MD

  • 1996 – 2002 Natural Resources Biologist, Maryland Marine Mammal & Sea Turtle Stranding Coordinator, Fish and Wildlife Health Program, Maryland Department of Natural Resources, Cooperative Oxford Laboratory, Oxford, MD

  • 1995 – 1996 Histology Technician, Maryland Department of Natural Resources, Cooperative Oxford Laboratory, Oxford, MD

Education and Certifications

  • Ph.D. Veterinary Pathology, University of Georgia, 2013

  • D.V.M., Virginia-Maryland Regional College of Veterinary Medicine, 2006

  • B.S. Biology, Bucknell University, 1995

Affiliations and Memberships*

  • Diplomate American College of Veterinary Pathologists

Science and Products

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Red-winged blackbird necropsy

Necropsy & Pathology

The Necropsy and Pathology services are performed by board-certified veterinary pathologists and necropsy technical staff whose principal role is to determine the cause of death for animals submitted to the USGS National Wildlife Health Center.

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Necropsy & Pathology

The Necropsy and Pathology services are performed by board-certified veterinary pathologists and necropsy technical staff whose principal role is to determine the cause of death for animals submitted to the USGS National Wildlife Health Center.

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Image: A Pocketbook Mussel

Native Freshwater Mussel Health

Native freshwater mussels are a keystone species and are considered both ecosystem engineers, improving habitat for other species, and indicator species important in assessing the health of the ecosystem.
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Ecosystems Mission Area, Species Management Research Program, National Wildlife Health Center
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Native Freshwater Mussel Health

Native freshwater mussels are a keystone species and are considered both ecosystem engineers, improving habitat for other species, and indicator species important in assessing the health of the ecosystem.
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Metabolomic analysis of pheasantshell mussel (Ortmanniana pectorosa; Order Unionida) from a mass mortality event in the Clinch River, Virginia and Tennessee, USA

This dataset uses the ITIS recommended Ortmanniana pectorosa, Conrad, 1834 in place of Actinonaias pectorosa, which was used in the Richard et al. 2020 manuscript. Biologists monitoring freshwater mussel (Order Unionida) populations rely on behavioral, often subjective, symptoms to identify “sick” or stressed animals, such as gaping valves and slow response to probing and lack clinical indicators
By
Upper Midwest Environmental Sciences Center

Paranannizziopsis spp. associated with skin lesions in wild snakes in North America and development of a real-time PCR assay for rapid detection of the fungus in clinical samples

The emergence of ophidiomycosis (or snake fungal disease) in snakes has prompted increased awareness of the potential impacts of fungal infections on wild reptile populations. Yet, aside from Ophidiomyces ophidiicola, little is known about other mycoses affecting wild reptiles. The closely related genus Paranannizziopsis has been associated with dermatomycosis in snakes and tuataras in captive col
By
National Wildlife Health Center

Experimental infection of Mexican free-tailed bats (Tadarida brasiliensis) with SARS-CoV-2

We experimentally challenged wild Mexican free-tailed bats (TABR) with SARS-CoV-2 to determine the susceptibility, reservoir potential, and population impacts of infection in this species. Of nine bats oronasally inoculated with SARS-CoV-2, five became infected and orally excreted moderate amounts of virus for up to 18 days post inoculation. These five subjects all seroconverted and cleared the vi
By
Biological Threats and Invasive Species Research Program, National Wildlife Health Center

A Novel Gonadotropic Microsporidian Parasite (Microsporidium clinchi n. sp.) Infecting a Declining Population of Pheasantshell Mussels (Actinonaias pectorosa) (Unioinidae) from the Clinch River, USA

Freshwater mussels of the order Unionida are among the most endangered animal groups globally, but the causes of population declines are often enigmatic with little known about the role of disease. In 2018, we collected wild adult pheasantshell (Actinonaias pectorosa) and mucket (Actinonaias ligamentina) during an epidemiologic survey investigating an ongoing mussel mass mortality event in the Cli
By
Biological Threats and Invasive Species Research Program, Species Management Research Program, National Wildlife Health Center

Data from pathology of Lagovirus europaeus GI.2/RHDV2/b (rabbit hemorrhagic disease virus 2) in native North American lagomorphs

Rabbit hemorrhagic disease, a notifiable foreign animal disease in the USA, was reported for the first time in wild native North American rabbits and hares in April 2020 in the southwestern USA. Affected species included the Desert Cottontail (Sylvilagus audubonii), Mountain Cottontail (S. nutallii), Black-tailed Jackrabbit (Lepus californicus), and Antelope Jackrabbit (L. alleni). Desert Cottonta
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Biological Threats and Invasive Species Research Program, National Wildlife Health Center

Domoic acid and saxitoxin in seabirds from California and Rhode Island 2015-2017

As harmful algal blooms (HABs) increase in magnitude and duration worldwide, they are becoming an expanding threat to marine wildlife. Over the past decade, domoic acid (DA) and saxitoxin (STX) have been increasingly problematic bicoastally in the United States. We investigated pooled seabird mortality data from opportunistic sampling events between 2007-2018, across three states, to examine the p
By
Biological Threats and Invasive Species Research Program, Species Management Research Program, National Wildlife Health Center

Bayou Sauvage NWR (LA) Haul Trail Snake Mortality, 2015-2017

Comprehensive list of carcasses detected at Haul Trail in Bayou Sauvage National Wildlife Refuge (Orleans Parish, LA) and relevant findings for specimens subject to postmortem examination at the USGS National Wildlife Health Center (Madison, WI).
By
Kansas Water Science Center

Necropsy reference number and summary collection information for Washington state population of northern sea otters examined during 1989-2010

Morbillivirus epidemics in marine mammals first gained prominence in 1988 when an outbreak of phocine distemper virus (PDV) occurred in European harbor seals (Phoca vitulina vitulina). Prior to 2001, all serosurveys for morbilliviruses in sea otters (Enhydra lutris) in California, Washington and Alaska documented a 0% seroprevalence. The first published serodetections of morbillivirus in sea otter
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Ecosystems Mission Area, Biological Threats and Invasive Species Research Program, National Wildlife Health Center

Data Associated with Algal Toxin Testing of Seabirds from the Bering and Chukchi Seas, 2017

This data set is comprised of three tables with results of algal toxin screening for saxitoxin and domoic acid. We used enzyme-linked immunosorbent assay (ELISA) and high-performance liquid chromatography (HPLC) to screen seabirds in the Bering and Chukchi Seas, 2017.
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Alaska Science Center

Occurrence of Chlamydia sp in apparently healthy birds associated with a mortality event caused by chlamydiosis: Data

hese data sets are is a compilation of bird and environmental samples obtained from 6 sites in Maricopa County, Arizona on the dates shown. Sites were only visited and sampled if they had Rosy-cheeked lovebirds coming to bird feeders at the location and with the permission of the property owner. Two swab samples were obtained from each captured bird and 3 swab samples were collected from the envir
By
Ecosystems Mission Area, Biological Threats and Invasive Species Research Program, National Wildlife Health Center

Dataset: Mortality trends in the Washington population of northern sea otters (Enhydra lutris kenyoni) during 2002—2015

These data document cause of death determination for stranded otters salvaged from the coast of Washington state and northern Oregon for post-mortem analysis.
By
Ecosystems Mission Area, Biological Threats and Invasive Species Research Program, Species Management Research Program, National Wildlife Health Center

Natural infections with Pigeon Paramyxovirus-1: Pathologic changes in Eurasian collared-doves (Streptopelia decaocto) and rock pigeons (Columba livia) in the USA: Data

We reviewed pathological findings and to a lesser extent epidemiological data from 70 free-ranging columbiforms naturally infected with Pigeon paramyxovirus-1 (PPMV-1) from 25 different PPMV-1 mortality events in columbiforms in the USA. In a subset of 17 birds from 10 of the studied outbreaks, we carried out immunohistochemistry targeting PPMV-1 nucleoprotein to determine the tissue distribution
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Ecosystems Mission Area, Biological Threats and Invasive Species Research Program, National Wildlife Health Center
Photomicrographs of the plagiopatagium from a Little Brown Bat showing nematodes.
Photomicrographs of the plagiopatagium from a Little Brown Bat
Photomicrographs of the plagiopatagium from a Little Brown Bat
Photomicrographs of the plagiopatagium from a Little Brown Bat showing nematodes.

Photomicrographs of the plagiopatagium from a Little Brown Bat

Photomicrographs of the plagiopatagium from a Little Brown Bat

Photomicrographs of the plagiopatagium from a Little Brown Bat (Myotis lucifugus) captured live in Wyoming, U.S.A. (A) Adult nematodes (asterisks) are present in the dermis. They are filled with larval nematodes (arrowhead). The overlying epidermis is hyperplastic (arrow). H&E stain.

By
National Wildlife Health Center, National Wildlife Health Center
Photomicrographs of the plagiopatagium from a Little Brown Bat showing nematodes.

Photomicrographs of the plagiopatagium from a Little Brown Bat

Photomicrographs of the plagiopatagium from a Little Brown Bat

Photomicrographs of the plagiopatagium from a Little Brown Bat (Myotis lucifugus) captured live in Wyoming, U.S.A. (A) Adult nematodes (asterisks) are present in the dermis. They are filled with larval nematodes (arrowhead). The overlying epidermis is hyperplastic (arrow). H&E stain.

By
National Wildlife Health Center, National Wildlife Health Center
Photomicrographs from a Mallard Duck with amyloidosis
Photomicrographs of Amyloidosis in a Mallard Duck
Photomicrographs of Amyloidosis in a Mallard Duck
Photomicrographs from a Mallard Duck with amyloidosis

Photomicrographs of Amyloidosis in a Mallard Duck

Photomicrographs of Amyloidosis in a Mallard Duck

Photomicrographs from a Mallard Duck (Anas platyrhynchos) found dead in Missouri, U.S.A. (A) The glomerular mesangium (asterisk) is expanded by amorphous, eosinophilic, acellular material. H&E stain. (B) Tubules in medullary cones are often surrounded by amorphous, eosinophilic, acellular material. H&E stain.

By
National Wildlife Health Center, National Wildlife Health Center
Photomicrographs from a Mallard Duck with amyloidosis

Photomicrographs of Amyloidosis in a Mallard Duck

Photomicrographs of Amyloidosis in a Mallard Duck

Photomicrographs from a Mallard Duck (Anas platyrhynchos) found dead in Missouri, U.S.A. (A) The glomerular mesangium (asterisk) is expanded by amorphous, eosinophilic, acellular material. H&E stain. (B) Tubules in medullary cones are often surrounded by amorphous, eosinophilic, acellular material. H&E stain.

By
National Wildlife Health Center, National Wildlife Health Center
Photomicrographs from a Common Grackle showing lesions in pulmonary blood vessel and nematodes in brain and pulmonary artery.
Photomicrographs from a Common Grackle (Quiscalus quiscula) found dead in Ohio
Photomicrographs from a Common Grackle (Quiscalus quiscula) found dead in Ohio
Photomicrographs from a Common Grackle showing lesions in pulmonary blood vessel and nematodes in brain and pulmonary artery.

Photomicrographs from a Common Grackle (Quiscalus quiscula) found dead in Ohio

Photomicrographs from a Common Grackle (Quiscalus quiscula) found dead in Ohio

Photomicrographs from a Common Grackle (Quiscalus quiscula) found dead in Ohio, U.S.A. H&E stains. (A) Longitudinal (arrow) and cross sections (arrowheads) of microfilariae in a pulmonary blood vessel. (B) Microfilariae (arrows) within a parabronchus. (C) Microfilaria (arrow) within the cerebellar parenchyma with no associated inflammation.

By
National Wildlife Health Center, National Wildlife Health Center
Photomicrographs from a Common Grackle showing lesions in pulmonary blood vessel and nematodes in brain and pulmonary artery.

Photomicrographs from a Common Grackle (Quiscalus quiscula) found dead in Ohio

Photomicrographs from a Common Grackle (Quiscalus quiscula) found dead in Ohio

Photomicrographs from a Common Grackle (Quiscalus quiscula) found dead in Ohio, U.S.A. H&E stains. (A) Longitudinal (arrow) and cross sections (arrowheads) of microfilariae in a pulmonary blood vessel. (B) Microfilariae (arrows) within a parabronchus. (C) Microfilaria (arrow) within the cerebellar parenchyma with no associated inflammation.

By
National Wildlife Health Center, National Wildlife Health Center
Photomicrographs from the intestine of a Brazilian Free-tailed Bat showing coccidia.
Photomicrographs from the intestine of a Brazilian Free-tailed Bat
Photomicrographs from the intestine of a Brazilian Free-tailed Bat
Photomicrographs from the intestine of a Brazilian Free-tailed Bat showing coccidia.

Photomicrographs from the intestine of a Brazilian Free-tailed Bat

Photomicrographs from the intestine of a Brazilian Free-tailed Bat

Photomicrographs from the intestine of a Brazilian Free-tailed Bat (Tadarida brasiliensis) found dead in Texas, USA.

By
National Wildlife Health Center, National Wildlife Health Center
Photomicrographs from the intestine of a Brazilian Free-tailed Bat showing coccidia.

Photomicrographs from the intestine of a Brazilian Free-tailed Bat

Photomicrographs from the intestine of a Brazilian Free-tailed Bat

Photomicrographs from the intestine of a Brazilian Free-tailed Bat (Tadarida brasiliensis) found dead in Texas, USA.

By
National Wildlife Health Center, National Wildlife Health Center
Photomicrographs of a liver from a muskrat showing a cluster of nematode eggs.
Photomicrographs from a muskrat (Ondatra zibethicus) found dead in Ohio
Photomicrographs from a muskrat (Ondatra zibethicus) found dead in Ohio
Photomicrographs of a liver from a muskrat showing a cluster of nematode eggs.

Photomicrographs from a muskrat (Ondatra zibethicus) found dead in Ohio

Photomicrographs from a muskrat (Ondatra zibethicus) found dead in Ohio

Photomicrographs from a muskrat (Ondatra zibethicus) found dead in Ohio, USA. (A) Within the liver, there is a cluster of nematode eggs with light brown to eosinophilic bi-operculated shells (arrowheads) with radial striations (arrow) that contain eosinophilic flocculent material (asterisk). H&E stain.

By
National Wildlife Health Center, National Wildlife Health Center
Photomicrographs of a liver from a muskrat showing a cluster of nematode eggs.

Photomicrographs from a muskrat (Ondatra zibethicus) found dead in Ohio

Photomicrographs from a muskrat (Ondatra zibethicus) found dead in Ohio

Photomicrographs from a muskrat (Ondatra zibethicus) found dead in Ohio, USA. (A) Within the liver, there is a cluster of nematode eggs with light brown to eosinophilic bi-operculated shells (arrowheads) with radial striations (arrow) that contain eosinophilic flocculent material (asterisk). H&E stain.

By
National Wildlife Health Center, National Wildlife Health Center
Photomicrographs with H&E stain from a Bald Eagle found dead in Wisconsin, USA
Photomicrographs with H&E stain from a Bald Eagle (Haliaeetus leucocephalus) found dead in Wisconsin, USA
Photomicrographs with H&E stain from a Bald Eagle (Haliaeetus leucocephalus) found dead in Wisconsin, USA
Photomicrographs with H&E stain from a Bald Eagle found dead in Wisconsin, USA

Photomicrographs with H&E stain from a Bald Eagle (Haliaeetus leucocephalus) found dead in Wisconsin, USA

Photomicrographs with H&E stain from a Bald Eagle (Haliaeetus leucocephalus) found dead in Wisconsin, USA

Photomicrographs with H&E stain from a Bald Eagle (Haliaeetus leucocephalus) found dead in Wisconsin, USA. (A) Hepatocytes contain one or more variably-sized intracytoplasmic round, clear vacuoles (arrowheads). (B) Bile ducts are plugged with bile (asterisk). (C) Multifocally in the brainstem, there are small perivascular hemorrhages (arrows).

By
National Wildlife Health Center
Photomicrographs with H&E stain from a Bald Eagle found dead in Wisconsin, USA

Photomicrographs with H&E stain from a Bald Eagle (Haliaeetus leucocephalus) found dead in Wisconsin, USA

Photomicrographs with H&E stain from a Bald Eagle (Haliaeetus leucocephalus) found dead in Wisconsin, USA

Photomicrographs with H&E stain from a Bald Eagle (Haliaeetus leucocephalus) found dead in Wisconsin, USA. (A) Hepatocytes contain one or more variably-sized intracytoplasmic round, clear vacuoles (arrowheads). (B) Bile ducts are plugged with bile (asterisk). (C) Multifocally in the brainstem, there are small perivascular hemorrhages (arrows).

By
National Wildlife Health Center
Photomicrographs from a Northern Shoveler (Spatula clypeata) from Utah, USA
Photomicrographs from a Northern Shoveler (Spatula clypeata) from Utah, USA
Photomicrographs from a Northern Shoveler (Spatula clypeata) from Utah, USA
Photomicrographs from a Northern Shoveler (Spatula clypeata) from Utah, USA

Photomicrographs from a Northern Shoveler (Spatula clypeata) from Utah, USA

Photomicrographs from a Northern Shoveler (Spatula clypeata) from Utah, USA

Photomicrographs from a Northern Shoveler (Spatula clypeata) from Utah, USA. H&E stain. (A) The air sac epithelium is replaced by or covered with a thick layer of fibrin admixed with heterophils and fewer macrophages and eosinophilic and cellular necrotic debris (*).

By
National Wildlife Health Center
Photomicrographs from a Northern Shoveler (Spatula clypeata) from Utah, USA

Photomicrographs from a Northern Shoveler (Spatula clypeata) from Utah, USA

Photomicrographs from a Northern Shoveler (Spatula clypeata) from Utah, USA

Photomicrographs from a Northern Shoveler (Spatula clypeata) from Utah, USA. H&E stain. (A) The air sac epithelium is replaced by or covered with a thick layer of fibrin admixed with heterophils and fewer macrophages and eosinophilic and cellular necrotic debris (*).

By
National Wildlife Health Center
Necropsy photos from crop, spleen, and liver of red crossbills and American goldfinches.
Photographs from red crossbills and American goldfinches from Montana
Photographs from red crossbills and American goldfinches from Montana
Necropsy photos from crop, spleen, and liver of red crossbills and American goldfinches.

Photographs from red crossbills and American goldfinches from Montana

Photographs from red crossbills and American goldfinches from Montana

Photographs from red crossbills (Loxia curvirostra; A, C) and American goldfinches (Spinus tristis; B, D) from Montana, U.S.A. (A) A large yellow/tan plaque (asterisk) is present on the mucosal surface of the crop. (B) White seed-like plaques (arrow) are present on the mucosal surface of the crop.

By
National Wildlife Health Center
Necropsy photos from crop, spleen, and liver of red crossbills and American goldfinches.

Photographs from red crossbills and American goldfinches from Montana

Photographs from red crossbills and American goldfinches from Montana

Photographs from red crossbills (Loxia curvirostra; A, C) and American goldfinches (Spinus tristis; B, D) from Montana, U.S.A. (A) A large yellow/tan plaque (asterisk) is present on the mucosal surface of the crop. (B) White seed-like plaques (arrow) are present on the mucosal surface of the crop.

By
National Wildlife Health Center
Photographs from raccoon tissue showing long tan nematodes.
Nematodes in raccoon tissue
Nematodes in raccoon tissue
Photographs from raccoon tissue showing long tan nematodes.

Nematodes in raccoon tissue

Nematodes in raccoon tissue

Photographs from a raccoon (Procyon lotor) from Arizona, US.  (A) Large tan nematodes (arrowheads) are present within the subcutaneous tissue and muscle fascia in the distal right forelimb. (B) Closer view of the distal right forelimb showing the large tan nematodes (arrowheads).

By
National Wildlife Health Center
Photographs from raccoon tissue showing long tan nematodes.

Nematodes in raccoon tissue

Nematodes in raccoon tissue

Photographs from a raccoon (Procyon lotor) from Arizona, US.  (A) Large tan nematodes (arrowheads) are present within the subcutaneous tissue and muscle fascia in the distal right forelimb. (B) Closer view of the distal right forelimb showing the large tan nematodes (arrowheads).

By
National Wildlife Health Center
Photomicrographs from a big brown bat nasal cavity and hair follicle.
Photomicrographs from a big brown bat (Eptesicus fuscus) from Wisconsi
Photomicrographs from a big brown bat (Eptesicus fuscus) from Wisconsi
Photomicrographs from a big brown bat nasal cavity and hair follicle.

Photomicrographs from a big brown bat (Eptesicus fuscus) from Wisconsi

Photomicrographs from a big brown bat (Eptesicus fuscus) from Wisconsi

Photomicrographs from a big brown bat (Eptesicus fuscus) from Wisconsin, USA. H&E stain. (A) Low magnification of a cross section through the nares showing nasal cavity (*), oral mucosa (arrowhead), and haired skin (arrow). (B) Higher magnification showing a normal hair follicle (arrow) surrounded by sebaceous glands.

By
National Wildlife Health Center
Photomicrographs from a big brown bat nasal cavity and hair follicle.

Photomicrographs from a big brown bat (Eptesicus fuscus) from Wisconsi

Photomicrographs from a big brown bat (Eptesicus fuscus) from Wisconsi

Photomicrographs from a big brown bat (Eptesicus fuscus) from Wisconsin, USA. H&E stain. (A) Low magnification of a cross section through the nares showing nasal cavity (*), oral mucosa (arrowhead), and haired skin (arrow). (B) Higher magnification showing a normal hair follicle (arrow) surrounded by sebaceous glands.

By
National Wildlife Health Center
Photographs from Canada Goose and two Bald Eagles with lead poisoning
Photographs from Canada Goose and two Bald Eagles with lead poisoning
Photographs from Canada Goose and two Bald Eagles with lead poisoning
Photographs from Canada Goose and two Bald Eagles with lead poisoning

Photographs from Canada Goose and two Bald Eagles with lead poisoning

Photographs from Canada Goose and two Bald Eagles with lead poisoning

Photographs (A &B) from a Canada Goose (Branta canadensis) found dead in Minnesota, US.  (A) The esophagus is dilated and impacted with a large amount of duckweed (arrows).  (B) Forty #9 lead pellets are recovered from the ventriculus.  (C) Photograph from a Bald Eagle

By
National Wildlife Health Center
Photographs from Canada Goose and two Bald Eagles with lead poisoning

Photographs from Canada Goose and two Bald Eagles with lead poisoning

Photographs from Canada Goose and two Bald Eagles with lead poisoning

Photographs (A &B) from a Canada Goose (Branta canadensis) found dead in Minnesota, US.  (A) The esophagus is dilated and impacted with a large amount of duckweed (arrows).  (B) Forty #9 lead pellets are recovered from the ventriculus.  (C) Photograph from a Bald Eagle

By
National Wildlife Health Center
Filter Total Items: 33

Paranannizziopsis spp. infections in wild snakes and a qPCR assay for detection of the fungus

The emergence of ophidiomycosis (or snake fungal disease) in snakes has prompted increased awareness of the potential effects of fungal infections on wild reptile populations. Yet, aside from Ophidiomyces ophidiicola, little is known about other mycoses affecting wild reptiles. The closely related genus Paranannizziopsis has been associated with dermatomycosis in snakes and tuataras in captive col
Authors
Jeffrey M. Lorch, Megan Winzeler, Julia S. Lankton, Stephen Raverty, Heindrich N Snyman, Helen M. Schwantje, Caeley Thacker, Susan Knowles, Hugh Y Cai, Daniel A. Grear
By
Ecosystems Mission Area, National Wildlife Health Center

Mussel mass mortality in the Clinch River, USA: Metabolomics detects affected pathways and biomarkers of stress

Biologists monitoring freshwater mussel (order Unionida) populations rely on behavioral, often subjective, signs to identify moribund (“sick”) or stressed mussels, such as gaping valves and slow response to probing, and they lack clinical indicators to support a diagnosis. As part of a multi-year study to investigate causes of reoccurring mortality of pheasantshell (Ortmanniana pectorosa; synonym 
Authors
Joel G. Putnam, John Steiner, Jordon Richard, Eric Leis, Tony Goldberg, Christopher D. Dunn, Rose Agbalog, Susan Knowles, Diane L. Waller
By
Ecosystems Mission Area, National Wildlife Health Center, Upper Midwest Environmental Sciences Center

Pathology and infectious agents of unionid mussels: A primer for pathologists in disease surveillance and investigation of mortality events

Freshwater mussels are one of the most imperiled groups of organisms in the world, and more than 30 species have gone extinct in the last century. While habitat alteration and destruction have contributed to the declines, the role of disease in mortality events is unclear. In an effort to involve veterinary pathologists in disease surveillance and the investigation of freshwater mussel mortality e
Authors
Susan Knowles, Michelle Dennis, Andrew McElwain, Eric Leis, Jordan C. Richard
By
Ecosystems Mission Area, National Wildlife Health Center

A bacteriological comparison of the hemolymph from healthy and moribund unionid mussel populations in the upper Midwestern U.S.A. prompts the development of diagnostic assays to detect Yokenella regensburgei

Recent bacteriological investigations of freshwater mussel mortality events in the southeastern United States have identified a variety of bacteria and differences in bacterial communities between sick and healthy mussels. In particular, Yokenella regensburgei and Aeromonas spp. have been shown to be associated with moribund mussels, although it remains unclear whether these bacteria are causes or
Authors
Eric Leis, Sara Dziki, Isaac Standish, Diane L. Waller, Jordan Richard, Jesse Weinzinger, Cleyo Harris, Susan Knowles, Tony Goldberg
By
Ecosystems Mission Area, National Wildlife Health Center, Upper Midwest Environmental Sciences Center

Further bacteriological analysis of annual Pheasantshell (Actinonaias pectorosa) mussel mortality events in the Clinch River (Virginia/Tennessee), USA, reveals a consistent association with Yokenella Regensburgei

Pheasantshell (Actinonaias pectorosa) mussels in the Clinch River (Tennessee/Virginia, USA) have declined dramatically in recent years. The bacterium Yokenella regensburgei was first isolated with high prevalence from Pheasantshells during the peak of a 2017 mortality event, but it was not identified after mortality subsided a few months later. Since 2017, Pheasantshell mortality in the Clinch Riv
Authors
Eric Leis, Sara Dziki, Jordan Richard, Rose Agbalog, Diane L. Waller, Joel G. Putnam, Susan Knowles, Tony Goldberg
By
Ecosystems Mission Area, National Wildlife Health Center, Upper Midwest Environmental Sciences Center

Experimental infection of Mexican free-tailed bats (Tadarida brasiliensis) with SARS-CoV-2

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) virus is thought to have originated in wild bats from Asia, and as the resulting pandemic continues into its third year, concerns have been raised that the virus will expand its host range and infect North American wildlife species, including bats. Mexican free-tailed bats (Tadarida brasiliensis) live in large colonies in the souther
Authors
Jeffrey S. Hall, Erik K. Hofmeister, Hon S. Ip, Sean Nashold, Ariel Elizabeth Leon, Carly Marie Malave, Elizabeth Falendysz, Tonie E. Rocke, M. Carossino, U. Balasuriya, Susan Knowles
By
Ecosystems Mission Area, National Wildlife Health Center

Freshwater mussels show elevated viral richness and intensity during a mortality event

Freshwater mussels (Unionida) are among the world’s most imperiled taxa, but the relationship between freshwater mussel mortality events and infectious disease is largely unstudied. We surveyed viromes of a widespread and abundant species (mucket, Actinonaias ligamentina; syn: Ortmanniana ligamentina) experiencing a mortality event of unknown etiology in the Huron River, Michigan, in 2019–2020 and
Authors
Jordan Richard, Eric Leis, Christopher D. Dunn, Cleyo Harris, Rose Agbalog, Lewis J. Campbell, Susan Knowles, Diane L. Waller, Joel G. Putnam, Tony Goldberg
By
Ecosystems Mission Area, Upper Midwest Environmental Sciences Center

Divergent gene expression profiles in Alaskan sea otters: An indicator of chronic domoic acid exposure?

An opportunistic investigation into ecosystem instability in Kachemak Bay (KBay), Alaska, has led us to investigate exposure to toxic algae in sea otters. We used gene expression to explore the physiological health of sea otters sampled in KBay in May 2019. We found altered levels of gene transcripts in comparison with reference sea otters from clinically normal, oil-exposed, and nutritionally cha
Authors
Lizabeth Bowen, Susan Knowles, Kathi Lefebvre, Michelle St Martin, Michael Murray, Kimberly A. Kloecker, Daniel Monson, Ben Weitzman, Brenda Ballachey, Heather Coletti, Shannon C. Waters, C Cummings
By
Ecosystems Mission Area, Alaska Science Center, National Wildlife Health Center, Western Ecological Research Center (WERC)

A novel gonadotropic microsporidian parasite (Microsporidium clinchi n. sp.) infecting a declining population of pheasantshell mussels (Actinonaias pectorosa) (Unioinidae) from the Clinch River, USA

Freshwater mussels of the order Unionida are among the most endangered animal groups globally, but the causes of their population decline are often enigmatic, with little known about the role of disease. In 2018, we collected wild adult pheasantshell (Actinonaias pectorosa) and mucket (Actinonaias ligamentina) during an epidemiologic survey investigating an ongoing mussel mass mortality event in t
Authors
Susan Knowles, Eric M. Leis, Jordan C. Richard, Rebecca A. Cole, Rose E. Agbalog, Joel G. Putnam, Tony L. Goldberg, Diane L. Waller
By
Ecosystems Mission Area, National Wildlife Health Center

Mussel mass mortality and the microbiome: Evidence for shifts in the bacterial microbiome of a declining freshwater bivalve

Freshwater mussels (Unionida) are suffering mass mortality events worldwide, but the causes remain enigmatic. Here, we describe an analysis of bacterial loads, community structure, and inferred metabolic pathways in the hemolymph of pheasantshells (Actinonaias pectorosa) from the Clinch River, USA, during a multi-year mass mortality event. Bacterial loads were approximately 2 logs higher in moribu
Authors
Jordan Richard, Lewis J. Campbell, Eric Leis, Rose Agbalog, Christopher D. Dunn, Diane L. Waller, Susan Knowles, Joel G. Putnam, Tony Goldberg
By
Ecosystems Mission Area, National Wildlife Health Center, Upper Midwest Environmental Sciences Center

Pathology of Lagovirus europaeus GI.2/RHDV2/b (rabbit hemorrhagic disease virus 2) in native North American lagomorphs

Rabbit hemorrhagic disease, a notifiable foreign animal disease in the US, was reported for the first time in wild native North American lagomorphs in April 2020 in the southwestern US. Affected species included the desert cottontail (Sylvilagus audubonii), mountain cottontail (Sylvilagus nuttallii), black-tailed jackrabbit (Lepus californicus), and antelope jackrabbit (Lepus alleni). Desert cotto
Authors
Julia S. Lankton, Susan Knowles, Saskia Keller, Valerie I. Shearn-Bochsler, Hon S. Ip
By
Ecosystems Mission Area, Biological Threats and Invasive Species Research Program, National Wildlife Health Center

Domoic acid and saxitoxin in seabirds in the United States between 2007 and 2018

As harmful algal blooms (HABs) increase in magnitude and duration worldwide, they are becoming an expanding threat to marine wildlife. Over the past decade, blooms of algae that produce the neurotoxins domoic acid (DA) and saxitoxin (STX) and documented concurrent seabird mortality events have increased bicoastally in the United States. We conducted a retrospective analysis of HAB related mortalit
Authors
Corinne Gibble, Raphael Kudela, Susan Knowles, Barbara Bodenstein, Kathi Lefebvre
By
Ecosystems Mission Area, National Wildlife Health Center

Non-USGS Publications**

Salter CE, O’Donnell K, Sutton DA, Marancik DP, Knowles S, Clauss TM, Berliner AL, Camus AC: Dermatitis and systemic mycosis in a group of lined seahorses Hippocampus erectus associated with a marine-adapted pathogen within the Fusarium solani species complex. Dis Aquat Org 101(1):23-31, 2012.
Page-Karjian A, Knowles S, Howerth E, Berliner A, Clauss T, Hyatt M, Camus A: Pathology in practice. J Am Vet Med Assoc 241(9):1159-1161, 2012.
Knowles S, Blas-Machado U, Butler AM, Gomez-Ibañez SE, Lowder MQ, Fayrer-Hosken RA: Ameloblastic fibro-odontoma associated with a retained molar in an Oldenburg mare. J Vet Diagn Invest 22:987-990, 2010.
Knowles S, Uhl EW, Blas-Machado U, Butler AM: Intrapericardial ectopic thyroid carcinoma in a cat. J Vet Diagn Invest 22:1010-1013, 2010.
Brown YK, Knowles S, Fiorello CV, Camus MS, Howerth EW: Pathology in practice. Morphologic diagnosis: Uterine adenocarcinoma with metastasis to the lungs, diaphragm, spleen, mesentery, and cecum. J Am Vet Med Assoc 237:1257-1259, 2010.
Knowles S, Hrubec TC, Smith SA, Bakal RS: Hematology and plasma chemistry reference intervals for cultured shortnose sturgeon (Acipenser brevirostrum). Vet Clin Pathol 35:434-440, 2006.
Blanchard TW, Santiago NT, Lipscomb TP, Garber RL, McFee WE, Knowles S: Two novel alphaherpesviruses associated with fatal disseminated infections in Atlantic bottlenose dolphins. J Wild Dis 37:297-305, 2001.
Evans JJ, Norden A, Cresswell F, Insley K, and Knowles S: Marine sea turtle strandings in Maryland, 1991 to 1995. The Maryland Naturalist 41:23-34, 1997.

**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.

Filter Total Items: 13
Pathology Case of the Month - Little Brown Bat

Pathology Case of the Month - Little Brown Bat

History: A Little Brown Bat (Myotis lucifugus) was captured in a harp trap in May 2023 as part of surveillance for Pseudogymnoascus destructans at a...

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New resource on pathology and infectious agents of freshwater mussels

New resource on pathology and infectious agents of freshwater mussels

A new publication by USGS National Wildlife Health Center scientists and partners (Knowles et al. 2023) was published to synthesize current disease...

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Pathology Case of the Month - Mallard Duck

Pathology Case of the Month - Mallard Duck

Case History: An adult male 1320-g Mallard Duck (Anas platyrhynchos) was found dead as part of a mortality event involving Snow Geese (Anser...

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Pathology Case of the Month - Common Grackle

Pathology Case of the Month - Common Grackle

Case History: An adult male 160-g Common Grackle (Quiscalus quiscula) was found dead as part of a mortality event involving 30 grackles in Ohio, U.S.A...

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Pathology Case of the Month - Red Crossbills and American Goldfinches

Pathology Case of the Month - Red Crossbills and American Goldfinches

Case History: In July, approximately 45 red crossbills (Loxia curvirostra) and American goldfinches (Spinus tristis) exhibited lethargy and were later...

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Pathology Case of the Month - Raccoon

Pathology Case of the Month - Raccoon

Case History: An adult male 4.04-kg raccoon (Procyon lotor) was found dead near a campground in Arizona, US.  Three raccoons and a gray fox (Urocyon...

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Pathology Case of the Month - Big Brown Bat

Pathology Case of the Month - Big Brown Bat

Case History: An adult male big brown bat (Eptesicus fuscus) from Wisconsin, USA was submitted for necropsy. There were no reported clinical signs.

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Pathology Case of the Month - Northern Pintail Duck

Pathology Case of the Month - Northern Pintail Duck

Case History: An adult male Northern Pintail Duck (Anas acuta) was found dead on a refuge in Arizona, US. Collectively at this location, 29 birds...

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Pathology case of the month - Mountain Cottontail

Pathology case of the month - Mountain Cottontail

Case History: In June 2020, one adult female, 950-g, mountain cottontail rabbit (Sylvilagus nuttallii) with bloody nasal discharge was found dead by a...

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Pathology Case of the Month - Canada Goose and Bald Eagles

Pathology Case of the Month - Canada Goose and Bald Eagles

May's Pathology Case of the Month details the cases of a Canada Goose and two Bald Eagles.

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Pathology Case of Month - Zebra Finch

Pathology Case of Month - Zebra Finch

Case History: An adult female 9.95-g Zebra Finch (Taeniopygia guttata) from a California aviary was found dead.  It was noted to be thin several days...

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Pathology Case of the Month - Mourning Dove

Pathology Case of the Month - Mourning Dove

Case History: An immature female 122-g Mourning Dove (Zenaida macroura) was found dead in a park in Arizona, US.  An estimated 18 birds including Inca...

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*Disclaimer: Listing outside positions with professional scientific organizations on this Staff Profile are for informational purposes only and do not constitute an endorsement of those professional scientific organizations or their activities by the USGS, Department of the Interior, or U.S. Government