Gregory A Bradley
- Research Scientist, Animal and Comparative Biomedical Sciences
- Member of the Graduate Faculty
- D.V.M. Veterinary Medicine
- Colorado State University, Ft. Collins, Colorado
Licensure & Certification
- Diplomate, American College of Veterinary Pathologists (1990)
No activities entered.
Independent StudyACBS 499 (Fall 2020)
Independent StudyMIC 499 (Spring 2017)
- Bradley, G. A., Fox, L., & Moreno, A. (2019). Mortality of four captive-born crested screamer chicks (Chauna torquata). Open Veterinary Journal, 9(2), 120125. doi:http://dx.doi.org/10.4314/ovj.v9i2.5
- Swenson, J., & Bradley, G. A. (2013). Suspected cholecalciferol rodenticide toxicosis in avian species at a zoological institution. Journal of Avian Medicine and Surgery, 27(2), 136-147.More infoPMID: 23971222;Abstract: Over a 2-month period, individual birds belonging to species in multiple avian families, including Bucerotidae, Sturnidae, Columbidae, Corvidae, and Anatidae, were presented to the Animal Care Center at the Phoenix Zoo for emergency medical care. Common clinical findings were subdued behavior, weight loss, and an inability to fly. Biochemical abnormalities commonly included high calcium and uric acid concentrations and high to high-normal phosphorus concentrations. In cases in which necropsies were done, mineralization of organs often was present, frequently of the kidneys and cardiovascular system. Because of the high calcium and phosphorus concentrations, mineralization of tissues, cases representing multiple avian species, and the recent addition of rodent bait boxes containing cholecalciferol to the zoo's pest control program, a presumptive diagnosis of cholecalciferol toxicosis was made. Treatment most commonly consisted of daily fluid diuresis. These cases demonstrate that, although cholecalciferol is considered unlikely to cause relay toxicosis, primary toxicosis still should be considered in cases with sudden onset of nonspecific signs when exposure to cholecalciferol was possible. © 2013 the Association of Avian Veterinarians.
- Swenson, J., & Bradley, G. A. (2013). Suspected cholecalciferol rodenticide toxicosis in avian species at a zoological institution. Journal of avian medicine and surgery, 27(2).More infoOver a 2-month period, individual birds belonging to species in multiple avian families, including Bucerotidae, Sturnidae, Columbidae, Corvidae, and Anatidae, were presented to the Animal Care Center at the Phoenix Zoo for emergency medical care. Common clinical findings were subdued behavior, weight loss, and an inability to fly. Biochemical abnormalities commonly included high calcium and uric acid concentrations and high to high-normal phosphorus concentrations. In cases in which necropsies were done, mineralization of organs often was present, frequently of the kidneys and cardiovascular system. Because of the high calcium and phosphorus concentrations, mineralization of tissues, cases representing multiple avian species, and the recent addition of rodent bait boxes containing cholecalciferol to the zoo's pest control program, a presumptive diagnosis of cholecalciferol toxicosis was made. Treatment most commonly consisted of daily fluid diuresis. These cases demonstrate that, although cholecalciferol is considered unlikely to cause relay toxicosis, primary toxicosis still should be considered in cases with sudden onset of nonspecific signs when exposure to cholecalciferol was possible.
- Swenson, J., Orr, K., & Bradley, G. (2012). Hemorrhagic and necrotizing hepatitis associated with administration of a modified live canine adenovirus-2 vaccine in a maned wolf (Chrysocyon brachyurus). J Zoo Wildl Med, 43(2), 375-83.
- Swenson, J., Orr, K., & Bradley, G. A. (2012). Hemorrhagic and necrotizing hepatitis associated with administration of a modified live canine adenovirus-2 vaccine in a maned wolf (Chrysocyon brachyurus). Journal of Zoo and Wildlife Medicine, 43(2), 375-383.More infoPMID: 22779244;Abstract: A 15-yr-old, female, maned wolf (Chrysocyon brachyurus) was euthanized after presenting semicomatose with severe, uncontrolled frank hemorrhage from her rectum 6 days following a routine physical examination and vaccination. Histopathology indicated severe hemorrhagic and necrotizing hepatitis with intranuclear basophilic inclusion bodies in the liver that were thought to be consistent with adenoviral infection. Further classification by polymerase chain reaction, immunohistochemical staining, virus isolation, and electron microscopy confirmed the etiologic agent to be canine adenovirus-2. A representative sample of the vaccine that had been used was submitted and sequenced along with the virus isolated from the maned wolf. The sequencing of the etiologic agent that had been isolated from the maned wolf was determined to be the same as the strain of virus used in the production of the modified live vaccine that had been administered 6 days prior to death. From this information, the diagnosis of vaccine-induced adenoviral hepatitis was made. This is the first confirmed case of vaccine-induced canine adenoviral hepatitis in a maned wolf. © 2012 American Association of Zoo Veterinarians.
- Pacheco, M. A., Escalante, A. A., Garner, M. M., Bradley, G. A., & Aguilar, R. F. (2011). Haemosporidian infection in captive masked bobwhite quail (Colinus virginianus ridgwayi), an endangered subspecies of the northern bobwhite quail. Veterinary Parasitology, 182(2-4), 113-120.More infoPMID: 21726940;PMCID: PMC3742108;Abstract: The avian haemosporidian parasites (phylum Apicomplexa) are taxonomically diverse and cosmopolitan in distribution; infecting most bird families. Sources of concern are reports of clinical haemosporidian infections in birds kept as part of zoo and aviary collections. Recently, severe and acute mortality episodes have been reported in masked bobwhite quail (Colinus virginianus ridgwayi), an endangered subspecies from the American Southwest. Two hundred and five eggs of the captive flock held in Arivaca, Arizona, were hatched at a zoo in the American Southwest. Thirty-four sub-adult or adult animals had lesions associated with tissue phases of haemoparasites, especially vasculitis, ventricular leiomyositis and ulcerative pododermatitis. Molecular techniques applied to blood collected from the zoo's last twelve remaining animals resulted in the detection of a Plasmodium juxtanucleare-like and Haemoproteus sp. parasites. A Raven (Corvus corax), in a contiguous exhibit, was positive for the same P. juxtanucleare-like parasite, but remained asymptomatic for three years following detection. These findings indicate that other birds in the exhibit within the zoo premises could act as reservoirs. We conclude that haemosporidian infections could be a factor in the demise of the captive masked bobwhite quails housed at the zoo. We suggest that active surveillance for haemoporidian parasites should be incorporated as a precaution to ex situ conservation efforts of susceptible endangered species. © 2011 Elsevier B.V.
- Pacheco, M., Escalante, A., Garner, M., Bradley, G., & Aguilar, R. (2011). Haemosporidian infection in captive masked bobwhite quail (Colinus virginianus ridgwayi), an endagnered subspecies of the norther bobwhite quail. Vet Parasitol, 182, 113-20.
- Fuji, R. N., Patton, K. M., Steinbach, T. J., Schulman, F. Y., Bradley, G. A., Brown, T. T., Wilson, E. A., & Summers, B. A. (2005). Feline systemic reactive angioendotheliomatosis: Eight cases and literature review. Veterinary Pathology, 42(5), 608-617.More infoPMID: 16145207;Abstract: A rare, multisystemic intravascular proliferative disorder was identified postmortem in eight cats. The majority of these cats died or were euthanized following episodes of dyspnea, lethargy, and anorexia. Microscopic examination revealed occlusive, intraluminal proliferations of spindle cells within small vessels. The heart was consistently involved, and myocardial dysfunction was the probable cause of illness in all cats. Immunohistochemically, the majority of intravascular cells expressed von Willebrand factor, and a smaller number expressed smooth muscle actin, compatible with a dual population of endothelial cells and pericytes, suggesting a reactive rather than a neoplastic process. Four cases of a similar feline vascular disorder from the veterinary literature are reviewed. The histopathology resembles reactive angioendotheliomatosis in humans, a benign cutaneous intravascular endothelial and pericytic proliferative condition. However, in contrast, this feline disease is multisystemic and fatal. We propose the name "feline systemic reactive angioendotheliomatosis" for this unique, idiopathic disorder of domestic cats.
- Keel, M. K., Patterson, J. G., Noon, T. H., Bradley, G. A., & Collins, J. K. (2003). Caprine herpesvirus-2 in association with naturally occurring malignant catarrhal fever in captive sika deer (Cervus nippon). Journal of Veterinary Diagnostic Investigation, 15(2), 179-183.More infoPMID: 12661731;Abstract: Three female sika deer from a single captive herd were submitted for postmortem examination over a 139-day period. The first 2 deer submitted were reported to have lost body mass for 20 days to 1 month before euthanasia. One of these deer had diarrhea, the other had a crusting dermatitis on the nasal planum and inner aspects of both pinnae. The third hind did not have any signs of disease before it was found seizuring and was immediately euthanatized. Microscopically, all 3 animals had a lymphocytic vasculitis typical of malignant catarrhal fever (MCF), with the most severe lesions in the brain. All 3 deer were polymerase chain reaction (PCR) positive for caprine herpesvirus 2 (CpHV-2) and were negative for ovine herpesvirus 2 (OHV-2). Two healthy goats that were housed adjacent to the deer were also PCR positive for CpHV-2 and PCR negative for OHV-2. The CpHV-2, PCR amplicons from the hinds, and the 2 healthy goats had an identical single base polymorphism. A male sika deer that was housed with the hinds and a fawn from 1 of the hinds remained asymptomatic and were PCR negative for CpHV-2. This represents the first report of mortality with MCF-like lesions in association with CpHV-2.
- Bradley, G. A., Rosen, P. C., Sredl, M. J., Jones, T. R., & Longcore, J. E. (2002). Chytridiomycosis in native Arizona frogs. Journal of Wildlife Diseases, 38(1), 206-212.More infoPMID: 11838218;Abstract: Twenty seven adult/sub-adult lowland leopard frogs (Rana yavapaiensis), two larval lowland leopard frogs, two adult Chirichahua leopard frogs (Rana chiricahuensis), and two adult canyon tree frogs (Hyla arenicolor) collected from populations experiencing mortality events at eight sites were found to have characteristic lesions of chytrid fungus infection (Batrachochytrium dendrobatidis). The mortalities occurred during December 1992 and between October and February in 1997-98 and December and February in 1998-99. Gross lesions varied from none to diffuse reddening of the skin of the abdomen, pelvic area, and legs. Microscopic lesions were characteristic of those previously reported for the disease and included diffuse epidermal hyperplasia, hyperkeratosis, and colonization of the keratinized layers of the epidermis by sporangia of the chytrid. Bacterial cultures did not yield a primary pathogenic agent. Virus isolation from frog tissues was negative. Batrachochytrium dendrobatidis was isolated from the skin of two of 10 R. yavapaiensis and one of two H. arenicolor cultured following necropsy. An additional nine of 11 clinically affected or dead R. yavapaiensis from the same locations, but not necropsied, were culture positive for B. dendrobatidis.
- Noon, T. H., Wesche, S. L., Cagle, D., Mead, D. G., Bicknell, E. J., Bradley, G. A., Riplog-Peterson, S., Edsall, D., & Reggiardo, C. (2002). Hemorrhagic disease in bighorn sheep in Arizona. Journal of Wildlife Diseases, 38(1), 172-176.More infoPMID: 11838210;Abstract: Two bighorn sheep from Arizona (USA) were submitted for necropsy. One was a Rocky Mountain bighorn (Ovis canadensis canadensis) and the other was a desert bighorn (Ocis canadensis mexicana). Both had lesions consistent with those of hemorrhagic disease (HD). Epizootic hemorrhagic disease virus (EHDV) type-2 and bluetongue virus (BTV) type-17, respectively, were isolated from the sheep tissues. To our knowledge, HD caused bv either EHDV or BTV infection has not been documented previously in Arizona bighorn sheep.
- Noon, T. H., Wesche, S. L., Heffelfinger, J., Fuller, A., Bradley, G. A., & Reggiardo, C. (2002). Hemorrhagic disease in deer in Arizona. Journal of Wildlife Diseases, 38(1), 177-181.More infoPMID: 11838211;Abstract: Two mule deer (Odocoileus hemionus) and one white-tailed deer (Odocoileus virginianus) in Arizona (USA) were submitted for necropsy. Gross and microscopic lesions compatible with hemorrhagic disease (HD) were observed in all three deer. Epizootic hemorrhagic disease virus type 2 (EHDV-2) was isolated from two of the deer. To our knowledge, this is the first documentation of HD in deer in Arizona. Two of the mortalities were attributed to EHDV-2 infection.
- Bradley, G. A., Orr, K., Reggiardo, C., & Glock, R. D. (2001). Enterotoxigenic Escherichia coli Infection in Captive Black-footed Ferrets. Journal of Wildlife Diseases, 37(3), 617-620.More infoPMID: 11504237;Abstract: Enterotoxigenic Escherichia coli with genes for heat stabile toxins Sta and STb was isolated from the gastrointestinal tract and multiple visceral organs of three adult and three juvenile black-footed ferrets (Mustela nigripes) that died in a captive breeding colony between 24 May 1998 and 2 July 1998. Similar isolates were obtained from rectal swabs of one adult and one juvenile that were clinically ill. All were fed a diet composed of mink chow, raw rabbit meat, beef liver powder, blood meal and lard. Escherichia coli of the same toxin genotype was isolated from the mixed ration. Clinical signs included sudden death, dehydration, anorexia and diarrhea. Necropsy lesions included acute enteritis with large numbers of rod shaped bacteria microscopically visible on intestinal villi.
- Shubitz, L. F., Matz, M. E., Noon, T. H., Reggiardo, C. C., & Bradley, G. A. (2001). Constrictive pericarditis secondary to coccidioides immitis infection in a dog. Journal of the American Veterinary Medical Association, 218(4), 537-540.More infoPMID: 11229504;
- Lozano-Alarcón, F., Bradley, G. A., Houser, B. S., & Visvesvara, G. S. (1997). Primary Amebic Meningoencephalitis Due to Naegleria fowleri in a South American Tapir. Veterinary Pathology, 34(3), 239-243.More infoPMID: 9163883;Abstract: Naegleria fowleri, Acanthamoeba spp., and Balamuthia mandrillaris are known to cause fatal central nervous system (CNS) disease in human beings. N. fowleri causes acute, fulminating primary amebic meningoencephalitis (PAM), which generally leads to death within 10 days. Acanthamoeba spp. and B. mandrillaris cause chronic granulomatous amebic encephalitis, which may last for 8 weeks. Acanthamoeba spp. and B. mandrillaris also cause CNS disease in animals. N. fowleri, however, has been described only in human beings. This report is the first of PAM in an animal, a South American tapir. Dry cough, lethargy, and coma developed in the animal, and its condition progressed to death. At necropsy, lesions were seen in the cerebrum, cerebellum, and lungs. The CNS had severe, suppurative meningoencephalitis with many neutrophils, fibrin, plasma cells, and amebas. Amebas were 6.5 μm to 9 μm in diameter and had a nucleus containing a large nucleolus. Amebas in the sections reacted with a monoclonal antibody specific for N. fowleri in the immunofluorescent assay and appeared bright green.
- Steele, K. E., Visvesvera, G. S., Bradley, G. A., Lipscomb, T. P., & Gardiner, C. H. (1997). Amebiasis in a dog with gastric ulcers and adenocarcinoma. Journal of Veterinary Diagnostic Investigation, 9(1), 91-93.More infoPMID: 9087935;
- Lozano-Alarcón, F., R., T., Clark, E. G., Bradley, G. A., Shupe, M. R., & Hargis, A. M. (1996). Persistent papillomavirus infection in a cat. Journal of the American Animal Hospital Association, 32(5), 392-396.More infoPMID: 8875353;Abstract: A seven-year-old, neutered male, crossbred Persian was diagnosed as having persistent, cutaneous papillomavirus infection. The skin lesions consisted of round, multifocal-to-confluent, raised, black plaques on the neck, thorax, shoulders, and forelegs. Papillomavirus virions were demonstrated in negative-stained, electron microscopic preparations of homogenized skin lesions and within the nuclei of cells from the stratum granulosum. Avidin-biotin immunoperoxidase stains were positive for papillomavirus in the same cells. The cat was euthanized due to a clinical diagnosis of concurrent, severe, chronic pancreatitis.
- Bradley, G. A., Metcalf, H. C., Reggiardo, C., Noon, T. H., Bicknell, E. J., Lozano-Alarcon, F., Reed, R. E., & Riggs, M. W. (1995). Neuroaxonal degeneration in sheep grazing Sorghum pastures.. Journal of veterinary diagnostic investigation : official publication of the American Association of Veterinary Laboratory Diagnosticians, Inc, 7(2), 229-236.More infoPMID: 7619906;Abstract: During the fall of 1992, 250 (10%) of 2,500 Rambouilet cross feeder lambs grazing Sorghum bicolor developed neurologic signs including weakness, ataxia, head shaking, knuckling of the fetlocks, inability to rise, and opisthotonos. One hundred fifteen (46%) of the affected lambs died. Twenty of the surviving lambs exhibited residual neurologic signs of ataxia when stressed. At the same time, 275 (25%) of 1,100 ewes grazing a nearby sudex pasture (S. sudanese x S. bicolor) gave birth to lambs that were weak and unable to rise. Newborn lambs exhibited extensor rigidity and opisthotonos when assisted to a standing position. The dystocias that occurred were due to lambs with contracted limbs (arthrogryposis). All affected lambs died or were euthanized. Histologic examination of the brains of 3 feeder lambs and 9 newborn lambs revealed similar microscopic lesions. The predominant change was the presence of focal axonal enlargements (spheroids) in the proximal segments of axons, which were restricted to the nuclei of the medulla, cerebellum, and midbrain. In addition, the spinal cord contained spheroids in the ventral horn gray matter of the 6 newborns examined. Ultrastructurally, the spheroids were composed of aggregates of neurofilaments, mitochondria, vesicular bodies, and dense bodies bounded by a thin myelin sheath. There was mild gliosis in the more severely affected animals of both groups. There was minimal Wallerian degeneration in the white matter adjacent to affected nuclei in the brain and the ventromedial and dorsolateral funiculi of the spinal cord. This is the first detailed report of Sorghum toxicity in sheep.
- Bradley, G. A., Shupe, M. R., Reggiardo, C., Noon, T. H., Lozano-Alarcon, F., & Bicknell, E. J. (1994). Inclusion body hepatitis in Gambel's quail (Callipepla gambelii).. Journal of wildlife diseases, 30(2), 281-284.More infoPMID: 8028119;Abstract: An acute necrotizing hepatitis in 1- to 3-wk-old Gambel's quail (Callipepla gambelii) caused by an adenovirus is described. The infection caused high mortality in captive raised, orphan chicks at two wildlife rehabilitation facilities in Arizona (USA). Gross lesions varied from pale livers to multiple, pinpoint, white foci scattered throughout the livers. Microscopically, scattered foci of hepatocellular necrosis were present. Intact hepatocytes at teh periphery of necrotic foci had eosinophilic and basophilic intranuclear inclusion bodies.
- Jackson, M. W., Helfand, S. C., Smedes, S. L., Bradley, G. A., & Schultz, R. D. (1994). Primary IgG secreting plasma cell tumor in the gastrointestinal tract of a dog.. Journal of the American Veterinary Medical Association, 204(3), 404-406.More infoPMID: 8150697;Abstract: A mixed-breed dog, evaluated because of a chronic history of diarrhea and intestinal bleeding, was found to have a multilobular mass involving the intestine. Surgical resection of the mass necessitated an ileocolic anastomosis. On the basis of histologic and electron microscopic appearance and staining characteristics, a tentative diagnosis of intestinal carcinoid was made. Recovery was uncomplicated; the owners declined further diagnostic tests or treatment. Eight weeks later, the dog was reexamined because of signs consistent with hyperviscosity syndrome and hyperproteinemia. At the owner's request, the dog was euthanatized. At necropsy, extensive metastases to liver and lymph nodes, but not to bone, were seen. Reevaluation of the intestinal mass supported classifying the tumor as an IgG-secreting extramedullary plasmacytoma. This case underscores the need for additional histologic techniques, especially when confronted with an unusual manifestation of hyperproteinemia.
- McNamara, P. J., Bradley, G. A., & Songer, J. G. (1994). Targeted mutagenesis of the phospholipase D gene results in decreased virulence of Corynebacterium pseudotuberculosis. Molecular Microbiology, 12(6), 921-930.More infoPMID: 7934899;Abstract: The chromosomal gene encoding the phospholipase D from Corynebacterium pseudotuberculosis (biovar ovis) isolate Whetten 1 was replaced with an allele containing a nonsense mutation. The virulence of the mutant strain (W1.31r1) and the isogenic parental strain were then compared by inoculation of goats. The wild-type strain caused abscessation at the site of infection, which then spread to the regional lymph node, while W1.31r1 had a reduced ability to establish a primary infection and was incapable of dissemination. Our results confirm that phospholipase D is a virulence determinant of C. pseudotuberculosis that increases the persistence and spread of the bacteria within the host.
- Babakhani, F. K., Bradley, G. A., & Joens, L. A. (1993). Newborn piglet model for campylobacteriosis. Infection and Immunity, 61(8), 3466-3475.More infoPMID: 8335377;PMCID: PMC281024;Abstract: An in vivo model system for human campylobacteriosis has been developed in which colostrum-deprived newborn piglets are orally challenged with an invasive strain of Campylobacter jejuni. Piglets developed clinical symptoms and histopathological lesions similar to those observed in humans infected with C. jejuni. Gross lesion examination at autopsy revealed the presence of edema, hyperemia, and mucus. Histopathologic examinations by light and transmission electron microscopy demonstrated damage to surface epithelial cells with the presence of intracellular bacteria, mainly in the large intestine. Similar lesions were not demonstrated in control piglets.
- Bradley, G. A., Tye, J., Lozano-Alarcon, F., Noon, T., Bicknell, E. J., & Reggiardo, C. (1992). Hemopericardium in a dog due to hemorrhage originating in a heart base thymic remnant.. Journal of veterinary diagnostic investigation : official publication of the American Association of Veterinary Laboratory Diagnosticians, Inc, 4(2), 211-212.More infoPMID: 1616993;
- Lozano-Alarcón, F., Bradley, G. A., Allen, T. R., & Reggiardo, C. (1992). Lymphosarcoma in a desert bighorn sheep.. Journal of veterinary diagnostic investigation : official publication of the American Association of Veterinary Laboratory Diagnosticians, Inc, 4(4), 492-494.More infoPMID: 1457563;
- Bradley, G. A. (1991). Myocardial necrosis in a pug dog with necrotizing meningoencephalitis.. Veterinary Pathology, 28(1), 91-93.More infoPMID: 2017834;
- Roth, L., & Bradley, G. A. (1991). Pulmonary hamartoma in a calf. Journal of Comparative Pathology, 105(4), 471-474.More infoPMID: 1770181;Abstract: A pulmonary hamartoma was found in a 5 weeks over term Jersey Holstein cross bull calf. A 36 x 22 x 22 cm, spongy, pale pink mass with a distinct lobulated pattern was continuous with the left caudal lung lobe and compromised other thoracic viscera. The mass was non-cystic and uniformly consisted of soft, pink tissue. Histologically, the mass consisted of a disproportionate number of bronchiolar and alveolar structures, arranged in a haphazard pattern. Ascites, localized subcutaneous oedema, and chronic passive congestion of the liver were additional findings.
- Bradley, G. A., & Mays, M. C. (1990). Immunoperoxidase staining for the detection of autoantibodies in canine autoimmune skin disease; Comparison to immunofluorescence results. Veterinary Immunology and Immunopathology, 26(2), 105-113.More infoPMID: 2260277;Abstract: Skin sections from 22 dogs with autoimmune skin disease were stained with anti-canine IgG, IgM and IgA using an immunobridge immunoperoxidase method. Eight cases of lupus erythematosus, three cases of pemphigus vulgaris, and 11 cases of pemphigus foliaceus were included. Results of previously performed, direct immunofluorescence tests for the detection of canine immunoglobulin on skin were available on 17 22 cases. The immunoperoxidase method yielded an overall positive result in 59% ( 5 8 lupus erythematosus, 2 3 pemphigus vulgaris and 6 11 pemphigus foliaceus) versus an overall positive result of 47% for direct immunofluorescence ( 3 5 lupus erythematosus, 2 2 pemphigus vulgaris and 2 10 pemphigus foliaceus). The immunobridge immunoperoxidase method compared favorably to direct immunofluorescence testing of canine skin for autoantibody in cases of lupus erythematosis and pemphigus vulgaris, and was superior in cases of pemphigus foliaceus. This method should prove useful as an aid in the diagnosis of canine autoimmune skin disease. © 1990.
- Bradley, G. A. (2010, Fall). Diagnostic Laboratory Newsletter.
- Bradley, G. A. (2010, Fall). Wednesday Slide Conference.
- Bradley, G. A. (2010, Fall). Western Regional Slide Conference.