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Biomedical subjects

W R Davidson

Publications and source records attributed to W R Davidson.

At least 19 recordsLinked to original sources
PubMed2002

Northern bobwhite and lead shot deposition in an upland habitat.

We estimated total lead shotshell pellets expended, resultant pellet availability near soil surface, and the frequency of pellet ingestion by northern bobwhites ( Colinus virginianus) attributable to nearly a quarter century of bobwhite hunting on a 202-ha upland habitat at Tall Timbers Research Station, Leon County, Florida. A total of 7776 shots were fired, resulting in the expenditure of approximately 4.5 million pellets (approximately 22519/ha). Sixteen of 235 (6.8%) soil samples collected in 1989 and 1992 contained one or two pellets. Soil samples indicated that approximately 7800 pellets/ha (about 35% of the projected 24-year deposition) were within 2.54 cm of the soil surface. Pellet ingestion by bobwhites was evaluated by examining 241 gizzards collected from 1989-92. Three bobwhites (1.3%) had ingested pellets ( x = 1.3 pellets). No instances of suspected lead poisoning were noted in bobwhites over the 24-year period. Sport hunting of wild bobwhite populations on upland habitats appears to produce a low potential for lead poisoning compared to lead deposition in association with waterfowl and dove hunting.

Animals↗
PubMed2002

Prevalence of antibodies to Neospora caninum in white-tailed deer, Odocoileus virginianus, from the southeastern United States.

Serum samples from 305 white-tailed deer (Odocoileus virginianus) from 14 states in the southeastern United States were examined for antibodies to Neospora caninum using a direct agglutination test. Positive agglutination titers were found in 145 (48%) of the white-tailed deer examined: 21 (7%) had titers of 1:25, 92 (30%) had titers of 1:50, and 32 (10%) had titers of > or = 1:500. These findings that antibodies to N. caninum are common in white-tailed deer support the concept that a sylvatic cycle might exist for this economically important parasite of domestic cattle.

Agglutination Tests↗
PubMed2001

Lead toxicosis and trace element levels in wild birds and mammals at a firearms training facility.

In May 1999, lead poisoning was diagnosed in a yellow-rumped warbler (Dendroica coronata) and a gray squirrel (Sciurus carolinensis) found at the Federal Law Enforcement Training Center (FLETC), Glynn County, GA, based on detection of 6.2 and 90.0 ppm wet weight (WW) lead in the liver of the warbler and squirrel, respectively. From October 21--26, 1999, 72 wild animals (37 mammals and 35 birds), comprised of 22 different species, were collected from a 24-ha area surrounding the FLETC outdoor firearms shooting range complex to evaluate exposure to lead and other trace elements. Ten animals were used as controls (five mammals and five birds) and were collected from areas 1.5--3 km outside the shooting range area. Kidney and liver tissues were analyzed for lead, zinc, and other trace elements. Bird gizzards and white-tailed deer abomasums were examined grossly and radiographically to detect metallic objects. Twenty-four (33.3%) animals (11 species) had kidney or liver tissue lead levels > 1.00 ppm, and 12 of these (6 species) had levels > 2.00 ppm. Carcasses of one brown-thrasher (Toxostoma rufum) and two white-tailed deer (Odocoileus virginianus) contained lead fragments. Elevated liver tissue levels of zinc (111.0 ppm) were detected in one brown thrasher that also had elevated kidney and liver tissue lead levels. In February 2000, seven yellow-rumped warblers and one solitary vireo (Vireo solitarius) found dead near the FLETC firearms shooting range also were diagnosed with lead poisoning, with liver and kidney tissue lead levels from 1.77--11.6 and 4.55--17.8 ppm WW, respectively. This frequency of elevated tissue lead levels among the animals examined, in combination with confirmed lead toxicosis in both avian and mammalian species at FLETC, indicates significant lead exposure of local wild bird and mammal communities via bullets and fragments in and on the soil surface of the four outdoor ranges. Most FLETC firearms training is being shifted to new baffled ranges (four walls with semiopen top) with bullet recovery capabilities to preclude future deposition of lead in the environment; existing outdoor ranges will be remediated to remove existing lead.

Animals↗
PubMed2001

Persistent Ehrlichia chaffeensis infection in white-tailed deer.

Four white-tailed deer (Odocoileus virginianus) were inoculated intravenously with a deer-origin isolate (15B-WTD-GA) of Ehrlichia chaffeensis. The course of infection was monitored using indirect fluorescent antibody (IFA), polymerase chain reaction (PCR), and culture over a 9 m period. All deer became rickettsemic within 24 days post inoculation (DPI), and all developed antibody titers >1:64 to E. chaffeensis by 17 DPI. Titers in all deer fell below 1:64 during 87 to 143 DPI. One deer exhibited a second period of seropositivity (peak titer of 1:256) from 207 to 271 DPI but was culture and PCR negative during this period. Rickettsemia was confirmed by reisolation of E. chaffeensis as late as 73 to 108 DPI in three deer. Positive PCR results were obtained from femur bone marrow of one deer and from rumenal lymph node of another (leer at 278 DPI. None of the deer developed clinical signs, hematologic abnormalities, or gross or microscopic lesions attributable to E. chaffeensis. Two uninoculated control deer were negative on all tests through 90 DPI at which time they were removed from the study. Herein we confirm that white-tailed deer become persistently infected with E. chaffeensis, have initial rickettsemias of several weeks duration and may experience recrudescence of rickettsemia, which reaffirm the importance of deer in the epidemiology of E. chaffeensis.

Animals↗
PubMed2001

Intracranial abscessation in white-tailed deer of North America.

From January 1996 through April 1997, the geographic distribution, etiology, demographics, seasonality, and prevalence of an intracranial abscessation/suppurative meningoencephalitits syndrome in white-tailed deer (Odocoileus virginianus) were evaluated by surveying wildlife disease diagnostic laboratories and by examining both natural mortality and hunter-harvested deer skulls from North America. Intracranial abscesses were diagnosed as the cause of death or illness in 97 of nearly 4,500 (2.2%) white-tailed deer examined from 12 states and four Canadian provinces by the diagnostic laboratories. The bacterium Arcanobacterium pyogenes was isolated from 61% of cases; 18 other genera of bacteria also were isolated. The disease was strongly gender-biased (P < 0.01) with 87% of cases occurring in males, and the overall prevalence among males was 4.9%. Cases were most common among antlered males (> or = 1 yr) with few cases among male fawns. Among antlered males, cases were seasonal, primarily occurring from September through April. Four hundred eighteen skulls from deer found dead in the field were examined from southeastern USA, and of the 119 used for further evaluation, 9% had characteristic lesions. Skulls from hunter-harvested males in the southeastern USA had a lesion prevalence of 1.4%. The similarity of disease prevalence among male deer found dead in the field (9.0%) and deer examined as southeastern diagnostic laboratory cases (8.4%) suggests that this disease accounts for slightly < 10% of the natural mortality for yearling and adult male white-tailed deer in the southeastern region. The strong bias for occurrence among males suggests this disease may affect quality deer management strategies.

Actinomycetales Infections↗
PubMed2000

Aortic dissection in a weight lifter with nodular fasciitis of the aorta.

We report a case of spontaneous aortic dissection in a young weight lifter without aortic medial disease but with a myofibroblastic proliferation of the aortic adventitia consistent with nodular fasciitis. Successful treatment included ascending aorta replacement with Dacron graft and aortic valve resuspension. We believe that the underlying aortic pathology most likely contributed to the development of the aortic dissection.

Adult↗
PubMed2000

Long-term outcome in congenitally corrected transposition of the great arteries: a multi-institutional study.

OBJECTIVES: The purpose of this study was to determine long-term outcome in adults with congenitally corrected transposition of the great arteries (CCTGA), with particular emphasis on systemic ventricular dysfunction and congestive heart failure (CHF). BACKGROUND: Patients with CCTGA have the anatomical right ventricle as their systemic pumping chamber, with ventricular dysfunction and CHF being relatively common in older adults. METHODS: Retrospective analysis of records of 182 patients from 19 institutions were reviewed to determine current status and possible risk factors for systemic ventricular dysfunction and CHF. Factors considered included age, gender, associated cardiac defects, operative history, heart block, arrhythmias and tricuspid (i.e., systemic atrioventricular) regurgitation (TR). RESULTS: Both CHF and systemic ventricular dysfunction were common in groups with or without associated cardiac lesions. By age 45, 67% of patients with associated lesions had CHF, and 25% of patients without associated lesions had this complication. The rates of systemic ventricular dysfunction and CHF were higher with increasing age, the presence of significant associated cardiac lesions, history of arrhythmia, pacemaker implantation, prior surgery of any type, and particularly with tricuspid valvuloplasty or replacement. Aortic regurgitation (a previously unreported problem) was also relatively common in this patient population. CONCLUSIONS: Patients with CCTGA are increasingly subject to CHF with advancing age; this complication is extremely common by the fourth and fifth decades. Tricuspid (systemic atrioventricular) valvular regurgitation is strongly associated with RV (anatomical right ventricle connected to aorta in CCTGA patients; systemic ventricle in CCTGA) dysfunction and CHF; whether it is causative or a secondary complication remains speculative.

Adult↗
PubMed1999

A receptor tyrosine kinase, UFO/Axl, and other genes isolated by a modified differential display PCR are overexpressed in metastatic prostatic carcinoma cell line DU145.

We have used a modified differential display PCR protocol for isolating 3' restriction fragments of cDNAs specifically expressed or overexpressed in metastatic prostate carcinoma cell line DU145. Several cDNA fragments were identified that matched to milk fat globule protein, UFO/Axl, a receptor tyrosine kinase, human homologue of a Xenopus maternal transcript, laminin and laminin receptor, human carcinoma-associated antigen, and some expressed sequence tags. The transcript for milk fat globule protein, a marker protein shown to be overexpressed in breast tumors, was elevated in DU145 cells. The expression of UFO/Axl, a receptor tyrosine kinase, was considerably higher in DU145 cells as compared to normal prostate cells and prostatic carcinoma cell line PC-3. The overexpression of UFO oncogene in DU145 cells is discussed in the context of prostate cancer metastasis.

DNA Primers↗
PubMed1999

Novel Ehrlichia organism (Rickettsiales: Ehrlichieae) in white-tailed deer associated with lone star tick (Acari: Ixodidae) parasitism.

Polymerase chain reaction (PCR) evidence of a novel Ehrlichia organism was found recently in wild white-tailed deer, Odocoileus virginianus Zimmermann, and lone star ticks, Amblyomma americanum L., from the southeastern United States. To evaluate whether lone star tick parasitism was associated with the presence of this novel Ehrlichia organism in deer, 2 retrospective studies were conducted using specific nested PCR to test archived deer serum samples. The 1st study of 150 serum samples collected from a single deer population over a 15-yr period examined the temporal association between the presence of the Ehrlichia organism in deer and parasitism by lone star ticks. The deer Ehrlichia was not detected in serum samples collected before 1986, when lone star ticks were absent or rare, but was detected in samples collected in 1986 and every year thereafter, when lone star ticks became increasingly abundant. In the 2nd study, serum samples from 120 deer from 24 sites in 14 southeastern states were tested to evaluate if a site-specific, spatial association existed between the presence of the deer Ehrlichia and lone star ticks. All 60 serum samples from the 12 deer populations without evidence of lone star tick infestation were negative for the deer Ehrlichia, whereas 83% of the 12 populations infested by lone star ticks had PCR evidence of infection. These data suggest that lone star ticks may be a vector of the deer Ehrlichia; however, they do not preclude the involvement of other arthropods in maintaining infection with this organism in deer populations.

Animals↗
PubMed1999

Evaluation of C3H/HeJ mice for xenodiagnosis of infection with Ehrlichia chaffeensis.

Because mice are experimentally susceptible to infection with Ehrlichia species, C3H/HeJ mice were evaluated as a potential xenodiagnostic model for detection of infection with and isolation of E. chaffeensis. Intraperitoneal inoculation of mice with E. chaffeensis-infected DH82 cell cultures produced seroconversion, with peak serum antibody titers of 1:256, at high dosages (>1.9 x 10(4) infected cells) but not at low dosages (1.9 or 1.9 x 10(2) infected cells). Ehrlichia chaffeensis was not reisolated from blood samples collected from inoculated mice on postinoculation day 21. Nested polymerase chain reaction (PCR), using primers specific for E. chaffeensis, was positive for only 2/70 (2.9%) tissue samples. A field evaluation in which C3H/HeJ mice were inoculated with blood and lymph node suspensions from 5 seropositive white-tailed deer, including 3 deer that were PCR positive for E. chaffeensis, failed to produce seroconversion in mice. The lack of seroconversion at low dosages, the failure to reisolate at any dosage, and the inability to confirm infection in PCR-positive field samples suggests C3H/HeJ mice are not a sensitive model for xenodiagnosis or detection of E. chaffeensis.

Animals↗
PubMed1999

Susceptibility of red and gray foxes to infection by Ehrlichia chaffeensis.

Red foxes (Vulpes vulpes) and gray foxes (Urocyon cinereoargenteus) were evaluated for their susceptibility to experimental infection with Ehrlichia chaffeensis, the causative agent of human monocytotropic ehrlichiosis. Two red foxes and three gray foxes were inoculated intravenously with E. chaffeensis (15B-WTD-GA strain) and were monitored at 7, 14, 21, and 28 days post inoculation (DPI) for evidence of infection using an indirect fluorescent antibody (IFA) assay, light microscopy, polymerase chain reaction (PCR), and cell culture methods. One red fox and one gray fox served as negative controls. Red foxes were susceptible to infection based on reisolation of E. chaffeensis from blood at 7 and 14 DPI, seroconversion by 7 DPI, and positive PCR assays on spleen and lymph nodes at 28 DPI. Morulae were not found in circulating leukocytes and clinical signs or lesions of ehrlichiosis were not observed. In contrast, gray foxes were refractory to infection based on negative results on all culture, PCR, serologic, and microscopic examinations. These findings imply that red foxes, but not gray foxes, are potential vertebrate reservoirs for E. chaffeensis. These findings also illustrate the need to verify serologic evidence of E. chaffeensis infection among wild animals.

Animals↗
PubMed1998

Lack of seroreactivity to Ehrlichia chaffeensis among rodent populations.

A retrospective serosurvey for antibodies to Ehrlichia chaffeensis was conducted on eight species of wild rodents (Mus musculus, Oryzomys palustris, Peromyscus leucopus, Rattus norvegicus, Reithrodontomys humulis, Sciurus carolinensis, Sciurus niger, and Sigmodon hispidus) from the southeastern United States. Serum samples (n = 281) collected between 1973 and 1993 were evaluated using an indirect fluorescent antibody test. All samples, screened at a dilution of 1:32, were negative for antibodies to E. chaffeensis. Sixty-three percent of the rodents tested were from areas where E. chaffeensis has been confirmed or is strongly suspected to be endemic. These data suggest limited or no involvement of rodents in the epidemiology of E. chaffeensis.

Animals↗
PubMed1998

Responses of red foxes to first and second infection with Sarcoptes scabiei.

The clinical response of red foxes (Vulpes vulpes) to the mange mite, Sarcoptes scabiei, was characterized by infection of five, 4-mo-old red foxes with S. scabiei originally isolated from a wild red fox. The infected foxes and three uninfected control foxes were monitored with weekly complete blood counts and biweekly serum chemistry profiles, hypersensitivity tests, and evaluation of skin biopsies. After 7 wk, the foxes were treated and held free of infection for 2 mo. Six foxes, three previously infected and three with no history of exposure, were then infected with the same isolate of S. scabiei and followed for another 7 wk; two additional previously infected foxes were held as treatment controls, and two foxes with no history of exposure as naive controls. All infected foxes developed significant immediate (Type I) hypersensitivity reactions to a S. scabiei mite extract within 2 wk of exposure and maintained this reaction as long as 4 mo after clearance of mites. Pronounced mast cell hyperplasia and infiltration with eosinophils were the earliest inflammatory cell responses noted in biopsy samples from infected foxes and were maintained throughout infection. Infected foxes also showed significant increases in white blood cell counts, due primarily to increases in numbers of circulating neutrophils and eosinophils. Clinical response, severity of disease, and relative numbers of mites per cm2 of skin of previously infected foxes and foxes undergoing their first infection did not differ. These results show that red foxes develop strong immediate hypersensitivity reactions to S. scabiei but, under our experimental conditions, did not exhibit resistance to reinfection.

Animals↗
PubMed1998

Diseases diagnosed in red foxes from the southeastern United States.

Diagnostic findings on 51 red foxes (Vulpes vulpes) from the southeastern United States examined from 1967 to 1995 were reviewed. Etiologic diagnoses included sarcoptic manage (n = 33), traumatic injury and associated complications (n = 5), suspected canine distemper (n = 2), capture myopathy (n = 1), congenital absence of guard hairs (n = 1), intradermal tick infestation (n = 1), otodectic manage (n = 1), and toxicosis (n = 1). The cause of morbidity was not determined for three of the foxes, and three others were classified as normal animals. Sarcoptic manage was diagnosed in 65% of the red foxes, was found in foxes submitted from four of the eight southeastern states represented, and was seen in 19 of 29 yr covered by this study.

Alopecia↗
PubMed1998

Natural coinfection of a white-tailed deer (Odocoileus virginianus) population with three Ehrlichia spp.

The ticks Amblyomma americanum and Ixodes scapularis, strongly implicated vectors of Ehrlichia chaffeensis and the human granulocytic ehrlichiosis (HGE) agent, respectively, commonly are found on white-tailed deer (Odocoileus virginianus). As deer can be infected with E. chaffeensis, the HGE agent, and another Ehrlichia-like organism, a deer population parasitized by both tick species in coastal Georgia was tested for evidence of Ehrlichia spp. infection using serologic, molecular, and culture techniques. Antibodies to both E. chaffeensis (geometric mean titer = 111) and Ehrlichia equi, surrogate antigen for the HGE agent, (geometric mean titer = 1,024) were detected by indirect fluorescent antibody testing. Nested polymerase chain reaction employing species-specific primers demonstrated sequence-confirmed 16S rDNA fragments of 3 distinct Ehrlichia spp. in this population: E. chaffeensis (1/5), the HGE agent (3/5), and an Ehrlichia-like organism previously described from white-tailed deer (5/5). Ehrlichia chaffeensis was isolated in culture from the inguinal lymph node of a single deer. An Ehrlichia-type morula was identified in a neutrophil of 1 deer on examination of blood smears. This work provides the first evidence of the HGE agent in a nonhuman host in the southeastern United States and documents infection with both E. chaffeensis and the HGE agent in a single deer population, thereby supporting the importance of white-tailed deer in the natural history of the human ehrlichioses agents.

Animals↗
PubMed1997

Isolation of Ehrlichia chaffeensis from wild white-tailed deer (Odocoileus virginianus) confirms their role as natural reservoir hosts.

Field and experimental studies have implicated white-tailed deer (Odocoileus virginianus) as probable reservoir hosts for Ehrlichia chaffeensis, the causative agent of human monocytic ehrlichiosis, but natural infection in deer has not been confirmed through isolation of E. chaffeensis. Thirty-five white-tailed deer collected from three Amblyomma americanum-infested populations in Georgia were examined for evidence of E. chaffeensis infection by serologic, molecular, cell culture, and xenodiagnostic methods. Twenty-seven deer (77%) had E. chaffeensis-reactive indirect fluorescent-antibody assay titers of > or = 1:64; and the blood, spleens, or lymph nodes of seven (20%) deer were positive in a nested PCR assay with E. chaffeensis-specific primers. E. chaffeensis was isolated in DH82 cell cultures from the blood of five (14%) deer, including two deer that were PCR negative. Combination of culture and PCR results indicated that six (17%) deer were probably rickettsemic and that nine (26%) were probably infected. Restriction digestion of PCR products amplified from deer tissues and cell culture isolates resulted in a banding pattern consistent with the E. chaffeensis 16S rRNA gene sequence. The sequences of all PCR products from deer tissues or cell culture isolates were identical to the sequence of the Arkansas type strain of E. chaffeensis. Xenodiagnosis with C3H mice inoculated intraperitoneally with deer blood, spleen, or lymph node suspensions was unsuccessful. When viewed in the context of previous studies, these findings provide strong evidence that E. chaffeensis is maintained in nature primarily by a tick vector-vertebrate reservoir system consisting of lone star ticks and white-tailed deer.

Animals↗
PubMed1997

Development and use of specific polymerase reaction for the detection of an organism resembling Ehrlichia sp. in white-tailed deer.

The role of white-tailed deer (Odocoileus virginianus) in the epidemiology of Ehrlichia chaffeensis and the agent of human granulocytic ehrlichiosis (HGE) is not fully understood, and diagnostic procedures may be complicated by the recent detection of 16S rDNA sequence from an Ehrlichia sp.-like organism in wild deer. A specific forward primer (DGA) and an Ehrlichia spp. reverse primer (GA1UR) were constructed to amplify this new, distinct Ehrlichia sp.-like 16S rDNA. The DGA primer, a forward primer specific for E. chaffeensis (DCH), and a forward primer specific for the E. phagocytophila genogroup (GE9f) were each used with GA1UR in nested polymerase chain reactions to amplify 16S rDNA sequences from control samples containing the deer Ehrlichia sp.-like organism, E. chaffeensis, or the HGE agent. Primer pairs DGA/GA1UR and DCH/GA1UR specifically amplified 16S rDNA sequences from the corresponding target organism, whereas GE9f/GA1UR amplified 16S rDNA sequence from both the HGE agent and the deer Ehrlichia sp.-like organism. With a nested PCR using DGA/GA1UR and DCH/GA1IUR on DNA extracted from white blood cells from 62 deer from 10 populations in four U.S. states, we observed a high prevalence (65%) of 16S rDNA sequences of the deer Ehrlichia sp.-like organism, and a low prevalence (5%) of the E. chaffeensis sequence. In this field survey, E. chaffeensis-reactive antibodies detected by indirect fluorescence assays were associated (P < 0.001) with PCR evidence of the deer Ehrlichia sp.-like organism, but not E. chaffeensis. Infestations of Amblyomma americanum also were associated (P < 0.001) with PCR evidence of the deer Ehrlichia sp.-like organism. The potential for serologic cross-reactions and non-specific PCR products arising from the deer Ehrlichia sp.-like organism should be considered when evaluating the role of deer and their ticks in the epidemiology of ehrlichial pathogens of humans.

Animals↗