Thomas Gidlewski

Novel Eurasian Highly Pathogenic Avian Influenza A H5 Viruses in Wild Birds, Washington, USA, 2014

Novel Eurasian lineage avian influenza A(H5N8) virus has spread rapidly and globally since January 2014. In December 2014, H5N8 and reassortant H5N2 viruses were detected in wild birds in Washington, USA, and subsequently in backyard birds. When they infect commercial poultry, these highly pathogenic viruses pose substantial trade issues.

Preliminary Observations of Genetic Susceptibility of elk (Cervus Elaphus Nelsoni) to Chronic Wasting Disease by Experimental Oral Inoculation

To compare the genetic susceptibility of elk (Cervus elaphus nelsoni) with various alleles of the PRNP gene, which encodes the normal cellular prion protein, to chronic wasting disease (CWD), eight 8-month-old elk calves of 3 genotypes (2 132MM, 2 132LM, and 4 132LL) were orally dosed with CWD-infected brain material from elk. During postinoculation (PI) month 23, both 132MM elk had lost appetite, developed clinical signs of weight loss and central nervous system (CNS) dysfunction, and were euthanized. Two other elk (both 132LM) developed similar clinical signs of disease and were euthanized during PI month 40. All 4 affected elk had microscopic lesions of spongiform encephalopathy (SE), and PrPres, the disease-associated form of the prion protein, was detected in their CNS and lymphoid tissues by use of immunohistochemical (IHC) and Western blot (WB) techniques. These findings indicate that elk with MM and LM at codon 132 are susceptible to orally inoculated CWD. All 4 LL elk are alive at PI year 4 and are clinically normal, which suggests that 132LL elk may have reduced susceptibility to oral infection with CWD-infected material or may have prolonged incubation time.

Elk with a long incubation prion disease phenotype have a unique PrPd profile

The transmissible spongiform encephalopathies (TSEs) invariably result in fatal neurodegeneration and accumulation of PrPd, an abnormal form of the host prion protein PrPc, encoded by the PRNP gene. A naturally occurring polymorphism (methionine/valine) at PRNP codon 129 is associated with variation in relative disease susceptibility, incubation time, clinical presentation, neuropathology, and/or PrPd biochemical characteristics in a range of human TSEs. A methionine/leucine polymorphism at the corresponding site in the Rocky Mountain elk PRNP gene is associated with variation in relative susceptibility and incubation time in the cervid TSE chronic wasting disease. We now report that elk lacking the predisposing 132-methionine allele develop chronic wasting disease after a long incubation period and display a novel PrPd folding pattern.

Chronic wasting disease in a Wisconsin white- tailed deer farm

In September 2002, chronic wasting disease (CWD), a prion disorder of captive and wild cervids, was diagnosed in a white-tailed deer (Odocoileus virginianus) from a captive farm in Wisconsin. The facility was subsequently quarantined, and in January 2006 the remaining 76 deer were depopulated. Sixty animals (79%) were found to be positive by immunohistochemical staining for the abnormal prion protein (PrPCWD)in at least one tissue; the prevalence of positive staining was high even in young deer. Although none of the deer displayed clinical signs suggestive of CWD at depopulation, 49 deer had considerable accumulation of the abnormal prion in the medulla at the level of the obex. Extraneural accumulation of the abnormal protein was observed in 59 deer, with accumulation in the retropharyngeal lymph node in 58of 59 (98%), in the tonsil in 56 of 59 (95%), and in the rectal mucosal lymphoid tissue in 48 of 58 (83%). The retina was positive in 4 deer, all with marked accumulation of prion in the obex. One deer was considered positive for PrPCWD in the brain but not in the extraneural tissue, a novel observation in white-tailed deer. The infection rate in captive deer was 20-fold higher than in wild deer. Although weakly related to infection rates in extraneural tissues, prion genotype was strongly linked to progression of prion accumulation in the obex. Antemortem testing by biopsy of rectoanal mucosal-associated lymphoid tissue (or other peripheral lymphoid tissue) may be a useful adjunct to tonsil biopsy for surveillance in captive herds at risk for CWD infection.

PATHOLOGY OF BRUCELLOSIS IN BISON FROM YELLOWSTONE NATIONAL PARK

Between February 1995 and June 1999, specimens from seven aborted bison (Bison bison) fetuses or stillborn calves and their placentas, two additional placentas, three dead neonates, one 2-wk-old calf, and 35 juvenile and adult female bison from Yellowstone National Park (USA) were submitted for bacteriologic and histopathologic examination. One adult animal with a retained placenta had recently aborted. Serum samples from the 35 juvenile and adult bison were tested for Brucella spp. antibodies. Twenty-six bison, including the cow with the retained placenta, were seropositive, one was suspect, and eight were seronegative. Brucella abortus biovar 1 was isolated from three aborted fetuses and associated placentas, an additional placenta, the 2-wk-old calf, and 11 of the seropositive female bison including the animal that had recently aborted. Brucella abortus biovar 2 was isolated from one additional seropositive adult female bison. Brucella abortus was recovered from numerous tissue sites from the aborted fetuses, placentas and 2-wk-old calf. In the juvenile and adult bison, the organism was more frequently isolated from supramammary (83%), retropharyngeal (67%), and iliac (58%) lymph nodes than from other tissues cultured. Cultures from the seronegative and suspect bison were negative for B. abortus. Lesions in the B. abortus-infected, aborted placentas and fetuses consisted of necropurulent placentitis and mild bronchointerstitial pneumonia. The infected 2-wk-old calf had bronchointerstitial pneumonia, focal splenic infarction, and purulent nephritis. The recently-aborting bison cow had purulent endometritis and necropurulent placentitis. Immunohistochemical staining of tissues from the culture-positive aborted fetuses, placentas, 2-wk-old calf, and recently-aborting cow disclosed large numbers of B. abortus in placental trophoblasts and exudate, and fetal and calf lung. A similar study with the same tissue collection and culture protocol was done using six seropositive cattle from a B. abortus-infected herd in July and August, 1997. Results of the bison and cattle studies were similar.

Seroconversion and abortion in cattle experimentally infected with Brucella sp. isolated from a Pacific harbor seal (Phoca vitulina richardsi).

Previously unrecognized Brucella species have been isolated from a number of marine mammals, including harbor seals (Phoca vitulina richardsi) in the Puget Sound area of the state of Washington. Because of the presence of dairy herds in proximity to the harbor seal populations, a study was conducted to determine the effects of the harbor seal Brucella isolate in experimentally inoculated cattle. Six pregnant cattle were exposed by intravenous injection (n = 3) or intraconjunctival inoculation (n = 3). Two pregnant cows were intravenously injected with saline and served as controls. All of the cows receiving the Brucella seroconverted on 1 or more tests commonly used for the detection of Brucella abortus infection. Two of the cattle receiving the intravenous inoculation aborted, and brucellae were demonstrated in the fetuses and dams immediately following abortion. The remaining 4 Brucella-inoculated animals and their fetuses were culture negative for the organism at 14 weeks postinoculation. Results of this study indicate the marine mammal Brucella is capable of producing seroconversion and abortion in cattle but is less pathogenic in that species than B. abortus.

Antemortem detection of PrPCWD in preclinical, ranch-raised Rocky Mountain elk (Cervus elaphus nelsoni) by biopsy of the rectal mucosa.

Antemortem biopsy of the rectal mucosa was evaluated as a method for the preclinical diagnosis of chronic wasting disease (CWD) in a herd of ranch-raised Rocky Mountain elk (Cervus elaphus nelsoni) quarantined because of exposure to CWD. Biopsy samples were obtained from 41 elk during the winter of 2005–2006 and from 26 elk from that herd still alive and available for testing during the winter of 2006–2007. Samples were examined for PrPCWD, the protein marker for CWD infection, by immunohistochemistry. PrPCWD was detected in follicles of the rectoanal mucosa–associated lymphoid tissue in biopsy samples from 1 elk with clinical signs of chronic wasting disease and 5 clinically normal elk. The diagnosis was confirmed in all 6 animals by postmortem analysis of brain and peripheral lymph nodes. PrPCWD was also observed in the submucosal plexus and myenteric plexus of the enteric nervous system, and in close association with nonmyelinated mucosal and submucosal nerve fibers. In antemortem rectal biopsy samples from positive animals, immunostaining was consistently observed in approximately 60% of the mucosa-associated lymphoid tissue follicles if 10 or more total follicles per biopsy were present for evaluation. Most antemortem biopsy samples obtained from elk younger than 6.5 years contained at least 10 follicles per rectal mucosal biopsy. These findings support the analysis of antemortem biopsy of the rectal mucosa samples as part of an integrated strategy to manage chronic wasting disease in Rocky Mountain elk.

Brucellosis in Yellowstone National Park bison: Quantitative serology and infection

We collected complete sets of tissues, fluids, and swabs (approx 30) from 37 Yellowstone National Park (YNP) female bison (Bison bison) killed as a result of management actions by the Montana Department of Livestock and YNP personnel. Our goal was to establish the relation between blood tests demonstrating an animal has antibody to Brucella and the potential of that animal to be infected during the second trimester of pregnancy, the time when most management actions are taken. Twenty-eight of the 37 bison were seropositive adults (27) or a seropositive calf (1). We cultured samples using macerated whole tissues plated onto 4 Brucella- selective media and incubated with added CO2 for 1 week. Specimens from 2 adult seropositive females were contaminated, thus eliminating them from our data. Twelve of the remaining 26 seropositive adult and calf female bison (46%) were culture positive for Brucella abortus from 1 or more tissues. Culture positive adult females had high serologic titers. All 11 adults measured 3+ at 1:40 for 10 of 11 (91%) animals. All culture positive female adults had either a PCFIA 50.080 or a CF reaction -4+ at 1:80. However 5 (36%) bison with high titers were culture negative for B. abortus. Our findings on the relation between Brucella serology and culture are similar to those reported from studies of chronically infected cattle herds.

Sentinel-based Surveillance of Coyotes to Detect Bovine Tuberculosis, Michigan

Coyotes could be used as sentinels to detect Mycobacterium bovis in the wild.

Diagnostic accuracy of rectal mucosa biopsy testing for chronic wasting disease within white-tailed deer (Odocoileus virginianus) herds in North America: Effects of age, sex, polymorphism at PRNP codon 96, and disease progression

An effective live animal diagnostic test is needed to assist in the control of chronic wasting disease (CWD), which has spread through captive and wild herds of white-tailed deer (Odocoileus virginianus) in Canada and the United States. In the present study, the diagnostic accuracy of rectal mucosa biopsy sample testing was determined in white-tailed deer from 4 CWD-infected captive herds. Specifically, the current study compared the immunohistochemical detection of disease-associated prion protein in postmortem rectal mucosa biopsy samples to the CWD status of each deer as determined by immunodiagnostic evaluations of the brainstem at the obex, the medial retropharyngeal lymph node, and the palatine tonsil. The effects of age, sex, genotype, and disease progression were also evaluated. Diagnostic sensitivity on rectal biopsy samples for CWD in white-tailed deer ranged from 63% to 100%; the pooled estimate of sensitivity was 68% with 95% confidence limits (95% CLs) of 49% and 82%. However, diagnostic sensitivity was dependent on genotype at prion protein gene (PRNP) codon 96 and on disease progression as assessed by obex grade. Diagnostic sensitivity was 76% (95% CLs: 49%, 91%) for 96GG deer but only 42% (95% CLs: 13%, 79%) for 96GS deer. Furthermore, diagnostic sensitivity was only 36% for deer in the earliest stage of disease (obex grade 0) but was 100% for deer in the last 2 stages of preclinical disease (obex grades 3 and 4). The overall diagnostic specificity was 99.8%. Selective use of antemortem rectal biopsy sample testing would provide valuable information during disease investigations of CWD-suspect deer herds.