Evaluation of a modified subchondroplasty technique in an equine full-thickness cartilage defect model: a pilot study.

OBJECTIVE: To perform a pilot study with the intent of assessing the feasibility of a modified subchondroplasty (mSCP) technique in a validated preclinical equine model of full-thickness articular cartilage loss and evaluate the short-term patient response to the injected materials. ANIMALS: 3 adult horses. PROCEDURES: Two 15-mm-diameter full-thickness cartilage defects were created on the medial trochlear ridge of each femur. Defects were treated with microfracture and then filled by 1 of 4 techniques: (1) autologous fibrin graft (FG) via subchondral injection of fibrin glue (FG), (2) autologous fibrin graft via direct injection of FG, (3) subchondral injection of a calcium phosphate bone substitute material (BSM) with direct injection of FG, and (4) untreated control. Horses were euthanized after 2 weeks. Patient response was evaluated via serial lameness examination, radiography, magnetic resonance imaging, computed tomography, gross evaluation, microcomputed tomography, and histopathology. RESULTS: All treatments were successfully administered. The injected material perfused through the underlying bone into the respective defects without adversely affecting the surrounding bone and articular cartilage. Increased new bone formation was seen at the margins of the trabecular spaces containing BSM. There was no treatment effect on the amount or composition of tissue within defects. CLINICAL RELEVANCE: The mSCP technique was a simple, well-tolerated technique in this equine articular cartilage defect model without significant adverse effects to host tissues after 2 weeks. Larger studies with long-term follow-ups are warranted.

Atypical Salmonellosis in a Horse: Implications for Hospital Safety.

A 17-year-old Quarter Horse mare was evaluated for colic of 24-hour duration. Clinical signs and diagnostic evaluation were consistent with duodenitis-proximal jejunitis. The horse's clinical condition deteriorated despite medical treatment and was euthanized. Aerobic culture collected from small intestinal ingesta was positive for Salmonella enterica subsp. enterica serovar Hadar. Salmonella sp. is commonly implicated in nosocomial infections in equine veterinary hospitals usually through feces containing the organism. Considering Salmonella sp. was cultured from the jejunal luminal contents and the large volume of nasogastric reflux that was evacuated in this case, a perceived risk of Salmonella sp. transmission from infected gastric reflux to other hospitalized cases was realized. Infectious agent biosecurity precautions should be undertaken in horses with nasogastric reflux to prevent hospital-acquired transmission.

Delayed diagnosis of fatal pneumonic canine plague: clinical and pathologic features in two naturally infected Colorado dogs.

BACKGROUND: Plague caused by Yersinia pestis is a highly infectious and potentially fatal zoonotic disease that can be spread by wild and domestic animals. In endemic areas of the northern hemisphere plague typically cycles from March to October, when flea vectors are active. Clinical forms of disease include bubonic, septicemic, and pneumonic plague. All clinical forms are uncommon in dogs and the pneumonic form is exceedingly rare. CASE PRESENTATION: Two mixed breed young-adult male domestic dogs presented to Colorado veterinarians with fever and vague signs that progressed to hemoptysis within 24 h. Case 1 presented in June 2014, while Case 2 occurred in December 2017. Thoracic radiography of Case 1 and 2 revealed right dorsal and right accessory lobe consolidation, respectively. In Case 1 initial differential diagnoses included pulmonary contusion due to trauma or diphacinone toxicosis. Case 1 was euthanized ~ 24 h post presentation due to progressive dyspnea and hemoptysis. Plague was confirmed 9 days later, after the dog's owner was hospitalized with pneumonia. Case 2 was treated as foreign body/aspiration pneumonia and underwent lung lobectomy at a veterinary teaching hospital. Case 2 was euthanized after 5 days of hospitalization when bacterial culture of the excised lobe yielded Yersinia pestis. Both dogs had severe diffuse necrohemorrhagic and suppurative pneumonia at post mortem examination. CONCLUSIONS: Both dogs were misdiagnosed due to the atypical lobar presentation of an extremely rare form of plague in a species that infrequently succumbs to clinical disease. Presentation outside of the typical transmission period of plague was also a factor leading to delayed diagnosis in Case 2. Erroneous identification by automated bacterial identification systems was problematic in both cases. In endemic areas, plague should be ruled out early in febrile dogs with acute respiratory signs, hemoptysis, lobar or diffuse pathology, and potential for exposure, regardless of season. Seasonal and geographic distributions of plague may shift with climate change, so vigilance by primary care veterinarians is warranted. Timely submission of samples to a veterinary diagnostic laboratory could expedite accurate diagnosis and reduce potential for human and domestic animal exposure.

Cardiopulmonary remodeling in fattened beef cattle: a naturally occurring large animal model of obesity-associated pulmonary hypertension with left heart disease.

The obesity epidemic in developed societies has led to increased cardiovascular diseases including pulmonary hypertension associated with left heart disease (PH-LHD), the largest and fastest-growing class of PH. Similar to obese humans, PH and heart failure (HF) are increasingly recognized in North American fattened beef cattle. We hypothesized that PH and HF in fattened beef cattle are novel, phenotypically distinct manifestations of bovine PH arising from left ventricular (LV) dysfunction similar to obesity-related PH-LHD in humans. We conducted a semi-quantitative histopathological assessment of cardiopulmonary tissues obtained from fattened beef cattle suffering end-stage HF compared to asymptomatic cattle of equivalent age undergoing the same fattening regimens. In HF animals we observed significant LV fibrosis, abundant cardiac adipose depots, coronary artery injury, and pulmonary venous remodeling recapitulating human obesity-related PH-LHD. Additionally, striking muscularization, medial hypertrophy, adventitial fibrosis, and vasa vasorum hyperplasia in the pulmonary arterial circulation were associated with sequela of pathologic right ventricular (RV) remodeling suggesting combined pulmonary venous and arterial hypertension. The association between obesity, pathologic cardiopulmonary remodeling, and HF in fattened beef cattle appears to recapitulate the complex pathophysiology of obesity-associated PH-LHD in humans. This novel, naturally occurring, and large animal model may provide mechanistic and translational insights into human disease.

Interstrain Differences in CO2-Induced Pulmonary Hemorrhage in Mice.

Carbon dioxide is the most commonly used gas for euthanasia of rodents. The current AVMA Guidelines recommend slowly filling the container with CO2 (SF) and now indicate that the practice of placing conscious animals in containers prefilled with CO2 (PF) is unacceptable. An investigator noted pulmonary hemorrhage (PH) in BALB/c mice euthanized by SF that was not observed after PF. Here we evaluated whether the air-displacement rate (SF compared with PF) influenced the development of PH or nasal hemorrhage (NH) in 2 commonly used mouse strains. In addition, we investigated the prevalence of PH and NH in mice euthanized by isoflurane overdose (IO). Male and female (age groups, 6 wk and 6 mo) BALB/c and C57BL/6 mice were euthanized by SF or PF. In addition, 6-mo-old BALB/c male mice were euthanized by IO. Lung, nasal turbinates, brain, and reproductive organs were collected for gross and histologic evaluation and scored for degree of hemorrhage (score, 0 to 3). Severity of hemorrhage did not differ according to mouse age or sex. PH in BALB/c mice was more severe after SF than PF, and SF and PF induced more severe PH in BALB/c than in C57BL/6 mice. PH in 6-mo-old male BALB/c mice was more severe after SF than IO. Neither SF, PF, nor IO influenced the prevalence of NH in any group. This study demonstrates that the method of euthanasia may need to be altered depending on the mouse strain used.

Significance of ERα, HER2, and CAV1 expression and molecular subtype classification to canine mammary gland tumor.

Canine mammary gland tumor (CMT) and human breast cancer (HBC) share many similarities regarding their risk factors, histological features, and behavior. Despite the increasing evidence of molecular marker expression as a prognostic indicator for HBC, few studies have applied this approach to CMT. The aim of the present study is to evaluate the significance of the expression of estrogen receptor-alpha (ERα), human epidermal growth factor receptor 2 (HER2), and caveolin-1 (CAV1) to the behavior and the clinical outcome of CMT. Additionally, the correlation between subtype classification (luminal A, luminal B, HER2-overexpressing, basal-like, and normal-like) and tumor behavior prognosis were assessed. Canine mammary gland tissues were immunohistochemically stained for ERα, HER2, and CAV1 and evaluated and classified into 5 subtypes on the basis of immunoreactivity. Although there were no statistically significant differences in the molecular marker immunoreactivity of different subtypes, the degree of positive staining for ERα, extranuclear ERα, HER2, and CAV1 showed significant correlations (P < 0.05) with the behavior and prognosis of the tumor. The current study indicates the prognostic value of immunohistochemical staining status of ERα, HER2, and CAV1 for CMT. In addition, some trends were seen in subtype classification on the prognosis of the tumor, implying that, although further analysis is needed, there is potential clinical application of 5-subtype classification for CMT.

Producer survey of herd-level risk factors for nursing beef calf respiratory disease.

OBJECTIVE: To identify herd-level risk factors for bovine respiratory disease (BRD) in nursing beef calves. DESIGN: Population-based cross-sectional survey. SAMPLE: 2,600 US cow-calf producers in 3 Eastern and 3 Plains states. PROCEDURES: The associations of herd characteristics with BRD detection in calves and cumulative BRD treatment incidence were determined. RESULTS: 459 (177%) surveys were returned and met the inclusion criteria; 48% and 52% of these surveys were completed by producers in Plains and Eastern states, respectively. Mean (95% confidence interval) number of animals in herds in Plains and Eastern states were 102 (77 to 126) and 48 (40 to 56), respectively. Bovine respiratory disease had been detected in ≥ 1 calf in 21% of operations; ≥ 1 calf was treated for BRD and ≥ 1 calf died because of BRD in 89.2% and 46.4% of operations in which calf BRD was detected, respectively. Detection of BRD in calves was significantly associated with large herd size, detection of BRD in cows, and diarrhea in calves. Calving season length was associated with BRD in calves in Plains states but not Eastern states. Cumulative incidence of BRD treatment was negatively associated with large herd size and examination of cows to detect pregnancy and positively associated with calving during the winter, introduction of calves from an outside source, offering supplemental feed to calves, and use of an estrous cycle synchronization program for cows. CONCLUSIONS AND CLINICAL RELEVANCE: Results of this study indicated factors associated with calf BRD risk; modification of these factors could potentially decrease the incidence of BRD in nursing calves.

Mucosal transmission and pathogenesis of chronic wasting disease in ferrets.

Chronic wasting disease (CWD) of cervids is almost certainly transmitted by mucosal contact with the causative prion, whether by direct (animal-to-animal) or indirect (environmental) means. Yet the sites and mechanisms of prion entry remain to be further understood. This study sought to extend this understanding by demonstrating that ferrets exposed to CWD via several mucosal routes developed infection, CWD prion protein (PrP(CWD)) amplification in lymphoid tissues, neural invasion and florid transmissible spongiform encephalopathy lesions resembling those in native cervid hosts. The ferrets developed extensive PrP(CWD) accumulation in the nervous system, retina and olfactory epithelium, with lesser deposition in tongue, muscle, salivary gland and the vomeronasal organ. PrP(CWD) accumulation in mucosal sites, including upper respiratory tract epithelium, olfactory epithelium and intestinal Peyer's patches, make the shedding of prions by infected ferrets plausible. It was also observed that regionally targeted exposure of the nasopharyngeal mucosa resulted in an increased attack rate when compared with oral exposure. The latter finding suggests that nasal exposure enhances permissiveness to CWD infection. The ferret model has further potential for investigation of portals for initiation of CWD infection.

Evidence for distinct chronic wasting disease (CWD) strains in experimental CWD in ferrets.

Chronic wasting disease (CWD) is an evolving prion disease of cervids (deer, elk and moose) that has been recognized in North America and Korea. Infection of non-cervid reservoir or transport species in nature is not reported. However, the ferret (Mustela putorius furo) is susceptible to CWD after experimental inoculation. Here, we report that infection of ferrets with either of two ferret CWD isolates by various routes of exposure has revealed biologically distinct strain-like properties distinguished by different clinical progression and survival period. The isolates of ferret CWD were also differentiated by the distribution of the infectious prion protein (PrP(CWD)) in the brain and periphery, and by the proteinase K sensitivity of PrP(CWD). These findings suggest that diversity in prion conformers exists in CWD-infected cervids.

Chronic wasting disease prion trafficking via the autonomic nervous system.

Chronic wasting disease (CWD) is a fatal spongiform encephalopathy that is efficiently transmitted among members of the mammalian family Cervidae, including deer, elk, and moose. Typical of prion diseases, CWD is characterized by the conversion of the native protease-sensitive protein PrP(C) to a protease-resistant isoform, denoted PrP(RES). In native species, spread of the disease likely results from the ingestion of prion-containing excreta, including urine, saliva, or feces. Although cervid prion protein-expressing transgenic [Tg(CerPrP)] mice have been shown to be effective surrogates of natural CWD, uncertainties remain regarding the mechanisms by which CWD prions traffic in vivo, including the manner by which CWD prions traffic from the gastrointestinal tract to the central nervous system. We used elk prion protein-expressing transgenic [Tg(CerPrP-E)] mice, infected by three different routes of inoculation, and tissue-based IHC to elucidate that centripetal and centrifugal CWD prion transit pathways involve cells and fibers of the autonomic nervous systems, including the enteric nervous system and central autonomic network. Moreover, we identified CWD PrP(RES) associated with the cell bodies and processes of enteric glial cells within the enteric nervous system of CWD-infected Tg(CerPrP-E) mice. The present findings demonstrate the importance of the peripheral and central autonomic networks in CWD neuroinvasion and neuropathogenesis and suggest that enteroglial cells may facilitate the shedding of prions via the intestinal tract.

Pathogenesis of chronic wasting disease in cervidized transgenic mice.

Chronic wasting disease (CWD) is a fatal, endemic prion disease of wild and captive cervids, including deer, elk, and moose. Typical of prion diseases, CWD is characterized by the conversion of the native, protease-sensitive protein PrP(C) to a protease-resistant isoform, denoted as PrP(RES). Here we have studied the expression of cervid PrP(C) and the pathogenesis of CWD infection in transgenic mice expressing the normal cervid prion protein (Tg[CerPrP] mice). Using tissue-based in situ immunohistochemistry protocols, we first identified cervid PrP(C) expression in the lymphoid, nervous, hemopoietic, endocrine, and certain epithelial tissues of Tg[CerPrP] mice. Tg[CerPrP] mice were then inoculated with CWD via one of four routes (intracerebral, intravenous, intraperitoneal, or oral); all groups developed spongiform encephalopathy, although the oral route required a larger infecting dose. Incubation periods were 184 +/- 13, 218 +/- 15, 200 +/- 7, and 350 +/- 27 days after inoculation, respectively. In longitudinal studies, we tracked the appearance of PrP(RES) in the brain, spleen, Peyer's patches, lymph nodes, pancreatic islets of Langerhans, bone marrow, and salivary glands of preclinical and terminal mice. In addition, we documented horizontal transmission of CWD from inoculated mice and to un-inoculated cohabitant cage-mates. This work documents the multiroute susceptibility, pathogenesis, and lateral transmission of CWD infection in Tg[CerPrP] mice, affirming this model as a robust system to study this cervid transmissible spongiform encephalopathy.

B cells and platelets harbor prion infectivity in the blood of deer infected with chronic wasting disease.

Substantial evidence for prion transmission via blood transfusion exists for many transmissible spongiform encephalopathy (TSE) diseases. Determining which cell phenotype(s) is responsible for trafficking infectivity has important implications for our understanding of the dissemination of prions, as well as their detection and elimination from blood products. We used bioassay studies of native white-tailed deer and transgenic cervidized mice to determine (i) if chronic wasting disease (CWD) blood infectivity is associated with the cellular versus the cell-free/plasma fraction of blood and (ii) in particular if B-cell (MAb 2-104(+)), platelet (CD41/61(+)), or CD14(+) monocyte blood cell phenotypes harbor infectious prions. All four deer transfused with the blood mononuclear cell fraction from CWD(+) donor deer became PrP(CWD) positive by 19 months postinoculation, whereas none of the four deer inoculated with cell-free plasma from the same source developed prion infection. All four of the deer injected with B cells and three of four deer receiving platelets from CWD(+) donor deer became PrP(CWD) positive in as little as 6 months postinoculation, whereas none of the four deer receiving blood CD14(+) monocytes developed evidence of CWD infection (immunohistochemistry and Western blot analysis) after 19 months of observation. Results of the Tg(CerPrP) mouse bioassays mirrored those of the native cervid host. These results indicate that CWD blood infectivity is cell associated and suggest a significant role for B cells and platelets in trafficking CWD infectivity in vivo and support earlier tissue-based studies associating putative follicular B cells with PrP(CWD). Localization of CWD infectivity with leukocyte subpopulations may aid in enhancing the sensitivity of blood-based diagnostic assays for CWD and other TSEs.

Escherichia coli O157:H7 strains that persist in feedlot cattle are genetically related and demonstrate an enhanced ability to adhere to intestinal epithelial cells.

A longitudinal study was conducted to investigate the nature of Escherichia coli O157:H7 colonization of feedlot cattle over the final 100 to 110 days of finishing. Rectal fecal grab samples were collected from an initial sample population of 788 steers every 20 to 22 days and microbiologically analyzed to detect E. coli O157:H7. The identities of presumptive colonies were confirmed using a multiplex PCR assay that screened for gene fragments unique to E. coli O157:H7 (rfbE and fliC(h7)) and other key virulence genes (eae, stx(1), and stx(2)). Animals were classified as having persistent shedding (PS), transient shedding (TS), or nonshedding (NS) status if they consecutively shed the same E. coli O157:H7 genotype (based on the multiplex PCR profile), exhibited variable E. coli O157 shedding, or never shed morphologically typical E. coli O157, respectively. Overall, 1.0% and 1.4% of steers were classified as PS and NS animals, respectively. Characterization of 132 E. coli O157:H7 isolates from PS and TS animals by pulsed-field gel electrophoresis (PFGE) typing yielded 32 unique PFGE types. One predominant PFGE type accounted for 53% of all isolates characterized and persisted in cattle throughout the study. Isolates belonging to this predominant and persistent PFGE type demonstrated an enhanced (P < 0.0001) ability to adhere to Caco-2 human intestinal epithelial cells compared to isolates belonging to less common PFGE types but exhibited equal virulence expression. Interestingly, the attachment efficacy decreased as the genetic divergence from the predominant and persistent subtype increased. Our data support the hypothesis that certain E. coli O157:H7 strains persist in feedlot cattle, which may be partially explained by an enhanced ability to colonize the intestinal epithelium.

Infectious prions in pre-clinical deer and transmission of chronic wasting disease solely by environmental exposure.

Key to understanding the epidemiology and pathogenesis of prion diseases, including chronic wasting disease (CWD) of cervids, is determining the mode of transmission from one individual to another. We have previously reported that saliva and blood from CWD-infected deer contain sufficient infectious prions to transmit disease upon passage into naïve deer. Here we again use bioassays in deer to show that blood and saliva of pre-symptomatic deer contain infectious prions capable of infecting naïve deer and that naïve deer exposed only to environmental fomites from the suites of CWD-infected deer acquired CWD infection after a period of 15 months post initial exposure. These results help to further explain the basis for the facile transmission of CWD, highlight the complexities associated with CWD transmission among cervids in their natural environment, emphasize the potential utility of blood-based testing to detect pre-clinical CWD infection, and could augur similar transmission dynamics in other prion infections.

Performing the field necropsy examination.

This article is designed to aid the practitioner by maximizing the effectiveness of field postmortem diagnostic investigations. Contents include an outline of the procedure for field necropsy of ruminants, recommended tools and supplies, and guidelines for sample collection and submission.

Infectious prions in the saliva and blood of deer with chronic wasting disease.

A critical concern in the transmission of prion diseases, including chronic wasting disease (CWD) of cervids, is the potential presence of prions in body fluids. To address this issue directly, we exposed cohorts of CWD-naïve deer to saliva, blood, or urine and feces from CWD-positive deer. We found infectious prions capable of transmitting CWD in saliva (by the oral route) and in blood (by transfusion). The results help to explain the facile transmission of CWD among cervids and prompt caution concerning contact with body fluids in prion infections.

Comparison of immunochemical (enzyme-linked immunosorbent assay) and immunohistochemical methods for the detection of central nervous system tissue in meat products.

Three methods are widely used in the United States to detect the presence of central nervous system (CNS) tissue in meat products: the fluorescent enzyme-linked immunosorbent assay (F-ELISA), developed in this laboratory, the colorimetric Ridascreen Risk Material 10/5 ELISA (R-ELISA), and the U.S. Department of Agriculture, Food Safety and Inspection Service immunohistochemical (IHC) procedure. These assays are based on the immunological detection of glial fibrillary acidic protein (GFAP), a neural antigen largely restricted to the CNS. The objective of the current study was to compare the sensitivity and repeatability of these tests for detecting the presence of neural tissue in meat. Ground beef spiked with 0.05 to 0.5% of bovine brain, spinal cord (SC), or dorsal root ganglia, as well as advanced meat recovery samples, were evaluated by each of the three GFAP detection procedures. Interassay coefficients of variation for the F-ELISA GFAP standards were 7 to 25%, and intra-assay variation due to sampling and extraction of spiked ground beef was 7 to 13% for SC and 8 to 14% for brain (n = 10). The F-ELISA was the most sensitive of the methods tested, capable of detecting 0.3 ng GFAP standard per well and the presence of 0.05% brain and SC in meat. The R-ELISA standards produced highly variable results (up to 36% variation) and, as a result, none of these standards were different from zero (n = 26). The R-ELISA resulted in high sample variation in SC-spiked ground beef samples (coefficients of variation were 23 to 50%) and did not detect the presence of brain contamination. After modification of the R-ELISA sampling and extraction methods, SC-spiked sample variation was reduced to 16 to 20%, and sensitivity was improved from 0.3 to 0.2% SC, although brain tissue was still not detected. The IHC analysis of CNS-adulterated ground beef had a sensitivity of 0.2% SC and 0.05% brain, with false-negative rates of 10 to 20% at and above the stated sensitivities. None of the methods examined detected dorsal root ganglia contamination. The F-ELISA detected the presence of CNS contamination in 20% of the advanced meat recovery samples, compared to 3.5 to 5% for the R-ELISA and 2% for IHC. This study suggests that the F-ELISA is much more sensitive and repeatable than either the R-ELISA or the IHC procedure method for the detection of CNS tissue in meat products.

Prevalence, outcome, and health consequences associated with persistent infection with bovine viral diarrhea virus in feedlot cattle.

OBJECTIVE: To estimate prevalence of cattle persistently infected (PI) with bovine viral diarrhea virus (BVDV) at arrival at a feedlot, prevalence of chronically ill and dead PI cattle, and the magnitude of excess disease attributable to a PI animal. DESIGN: Cross-sectional and cohort studies. ANIMALS: 2,000 cattle at the time they arrived at a feedlot, 1,383 chronically ill cattle from 7 feedlots, and 1,585 dead cattle from a single feedlot. PROCEDURE: Skin biopsy specimens were collected and evaluated via immunohistochemistry. Cattle were characterized as either PI or not PI with BVDV on the basis of characteristic immunostaining. Follow-up was obtained for the 2,000 cattle from which samples were collected at arrival, and health outcomes were determined for cattle exposed and not exposed to a PI animal. RESULTS: Prevalence of PI cattle was 0.3% at arrival, 2.6% in chronically ill cattle, and 2.5% in dead cattle. Risk of initial treatment for respiratory tract disease was 43% greater in cattle exposed to a PI animal, compared with those not exposed to a PI animal. Overall, 15.9% of initial respiratory tract disease events were attributable to exposure to a PI animal. CONCLUSIONS AND CLINICAL RELEVANCE: Relatively few PI cattle arrive at feedlots. However, those cattle are more likely to require treatment for respiratory tract disease and either become chronically ill or die than cattle that are not PI. In addition, they are associated with an increase in the incidence of respiratory tract disease of in-contact cattle.

Microbiologic findings in feedlot cattle with acute interstitial pneumonia.

OBJECTIVE: To test the hypothesis that feedlot cattle with acute interstitial pneumonia (AIP) have bacterial infection of the lung or liver and concurrent bovine respiratory syncytial virus (BRSV) infection significantly more often than pen mates without AIP ANIMALS: 39 feedlot cattle with signs consistent with AIP and no history of treatment with antimicrobials and 32 healthy control cattle from the same pens. PROCEDURES: Lung and liver specimens were obtained postmortem for bacterial or mycoplasmal culture and histologic examination; lung tissue was assessed for BRSV infection immunohistochemically. RESULTS: Among affected cattle, 26 had AIP confirmed histologically. Lung tissue from 11 cattle with AIP yielded microbial respiratory tract pathogens on culture; tissues from control animals yielded no microbial growth. In 4 cattle with AIP and 2 control animals, liver abscesses were detected; bacteria were isolated from abscessed tissue in 3 and 1 of those animals, respectively. Immunohistochemically, 9 cattle with AIP and no control animals were BRSV-positive. Histologically, 9 AIP-affected cattle had only acute alveolar damage with exudation, and the other 17 had acute exudation with type II pneumocyte hyperplasia. No lesions of AIP were detected in control animals. Only 4 AIP-affected cattle had bacterial infection of the lung with concurrent BRSV infection. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that microbial respiratory tract pathogens are more common in cattle with AIP than in healthy pen mates. Control of bacterial pneumonia late in the feeding period may reduce the incidence of AIP at feedlots where AIP is a problem.

Transmission of prions from mule deer and elk with chronic wasting disease to transgenic mice expressing cervid PrP.

We generated mice expressing cervid prion protein to produce a transgenic system simulating chronic wasting disease (CWD) in deer and elk. While normal mice were resistant to CWD, these transgenic mice uniformly developed signs of neurological dysfunction approximately 230 days following intracerebral inoculation with four CWD isolates. Inoculated transgenic mice homozygous for the transgene array developed disease after approximately 160 days. The brains of sick transgenic mice exhibited widespread spongiform degeneration and contained abnormal prion protein and abundant amyloid plaques, many of which were florid plaques. Transmission studies indicated that the same prion strain caused CWD in the analyzed mule deer and elk. These mice provide a new and reliable tool for detecting CWD prions.