Objective-To use mathematical modeling to assess the effectiveness of control strategies for porcine reproductive and respiratory syndrome (PRRS) virus on a swine farm. Sample-A hypothetical small, medium, or large farrow-to-weaning swine farm in the Midwestern United States. Procedures-Stochastic models were formulated to simulate an outbreak of PRRS on a farm. Control strategies assessed in those models included none (baseline) and various combinations of mass immunization, herd closure, and gilt acclimatization. Nine different models resulting from the combination of low, moderate, or high PRRS virus virulence and small, medium, or large herd size were simulated. A stabilized status, the outcome of interest, was defined as the absence of positive PCR assay results for PRRS virus in 3-week-old piglets. For each scenario, the percentage of simulations with a stabilized status was used as a proxy for the probability of disease control. Results-Increasing PRRS virus virulence and herd size were negatively associated with the probability of achieving a stabilized status. Repeated mass immunization with herd closure or gilt acclimitization was a better alternative than was single mass immunization for disease control within a farm. Conclusions and Clinical Relevance-Repeated mass immunization with a PRRS modified-live virus vaccine with herd closure or gilt acclimitization was the scenario most likely to achieve a stabilized status. Estimation of the cost of various PRRS control strategies is necessary.

Objective-To compare bronchoalveolar lavage (BAL) fluid obtained by manual aspiration (MA) with a handheld syringe with that obtained by suction pump aspiration (SPA) in healthy dogs. Animals-13 adult Beagles. Procedures-Each dog was anesthetized and bronchoscopic BAL was performed. The MA technique was accomplished with a 35-mL syringe attached to the bronchoscope biopsy channel. The SPA technique was achieved with negative pressure (5 kPa) applied to the bronchoscope suction valve with a disposable suction trap. Both aspiration techniques were performed in each dog in randomized order on opposite caudal lung lobes. Two 1 mL/kg aliquots of warm saline (0.9% NaCl) solution were infused per site. For each BAL fluid sample, the percentage of retrieved fluid was calculated, the total nucleated cell count (TNCC) and differential cell count were determined, and semiquantitative assessment of slide quality was performed. Comparisons were made between MA and SPA techniques for each outcome. Results-1 dog was removed from the study because of illness. The mean percentage of fluid retrieved (mean difference, 23%) and median TNCC (median distribution of differences, 100 cells/μL) for samples obtained by SPA were significantly greater than those for samples obtained by MA. Conclusions and Clinical Relevance-In healthy dogs, BAL by SPA resulted in a significantly higher percentage of fluid retrieval and samples with a higher TNCC than did MA. Further evaluation of aspiration techniques in dogs with respiratory tract disease is required to assess whether SPA improves the diagnostic yield of BAL samples.

Objective—To compare the anesthetic efficacy and adverse effects associated with peribulbar injection of ropivacaine (1% solution) performed with and without ultrasound guidance (UG) in dogs. Animals—15 dogs without ophthalmologic abnormalities. Procedures—Each dog was sedated and anesthetized. A peribulbar injection of ropivacaine (1% solution; 0.3 mL/kg) was performed with UG in 1 eye and without UG in the contralateral eye (control). For each eye, the intraocular pressure (IOP) immediately after eye centralization and number of punctures were recorded; ophthalmic complications, postinjection corneal sensitivity (determined by Cochet-Bonnet esthesiometry), durations of the sensory and motor blockades (the latter determined as the interval to restoration of the vestibuloocular reflex, pupillary light reflex, and conjugate eye movement), and blockade quality were assessed in both eyes following anesthetic recovery. Results—Needle placement was fully visualized in 8 of the 15 eyes injected with UG. For eyes injected with or without UG, there was no difference with regard to the number of punctures, postinjection corneal sensitivity, and sensory or motor blockade duration and quality; however, restoration of conjugate eye movement occurred later in control eyes. For eyes injected with UG, mean IOP was 18.6 mm Hg, compared with 23.3 mm Hg for control eyes. Incidence of subconjunctival hemorrhage was higher for control eyes; severity of chemosis and hyperemia varied over time within both groups of eyes. Conclusion and Clinical Relevance—In dogs, peribulbar injection of ropivacaine with UG is feasible in dogs and provides effective sensory and motor blockades similar to those achieved with conventional techniques.

Objective—To determine dose dependency of tranexamic acid–induced emesis and the time course of the antifibrinolytic potency of tranexamic acid in dogs. Animals—10 Beagles. Procedures—In a dose-escalating experiment, ascending doses of tranexamic acid (10, 20, and 30 mg/kg, IV) were administered at 5-minute intervals until vomiting was observed. In a separate single-dose experiment, ascending doses of tranexamic acid (20, 30, 40, and 50 mg/kg, IV) were administered at 1-week intervals until vomiting was observed. Time to onset of vomiting and number of vomiting episodes were measured in both experiments. In a coagulation experiment, a single 50 mg/kg bolus of tranexamic acid was administered, and blood was obtained 1 hour before and 20 minutes, 3 hours, and 24 hours after administration. Antifibrinolytic potency of tranexamic acid was evaluated by use of a modified rotational thromboelastography method. Results—Tranexamic acid induced vomiting in a dose-dependent manner. Vomiting frequency was < 2 episodes, and vomiting concluded < 250 seconds after administration. Antifibrinolytic potency of tranexamic acid was significantly higher at 20 minutes following administration, but not different by 24 hours, when compared with the potency measured before administration. No adverse effects were observed in any experiment. Conclusions and Clinical Relevance—IV administration of tranexamic acid induced emesis in a dose-dependent manner. The antifibrinolytic potency of tranexamic acid decreased in a time-dependent manner and was resolved < 24 hours after administration. Further studies are warranted to investigate the emetic and other adverse effects of tranexamic acid in dogs of various breeds and ages.

Objective—To image the spatial distribution of pulmonary blood flow by means of scintigraphy, evaluate ventilation-perfusion (VA/Q) matching and pulmonary blood shunting (Qs/Qt) by means of the multiple inert gas elimination technique (MIGET), and measure arterial oxygenation and plasma endothelin-1 concentrations before, during, and after pulse-delivered inhaled nitric oxide (PiNO) administration to isoflurane-anesthetized horses in dorsal recumbency. Animals—3 healthy adult Standardbreds. Procedures—Nitric oxide was pulsed into the inspired gases in dorsally recumbent isoflurane-anesthetized horses. Assessment of VA/Q matching, Qs/Qt, and Pao2 content was performed by use of the MIGET, and spatial distribution of pulmonary blood flow was measured by perfusion scintigraphy following IV injection of technetium Tc 99m–labeled macroaggregated human albumin before, during, and 30 minutes after cessation of PiNO administration. Results—During PiNO administration, significant redistribution of blood flow from the dependent regions to the nondependent regions of the lungs was found and was reflected by improvements in VA/Q matching, decreases in Qs/Qt, and increases in Pao2 content, all of which reverted to baseline values at 30 minutes after PiNO administration. Conclusions and Clinical Relevance—Administration of PiNO in anesthetized dorsally recumbent horses resulted in redistribution of pulmonary blood flow from dependent atelectatic lung regions to nondependent aerated lung regions. Because hypoxemia is commonly the result of atelectasis in anesthetized dorsally recumbent horses, the addition of nitric oxide to inhaled gases could be used clinically to alleviate hypoxemia in horses during anesthesia.

Objective—To evaluate the use of a micro-lightguide tissue spectrophotometer for measurement of tissue oxygenation and blood flow in the small and large intestines of horses under anesthesia. Animals—13 adult horses without gastrointestinal disease. Procedures—Horses were anesthetized and placed in dorsal recumbency. Ventral midline laparotomy was performed. Intestinal segments were exteriorized to obtain measurements. Spectrophotometric measurements of tissue oxygenation and regional blood flow of the jejunum and pelvic flexure were obtained under various conditions that were considered to have a potential effect on measurement accuracy. In addition, arterial oxygen saturation at the measuring sites was determined by use of pulse oximetry. Results—12,791 single measurements of oxygen saturation, relative amount of hemoglobin, and blood flow were obtained. Errors occurred in 381 of 12,791 (2.98%) measurements. Most measurement errors occurred when surgical lights were directed at the measuring site; covering the probe with the surgeon's hand did not eliminate this error source. No measurement errors were observed when the probe was positioned on the intestinal wall with room light, at the mesenteric side, or between the mesenteric and antimesenteric side. Values for blood flow had higher variability, and this was most likely caused by motion artifacts of the intestines. Conclusions and Clinical Relevance—The micro-lightguide spectrophotometry system was easy to use on the small and large intestines of horses and provided rapid evaluation of the microcirculation. Results indicated that measurements should be performed with room light only and intestinal motion should be minimized.

Objective—To evaluate the efficacy and effects of labeling equine umbilical cord blood (UCB)– and bone marrow (BM)–derived multipotent mesenchymal stromal cells (MSCs) with an ultrasmall uperparamagnetic iron oxide (SPIO) contrast agent and the detection of labeled MSCs by use of MRI. Sample—UCB MSCs from placental tissues of 5 foals and BM MSCs from 5 horses. Procedures—UCB and BM MSC cultures were seeded in duplicate (5,000 cells/cm2). One duplicate was incubated with SPIO (50 μg/mL); the other was processed identically, but without SPIO. Mesenchymal stromal cells were expanded in triplicates for 5 passages and assessed for viability and proliferative capacity, labeling efficacy, and labeled cell proportion. For MRI detection, 5 × 106 labeled BM MSCs from passage 1 or 2 were injected into a collagenase-induced superficial digital flexor tendon defect of an equine cadaveric forelimb from 2 horses. Results—For passages 1, 2, and 3, labeling efficacy and cell proportion for UCB MSCs (99.6% [range, 98.8% to 99.9%], 16.6% [range, 6.5% to 36.1%], and 1.0% [range, 0.4% to 2.8%], respectively) were significantly higher than for BM MSCs (99.2% [range, 97.8% to 99.7%], 4.5% [range, 1.6% to 11.8%], and 0.2% [range, 0.1% to 0.6%], respectively). Labeling was not detectable after passage 3. Viability of MSCs was not affected, but cell doubling time increased in labeled MSCs, compared with that of unlabeled MSCs. On MRI 3-D T2*-weighted fast gradient echo sequences, decreased signal intensity was observed for BM passage 1 MSCs. Conclusions and Clinical Relevance—Equine UCB and BM MSCs were labeled with SPIO at high efficiencies.

Objective-To determine the usefulness of retina samples for detection of disease-associated prion protein by use of a commercially available enzyme immunoassay (EIA) intended for rapid identification of sheep and cattle with transmissible spongiform encephalopathies (TSEs). Samples-Retina, brainstem at the level of the obex, and retropharyngeal lymph node samples obtained from 15 TSE-inoculated sheep (scrapie [n = 13] or transmissible mink encephalopathy passaged through a bovid [2]); retina and brainstem samples obtained from 11 TSE-inoculated cattle (transmissible mink encephalopathy passaged through a bovid [7] or classical BSE [4]); and negative control tissue samples obtained from 2 sheep and 2 cattle that were not inoculated with TSEs. Procedures-Tissue samples were homogenized and analyzed for detection of abnormally folded disease-associated prion protein with a commercially available EIA and 2 confirmatory assays (western blot analysis or immunohistochemical analysis). Results-Retina sample EIA results were in agreement with results of brainstem sample EIA or confirmatory assay results for negative control animals and TSE-inoculated animals with clinical signs of disease. However, TSE-inoculated animals with positive confirmatory assay results that did not have clinical signs of disease had negative retina sample EIA results. Retina sample EIA results were in agreement with brainstem sample immunohistochemical results for 4 TSE-inoculated sheep with negative retropharyngeal lymph node EIA results. Conclusions and Clinical Relevance-Results of this study suggested that retina samples may be useful for rapid EIA screening of animals with neurologic signs to detect TSEs.

The objective of this pilot study was to determine the efficacy of inactivated (1 or 2 dose) and live-attenuated chimeric porcine circovirus (PCV)1-2 vaccines in sows using the PCV2-spiked semen model. Thirty-five sows were randomly divided into 6 groups: negative and positive controls, 1 dose inactivated PCV1-2 vaccine challenged (1-VAC-PCV2), 2 dose inactivated PCV1-2 vaccine challenged (2-VAC-PCV2), 1 dose live-attenuated PCV1-2 vaccine unchallenged (1-LIVE-VAC), and 1 dose live-attenuated PCV1-2 vaccine challenged (1-LIVE-VAC-PCV2). The inactivated PCV1-2 vaccine induced higher levels of PCV2-specific antibodies in dams. All vaccination strategies provided good protection against PCV2 viremia in dams, whereas the majority of the unvaccinated sows were viremic. Four of the 35 dams became pregnant: a negative control, a positive control, a 2-VAC-PCV2 sow, and a 1-LIVE-VAC-PCV2 sow. The PCV2 DNA was detected in 100%, 67%, and 29% of the fetuses obtained from the positive control, inactivated vaccinated, or live-attenuated vaccinated dams, respectively. The PCV2 antigen in hearts was only detectable in the positive control litter (23% of the fetuses). The PCV1-2 DNA was detected in 29% of the fetuses in the litter from the 1-LIVE-VAC-PCV2 dam. Under the conditions of this pilot study, both vaccines protected against PCV2 viremia in breeding age animals; however, vertical transmission was not prevented.