The purpose of this study was to investigate the relationship between swine health status and the concentration of the serum acute phase proteins, haptoglobin (HP), and C-reactive protein (CRP). A total of 378 clinically healthy pigs from farms A and B, plus 20 pigs culled from farm A due to poor growth, were used in this experiment. Each pig was examined and blood samples were collected during slaughter. The HP concentration was measured by using an HP-hemoglobin binding assay. The CRP concentration was measured by using a CRP enzyme immunoassay. Gross and histopathological lesions were examined and recorded at slaughter. Representative samples were then collected in order to isolate pathogens. Swine enzootic pneumonia, found in 47.7% of the pigs, was the most common lesion. Other lesions included pleuropneumonia (32.7%), suppurative pneumonia (10.3%), fibrinous pericardititis (4.3%), Ascaris migration in the liver (33.9%), and intestinal serositis (3.0%). On farm A, the percentage of pigs with 1 or more lesions was 88.2%. For culled pigs from farm A, the mean serum concentrations of HP and CRP were 2.23 +/- 0.14 mg/mL and 252.93 +/- 11.62 μg/mL, which were significantly higher than concentrations in clinically normal pigs (1.42 +/- 0.02 mg/mL and 84.88 +/- 2.61 μg/mL, respectively, P < 0.01). Moreover, among clinically normal farm A pigs, the mean HP concentration in pigs with lesions (1.43 +/- 0.02 mg/mL) was significantly higher than in pigs without lesions (1.32 +/- 0.07 mg/mL) (P < 0.05). However, the mean serum CRP concentrations in these animals were not significantly different. On farm B, the percentage of pigs with one or more lesions was 50.0%. Interestingly, the mean serum HP concentration in clinically normal pigs with lesions was significantly lower in farm B pigs (1.23 +/- 0.07 mg/mL) than in the farm A pigs (1.43 +/- 0.02 mg/mL; P < 0.01). However, serum CRP concentrations in farm A and B pigs were not significantly different. Serum HP concentration, which is a better indicator of inflammatory reactions in pig herds than serum CRP concentration, provides an important marker for swine health status.

Objective-To develop a spatial epidemic model to simulate intraherd and interherd transmission of footand- mouth disease (FMD) virus. Sample Population-2,238 herds, representing beef, dairy, swine, goats, and sheep, and 5 sale yards located in Fresno, Kings, and Tulare counties of California. Procedure-Using Monte-Carlo simulations, a spatial stochastic epidemic simulation model was developed to identify new herds that would acquire FMD following random selection of an index herd and to assess progression of an epidemic after implementation of mandatory control strategies. Results-The model included species-specific transition periods for FMD infection, locations of herds, rates of direct and indirect contacts among herds, and probability distributions derived from expert opinions on probabilities of transmission by direct and indirect contact, as well as reduction in contact following implementation of restrictions on movements in designated infected areas and surveillance zones. Models of supplemental control programs included slaughter of all animals within a specified distance of infected herds, slaughter of only high-risk animals identified by use of a model simulation, and vaccination of all animals within a 5- to 50-km radius of infected herds.

During infection, nutrient deprivation can alter bacterial phenotype. This, in turn, may have implications for pathogenesis and prophylaxis. Actinobacillus pleuropneumoniae (biotype 1) and Haemophilus parasuis, respiratory tract pathogens of swine, are both V-factor-dependent. The concentrations of V factor in the extracellular fluids of pigs are unknown and may limit the growth of these bacteria in vivo. The aim of this study was to determine the concentrations of nicotinamide adenine dinucleotide (NAD) in select porcine body fluids and to compare the availability of NAD in vivo with the affinities of the organisms for this compound. Levels in plasma, tissue fluids (peritoneal, pleural, synovial, and cerebrospinal), and laryngeal, tracheal, and lung washings were determined with an enzymatic cycling assay. We concluded that, although the NAD supply in the respiratory tract is probably not growth-limiting, it may become limiting if the organisms are disseminated.

Objective-To compare measurements of blood flow in the common femoral artery obtained by duplex Doppler ultrasonography (DDU) and a reference ultrasonic transit-time flow (TTF) method and to examine the impact of Doppler spectral waveform measurement techniques on volumetric estimates. Animals-5 healthy female pigs. Procedure-Femoral arterial blood flow was measured simultaneously in anesthetized pigs by use of a TTF probe (left femoral artery) and transcutaneous DDU (right femoral artery). A range of flow states was induced pharmacologically by using xylazine, bradykinin, dobutamine, and isoflurane. Volumetric blood flow was calculated from DDU waveforms, using the product of the flow velocity integral (FVI), the cross-sectional vessel area, and heart rate. Three calculations of FVI were obtained by manually tracing the Doppler spectral envelopes at the outer envelope, the modal, and the inner envelope of the spectral dispersion pattern. Data analysis included calculation of Pearson correlation coefficients and Bland-Altman limits of agreement. Results-Blood flow measured by DDU was more closely correlated with TTF measurements when the modal or inner envelope tracing method was used ( r, 0.76 and 0.78; limits of agreement, -100 to 54.2 and -48.5 to 77.0 mL/min, respectively). Limits of agreement for the outer envelope tracing method were -238.5 to 64 mL/min. Conclusion and Clinical Relevance-Transcutaneous DDU is a reliable noninvasive technique for measuring blood flow in the femoral artery of pigs over a range of flow states. Tracing the inner envelope of the Doppler spectral dispersion pattern provided the best estimate of blood flow in this study.

A polymerase chain reaction (PCR) assay was combined with a broth-culture enrichment system to detect Salmonella shed in feces from subclinically infected swine. The effectiveness of the broth culture-polymerase chain reaction (BC-PCR) assay to identify pigs shedding Salmonella in feces was compared with a microbiological culture and a commercial enzyme linked immunosorbent assay (ELISA) kit to detect Salmonella-specific serum antibody. A total of 67 pigs were tested by each of the 3 methodologies. Forty-one pigs tested positive for Salmonella by BC-PCR and ELISA identified 6 positives and 23 suspicious samples. It was shown that the BC-PCR assay is a rapid diagnostic tool for detecting of Salmonella shed by asymptomatic swine compared with current diagnostic technologies.

Previous studies demonstrated that the polyanion dextran sulfate (DS) protects rat coronary and porcine aortic endothelium (PAE) from oxygen-derived free radical (OFR) injury due to hydrogen peroxide (H2O2) or xanthine/xanthine oxidase (X/XO). To determine if DS has a similar protective effect in bovine aortic endothelium (BAE) and bovine brain microvascular endothelium (BBME), H2O2 or X/XO was added to confluent cultures. Cell injury was assessed 1 d later by measuring the percentage of viable cells (by trypan blue exclusion) and the release of lactate dehydrogenase (LDH) into the medium. After H2O2 doses of 6.0 mM for BAE and BBME and 0.8 mM for PAE, and after X doses of 10 μM and XO doses of 0.3 U/mL for all cell types, approximately 50% of cells were viable. Cultures were pretreated with DS (0.001 to 500 μg/mL) 24 to 26 h prior to H2O2 or X/XO exposure. Pretreatment at concentrations of 0.5, 5, and 50 μg/mL significantly increased the percentage of viable cells and reduced LDH release in cultures of PAE, but not BAE or BBME, treated with H2O2. Similarly, pretreatment with DS concentrations of 5 and 50 μg/mL significantly increased the percentage of viable cells and reduced LDH release in cultures of PAE, but not BAE or BBME, treated with X/XO. Thus, DS protected porcine but not bovine endothelium. Catalase (10 U/mL) increased the percentage of viable cells and reduced LDH release in H2O2-treated BAE and BBME, suggesting that DS likely acts by a different mechanism and does not neutralize H2O2. These results suggest that the protective effect of DS on OFR-injured endothelium is species-dependent.

The objective of this study was to determine whether mosquitoes, Aedes vexans (Meigen), could serve as biological vectors of porcine reproductive and respiratory syndrome virus (PRRSV). Specifically, the study assessed the duration of viability and the site of PRRSV within mosquitoes, and evaluated whether PRRSV could be transmitted to a susceptible pig by mosquitoes following a 7- to 14-day incubation period after feeding on an infected pig. For the first experiment, a total of 100 mosquitoes were allowed to feed on a pig, experimentally infected with PRRSV (day 7 post-inoculation) and were then maintained alive under laboratory conditions. A set of 10 mosquitoes were collected at 0 hour (h), 6 h, 12 h, 24 h, 48 h, 72 h, 5 days (d), 7 d, 10 d, and 14 d post-feeding (pf). Samples of exterior surface washes, salivary glands, thorax carcasses, and gut homogenates were collected from each set of mosquitoes, and tested for PRRSV. Infectious PRRSV was detected by polymerase chain reaction and swine bioassay only from the gut homogenates of mosquitoes collected at 0 h and 6 h pf. For the second experiment, a total of 30 mosquitoes were allowed to feed on a pig, experimentally infected with PRRSV and the mosquitoes were then maintained under laboratory conditions. On each of day 7, 10, and 14 pf, a set of 10 mosquitoes were allowed to feed on a susceptible pig. Transmission of PRRSV to susceptible pigs did not occur, and PRRSV was not detected from the mosquitoes. These findings indicate that mosquitoes are not likely to serve as biological vectors of PRRSV.

Four different experimental models for Streptococcus suis-induced disease were compared to find a model that closely mimics naturally occurring disease in conventional pigs. Fourteen, 2-week old pigs free of S. suis type 2 were used in 2 experiments. In experiment 1, 3 pigs were inoculated intravenously (IV) and 3 pigs intranasally (IN) with S. suis. Two out of 3 of the IV-inoculated pigs exhibited signs of severe central nervous system disease (CNS) and were euthanized. Streptococcus suis type 2 was isolated from whole blood, joints, and serosal surfaces of both pigs. No clinical signs and no growth of S. suis were detected in the IN-inoculated pigs. In experiment 2, 4 pigs were inoculated IV and another 4 were inoculated IN with the same isolate as in experiment 1. One hour before inoculation the IN-inoculated pigs were given 5 mL of 1% acetic acid intranasally (IN-AA). All the IV-inoculated pigs showed CNS disease and lameness, and 2 of the pigs became severely affected and were euthanized. All the IN-AA inoculated pigs exhibited roughened hair coats and 2 pigs developed severe CNS disease and were euthanized. Streptococcus suis was isolated from the joints and blood of 3 pigs in the IV-inoculated group. Streptococcus suis was isolated from blood of 2 pigs, meninges of 3 pigs, and joints of 1 pig in the IN-AA inoculated group. Natural exposure to S. suis most likely occurs by the intranasal route. The IN-AA model should serve as a good model for S. suis-induced disease, because the natural route of exposure is intranasal and the IN-AA model was effective in inducing disease that mimics what is observed in the field.

The objectives of the study were to determine the duration of porcine reproductive and respiratory syndrome virus (PRRSV) survival in houseflies (Musca domestica Linnaeus) following feeding on an infected pig, and to determine whether the virus was present on the exterior surface or within the internal viscera of the fly. A total of 210 laboratory-colonized houseflies were allowed to feed to repletion on a pig, experimentally infected with PRRSV on day 7 postinoculation, and then maintained alive under laboratory conditions (27°C). Two subsets (A and B) of 30 flies were collected at each of the following sampling points; 0, 6, and 12 hours post feeding (pf). Subset A contained an extra group of 30 flies collected at 24 hours pf due to the availability of extra flies. Flies in subset A were processed as whole fly homogenates, while the exterior surface washes and digestive organs were collected from flies in subset B. Whole fly homogenates, collected at 0, 6, and 12 hours pf, were positive by both polymerase chain reaction (PCR) and swine bioassay. Digestive organs, collected at 0 and 12 hours pf, were positive by PCR and swine bioassay. The PRRSV RNA was detected by PCR from the exterior surface wash of subset B flies collected at 0, 6, and 12 hours pf; however, only the subset collected at 0 hour pf was swine bioassay-positive. This study indicates that infectious PRRSV can survive within the intestinal tract of houseflies for up to 12 hours following feeding on an infected pig, but only for a short period on the exterior surface of the flies.

The reference strains representing serotypes 1 to 12 of Actinobacillus pleuropneumoniae biotype 1 were examined for their ability to utilize porcine hemoglobin (Hb) or porcine hemin (Hm) as iron sources for growth. In a growth promotion assay, all of the reference strains were able to use porcine Hb, and all strains except 2 were able to use porcine Hm. Using a preliminary characterization procedure with Hm- or Hb-agarose, Hm- and Hb-binding outer membrane proteins (OMPs) of approximately 75 kDa were isolated from A. pleuropneumoniae serotype 1 strain 4074 grown under iron-restricted conditions. Matrix-assisted laser desorption ionization/time-of-flight (MALDI-TOF) analysis revealed a number of common tryptic peptides between the Hb-agarose- and Hm-agarose-purified 75 kDa OMPs, strongly suggesting that these peptides originate from the same protein. A database search of these peptide sequences revealed identities with proteins from various Gram-negative bacteria, including iron-regulated OMPs, transporter proteins, as well as TonB-dependent receptors. Taken together, our data suggest that A. pleuropneumoniae synthesizes potential Hm- and Hb-binding proteins that could be implicated in the iron uptake from porcine Hb and Hm.