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The purpose of the present study was to evaluate the diagnostic performance of a commercial serum antibody enzyme-linked immunosorbent assay (ELISA) modified to detect anti– Porcine reproductive and respiratory syndrome virus (PRRSV) antibodies in pen-based oral fluid specimens. Experimental and field oral fluid samples of defined status in reference to exposure of swine with PRRSV were used to derive the kinetics of detectable concentrations of antibody against PRRSV. Immunoglobulin (Ig)M and IgA were readily detected in oral fluid specimens from populations in which PRRSV infection was synchronized among all individuals but not in samples collected in commecial herds. In contrast, IgG was readily detected at diagnostically useful levels in both experimental and field samples for up to 126 days. Estimates of the IgG oral fluid ELISA performance were based on results from testing positive oral fluid samples ( n = 492) from experimentally inoculated pigs ( n = 251) and field samples ( n = 241) and negative oral fluid samples ( n = 367) from experimentally inoculated pigs ( n = 84) and field samples ( n = 283). Receiver operating characteristic analysis estimated the diagnostic sensitivity and specificity of the assay as 94.7% (95% confidence interval [CI]: 92.4, 96.5) and 100% (95% CI: 99.0, 100.0), respectively, at a sample-to-positive ratio cutoff of ≥0.40. The results of the study suggest that the IgG oral fluid ELISA can provide efficient, cost-effective PRRSV monitoring in commercial herds and PRRSV surveillance in elimination programs.

A 300-sow farrow-to-finish swine operation in the United States experienced a sudden and severe increase in mortality in neonatal piglets with high morbidity followed by vesicular lesions on the snout and feet of adult females and males. Affected live piglets were submitted for diagnostic investigation. Samples tested polymerase chain reaction (PCR) negative for foot-and-mouth disease virus, porcine delta coronavirus, porcine epidemic diarrhoea virus, porcine rotavirus types A, B and C, transmissible gastroenteritis virus, and porcine reproductive and respiratory syndrome virus. Senecavirus A (SV-A) formerly known as Seneca Valley virus was detected by real-time reverse-transcription polymerase chain reaction (rRT-PCR) from serum, skin and faeces of piglets and from serum and faeces of sows. SV-A was isolated in cell culture from piglet samples. SV-A VP1 gene region sequencing from piglet tissues was also successful. A biosecurity and disease entry evaluation was conducted and identified potential biosecurity risks factors for the entry of new pathogens into the operation. This is the first case report in the United States associating SV-A with a clinical course of severe but transient neonatal morbidity and mortality followed by vesicular lesions in breeding stock animals. Veterinarians and animal caretakers must remain vigilant for vesicular foreign animal diseases and report suspicious clinical signs and lesions to state animal health authorities for diagnostic testing and further investigation.

Senecavirus A has been infrequently associated with vesicular disease in swine since 1988. However, clinical disease has not been reproduced after experimental infection with this virus. We report vesicular disease in 9-week-old pigs after Sencavirus A infection by the intranasal route under experimental conditions.

bWe performed a longitudinal field study in a swine breeding herd that presented with an outbreak of vesicular disease (VD) that was associated with an increase in neonatal mortality. Initially, a USDA Foreign Animal Disease (FAD) investigation confirmed the presence of Senecavirus A (SVA) and ruled out the presence of exotic agents that produce vesicular lesions, e.g., foot-andmouth disease virus and others. Subsequently, serum samples, tonsil swabs, and feces were collected from sows (n ‫؍‬ 22) and their piglets (n ‫؍‬ 33) beginning 1 week after the onset of the clinical outbreak and weekly for 6 weeks. The presence of SVA RNA was evaluated in all specimens collected by reverse transcriptase quantitative PCR (RT-qPCR) targeting a conserved region of the 5= untranslated region (5=-UTR). The serological response (IgG) to SVA was evaluated by the weekly testing of sow and piglet serum samples on a SVA VP1 recombinant protein (rVP1) indirect enzyme-linked immunosorbent assay (ELISA). The rVP1 ELISA detected seroconversion against SVA in clinically affected and non-clinically affected sows at early stages of the outbreak as well as maternal SVA antibodies in offspring. Overall, the absence of vesicles (gross lesions) in SVA-infected animals and the variability of RT-qPCR results among specimen type demonstrated that a diagnostic algorithm based on the combination of clinical observations, RT-qPCR in multiple diagnostic specimens, and serology are essential to ensure an accurate diagnosis of SVA. S enecavirus A (SVA), formerly Seneca Valley virus (SVV), is a nonenveloped, single-stranded, positive-sense RNA virus that belongs to the genus Senecavirus in the family Picornaviridae (1). The virus was first described as a contaminant of a PER C6 cell line (2). The virus encodes one polyprotein that is posttranslationally processed by virus-encoded proteases into 4 structural (VP1 to VP4) and 7 nonstructural (2A to 2C and 3A to 3D) proteins (2, 3). The pathogenic role of these SVA proteins is unknown, but VP1 is considered to be the most immunogenic protein in viruses of the Picornaviridae family (4, 5).Idiopathic vesicular disease (IVD), a sporadic and transient condition affecting swine, has been reported in pigs in Australia, New Zealand, and the United States (6-8). It was not until 2007 that the presence of SVA was linked with IVD outbreaks in Canada (9). Most recently, SVA was detected in sporadic and transient outbreaks of IVD in the United States, Brazil, and China (10-13). Lesions observed in cases of IVD associated with SVA infection are characterized by vesicle formations and epidermal erosions that progress to ulcers of the coronary band, oral cavity, and nasal planum. Affected animals present transient fever and lameness. Vesicular lesions in pigs resemble those in other foreign vesicular diseases, such as foot-and-mouth disease (FMD), vesicular stomatitis (VS), swine vesicular disease (SVD), and vesicular exanthema of swine (VES). In addition, numerous reports associate the presence of SVA with increased ne...

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Pen-based oral fluid sampling has proven to be an efficient method for surveillance of infectious diseases in swine populations. To better interpret diagnostic results, the performance of oral fluid assays (antibody- and nucleic acid-based) must be established for pen-based oral fluid samples. Therefore, the objective of the current study was to determine the probability of detecting Porcine reproductive and respiratory syndrome virus (PRRSV) infection in pen-based oral fluid samples from pens of known PRRSV prevalence. In 1 commercial swine barn, 25 pens were assigned to 1 of 5 levels of PRRSV prevalence (0%, 4%, 12%, 20%, or 36%) by placing a fixed number (0, 1, 3, 5, or 9) of PRRSV-positive pigs (14 days post PRRSV modified live virus vaccination) in each pen. Prior to placement of the vaccinated pigs, 1 oral fluid sample was collected from each pen. Thereafter, 5 oral fluid samples were collected from each pen, for a total of 150 samples. To confirm individual pig PRRSV status, serum samples from the PRRSV-negative pigs ( n = 535) and the PRRSV vaccinated pigs ( n = 90) were tested for PRRSV antibodies and PRRSV RNA. The 150 pen-based oral fluid samples were assayed for PRRSV antibody and PRRSV RNA at 6 laboratories. Among the 100 samples from pens containing ≥1 positive pig (≥4% prevalence) and tested at the 6 laboratories, the mean positivity was 62% for PRRSV RNA and 61% for PRRSV antibody. These results support the use of pen-based oral fluid sampling for PRRSV surveillance in commercial pig populations.

Epidemiological investigations were conducted on a case series of six Senecavirus A (SVA)-affected breeding herds in the United States to determine potential routes of introduction and enhance the swine industry's knowledge of SVA's clinical presentation and spread. Each SVA-affected herd was evaluated using a standard form to ensure that all relevant data were collected. The form was used to guide a detailed discussion about the clinical presentation of SVA and risk events that occurred in the 4 weeks prior to the first observation of clinical signs with the herd veterinarian and farm personnel. Each event was then subjectively assigned a risk level of low, medium or high likelihood for SVA introduction by the investigation team. The clinical presentation of SVA varied by case. All SVA-affected herds (six of six) reported increases in pre-weaning mortality and sow anorexia. Vesicular lesions were observed in four of six herds, and mild-to-moderate neonatal diarrhoea was observed in three of six herds. No gross anatomic or histologic lesions were observed in neonatal pigs that tested positive for SVA via PCR. Multiple potential routes of introduction were identified. Events subjectively rated as high risk for SVA introduction were on-farm employee entry (six of six), carcass disposal (four of six), cull sow removal (three of six) and breeding replacement entry (two of six). Non-swine domestic animals, rodents, other visitors, repairs outside swine barns, feed delivery, weaned pig removal and semen entry were assigned a high risk level in one of six herds. Cases occurred in breeding herds of all sizes with variable biosecurity in both swine dense and swine sparse areas.