Paul Yeske

Role of transportation in spread of porcine epidemic diarrhea virus infection, United States.

After porcine epidemic diarrhea virus (PEDV) was detected in the United States in 2013, we tested environmental samples from trailers in which pigs had been transported. PEDV was found in 5.2% of trailers not contaminated at arrival, , suggesting that the transport process is a source of transmission if adequate hygiene measures are not implemented.

Porcine reproductive and respiratory syndrome virus infection in neonatal pigs characterised by marked neurovirulence

Neonatal pigs from three herds of pigs were somnolent and inappetent and had microscopic lesions characterised by severe meningoencephalitis, necrotic interstitial pneumonia and gastric muscular inflammation. Porcine reproductive and respiratory syndrome virus (PRRSV) infection was diagnosed and confirmed by virus isolation, fluorescent antibody examination of frozen lung sections, serology, immunohistochemistry and in situ hybridisation. Each herd had a history of PRRSV infection and was using or had used a modified-live vaccine. The isolates from the affected pigs were genetically distinct from the modified-live vaccine strain of the virus when compared by restriction enzyme analysis and nucleotide sequencing of PRRSV open reading frames 5 and 6. The virus was identified in macrophages or microglia of brain lesions by immunohistochemical staining of brain sections with an anti-PRRsv monoclonal antibody and an anti-macrophage antibody. The replication of the virus in the brain was verified by in situ hybridisation. The meningoencephalitis induced by the virus in pigs from each of the herds was unusually severe and the brain lesions were atypical when compared with other descriptions of encephalitis induced by the virus, which should therefore be considered as a possible diagnosis for neonatal pigs with severe meningoencephalitis. In addition, field isolates of the virus which are capable of causing disease can emerge and coexist with modified-live vaccine virus in some pig herds.

Previous infection of sows with a “mild” strain of porcine epidemic diarrhea virus confers protection against infection with a “severe” strain

Porcine epidemic diarrhea virus (PEDv) infected approximately 50% of the US swine breeding herds from July 2013 to July 2014 as estimated by the Swine Health Monitoring Project. In the absence of effective vaccines or standard control protocols, there is an urgent need for evidence of cross-protective immune countermeasures. Here, we evaluated the response of 3-day-old piglets born to sows exposed seven months earlier to a mild strain of PEDv to challenge with a virulent PEDv isolate. Piglet survival to one week of age was 100% compared to 67% in piglets born to sows not previously exposed, and morbidity was 43% compared to 100%, respectively. At necropsy at 7 days of age, the PEDv Ct value was 23.6 (range 16.6-30.6) in intestinal contents, compared to 17.2 (range 15.9-18.5) (p<0.06) in litters from sows with no previous exposure to PEDv. The findings indicated that durable lactogenic immunity was present in sows previously exposed to a mild strain of PEDv and this immunity induced cross-protection to representative virulent PEDv. Thus, a naturally attenuated form of PEDv provided significant passive immune protection for seven months against piglet challenge with virulent PEDv.

Diarrhea Associated with Clostridium Perfringens Type A Enterotoxin in Neonatal Pigs

2,7,12 but has not been reported in the United States. In this report, we describe the clinical, microbiological, and histological features of an epizootic of neonatal pig diarrhea associated with the overgrowth of spore-bearing C. perfringens type A in the small intestine. A 120-sow, continuously farrowing swine unit from southcentral Minnesota experienced an epizootic of diarrhea in l3-day-old pigs. Clinical illness, which usually began shortly after birth, was characterized by high morbidity (nearly 100%) and negligible mortality (< 1%). Scouring pigs remained vigorous, continued to nurse, and recovered spontaneously in approximately 4 days. Diarrhea was clinically nonresponsive to treatment with gentamicin or trimethoprim-sulfadimeth

Temporal and spatial dynamics of porcine reproductive and respiratory syndrome virus infection in the United States.

OBJECTIVE To measure incidence and estimate temporal and spatial dynamics of porcine reproductive and respiratory syndrome virus (PRRSV) infection in US sow herds. ANIMALS 371 sow herds in the United States from 14 production companies. PROCEDURES The exponentially weighted moving average was used to monitor incident PRRSV infections for onset of an epidemic. The spatial scan statistic was used to identify areas at significantly high risk of PRRS epidemics. A χ(2) test was used to estimate whether there were significant differences in the quarterly and annual PRRS incidence among time periods, and a bivariable logistic regression model was used to estimate whether PRRSV infection during a given year increased the odds of that herd being infected in the following year. RESULTS During the 4-year period of this study, 29% (91/319; 2009 to 2010), 33% (106/325; 2010 to 2011), 38% (135/355; 2011 to 2012), and 32% (117/371; 2012 to 2013) of the herds reported new infections. Weekly incidence was low during spring and summer and high during fall and winter. The exponentially weighted moving average signaled the onset of a PRRSV epidemic during the middle 2 weeks of October each year. Disease incidence was spatially clustered. Infection in the previous year increased the odds of infection in 2010 to 2011 and 2011 to 2012. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated a striking repeatability in annual PRRSV temporal and spatial patterns across 4 years of data among herds from 14 production companies, which suggested that efforts to control PRRSV at a regional level should continue to be supported.