Derald J. Holtkamp

Detection of antibodies against porcine epidemic diarrhea virus in serum and colostrum by indirect ELISA

Abstract An indirect porcine epidemic diarrhea virus (PEDV) anti-immunoglobulin (Ig) G ELISA based on the S1 portion of the spike protein was validated and compared with an indirect immunofluorescence assay. In serum samples from experimentally infected pigs (n = 35), anti-IgG PEDV antibodies were detected as early as 7 days post-infection. In field serum samples (n = 239), the diagnostic sensitivity of the S1 ELISA was 100% and the diagnostic specificity was 94%. The S1 ELISA showed no cross-reactivity with antibodies against other porcine coronaviruses. Colostrum samples (n = 133) were also tested for anti-PEDV IgG and IgA. The diagnostic sensitivity was 92% for IgG and 100% for IgA, and the diagnostic specificity was 90% for IgG and 99.4% for IgA. These data suggest that the S1 ELISA is a sensitive and specific test that could also be used to evaluate PEDV colostral immunity.

Neonatal Mortality, Vesicular Lesions and Lameness Associated with Senecavirus A in a U.S. Sow Farm.

Summary 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.

Crop Insurance as a Mechanism for Reducing Pesticide Usage: A Representative Farm Analysis

Crop insurance provides a potential tool for reducing agricultural chemical use by providing a substitute for the risk management benefits of pesticides. This article describes the results obtained from an integrated modeling system developed to assess the efficacy of crop insurance used in this manner. While crop insurance is found to reduce pesticide application, the extent of its impact depends significantly upon the distribution of risk aversion in the target population and the reductions can be costly, ranging from

Occurrence of Incisional Complications and Associated Risk Factors Using a Right Ventral Paramedian Celiotomy Incision in 159 Horses

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Evaluation of external biosecurity practices on southern Ontario sow farms

45 per pound of active ingredient.

Quantitative Risk from Fluoroquinolone-Resistant Salmonella and Campylobacter Due to Treatment of Dairy Heifers with Enrofloxacin for Bovine Respiratory Disease

OBJECTIVE To evaluate the occurrence of, and variables associated with, incisional complications after right ventral paramedian celiotomy in horses. STUDY DESIGN Case series. ANIMALS Horses (n=159). METHODS Occurrence of incisional complications after right ventral paramedian celiotomy was determined in 159 horses (161 celiotomies) that survived at least 30 days after surgery at a private equine hospital (2003-2007). Follow-up information for 121 horses was obtained ≥90 days after surgery. Univariate analysis and multivariate logistic regression was performed to evaluate variables associated with incisional complications after celiotomy. RESULTS Of 161 celiotomies, ≥1 incisional complications occurred in 27 (16.8%) during hospitalization and/or after discharge, including: drainage (15.5%), skin dehiscence (3.7%), noticeable cutaneous scarring (1.9%), and herniation (0.6%). Variables significantly associated with incisional complications after multivariate analysis included: Quarter horse-type breed (odds ratio [OR]: 3.9, 95% confidence interval [95% CI]: 1.3-11.7); use of an abdominal bandage (OR: 9.5, 95% CI: 2.9-30.8); and >4 postoperative febrile (>38.3°C) days (OR: 12.9, 95% CI: 2.8-58.2). CONCLUSIONS Overall occurrence of incisional complications after right paramedian ventral celiotomy compared favorably to those reported for ventral median celiotomies. Several variables were associated with, but not necessarily predictive for, the occurrence of incision complications.Objective: To evaluate the occurrence of, and variables associated with, incisional complications after right ventral paramedian celiotomy in horses. Study Design: Case series. Animals: Horses (n=159). Methods: Occurrence of incisional complications after right ventral paramedian celiotomy was determined in 159 horses (161 celiotomies) that survived at least 30 days after surgery at a private equine hospital (2003–2007). Follow-up information for 121 horses was obtained ≥90 days after surgery. Univariate analysis and multivariate logistic regression was performed to evaluate variables associated with incisional complications after celiotomy. Results: Of 161 celiotomies, ≥1 incisional complications occurred in 27 (16.8%) during hospitalization and/or after discharge, including: drainage (15.5%), skin dehiscence (3.7%), noticeable cutaneous scarring (1.9%), and herniation (0.6%). Variables significantly associated with incisional complications after multivariate analysis included: Quarter horse-type breed (odds ratio [OR]: 3.9, 95% confidence interval [95% CI]: 1.3–11.7); use of an abdominal bandage (OR: 9.5, 95% CI: 2.9–30.8); and >4 postoperative febrile (>38.3°C) days (OR: 12.9, 95% CI: 2.8–58.2). Conclusions: Overall occurrence of incisional complications after right paramedian ventral celiotomy compared favorably to those reported for ventral median celiotomies. Several variables were associated with, but not necessarily predictive for, the occurrence of incision complications.

Identifying questions in the American Association of Swine Veterinarian's PRRS risk assessment survey that are important for retrospectively classifying swine herds according to whether they reported clinical PRRS outbreaks in the previous 3 years

External biosecurity protocols, aimed at preventing the introduction of new pathogens to the farm environment, are becoming increasingly important in the swine industry. Although assessments at the individual farm level occur regularly, efforts to cluster swine herds into meaningful biosecurity groups and to summarize this information at the regional level are relatively infrequent. The objectives of this study were: (i) to summarize external biosecurity practices on sow farms in southern Ontario; (ii) to cluster these farms into discrete biosecurity groups and to describe their characteristics, the variables of importance in differentiating between these groups, and their geographic distribution; and (iii) to identify significant predictors of biosecurity group membership. Data were collected using the Production Animal Disease Risk Assessment Programs Survey for the Breeding Herd. A subset of variables pertaining to external biosecurity practices was selected for two-step cluster analysis, which resulted in 3 discrete biosecurity groups. These groups were named by the authors as: (i) high biosecurity herds that were open with respect to replacement animals, (ii) high biosecurity herds that were closed with respect to replacement animals, and (iii) low biosecurity herds. Variables pertaining to trucking practices and the source of replacement animals were the most important in differentiating between these groups. Multinomial logistic regression provided insight into which demographic and neighborhood variables serve as significant predictors of biosecurity group membership (p<0.05). Variables in the final regression model include: herd density within a 4.8 km radius, number of sows on the premises, and site production type. The odds of belonging to the high biosecurity group that was open with respect to replacement animals, relative to the low biosecurity group, increased 1.001 times for each additional sow (p=0.001). The odds of belonging to the high biosecurity group that was open with respect to replacement animals, relative to the low biosecurity group, were 6.5 times greater for farms that produced genetic animals than for farms that produced commercial animals (p=0.003). The information obtained through this work allows a better understanding of biosecurity in sow herds at the regional level, and the implementation of biosecurity protocols in North American swine herds in general.

Unraveling the contact patterns and network structure of pig shipments in the United States and its association with porcine reproductive and respiratory syndrome virus (PRRSV) outbreaks

The objective of this study was to evaluate the human health impact of using fluoroquinolones to treat bovine respiratory disease (BRD) in dairy heifers less than 20 months of age. Specifically, this study quantified the probability of persistent symptoms in humans treated with a fluoroquinolone, for a fluoroquinolone-resistant Campylobacter, Salmonella, or multidrug-resistant (MDR) Salmonella infection acquired following the consumption of ground beef. To comply with a Food and Drug Administration requirement for approval of enrofloxacin use in dairy heifers, a binomial event tree was constructed following Food and Drug Administration guidance 152. Release was estimated from the slaughter of dairy cattle carrying fluoroquinolone-resistant bacteria attributed to the proposed use in dairy heifers. For exposure, human foodborne exposure to Campylobacter, Salmonella, and MDR Salmonella after consumption of ground beef was estimated. The consequence assessment included illness, fluoroquinolone treatment, and persistent symptoms in patients treated with a fluoroquinolone. Using best available data to estimate the parameters and probabilities of each event, stochastic simulation was used to represent uncertainty and variability in many of the parameters. A scenario analysis was performed to evaluate the uncertainty of the following parameters: (1) probability of resistance development in treated animals, (2) portion of illnesses attributable to ground beef, and (3) probability of persistent symptoms in patients 18 years of age and over treated with a fluoroquinolone. The population at risk was restricted to people 18 years of age and over, as fluoroquinolones are not labeled for treatment of gastroenteritis in children. The mean annual increased risk of cases in the U.S. population (18 years of age and over) where compromised fluoroquinolone treatment resulted in persistent symptoms was estimated to be 1 in 61 billion (one case every 293 years) for Salmonella, 1 in 33 billion (one case every 158 years) for MDR Salmonella, and 1 in 2.8 billion (one case every 13 years) for Campylobacter.

Systematic Epidemiological Investigations of Cases of Senecavirus A in US Swine Breeding Herds.

The American Association of Swine Veterinarians (AASV) Production Animal Disease Risk Assessment Program (PADRAP) is a web-based program that offers a set of risk assessment surveys being used by veterinarians who are members of the AASV. Members use PADRAP to help producers systematically assess risk factors that may be associated with clinical outcomes. As assessments are performed the completed surveys are added to the dataset maintained at the Iowa State University College of Veterinary Medicine. One of the surveys included in PADRAP is the porcine reproductive and respiratory syndrome (PRRS) Risk Assessment for the Breeding Herd. The aim of the study was to categorize questions in version 2 of the PRRS Risk Assessment for the Breeding Herd survey as important or unimportant for classifying herds according to whether they reported clinical PRRS outbreaks in the previous 3 years. The results elucidate the relative importance of risk factors and areas of risk factors for clinical outcomes and removing unimportant questions may reduce the time required to complete the survey without affecting the quality of information obtained. Surveys from 896 sow herd sites in the United States and Canada completed between March 2005 and March 2009 were included in the analysis. The survey contained a large number of questions with a complex correlation structure among the questions. Responses for several questions were dependent upon responses to others. To address these issues, an approach was developed using a series of statistical methods including random forest, principle component analysis, logistic regression and receiver operating characteristic (ROC) analysis to classify the herds using the questions in the survey as explanatory variables. Questions were ranked by importance and systematically excluded from least important to most important. The questions excluded, without significantly affecting the performance of the model for classifying herds were identified as unimportant. Thirty-eight of the 127 questions analyzed were identified as unimportant for classifying herds according to whether they reported clinical PRRS outbreaks in the previous 3 years. Sections of the survey where a large number of questions were identified as unimportant included (1) entry of semen into the breeding herd and (2) transportation of live animals. Sections with a high percentage of questions identified as unimportant included (1) characteristics of the site, (2) disposal of dead animals and waste management and (3) employee and visitors.

Construction of disease risk scoring systems using logistic group lasso: application to porcine reproductive and respiratory syndrome survey data

The analysis of the pork value chain is becoming key to understanding the risk of infectious disease dissemination in the swine industry. In this study, we used social network analysis to characterize the swine shipment network structure and properties in a typical multisite swine production system in the US. We also aimed to evaluate the association between network properties and porcine respiratory and reproductive syndrome virus (PRRSV) transmission between production sites. We analyzed the 109,868 swine shipments transporting over 93 million swine between more than 500 production sites from 2012 to 2014. A total of 248 PRRSV positive occurrences were reported from 79 production sites during those 3 years. The temporal dynamics of swine shipments was evaluated by computing network properties in one-month and three-month networks. The association of PRRS occurrence in sow farms with centrality properties from one-month and three-month networks was assessed by using the multilevel logistic regression. All monthly networks showed a scale-free network topology with positive degree assortativity. The regression model revealed that out-degree centrality had a negative association with PRRS occurrence in sow farms in both one-month and three-month networks [OR=0.79 (95% CI, 0.63-0.99) in one-month network and 0.56 (95% CI, 0.36, 0.88) in three-month network] and in-closeness centrality model was positively associated with PRRS occurrence in sow farms in the three-month network [OR=2.45 (95% CI, 1.14-5.26)]. We also describe how the occurrence of porcine epidemic diarrheac (PED) outbreaks severely affected the network structure as well as the PRRS occurrence reports and its association with centrality measures in sow farms. The structure of the swine shipment network and the connectivity between production sites influenced on the PRRSV transmission. The use of network topology and characteristics combining with spatial analysis based on fine scale geographical location of production sites will be useful to inform the design of more cost-efficient, risk-based surveillance and control measures for PRRSV as well as other diseases in the US swine industry.