Recipient Organization
IOWA STATE UNIVERSITY
2229 Lincoln Way
AMES,IA 50011
Performing Department
Veterinary Medicine
Non Technical Summary
While a variety of methods have been applied for the elimination of PRRSv from swine production sites, the initial success of these methods has been variable, and the reasons for failure are not well understood. For those sites that are successful with their initial PRRSv elimination efforts, success in maintaining a PRRS-negative or na?ve status for extended periods of time following elimination projects has been inconsistent and unpredictable. The high level of uncertainty for maintaining a na?ve status has limited the number of operations willing to invest in disease elimination. In addition, application of effective bio-security measures has been impossible without an understanding of what key practices must be implemented to reduce PRRSV introduction into production sites. This single reality has cost the industry hundreds of millions of dollars, both through in our inability to limit the spread of new PRRSv into swine herds and in expensive and inconsistently effective bio-security practices. Over the last 5 years, with the development of the AASV PRRS Risk Assessment (PRA) for the Breeding Herd, progress has been made in assessing high and low risk sites for PRRSv introduction. With this tool, a focused list of potential risk factors has been identified but to date individual risk factors have not be validated or prioritized. The objective of this study is assess which risk factors are the most common causes of lateral introduction of novel PRRSV into production sites. The availability of large numbers of PRRS na?ve pigs at weaning presents a unique model to monitor infection over a defined period with multiple replications at the same site. For this study, 500 (250 per year) cohorts of PRRS na?ve growing pigs located on at least 100 sites in the major swine producing regions of the US will be enrolled in the study. Risk Assessments will be performed and specific diagnostic and production data will be obtained for each cohort. The PRRS status of enrolled lots will be monitored in the middle and at the end of the feeding period to determine if the cohort became infected or not. Logistic regression for specific risk factors will be conducted. Outcomes from this study include identification of modifiable factors to lower the rate of lateral PRRSV transmission into swine production sites. While the model that we have chosen is focused on growing pigs the risks that are identified will be broadly applicable, as the biology of PRRSv is not impacted by animal type. When the key risk factors are identified, our ability to create more effective bio-security programs will lead to greater returns on bio-security investments though a proper weighting of risk and a subsequent reduction in the number of new infections.
Animal Health Component
(N/A)
Research Effort Categories
Basic
(N/A)
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
Objectives: To determine and prioritize individual and composite risk factors for introduction of novel PRRSV into swine herds through the use of the American Association of Swine Veterinarians (AASV) PRRS Risk Assessment for the Growing Pig Herd. Assess which risk factors are the most common causes of lateral introduction of novel PRRSV into growing pig production sites. Milestones: Phase 1 (Year 1) November 1, 2008-November 1, 2009 -Training on use of Risk Assessment Tools -Enrollment of 250 cohorts - goal of 20/month -Risk assessments on all cohorts enrolled -Collection of diagnostic and production data to confirm status of cohorts enrolled after the start of the study (Last cohort will be enrolled in November 2009 - six months is allowed for last cohort to be marketed) Preliminary analysis and written report: April 1, 2010-June 1, 2010 Phase 2 (Year 2) November 1, 2009-November 1, 2010 -Enrollment of 250 cohorts - goal of 20 per month -Risk assessments on all cohorts enrolled -Collection of diagnostic and production data to confirm status of cohorts enrolled after the start of the study (Last cohort will be enrolled in November 2010 - six months is allowed for last cohort to be marketed) Final analysis and written report: April 1, 2011-October 31, 2011
Project Methods
A total of 500 (250 per year) cohorts of PRRS naive growing pigs at the time of enrollment will be used in the study. Cohorts will be housed on at least 100 sites in the major swine producing regions of the US with all cohorts being housed on sites that are operated on an AIAO manner. Pigs sources for cohorts will be defined as either negative or naive where a naive source is defined as the entire swine population at the site (originating from a PRRS-naive source) has never been exposed to the PRRSv as evidenced by lack of clinical signs and laboratory diagnostic confirmation OR Some or all of the animals that were PRRS-naive at placement (originating from a PRRS-naive source) which currently make up 100% of the population at the site but that have had past contact with other swine that were previously exposed to the PRRSv and which previously were present at this site during a non-depopulation/repopulation elimination procedure AND The entire new placed-naive swine population at the site (originating from a PRRS-naive source) has remained serologically negative to PRRSv (as confirmed by ELISA/IFA and PCR/VI). Negative sources will be defined as sites, which have previously had antibodies against PRRS where not all of the animals currently in inventory originated from a PRRS-naive source OR where breeding swine currently in the herd have antibodies against PRRS. In either case, to be considered negative the offspring have been demonstrated to be free of PRRSv by statistical sampling (>30 head) of offspring at the time of weaning with PRRS PCR for at least 6 samplings with at least 4 weeks between all samplings. Measuring risk index scores for each site in the study: Version 1 of the AASV PRRS Risk Assessment (PRA) for the Growing Pig will be used to collect information about risk factors and calculate risk index scores for each site in the study. The PRA for growing pigs is based on the AASV PRRS Risk Assessment for the Breeding Herd, which has been validated to both its methodology and prediction of risk. A risk assessment will be completed when the cohort is enrolled in the study. The respondents will be asked to provide responses for the sites that apply at the time the cohort was established. Determining infection and production outcomes: To determine if a cohort was infected with PRRS, each cohort will be sampled just prior to when the cohort is closed. Each sampling will consist of 10 serum samples collected via routine vena puncture that will be analyzed using the IDEXX PRRS Elisa at a commercial veterinary diagnostic laboratory. All samplings with 1-3 positive (S:P>0.4) will have three different North American and one European PRRS IFA tests conducted to confirm that they are true positives. Any sampling with 1 or more true-positives will be considered infected. Statistical Analysis: Logistic regression will be conducted to evaluate predictors for conversion of cohorts to a positive PRRS status.