Biosecurity scores to measure vulnerability to PRRS outbreak in sow farms

Development and validation of a scoring system to assess the relative vulnerability of swine breeding herds to the introduction of PRRS virus

Author links open overlay panelGustavo S.Silvaab Luis G.Corbellinib Daniel L.C.Linharesa Kimberlee L.Bakera Derald J.Holtkampa

Veterinary Diagnostic and Production Animal Medicine Department, Iowa State University, Ames, IA, United States

b

Laboratory of Veterinary Epidemiology (Epilab), Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil

Received 9 March 2018, Revised 8 October 2018, Accepted 9 October 2018, Available online 10 October 2018.

https://doi.org/10.1016/j.prevetmed.2018.10.004Get rights and content

Abstract

Biosecurity is defined as the set of practices carried out to prevent the introduction and spread of infectious agents in a herd. These practices are essential in swine production, especially for highly infectious agents such as porcine reproductive and respiratory syndrome virus (PRRSv). Even with years of research and experience over the last three decades, PRRSv is still causing productivity losses and is the major health problem affecting the global swine industry. Despite knowledge of the various ways in which the virus can be transmitted from one herd to another (e.g. animals, semen, truck, air, and people), determining the most frequent ways in which the virus is transmitted in the field is difficult. A systematic approach to assess vulnerabilities at a herd level related to PRRSv transmission could help producers prioritize biosecurity practices to reduce or avoid the occurrence of outbreaks. The aim of this study was to develop a biosecurity vulnerability score that represents the relative vulnerability of swine breeding herds to the introduction of PRRSv. To create the biosecurity vulnerability score (outcome), a multi-criteria decision analysis methodology was used to rank and quantify biosecurity practices based on expert opinion. To validate the biosecurity vulnerability score, a survey of biosecurity practices and PRRS outbreak histories in 125 breed-to-wean herds in the U.S. swine industry was used. Data on the frequency of PRRS outbreaks was used to test the hypothesis that biosecurity vulnerability scores were different between farms that have a low incidence of PRRS outbreaks, compared to farms that have a high incidence. In the two databases used, the scores consistently showed that farms with higher scores have a higher frequency of PRRS outbreaks. In the first validation, farms that had never had an outbreak investigation before had a significant (p < 0.02) lower score (0.29; 0.21-0.37) when compared to farms that had had 2 or more outbreaks (0.43; 0.39-0.46). In the second, the farms of the control group also had significant (p < 0.004) lower scores (0.30; 0.27-0.33) compared to the case group (0.35; 0.33-0.38). Also, the results suggest that events related to swine movements, transmission by air and water, and people movements should be prioritized. The biosecurity vulnerability scores may be useful to assess vulnerabilities on biosecurity protocols in order to reduce the frequency of PRRS outbreaks and may help producers and veterinarians prioritize investments in improving biosecurity practices over time.

Keywords

biosecurity

swine farms

PRRS

biosecurity vulnerability score

risk events

carrying agents

Effects of sample handling on PRRSv detection in oral fluids by PCR

J Vet Diagn Invest. 2018 Oct 4:1040638718805534. doi: 10.1177/1040638718805534. [Epub ahead of print]

Effects of sample handling on the detection of porcine reproductive and respiratory syndrome virus in oral fluids by reverse-transcription real-time PCR.

Weiser AC1,2, Poonsuk K1,2, Bade SA1,2, Gauger PC1,2, Rotolo M1,2, Harmon K1,2, Gonzalez WM1,2, Wang C1,2, Main R1,2, Zimmerman JJ1,2.

Author information

1

Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine (Weiser, Poonsuk, Bade, Gauger, Rotolo, Harmon, Gonzalez, Main, Zimmerman).

2

Department of Statistics, College of Liberal Arts and Sciences (Wang), Iowa State University, Ames, IA.

Abstract

We evaluated effects of handling procedures on detection of porcine reproductive and respiratory syndrome virus (PRRSV) in oral fluids (OFs) by reverse-transcription real-time PCR (RT-rtPCR). The experiments were conducted using a composite sample of PRRSV-positive OF collected from 5-wk-old pigs vaccinated 15 d earlier with a modified-live PRRSV vaccine. Five pre-extraction sample-handling steps and all combinations thereof were evaluated: 1) thaw temperature (4°C or 25°C); 2) sample diluent (1:1 dilution with nuclease-free water or guanidinium thiocyanate-phenol); 3a) sonication of the sample (yes or no); 3b) temperature (4°C or 25°C) at which step 3a was conducted; and 4) temperature at which the sample was maintained after step 3b and until RNA extraction was initiated (4°C or 25°C). All combinations of the 5 sample-handling steps (i.e., 32 unique treatments) were tested in a completely randomized factorial design with 4 replicates and 1 negative control for each treatment. The entire experiment was repeated on 5 separate days to produce a total of 800 PRRSV RT-rtPCR results. Binary (positive or negative) data were analyzed by logistic regression and results (Ct) were analyzed using a generalized linear model. Overall, 1 false-positive result was observed among 160 negative controls (99.4% specificity), and 85 false-negative results were observed among the 640 known-positive samples (86.7% sensitivity). The most significant factor affecting test outcome was thaw temperature (4°C or 25°C); samples thawed at 4°C had higher positivity rate (94% vs. 80%, p < 0.0001) and lower Ct (36.2 vs. 37.5, p < 0.0001).

KEYWORDS: 

Oral fluid; RT-rtPCR; porcine reproductive and respiratory syndrome virus

PMID:

 

30284505

 

DOI:

 

10.1177/1040638718805534