Factors affecting PRRSV time-to-stability in US breeding herds

Transbound Emerg Dis. 2018 Dec 6. doi: 10.1111/tbed.13091. [Epub ahead of print]

Factors affecting Porcine Reproductive and Respiratory Syndrome virus time-to-stability in breeding herds in the Midwestern United States.

Sanhueza JM1, Vilalta C1, Corzo C1, Arruda AG2.

Author information

Abstract

The time needed to wean porcine reproductive and respiratory syndrome (PRRS) virus negative pigs consistently from a breeding herd after an outbreak is referred to as time-to-stability (TTS). TTS is an important measure to plan herd closure as well as to manage economic expectations. Weekly PRRS incidence data from 82 sow farms in six production systems located in the Midwestern United States were used for the analysis. The objective of this study was to evaluate the effect of recorded predictors on TTS in participant sow farms. The median TTS was 41.0 weeks (1st quartile 31.0 weeks-3rd quartile 55.0 weeks). In the final multivariable mixed-effects Cox model, farms that experienced winter (hazard ratio (HR) 2.46, 95% confidence interval (CI) 1.37-4.43) and autumn (HR 1.73, 95% CI 1.00-2.99) PRRS outbreaks achieved stability sooner than farms that experienced PRRS outbreaks during summer. No statistically significant difference (p=0.76) was observed between the TTS of farms that had a PRRS outbreak during spring and summer (HR 1.09, 95% CI 0.59-1.88). Additionally, farms that had a PRRS outbreak associated with a 1-7-4 restriction fragment length polymorphism (RFLP) cut pattern took significantly longer to achieve stability (HR 0.4, 95% CI 0.3-0.7) compared to farms which had a non-1-7-4 PRRS outbreak. Finally, farms that had a previous PRRS outbreak within a year achieved stability sooner (HR 2.18, 95% CI 1.23-3.86) than farms that did not have a previous PRRS outbreak within a year. This study provides information that may result useful for planning herd closure and managing expectations about the time needed to wean PRRS virus negative pigs in breading herds according to the season of the year when the outbreak occurred and the RFLP cut pattern associated with the outbreak virus. This article is protected by copyright. All rights reserved.

KEYWORDS: 

PRRS ; RFLP ; season; swine; time-to-stability

PMID:

 

30520570

 

DOI:

 

10.1111/tbed.13091

Vaccination of neonatal pigs with MLV PRRSV vaccine is able to overcome maternal immunity

Porcine Health Manag. 2018 Nov 15;4:25. doi: 10.1186/s40813-018-0101-x. eCollection 2018.

Vaccination of 1-day-old pigs with a porcine reproductive and respiratory syndrome virus (PRRSV) modified live attenuated virus vaccine is able to overcome maternal immunity.

Balasch M1, Fort M1, Taylor LP2, Calvert JG2.

Author information

Abstract

BACKGROUND: 

The objective of the study was to evaluate the influence of maternally derived antibodies (MDA) on the efficacy of a PRRSV-1 based attenuated vaccine, when administered in 1 day-old piglets by the intramuscular route. The protective immunity of the modified live virus vaccine was evaluated in pigs born from seropositive sows, vaccinated at 1 day of age, upon inoculation with a PRRSV-1 isolate. The animals were challenged when the levels of MDAs detected by seroneutralization test (SNT) in the non-vaccinated control group became undetectable (10 weeks after vaccination).

RESULTS: 

A protective effect of vaccination was observed since a significant reduction of viral load in serum compared to the control group was detected in all sampling days after challenge; efficacy was supported by the significant reduction of nasal and oral shedding as well as in rectal temperatures. Clinical signs were not expected after the inoculation of a PRRSV-1 subtype 1 challenge strain. However, the challenge virus was able to develop fever in 61% of the control pigs. Vaccination had a positive impact on rectal temperatures since the percentage of pigs that had fever at least once after challenge was reduced to 31% in vaccinated animals, and control pigs had significantly higher rectal temperatures than vaccinated pigs 3 days post-challenge. The lack of a vaccination effect in body weight gain was probably due to the short evaluation period after challenge (10 days). In the vaccinated group, 9/16 pigs (56%) experienced an increase in ELISA S/P ratio from the day of vaccination to 67 days post-vaccination. All vaccinated pigs were seropositive before challenge, indicating the development of an antibody response following vaccination even in the face of MDAs. In contrast to ELISA results, only 2/16 vaccinated pigs developed neutralizing antibodies detectable by a SNT that used a subtype 1 MA-104 adapted strain. Even in the absence of SN antibodies, vaccinated pigs were protected from challenge with a heterologous strain. The role of cell-mediated immunity should be considered, if protection was not mediated by SN antibodies only.

CONCLUSIONS: 

The efficacy of the attenuated PRRSV-1 vaccine in 1-day-old pigs seropositive to PRRSV prior to a PRRSV-1 challenge was demonstrated by improvement of clinical, virological and immunological variables. With the current experimental design, maternal immunity did not interfere with the development of a protective immune response against a PRRSV-1 challenge, after vaccination of 1 day-old pigs. Confirmation of these results under field conditions will be needed.

KEYWORDS: 

Maternal-derived immunity; Modified live vaccine; Porcine reproductive and respiratory syndrome

PMID:

 

30459958

 

PMCID:

 

PMC6237022

 

DOI:

 

10.1186/s40813-018-0101-x

Biosecurity scoring system for PRRS - measure and benchmark vulnerability to PRRS infection!

Prev Vet Med. 2018 Nov 15;160:116-122. doi: 10.1016/j.prevetmed.2018.10.004. Epub 2018 Oct 10.

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

Silva GS1, Corbellini LG2, Linhares DLC3, Baker KL3, Holtkamp DJ4.

Author information

1

Veterinary Diagnostic and Production Animal Medicine Department, Iowa State University, Ames, IA, United States; Laboratory of Veterinary Epidemiology (Epilab), Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.

2

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

3

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

4

Veterinary Diagnostic and Production Animal Medicine Department, Iowa State University, Ames, IA, United States. Electronic address: holtkamp@iastate.edu.

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 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; Biosecurity vulnerability score; Carrying agents; PRRS; Risk events; Swine farms

PMID:

 

30388993

 

DOI:

 

10.1016/j.prevetmed.2018.10.004

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

Oral fluids-based monitoring of PRRS at the slaughter plant

Prev Vet Med. 2018 Oct 1;158:137-145. doi: 10.1016/j.prevetmed.2018.08.002. Epub 2018 Aug 9.

Assessment of abattoir based monitoring of PRRSV using oral fluids.

Almeida MN1, Zimmerman JJ1, Wang C1, Linhares DCL2.

Author information

1

Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, Iowa, United States.

2

Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames, Iowa, United States. Electronic address: linhares@iastate.edu.

Abstract

Various porcine reproductive and respiratory syndrome virus (PRRSV) regional elimination projects have been implemented in the U.S., but none have yet succeeded. In part, this reflects the need for efficient methods to monitor over time the progress of PRRSV status of participating herds. This study assessed the feasibility of monitoring PRRSV using oral fluids collected at the abattoir. A total of 36 pig lots were included in the study. On-farm oral fluid (n = 10) and serum (n = 10) collected within two days of shipment to the abattoir were used to establish the reference PRRSV status of the population. Oral fluids (n = 3 per lot) were successfully collected from 32 lots (89%) at the lairage. Three veterinary diagnostic laboratories (VDLs) tested the sera (VDL1 and VDL3: n = 316, VDL2: n = 315) and oral fluids (VDL1 and VDL3: n = 319, VDL2: n = 320) for PRRSV antibodies (ELISA) and RNA (rRT-PCR). Environmental samples (n = 64, 32 before and 32 after pigs were placed in lairage) were tested for PRRSV RNA at one VDL. All oral fluids (farm and abattoir) tested positive for PRRSV antibody at all VDLs. PRRSV positivity frequency on serum ranged from 92.4% to 94.6% among VDLs, with an overall agreement of 97.6%. RNA was detected on 1.3% to 1.9%, 8.1% to 17.7%, and 8.3% to 17.7% of sera, on-farm and abattoir oral fluids, respectively. Between-VDLs rRT-PCR agreement on sera and oral fluids (farm and abattoir) ranged from 97.8% to 99.0%, and 79.0% to 81.2%, respectively. Between-locations agreement of oral fluids varied from 31.3% to 50% depending on the VDL. This study reported the application of swine oral fluids collected at the abattoir for monitoring PRRSV, and describes the between-VDL agreement for PRRS testing of serum and oral fluid field samples.

KEYWORDS: 

Abattoir; Agreement; Monitoring; PRRS; Surveillance; Swine

PMID:

 

30220387

 

DOI:

 

10.1016/j.prevetmed.2018.08.002

Production losses associated with PRRS in US sow farms

Front Vet Sci. 2018 May 16;5:102. doi: 10.3389/fvets.2018.00102. eCollection 2018.

Production Losses From an Endemic Animal Disease: Porcine Reproductive and Respiratory Syndrome (PRRS) in Selected Midwest US Sow Farms.

Valdes-Donoso P1,2, Alvarez J2, Jarvis LS1, Morrison RB2, Perez AM2,3.

Author information

1

Department of Agricultural and Resource Economics, University of California Davis, Davis, CA, United States.

2

Department of Veterinary Population Medicine, College of Veterinary Medicine, University of Minnesota, Saint Paul, MN, United States.

3

Center for Animal Health and Food Safety, University of Minnesota, St. Paul, MN, United States.

Abstract

Porcine reproductive and respiratory syndrome (PRRS) is an endemic disease causing important economic losses to the US swine industry. The complex epidemiology of the disease, along with the diverse clinical outputs observed in different types of infected farms, have hampered efforts to quantify PRRS' impact on production over time. We measured the impact of PRRS on the production of weaned pigs using a log-linear fixed effects model to evaluate longitudinal data collected from 16 sow farms belonging to a specific firm. We measured seven additional indicators of farm performance to gain insight into disease dynamics. We used pre-outbreak longitudinal data to establish a baseline that was then used to estimate the decrease in production. A significant rise of abortions in the week before the outbreak was reported was the strongest signal of PRRSV activity. In addition, production declined slightly one week before the outbreak and then fell markedly until weeks 5 and 6 post-outbreak. Recovery was not monotonic, cycling gently around a rising trend. At the end of the study period (35 weeks post-outbreak), neither the production of weaned pigs nor any of the performance indicators had fully recovered to baseline levels. This result suggests PRSS outbreaks may last longer than has been found in most other studies. We assessed PRRS' effect on farm efficiency as measured by changes in sow production of weaned pigs per year. We translated production losses into revenue losses assuming an average market price of $45.2/weaned pig. We estimate that the average PRSS outbreak reduced production by approximately 7.4%, relative to annual output in the absence of an outbreak. PRRS reduced production by 1.92 weaned pigs per sow when adjusted to an annual basis. This decrease is substantially larger than the 1.44 decrease of weaned pigs per sow/year reported elsewhere.

KEYWORDS: 

Endemic Animal Disease; Fixed effects model ; Porcine Reproductive and Respiratory Syndrome; Production Impacts; Sow Farms; US Swine Industry

PMID:

 

29922683

 

PMCID:

 

PMC5996871

 

DOI:

 

10.3389/fvets.2018.00102

Vet Immunol Immunopathol. 2018 Jun;200:32-39. doi: 10.1016/j.vetimm.2018.04.007. Epub 2018 Apr 22.

Comparative evaluation of immune responses of swine in PRRS-stable and unstable herds.

Drigo M1, Giacomini E2, Lazzaro M2, Pasotto D1, Bilato D3, Ruggeri J2, Boniotti MB4, Alborali GL2, Amadori M5.

Author information

1

Department of Animal Medicine, Production and Health, Veterinary Padua University, Viale dell'Università 16-Agripolis, 35020 Legnaro, PD, Italy.

2

Diagnostic Laboratory, Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna, via A. Bianchi 9, 25124 Brescia, Italy.

3

Laboratory of Cellular Immunology, Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna, via A. Bianchi 9, 25124 Brescia, Italy.

4

Genomics Department, Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna, via A. Bianchi 9, 25124 Brescia, Italy.

5

Laboratory of Cellular Immunology, Istituto Zooprofilattico Sperimentale della Lombardia e dell'Emilia Romagna, via A. Bianchi 9, 25124 Brescia, Italy. Electronic address: massimo.amadori@izsler.it.

Abstract

Porcine Reproductive and Respiratory Syndrome (PRRS) is an elusive model of host/virus relationship in which disease is determined by virus pathogenicity, pig breed susceptibility and phenotype, microbial infectious pressure and environmental conditions. Successful disease control in PRRS-endemic Countries corresponds to "stability", i.e. a condition with no clinical signs of PRRS in the breeding-herd population and no viremia in weaning-age pigs. The aim of this work was to compare the profile and time-course of humoral and cell-mediated immunity in stable and unstable herds, respectively. In particular, we investigated PRRS virus (PRRSV) in serum and group oral fluid samples by Real-time RT-PCR, PRRSV-specific IgA and IgG in oral fluids, serum IgG antibody and the cell-mediated response (PRRSV-specific release of interferon-gamma) in whole blood samples. These parameters were measured in order to identify possible discrepancies in the development and kinetics of the immune response against PRRSV. PRRS-free gilts got regularly infected after entering PRRS-stable and unstable farms. In an open cycle, unstable pig farm PRRSV infection could be demonstrated in all groups of pigs, including suckling piglets. Four main results should be highlighted: A) the precocity of the Ab response in group oral fluids was generally similar to that recorded in sera; B) circulation of PRRSV was consistently detected in all age groups in the unstable herds, as opposed to the stable ones; C) an early, balanced, IgA and IgG response in oral fluids was only observed in the stable herds; D) an early IFN-gamma response after PRRSV infection was often observed in stable herds, as opposed to the unstable ones. These were characterized by IFN-gamma responses in piglets, likely due to transfer of maternal immunity. Most important, the mucosal IgA response was associated with cessation of virus excretion in oral fluid samples of PRRS-unstable herds. The above findings indicate that a peculiar profile of immune response to PRRSV can be found in PRRS-stable herds. Therefore, the outlined immune parameters can represent a useful readout system to evaluate successful adaptation to PRRSV based on acclimatization of breeding animals and management of pig flow.

KEYWORDS: 

Cell-mediated immunity; Herd; Mucosal immunity; PRRS; Pig; Stability

PMID:

 

29776610

 

DOI:

 

10.1016/j.vetimm.2018.04.007

Susceptibility to PRRSV infection among Chinese native pig breeds

Arch Virol. 2018 Apr 24. doi: 10.1007/s00705-018-3821-y. [Epub ahead of print]

Different susceptibility to porcine reproductive and respiratory syndrome virus infection among Chinese native pig breeds.

Meng C1,2, Su L1,3, Li Y1,2, Zhu Q3, Li J3, Wang H1,2, He Q1, Wang C3, Wang W3, Cao S4,5,6.

Author information

Abstract

China is rich in native pig breeds, yet information regarding the susceptibility/resistance of local breeds to porcine reproductive and respiratory syndrome virus (PRRSV) infection is lacking. In the present study, an in vitro method based on assessing PRRSV replication in porcine alveolar macrophages (PAMs) was established to evaluate PRRSV susceptibility/resistance in a commercial pig breed (Landrace) and five native pig breeds from Jiangsu and Anhui provinces in China. Expression levels of cytokines (IL-8, IL-10, TNF-α and IFN-γ), Toll-like receptor 3 (TLR3), CD163 (PRRSV receptor), and sialoadhesin (Sn, PRRSV receptor) in infected pigs were determined using real-time PCR, and the association between PRRSV susceptibility/resistance and the abundance of the cytokines and receptors was investigated. The viral replication rate and titer at 0, 6, 12 18, 24 and 36 hours postinfection (hpi) were determined to assess the proliferation dynamics of PRRSV NJGC in PAMs. Based on the PRRSV proliferation dynamics, the results indicated that Dingyuan pigs were the most susceptible to PRRSV infection, whereas Jiangquhai pigs were the least susceptible to PRRSV infection among the six pig breeds tested, as indicated by measuring PRRSV replication and the viral load in PAMs. The different levels of susceptibility to PRRSV infection in PAMs may be associated with differences in the abundance of CD163 (PRRSV receptor), cytokines IL-8, IFN-γ, and TNF-α in Jiangquhai and Dingyuan pig breeds after viral inoculation.

PMID:

 

29691704

 

DOI:

 

10.1007/s00705-018-3821-y

Assessing PRRS area spread

Transbound Emerg Dis. 2018 Apr 14. doi: 10.1111/tbed.12875. [Epub ahead of print]

Assessment of area spread of porcine reproductive and respiratory syndrome (PRRS) virus in three clusters of swine farms.

Arruda AG1, Sanhueza J2, Corzo C2, Vilalta C2.

Author information

Abstract

Despite decades of porcine reproductive and respiratory syndrome (PRRS) research, outbreaks with emerging and re-emerging PRRS virus (PRRSV) strains are not uncommon in North America. The role of area spread, commonly referred but not limited to airborne transmission, in originating such outbreaks is currently unknown. The main objective of this study was to explore the role of area spread on the occurrence of new PRRSV cases by combining information on genetic similarity among recovered PRRSV isolate's open-reading frame (ORF) 5 sequences and publicly available weather data. Three small regions were enrolled in the study for which high farm-level participation rate was achieved, and swine sites within those regions were readily sampled after reporting of an outbreak in a sow farm. Oral fluid PCR testing was used to determine PRRSV status of farms, and wind roses were generated for assessment of prevailing wind directions during 2-14 days preceding the outbreak. Under the conditions of this study, the data did not support the area spread theory as the main cause for these outbreaks. We suggest that for future studies, analysis of animal movement and other links between farms such as personnel, equipment and sharing of service providers should be incorporated for better insights on source of the virus. Furthermore, the development of rapid and easy diagnostic methods for ruling out resident PRRSV is urgently needed.

KEYWORDS: 

PRRS area spread; PRRS epidemiology; PRRS risk factors; porcine reproductive and respiratory syndrome; swine

PMID:

 

29654632

 

DOI:

 

10.1111/tbed.12875

Time series analysis for PRRS in the US

PLoS One. 2018 Apr 3;13(4):e0195282. doi: 10.1371/journal.pone.0195282. eCollection 2018.

Time-series analysis for porcine reproductive and respiratory syndrome in the United States.

Arruda AG1, Vilalta C2, Puig P3, Perez A2, Alba A2.

Author information

1

Department of Veterinary Preventive Medicine, The Ohio State University, Columbus, Ohio, United States of America.

2

Department of Veterinary Population Medicine, University of Minnesota, St. Paul, Minnesota, United States of America.

3

Department of Mathematics, Autonomous University of Barcelona, Barcelona, Spain.

Abstract

Industry-driven voluntary disease control programs for swine diseases emerged in North America in the early 2000's, and, since then, those programs have been used for monitoring diseases of economic importance to swine producers. One example of such initiatives is Dr. Morrison's Swine Health Monitoring Project, a nation-wide monitoring program for swine diseases including the porcine reproductive and respiratory syndrome (PRRS). PRRS has been extensively reported as a seasonal disease in the U.S., with predictable peaks that start in fall and are extended through the winter season. However, formal time series analysis stratified by geographic region has never been conducted for this important disease across the U.S. The main objective of this study was to use approximately seven years of PRRS incidence data in breeding swine herds to conduct time-series analysis in order to describe the temporal patterns of PRRS outbreaks at the farm level for five major swine-producing states across the U.S. including the states of Minnesota, Iowa, North Carolina, Nebraska and Illinois. Data was aggregated retrospectively at the week level for the number of herds containing animals actively shedding PRRS virus. Basic descriptive statistics were conducted followed by autoregressive integrated moving average (ARIMA) modelling, conducted separately for each of the above-mentioned states. Results showed that there was a difference in the nature of PRRS seasonality among states. Of note, when comparing states, the typical seasonal pattern previously described for PRRS could only be detected for farms located in the states of Minnesota, North Carolina and Nebraska. For the other two states, seasonal peaks every six months were detected within a year. In conclusion, we showed that epidemic patterns are not homogeneous across the U.S, with major peaks of disease occurring through the year. These findings highlight the importance of coordinating alternative control strategies in different regions considering the prevailing epidemiological patterns.

PMID:

 

29614099

 

DOI:

 

10.1371/journal.pone.0195282