Thursday, June 21, 2018
Front Vet Sci. 2018 May 16;5:102. doi: 10.3389/fvets.2018.00102. eCollection 2018.
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.
Endemic Animal Disease; Fixed effects model ; Porcine Reproductive and Respiratory Syndrome; Production Impacts; Sow Farms; US Swine Industry
Wednesday, May 30, 2018
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.
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.
Cell-mediated immunity; Herd; Mucosal immunity; PRRS; Pig; Stability
Thursday, April 26, 2018
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.
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.
Monday, April 16, 2018
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.
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.
PRRS area spread; PRRS epidemiology; PRRS risk factors; porcine reproductive and respiratory syndrome; swine
Wednesday, April 4, 2018
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.
Friday, March 23, 2018
Prev Vet Med. 2018 Apr 1;152:89-102. doi: 10.1016/j.prevetmed.2018.02.005. Epub 2018 Feb 9.
Modelling the economic efficiency of using different strategies to control Porcine Reproductive & Respiratory Syndrome at herd level.
Cost of interventions; Economic modelling; Farm-level measures; PRRS control; PRRSV epidemiology
Saturday, March 17, 2018
Effect of vaccination with a PRRSV subunit vaccine on sow reproductive performance in endemic farms in South Korea.
Vet Rec. 2018 Mar 15. pii: vetrec-2017-104547. doi: 10.1136/vr.104547. [Epub ahead of print]
Effect of vaccination with a porcine reproductive and respiratory syndrome subunit vaccine on sow reproductive performance in endemic farms.
porcine reproductive and respiratory syndrome (prrs); reproductive failure; sow; vaccine