Association Influenza A virus and PRRSv in sow farms with post-weaning mortality.

Alvarez J, Sarradell J, Kerkaert B, Bandyopadhyay D, Torremorell M, Morrison R, Perez A. Association of the presence of influenza A virus and porcine reproductive and respiratory syndrome virus in sow farms with post-weaning mortality. Prev Vet Med. 2015 Jul 17. pii: S0167-5877(15)00235-4. doi: 10.1016/j.prevetmed.2015.07.003.

Abstract

Influenza A virus (IAV) and porcine reproductive and respiratory syndrome virus (PRRSV) are among the most important pathogens affecting pigs worldwide. Their effect on post-weaning mortality can be substantial and may be potentiated by other concomitant factors. Here, the objective was to evaluate the association between IAV and PRRSV infection at weaning with post-weaning mortality observed in wean-to-finish farms in order to better quantify the full impact of their presence in breeding herds. IAV and PRRSV presence was assessed by real time reverse transcription (RRT)-PCR on oral fluid samples from suckling piglets in nine sow farms. Production data from 177 batches of growing pigs weaned one week before/after IAV and PRRSV testing were analyzed to measure the association between IAV and/or PRRSV test results and mortality recorded for a given batch through the use of Bayesian mixed effects negative binomial multivariable regression model. The model accounted for potential confounders such as flow, date at weaning, days on feed and batch size. A statistically important association between IAV (incidence ratio (IR)=1.18, 95% posterior probability interval 1.15-1.21) and PRRSV (IR=1.41, 95% PPI 1.30-1.52) with post-weaning mortality was detected, with season and number of days on feed also associated. Our results suggest that infection with IAV or PRRSV in the pre-weaning period is associated with an increase in post-weaning mortality. This association should be taken into consideration when measuring the impact of IAV and PRRSV in breeding herds.

Copyright © 2015 Elsevier B.V. All rights reserved.

KEYWORDS:

Bayesian modeling; Influenza A virus; Porcine reproductive and respiratory syndrome virus; Post-weaning mortality; Swine

PMID:

 

26210012

 

[PubMed - as supplied by publisher]

Simulation of between-farm transmission of PRRSv

Thakur KK¹, Revie CW², Hurnik D², Poljak Z³, Sanchez J². Simulation of between-farm transmission of porcine reproductive and respiratory syndrome virus in Ontario, Canada using the North American Animal Disease Spread Model. Prev Vet Med. 2015 Mar 1;118(4):413-26. doi: 10.1016/j.prevetmed.2015.01.006. Epub 2015 Jan 16.

            ¹Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PEI, Canada. Electronic address: kthakur@upei.ca.

            ²Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PEI, Canada.

            ³Department of Population Medicine, Ontario Veterinary College, University of Guelph, Guelph, ON, Canada.

Abstract

Porcine reproductive and respiratory syndrome (PRRS), a viral disease of swine, has major economic impacts on the swine industry. The North American Animal Disease Spread Model (NAADSM) is a spatial, stochastic, farm level state-transition modeling framework originally developed to simulate highly contagious and foreign livestock diseases. The objectives of this study were to develop a model to simulate between-farm spread of a homologous strain of PRRS virus in Ontario swine farms via direct (animal movement) and indirect (sharing of trucks between farms) contacts using the NAADSM and to compare the patterns and extent of outbreak under different simulated conditions. A total of 2552 swine farms in Ontario province were allocated to each census division of Ontario and geo-locations of the farms were randomly generated within the agriculture land of each Census Division. Contact rates among different production types were obtained using pig movement information from four regions in Canada. A total of 24 scenarios were developed involving various direct (movement of infected animals) and indirect (pig transportation trucks) contact parameters in combination with alternating the production type of the farm in which the infection was seeded. Outbreaks were simulated for one year with 1000 replications. The median number of farms infected, proportion of farms with multiple outbreaks and time to reach the peak epidemic were used to compare the size, progression and extent of outbreaks. Scenarios involving spread only by direct contact between farms resulted in outbreaks where the median percentage of infected farms ranged from 31.5 to 37% of all farms. In scenarios with both direct and indirect contact, the median percentage of infected farms increased to a range from 41.6 to 48.6%. Furthermore, scenarios with both direct and indirect contact resulted in a 44% increase in median epidemic size when compared to the direct contact scenarios. Incorporation of both animal movements and the sharing of trucks within the model indicated that the effect of direct and indirect contact may be nonlinear on outbreak progression. The increase of 44% in epidemic size when indirect contact, via sharing of trucks, was incorporated into the model highlights the importance of proper biosecurity measures in preventing transmission of the PRRS virus. Simulation of between-farm spread of the PRRS virus in swine farms has highlighted the relative importance of direct and indirect contact and provides important insights regarding the possible patterns and extent of spread of the PRRS virus in a completely susceptible population with herd demographics similar to those found in Ontario, Canada.

Copyright © 2015 Elsevier B.V. All rights reserved.

KEYWORDS:

Between-farm; Infectious diseases; NAADSM; PRRS Virus; Porcine reproductive and respiratory syndrome virus; Spread model; Swine

PMID: 25636969 [PubMed - in process] 

PRRSv attenuated vaccine [Porcilis PRRS ID] reduced virus transmission in experimental conditions

Rose N, Renson P, Andraud M, Paboeuf F, Le Potier MF, Bourry O. Porcine reproductive and respiratory syndrome virus (PRRSv) modified-live vaccine reduces virus transmission in experimental conditions. Vaccine. 2015 May 15;33(21):2493-9. doi: 10.1016/j.vaccine.2015.03.040. Epub 2015 Mar 26.

Abstract

Some vaccination strategies have shown good results in reducing the clinical outcomes of PRRS. Nevertheless the effect of vaccines on viral transmission is poorly described, so we aimed to fill this gap with the present study. Twelve Specific Pathogen Free (SPF) piglets, vaccinated against PRRSv at 3 weeks of age (Porcilis PRRS ID(®), MSD), were inoculated at 31 days post-vaccination with a heterologous genogroup 1.1 strain, and put in contact with 12 vaccinated piglets during 49 days. The same protocol was carried out simultaneously with SPF non-vaccinated piglets. Piglets were monitored individually for clinical symptoms on a daily basis and individual blood samples were taken twice a week. In inoculated piglets, the genome viral load specific to the inoculated strain was reduced and viraemia shortened in vaccinated piglets (28 days versus 38 days in non vaccinated piglets). In contact pigs, the challenge strain was detected in the serum of only one vaccinated piglet whereas it was detected in all contact non-vaccinated piglets. Transmission parameters were estimated by a Bayesian analysis of transmission data in the two groups. The estimated transmission rate was 10-times lower in vaccinated than in non-vaccinated piglets and the duration of infectiousness was reduced, leading to a reproduction ratio R significantly lower (0.30 [0.05-0.96] versus 5.42 [2.94-9.04] in non vaccinated piglets). Hence, in our experimental conditions, vaccination was able to decrease considerably PRRSv spread. A complementary evaluation in field conditions would be required to identify circumstances associated with infection control failures that can be observed in pig farms.

Copyright © 2015 Elsevier Ltd. All rights reserved.

KEYWORDS:

Porcine reproductive and respiratory syndrome virus; Reproduction number; Transmission; Vaccination

PMID: 25820061 [PubMed - in process]

Lessons learned and knowledge gaps about the epidemiology and control of PRRSv in North America

Perez AM, Davies PR, Goodell CK, Holtkamp DJ, Mondaca-Fernández E, Poljak Z, Tousignant SJ, Valdes-Donoso P, Zimmerman JJ, Morrison RB. Lessons learned and knowledge gaps about the epidemiology and control of porcine reproductive and respiratory syndrome virus in North America. J Am Vet Med Assoc. 2015 Jun 15;246(12):1304-17. doi: 10.2460/javma.246.12.1304.

[This paper has no abstract]

PMID: 26043128 [PubMed - in process]

Comparison of specimens for detection of PRRSv in boar studs

Pepin BJ, Kittawornrat A, Liu F, Gauger PC, Harmon K, Abate S, Main R, Garton C, Hargrove J, Rademacher C, Ramirez A, Zimmerman J. Comparison of specimens for detection of porcine reproductive and respiratory syndrome virus infection in boar studs. Transbound Emerg Dis. 2015 Jun;62(3):295-304. doi: 10.1111/tbed.12135. Epub 2013 Jul 30.

Abstract

Porcine reproductive and respiratory syndrome virus (PRRSV)-contaminated semen from boars is a route of transmission to females, and early detection of PRRSV infection in boars is a key component in sow farm biosecurity. The purpose of this study was to determine the optimum diagnostic specimen(s) for the detection of acute PRRSV infection in boars. Individually housed boars (n = 15) were trained for semen and oral fluid collection and then vaccinated with a commercial PRRSV modified live virus vaccine. Starting on the day of vaccination and for 14 days thereafter, oral fluid specimens were collected daily from all boars. The 15 boars were subdivided into three groups of 5, and serum, blood swabs and 'frothy saliva' were collected at the time of semen collection on a 3-day rotation. Frothy saliva, derived from the submandibular salivary gland, is produced by aroused boars. Semen was centrifuged, and semen supernatant and cell fractions were tested separately. All samples were randomly ordered and then tested by PRRSV real-time quantitative reverse-transcription polymerase chain reaction assay (rRT-PCR) and PRRSV antibody ELISA. In this study, a comparison of serum, blood swab, and oral fluid rRT-PCR results found no statistically significant differences in the onset of detection or proportion of positives, but serum was numerically superior to oral fluids for early detection. Serum and oral fluid provided identical rRT-PCR results at ≥ 5 day post-vaccination. Likewise, the onset of detection of PRRSV antibody in serum, oral fluid and frothy saliva was statistically equivalent, with serum results again showing a numerical advantage. These results showed that the highest assurance of providing PRRSV-negative semen to sow farms should be based on rRT-PCR testing of serum collected at the time of semen collection. This approach can be augmented with oral fluid sampling from a random selection of uncollected boars to provide for statistically valid surveillance of the boar stud.

© 2013 Blackwell Verlag GmbH.

KEYWORDS:

PRRSV; boar; oral fluid; semen; serum; surveillance

PMID: 23895185 [PubMed - in process]