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

Today, we are sharing an open-access publication from Dr. Andreia Arruda, Dr. Ana Alba and members of the MSHMP team in the journal PlosOne.

This study was conducted using data collected from the Morrison Swine Health Monitoring Project. The main objective of this study was to use time-series analysis to investigate whether yearly patterns commonly described for PRRS were in fact conserved across different U.S. states.

Methods

The 268 breeding herds enrolled in this project were the ones that participated in the MSHMP from July 2009 to October 2016. PPRS status of each farm was reported weekly following the AASV guidelines. The five states examined included Minnesota (MN), Iowa (IA), North Carolina (NC), Nebraska (NE), and Illinois (IL).

Results

81 MN farms, 72 IA, 45 NC, 30 NE, 40 from IL, were enrolled in the study with a mean number of animals per site of 2,666; 3,543; 2,342; 4,041; and 4,018 respectively.

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Graphs showing the prevalence (black line) and upper and lower 95% confidence intervals (grey dotted lines) of PRRS virus positive farms for the five different U.S. states participating in this study: A: Minnesota; B: Iowa; C: Nebraska, D: North Carolina and E: Illinois

The main finding of this study was that PRRS seasonality varies according to geographical region, and the commonly referred “PRRS season” is not necessarily the only time of increase in disease incidence.

Another interesting finding from this study was the presence of an alternating trend for all examined states within of the U.S., except for the state of Iowa, the largest pork producing states in the country (approximately 31.4% of the total US hog and pig inventory), which had an increasing linear trend over the examined years.

In conclusion, PRRS seasonal patterns are not homogeneous across the U.S., with some important pork producing states having biannual PRRS peaks instead of the previously reported winter peak. Findings from this study highlight the importance of coordinating alternative control strategies in different regions considering the prevailing epidemiological patterns, and the need to reinforce strict biosecurity practices beyond the typically described “PRRS season”.

You can also listen to Dr. Arruda present some of these research findings at the 2017 Leman conference.

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.

What your favorite posts of 2018 are so far

On Friday, we usually share with you the latest Science Page from the Bob Morrison’s Swine Health Monitoring Project. Today, we decided to do something a little different but you can always go read our  previous editions of the science page on our website.

Today, we are bringing back to 2 most popular blog posts from 2018, in case you missed them.

Swine microbiome studies: why, how and where are we going?

In this article written by Dr. Andres Gomez, we talk about what the microbiome is, how we characterize it and why it is important to define what a normal microbiome is.

Sow farm classification according to Mycoplasma hyopneumoniae status

Here are the key points of this article by Dr. Maria Pieters in collaboration with the University of Barcelona:

  • Sow farm classification according to M. hyopneumoniae status helps to manage this bacterium’s transmission chain.
  • The proposed farm classification system for M. hyopneumoniae can be used for one (farrow-to-finish) or multiple-site (farrow-to-wean and farrow-to-nursery) production systems.
  • Monitoring of M. hyopneumoniae to classify farms requires the combination of observational and laboratory analyses.

Swine Influenza virus A: podcast 1/3

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Podcasts are perfect for summer! We are presenting you with a new series on swine influenza from “At The Meeting… Honoring Dr. Bob Morrison in collaboration with SwineCast.

In this first episode,  Dr. Montserrat Torremorell (University of Minnesota), Dr. Marie Culhane (University of Minnesota), Dr. Gordon Spronk (Pipestone Veterinary Services), and Dr. Tom Wetzell (Boehringer Ingelheim), talk about the issues of influenza in humans and swine, the state of surveillance of influenza in pigs and humans, and the biosecurity needed to help prevent the spread of the influenza virus between human and pigs.

Click to listen to the entire recording (20min).

NHF: PRRS is also a summer disease

Our latest collaboration with the National Hog Farmer was written by the Morrison Swine Health Monitoring Program team regarding the incidence of PRRS in the summer.

Although our understanding of disease and control methods has improved in recent years, we continue to learn new features of PRRSV epidemiology in part thanks to the Morrison Swine Health Monitoring Project. One of the most recent questions that we have addressed based on enquires from MSHMP participants is whether PRRS incidence during the summer was higher in recent years (i.e. 2016-17) compared to previous years (i.e. 2009-15). We know that PRRSV outbreaks tend to have a seasonal pattern and that they are more frequent during the fall and winter, but we know little about the breaks that happen in the summer and spring.

In order to dig into this question, we analyzed MSHMP data from 2009 to 2017 which included 1,329 outbreaks. Of these, 66% of the breaks occurred during fall and winter and 14% and 20% of the breaks occurred during summer and spring, respectively. Although there were fewer breaks in the spring and summer, the number of breaks in warmer seasons was still significant which represents an on-going frustration to producers because the “PRRSV season” is supposed to be over.

As part of the analysis we learned that between 3% and 6% of the herds break yearly during the summer and spring seasons, respectively. This represents approximately 83 herds out of the 917 reporting in the MSHMP database. If we estimate that the average sow farm has 3,000 sows, then almost a quarter of a million sows break yearly during these two seasons.

Remember, although the risk of PRRSV introduction is lower during the spring and summer, PRRSV breaks still happen, so biosecurity efforts should not be decreased. PRRSV is a sneaky virus so keep your biosecurity up, even in the summer.

All of our collaborations with the National Hog Farmer can be found here.

Science Page: Incidence Year 2017/2018 Annual Summary

This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.

This week, Dr. Cesar Corzo is giving us a summary of the 2017/2018 year.

Objective 1 – Disease incidence and monitoring

PRRS – Unfortunately 31% of the herds in the project broke with PRRS making it the third highest incidence in the MSHMP history. The epidemic initiated at the same time of the year following previous years’ pattern. As with previous years, we continue to see viral introduction into 1) status 4 breeding herds in low dense regions and 2) filtered sow herds reminding us that there continues to be unanswered questions from a transmission standpoint.

PEDv – The year ended at 8% (1% increase compared to the previous year) with a series of outbreaks occurring in 12 farms that had never been exposed to PEDv.

PDCoV – Even though we have not been including a graph we continue to monitor for this virus. There has been minimal activity.

SVV – Incidence of this virus remained low and did not follow the seasonal pattern seen in the previous 2 years.

Atypical CNS Cases – These viruses continue to be found in specific cases with no apparent trend.

Objective 2 – Prospective monitoring of PRRSv

PRRSv sequences continue to be collected building a library for MSHMP participant use. We have used this approach a few times while outbreak investigations have been conducted. We are currently conducting monitoring in a three-company based region detecting newly emerged viruses. On the other hand, the database is being analyzed in a way that provides epidemiological sense. We will report more on this in an upcoming report.

Objective 3 – Develop capacity to capture and analyze movement data

We have been able to generate a process to record movement data (i.e. starting and ending location,speed, trip duration) together with a visualization package in Google Earth. Although we have proved the concept we have faced technology challenges during the development phase and we are currently revisiting our approach.

Objective 4 – To expand participation of producers to allow all to be involved

Expansion continues with existing participants adding more farms. There have been other production systems that have either signed the
enrollment forms and are in the process of submitting their data or other production companies that have verbally agreed to join.

DVM students: we invite you to apply to the Morrison Swine Innovator Prize!

Veterinary students: Are you shadowing a swine practitioner this summer or have you been involved in an interesting clinical case investigation? Did you work on your veterinary skills by designing a differential diagnosis list or working on a treatment plan? Did you investigate a problem by analyzing production records? Share your work at the Allen D. Leman Swine Conference to win the Morrison Swine Innovator Prize!

Attending the Leman Conference is a great opportunity for veterinary students who want to network with industry leaders. Submissions to enter in the selection to present at the DVM student session at the Leman Conference should be uploaded at z.umn.edu/MSIP by August 15th at the end of the day.

 

If you have any questions, please contact Dr. Perle Boyer at pboyer@umn.edu. For more information about the Morrison Swine Innovator Prize visit z.umn.edu/MSIP.

Beer and Bacon conversations: a new session at the Leman swine conference!

The organizing committee of the Allen D. Leman swine conference is proud to present a new session: Beer and Bacon conversations! The goal of this unique session is to invite industry leaders to share personal views and experiences with participants in a fun and relaxed environment.

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This year, we are honored that Dr. Matthew Turner, veterinarian and head of pork live operations at JBS, accepted our invitation.

A graduate of North Carolina State University College of Veterinary Medicine, Dr. Turner joined JBS after being a staff swine veterinarian for Prestage Farms for more than 10 years. He was recognized by the American Association of Swine Veterinarian as the 2014 Swine Practitioner of the year and presented the Dr. Alex Hogg Memorial Lecture at the 2017 AASV annual meeting. Dr. Turner is currently an at large member of the Board of Directors of the Swine Health Information Center (SHIC).

The session will be held at the InterContinental hotel on Sunday, September 16th at 5:15pm. Dr. Marie Culhane will get the conversation started but participation from the audience is more than welcome!

Seating for this event is limited. Do mot miss out by registering today!