Each year approximately 3% of the sow farms have a PRRS outbreak during the summer.
The incidence of summer PRRS breaks has been constant over the last 9 years.
There are geographical areas with higher or lower risk of summer breaks.
A summer outbreak was defined as a PRRS case that happened between June 21st and September 21st of the year. The mean incidence of PRRS summer outbreaks was 3.2% between 2009 and 2017, ranging between 1.6% and 4.4%. The trend was stable among the years. (Figure 1) Not all areas are equal against summer outbreaks. Indeed, the region of Southern Minnesota – Northern Iowa is more at risk of outbreaks than others like Southern Iowa or Eastern North Carolina. (Figure 2)
Biosecurity measures against PRRSV should therefore be a concern all year round for swine producers!
The first week-end in December is usually the time of the North American PRRS symposium. This year did not upset the tradition but this time, the conference was in collaboration with the National Swine Improvement Federation.
The meeting was dedicated to our friend and colleague Dr. Bob Morrison. A memorial fellowship organized by Dr. Montse Torremorell (U of MN) and Dr. Joan Lunney (USDA) provided travel support to future scientists who wish to follow in his footsteps.
Stephen Gerike from the Pork Checkoff shared information on the state of pork products used in restaurant. Bacon represents 20% of products used but is still growing (+4% since last year).
Stephen Gerike shared the updated cooking recommendations for pork product.
Overall, 82% of restaurant customers eat the same or larger amount of pork which is a good trend for the industry. Mr. Gerike also shared the efforts done by Pork Checkoff to convince consumers to not overcook their pork. Reminder: 145F is safe. “Cook your pork like you cook your steak!”
The University of Minnesota was well represented during the conference. Dr. Montse Torremorell moderated the Saturday morning session on PRRS in the field. Drs. Cesar Corzo, Carles Vilalta and Juan Sanhueza shared the updates on the Morrison Swine Health Monitoring Program as well as regarding the studies that they are involved with. Take away messages:
MSHMP is now collecting information from 50% of the sows in the United States.
Based on this data, 58% of the farms breaking with PRRSV today will break again within a year.
PRRS summer outbreaks happen and vary based on location (see figure below).
Farms take a longer time to reach stability after a summer outbreak (median 41.5 weeks)
Processing fluids can be used as a monitoring method for PRRS.
After being introduced in 1999, PRRS was eradicated from the country in 2012.
In 2013 PRRS was again detected, sequence analysis suggested this was a new introduction to the country.
The Chilean swine industry and the Chilean Veterinary Services (SAG) expect to again eliminate the disease in the near future.
PRRS is a notifiable disease in Chile. It was first detected in 1999, and in 2000 both the swine industry and government joined efforts to eradicate the disease by a series of coordinated events including a mixture of herd closure and depopulation of infected premises. Vaccination was not allowed in the country to control PRRSV infection. The eradication program was completed in 2007 and as a result, Chile was declared PRRSV free in 2012. Nevertheless, on October 2013 clinical signs compatible with PRRSV were reported in a commercial sow farm. Since then, all commercial herds performed surveillance activities according to a risk score based on location and biosecurity measures. From October 2013 to October 2017, approximately 153,000 blood samples have been analyzed.
Viral sequences obtained during the 2013 outbreak were compared to sequences from the early 2000s outbreak in Chile. Results showed a large genetic difference between isolates from both outbreaks. Further analyses demonstrated that the Chilean virus was closely related to a virus circulating in the state of Indiana in the US at the time of introduction. These results suggested that the latest PRRSV outbreak in Chile was most likely due to a new introduction into the country rather than a reemergence of a strain previously detected in Chile.
By October 2017, the disease was restricted to approximately 45,000 animals in six commercial farms owned by two companies that currently have eradication programs in place. These six infected commercial sites are clustered in three areas. (See figure above)
The Torremorell lab is continuing to explore swine influenza epidemiology in this recent publication from Dr. Fabian Chamba Pardo in Frontiers in Veterinary Science. After showing that multiple genome constellations of similar and distinct influenza viruses co-circulate in pigs, the group is now presenting new data about influenza herd-level prevalence in the Midwest, and how it is influenced by seasons. Click on the banner below to read the entire research article.
60 sow farms from a single Midwestern production system were enrolled in this study. Between one and seven oral fluid samples were collected at each farm weekly and meteorological data (air temperature and relative humidity) was compiled from stations located from the farms.
28% of submissions had at least one influenza positive result. All farms tested positive at least once during study period. Herd-level prevalence ranged from 7% to 57% as show in the figure above. Prevalence was low in summer, rose during fall, and peaked twice in both early winter (December) and late spring (May). August was the month with the lowest prevalence. Influenza herd-level prevalence was higher when both mean outdoor air temperature and air humidity were lower.
The most common clades identified were H1 delta 1, H1 gamma 1, and clusters H3 IV A and H3 IV B. Furthermore, 21% of the farms had 3 different influenza genetic clades circulating during the study period and 18% had 2.
Influenza is a costly disease for pig producers and understanding its epidemiology is critical to control it. In this study, we aimed to estimate the herd-level prevalence and seasonality of influenza in breed-to-wean pig farms, evaluate the correlation between influenza herd-level prevalence and meteorological conditions, and characterize influenza genetic diversity over time. A cohort of 34 breed-to-wean farms with monthly influenza status obtained over a 5-year period in piglets prior to wean was selected. A farm was considered positive in a given month if at least one oral fluid tested influenza positive by reverse transcriptase polymerase chain reaction. Influenza seasonality was assessed combining autoregressive integrated moving average (ARIMA) models with trigonometric functions as covariates. Meteorological conditions were gathered from local land-based weather stations, monthly aggregated and correlated with influenza herd-level prevalence. Influenza herd-level prevalence had a median of 28% with a range from 7 to 57% and followed a cyclical pattern with levels increasing during fall, peaking in both early winter (December) and late spring (May), and decreasing in summer. Influenza herd-level prevalence was correlated with mean outdoor air absolute humidity (AH) and temperature. Influenza genetic diversity was substantial over time with influenza isolates belonging to 10 distinct clades from which H1 delta 1 and H1 gamma 1 were the most common. Twenty-one percent of farms had three different clades co-circulating over time, 18% of farms had two clades, and 41% of farms had one clade. In summary, our study showed that influenza had a cyclical pattern explained in part by air AH and temperature changes over time, and highlighted the importance of active surveillance to identify high-risk periods when strategic control measures for influenza could be implemented.
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, we are sharing a study from Dr. Carmen Alonso and collaborators at Elanco.
Objectives of the study:
The objectives of the study, were: 1) to analyze the trends in prolapses of sows from 2012 to 2016, and 2) to evaluate the role of management practices, production parameters, and PRRS and PED disease status as covariates in the trend analysis of uterine sow prolapses.
Uterine prolapse primarily affects sows around parturition and is still defined by an uncertain list of verified etiologies.
Since early 2013, swine companies have been experiencing an increase in the incidence of uterine prolapses in their herds.
Understanding the trends and potential risk factors would be crucial to improve the economics and welfare of the affected sow farms.
Results from this study indicate that the percentage of prolapsed sows has consistently increased every year (significant from 2014-2016) as a percentage of total deaths with the incidence being higher during the winter months and the lowest during the summer months. Total born, the use of toxin binder, assistance during farrowing, and PED health status had an association to sow deaths with prolapse per sows farrowed.