Month: June 2017

Science Page: PRRS cumulative incidence by status

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.

How does PRRS incidence vary based on farm status? This is the question answered in this week’s edition of the Science Page. Three different formulas were used to calculate the incidence in each of the group over type. First, the initial number of farms of each status at the beginning of the year was used as the denominator. Then, the denominator was changed to the total number of farms that entered each status since the beginning of the year. Lastly, weekly incidences calculated for each of the group since the beginning of the year were added. Calculations went back for the last 3 years.

Key points from this week edition:

  • Cumulative incidence is higher in those farms that are under status 2, 2vx and 2fvi.
  • The incidence is lower in farms that had recently an outbreak or those that are completely negative.
  • Different ways of calculating incidence by herd status lead to the same overall conclusion.

Take a look at PRRS incidences in farms of group 2 status, vaccinated or inoculated with live virus over the past years.

Obituary for Dr. Bob Morrison

05-16-4001a
Credits: National Hog Farmer

Morrison, Robert (Bob) of Roseville, MN, died tragically in a car accident on May 2, 2017 at age 64 while traveling in the Czech Republic.

He is survived by wife Jeanie Morrison, three children, Jessie (Eric) Bain, Peter (Eva) Morrison, and William Morrison, and grandson Ian Bain.

A man of the utmost integrity, Bob was a beloved father, husband, grandpa, uncle, brother, father-in-law, brother-in-law and friend. He was honest, hard-working, loyal, open-minded, grateful, genuine and humble. Bob was a kind man with a gentle soul. Bob was a lifelong learner and born teacher.

He served as Faculty in the Department of Veterinary Population Medicine at the University of Minnesota since 1986. He was a brilliant data scientist and leader in his industry, guiding responsible vaccination and antibiotic use domestically and globally, responding to outbreaks and pandemics, and advocating for safe and ethical pork production.

Memorial contributions may be made to one of two organizations close to Bob’s heart:

  1. The University of Minnesota Foundation SquashScholars Scholarship (established by Bob and Jeanie) by mail to U of M Foundation, PO Box 860266, Minneapolis, MN, 55486-0266, or online at give.umn.edu/giveto/… (Tax ID: 41-6042488)
  2. Global Health Ministries (Project #79 AL -P0001) for Dr. Mark Jacobson’s HealthMinistries in Arusha, Tanzania by mail to 7831 Hickory St NE, Fridley, MN 55432 (Tax ID: 36-3532234).

Visitation will be at Falcon Heights United Church of Christ (1795 Holton St, Falcon Heights, MN 55113) on Thursday, July 6, 5:30-7:30 PM. Funeral Services will be at Roseville Lutheran Church (1215 Roselawn Ave W, Roseville, MN 55113) on Friday, July 7, 7 PM.

PhD seminar: Epidemiological investigation of a non-reportable endemic disease: PRRS in the US

Title: Epidemiological investigation of a non-reportable endemic disease: Porcine reproductive and respiratory syndrome (PRRS) in the US

Presented by:   Pablo Valdes-Donoso

Date:    Friday, June 9, 2017
Time:    3:00 – 4:00 pm
Place:    385-J, AS/VM Building

Abstract: Porcine reproductive and respiratory syndrome (PRRS), caused by a highly mutagenic and resistant RNA-virus, is an endemic disease that has been noted as one of the most important animal production diseases in the US because of its large economic damage on the swine industry. Nonetheless, there is no official control framework for this disease, so producers rely on voluntary regional control programs (RCPs) for its mitigation. Despite efforts to control PRRS, it persists in the environment, affecting a large number of farms every year. Using information shared by a specific RCP (RCP-N212), this dissertation focused on important aspects of PRRS dynamics within an RCP. Specifically, this dissertation encompassed five chapters. An introductory chapter is followed by the second chapter, which quantifies the extent to which RCPs contribute to PRRS control. After that, a prediction of network structure was made to forecast animal movements among farms within the RCP-N212. Then, longitudinal data collected from sow farms were used to measure the impacts of PRRS on production. Finally, a disaggregated disease diffusion model was used to depict PRRS dynamics within the RCP-N212, as well as to evaluate individual and collective strategies adopted by producers. This dissertation provides insight to the evaluation of regional control strategies that may be used as a framework for a formal PRRS control program.

The latest trends in PRRSV diagnostics: less serum samples, more oral fluids, and more 1-7-4 RFLP pattern

Today, Dr. Albert Rovira from the University of Minnesota, Veterinary Diagnostic Laboratory shares with us the trends he has observed in PRRSV diagnostics over the past years. The findings can be found in the slideshow below.

  • The use of tissue samples follows a seasonal pattern and represents clinical cases with a percent of positives of 30%
  • The number of oral fluid samples is increasing. Used for monitoring positive farms and more recently for surveillance in negative farms as well:: 15% of positive samples
  • The number of blood swabs, serum samples, and semen samples, typically used for surveillance in negative farms, is decreasing. Lowest percent of positive samples: 8%
  • RFLP patterns are changing over time. In the past years, 1-7-4 > 1-3-4 or 1-8-4 or 1-4-4
Reminder: what is a RFLP pattern?

RFLP stands for Restriction Fragment Length Polymorphism and is a technique used to detect nucleotide changes in a genetic sequence. The genetic material is put in contact with restriction enzymes which are very specific to a genetic sequence. If the enzyme recognizes the sequence pattern, it will cleave the DNA or RNA fragment. After that, a type is determined based on the number of fragments and its size.

For example with PRRSV, three enzymes are used and the number of fragments each of them produces makes up the numbers of the RFLP pattern. Currently, the RFLP type is not actually performed in the lab. Instead, it is predicted based on the ORF5 RNA sequence and the knowledge of the cutting capabilities of each enzyme.

Therefore, the RFLP pattern gives us a way to cluster PRRSV strains in groups but very little indication about how similar they are to each other.

Science page: How farm structure and demography impact disease detection

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’s edition reports the latest research on modeling the spread of swine vesicular diseases based on farm structure and number of sites. The model was then used to establish an expected time to detection. Two virus strains (high versus low virulence) were evaluated with the model to assess how the strain would influence the time to detection in a farm.

Key points from this week edition:

  • The models showed that the virus persisted longer in farms with a farrowing unit.
  • It is more difficult to diagnose FMD when the strains cause low mortality or no mortality.

Click on the link to see the details about disease spread models.