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 Science page is a follow-up from the one presented last week and focuses on the difference between incidence rate and incidence risk. Those two epidemiological measurements are often mistaken for one another.
Key points from this week edition:
Incidence risk is a measure of disease occurrence over a defined period of time. It is a proportion, therefore takes values from 0 to 1 (0% to 100%).
Incidence rate takes into account the time an individual is at risk of disease. It is not a proportion since it defines the number of cases per animal or farm time at risk.
Incidence risk and Incidence rate are often confused. Incidence risk and rate are numerically the same when the period at risk does not vary across individuals being studied.
Take a look at the complete report to see an example of the difference between incidence risk and incidence rate on farms.
In this article published by the National Hog Farmer, nutritionists and microbiome analysts from the University of Minnesota discuss what consequences antimicrobials can have on the gut microbiome.
What does microbiome mean?
Microbiome refers to all of the microbes present in an area. For example, gut microbiome is the entire population of microorganisms (most of the time bacteria) present in the intestinal tract.
The purpose of this research program is to study the effects antimicrobials can have on the bacterial populations present in the gut and how those changes influence the metabolites present in the pig.
What is a metabolite?
Metabolites are usually small molecules and are created by enzymatic reactions happening through the natural life of a cell or organism.
One of the effects of administering tylosin to pigs was the increased growth of bacteria producing short-chain fatty acids in the intestinal flora. The use of this antimicrobial also led to the development of Lactobacillus in the gut.
Relating changes in metabolites to the gut microbiome allows for a more complete understanding and investigation of the impact that antibiotics have in enhancing growth. Without completely understanding the mechanism of increased growth, antibiotic alternatives could be used inappropriately without much added benefit.
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:
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)
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.
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.
A lot of research has been done at the University of Minnesota regarding the survival of porcine coronaviruses in the feed and how to impact their survival. We are presenting today two papers published this spring looking at this important topic. First, Trudeau et al. showed that the feed ingredient which lead to the longest porcine coronaviruses’ survivability was soybean meal. Then, Cottingim et al. showed that some feed additives could inactivate PDCoV.
Importance of porcine coronaviruses and their relationship to swine feed
Porcine coronaviruses of importance in the swine industry nowadays are Porcine Epidemic Diarrhea virus (PEDV), Transmissible Gastroentiritis virus (TGEV), and Porcine Delta Coronavirus (PDCoV). All cause enteric issues in swine and some can lead to up to 100% mortality in nursing piglets. The role of feed ingredients in spreading PEDV and causing outbreaks in Northern America in 2013 has been questioned since then.
Survival of PEDV, TGEV, and PDCoV in complete feed and feed ingredients
The first research project evaluated the persistence of PEDV, TGEV, and PDCoV in porcine feed and feed ingredients. To do so, complete feed and major feed ingredients samples (spray dried porcine plasma, meat meal, meat and bone meal, blood meal, corn,
soybean meal, and corn dried distillers grains with solubles) where inoculated with PEDV, TGEV, or PDCoV and kept for up to 56 days. Aliquots were tested 11 times between the inoculation day and the end of the trial. Time necessary to reduce the viral concentration by 1 log was recorded.
Soybean meal took the longest time to attain the reduction in concentration for all of the coronaviruses, reaching 7.5 days for PEDV, and 42 days for both PDCoV and TGEV. This study also demonstrated that there was a modest positive correlation between moisture content and persistence of TGEV and PDCoV. On the other end, there was a moderate negative correlation between ether extract content and TGEV survival, not observed with the other two viruses.
Click on the banner below to access the full article in open access.
Feed additives and PDCoV survival
In this second project, the survival of PDCoV was evaluated after being put in contact with nursery feed samples containing one of six different commercial feed acids (UltraAcid P, Activate DA, KEMGEST, Acid Booster, Luprosil, and Amasil), salt, or sugar. Acids were added following the recommended concentrations in the first part of the experiment and then, were double-dosed. Feed samples were inoculated with PDCoV and kept for up to 35 days. Like in the previous article, days to achieve a reduction of virus concentration by 1 log were recorded.
At recommended values, there was no difference between viral load reduction in feed samples with or without additives. When acids were added to the feed at a double concentration, the time period to attain the reduction in viral load was decreased to 0.28 days or less for all acids except for Amasil which increased it to 4.95 days (control: 0.35 days). The difference between acidifiers may be explained by the active ingredients used in the products. Furthermore, the addition of salt decreased PDCoV survival whereas sugar increased it.
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