N&H TOP LINE: Influenza D research moves ahead

Research focuses on new flu virus and its virulence. ALSO: Fermentation product studied in swine; poultry litter treatment reduces emissions.

Research on a new influenza virus that affects pigs and cattle has helped South Dakota State University (SDSU) doctoral student Chithra Sreenivasan earn the Joseph P. Nelson Graduate Scholarship Award, which recognizes original scientific research and provides $8,500 for tuition and expenses.

The new influenza virus, called influenza D, does not affect humans, Sreenivasan explained. SDSU alumnus Ben Hause, now a research assistant professor at Kansas State University, discovered the virus, which he identified and characterized as part of his doctoral work under the tutelage of professor Feng Li.

Li and professor Radhey Kaushik secured a National Institutes of Health grant for nearly $400,000 to continue this work. Both faculty members have joint appointments in the biology and microbiology and veterinary and biomedical sciences departments at SDSU.

Ultimately, the goal is to determine whether the virus can cause problems in people, Kaushik explained. “If the virus can undergo reassortment in combination with a closely related human influenza virus, it may be able to form a new strain that could pose more of a threat to humans.”

Identifying hosts, animal model. To identify exposure to the virus, Sreenivasan tests blood samples for influenza D antibodies. Working with the Minnesota Poultry Testing Lab, she found no evidence of the new influenza strain in poultry; however, she did find antibodies to the virus in sheep and goats from the Midwest through blood samples archived at Washington State University.

Sreenivasan co-authored a paper on those findings that was published last year in the international journal Veterinary Microbiology. In ongoing work, she and her colleagues have also identified antibodies in horses.

Using the bovine influenza D strain, Sreenivasan became the first to prove that the guinea pig could be used as an animal model to study the virus. Although guinea pigs showed no symptoms, she successfully isolated antigens in tracheal and lung tissues. In addition, her research showed that the virus is spread only through direct contact. Those results were published in the Journal of Virology.

Studying virulence among strains. Sreenivasan's current study uses the guinea pig model to compare virulence among bovine and swine influenza D strains and human influenza C. She has just begun analyzing the data.

Influenza D has about 50% similarity to human influenza C, which "affects mostly children,” Sreenivasan explained, noting that the most common symptom is a runny nose. “It’s not a serious disease. We all have some antibodies because we were infected as children.”

In addition, she is developing a way to study the virus in living cells: trachea and lung epithelial cells from swine and cattle. “I isolate the cells and allow them to grow and then infect them to study the genetic and biologic characteristics of the virus,” Sreenivasan said.

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Antibiotic alternatives

Veterinarians are leading the effort to optimize antibiotic use and preserve the efficacy of current therapeutic treatments. Interest is high in research that evaluates natural alternatives to promote pig health.

In young pigs, pathogenic strains of Escherichia coli and salmonella are a particular challenge. New research presented at the recent annual meeting of the American Association of Swine Veterinarians included "Quantitative Assessment of Prevalence & Severity to Understand Impact of Lactobacillus acidophilus Fermentation Product (SynGenX) in a Herd with Endemic (E. coli) K88 & Salmonella Post-Wean" by independent researcher Sarah Probst Miller and co-authors Alex Ramirez, researcher with Iowa State University, and Benjamin Bass and Jason Frank, researchers with Diamond V.

"Previous controlled studies have shown that (the fermentation product) supports feed intake, weight gain and gut health and wellness in young pigs," Bass said. "The product has also been shown to affect enteric bacteria concentrations and the immune response. The purpose of Dr. Probst Miller’s research was to evaluate how these effects may assist pigs in coping with both E. coli and salmonella before they cause disease."

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Emissions reduction

A recent life-cycle assessment of PLT poultry litter treatment showed that the product has the ability to significantly reduce greenhouse gas emissions from poultry houses.

The Sustainability Research Group at the University of Toledo in Ohio evaluated life-cycle greenhouse gas emissions from the application of poultry litter treatment in poultry house operations.

The assessment identified reductions in greenhouse gas emissions from lower energy usage for a six-week growout period as well as the carbon dioxide impact from the production and distribution of PLT.

The researchers found that when the litter treatment was applied, the reduction in heating fuel and ventilation electricity usage equaled 16,200 lb. of carbon dioxide in the winter and 3,100 lb. of carbon dioxide in the summer. The production and distribution of one ton of PLT generates about 700 lb. of carbon dioxide-equivalent life-cycle greenhouse gas emissions, meaning every applied ton of the product reduces the carbon dioxide equivalent 20-fold.

In addition to the carbon dioxide reduction, field studies have recorded significant bird weight improvement in poultry house operations with the use of the litter treatment.

The complete LCA can be found here.

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