Swine barns not a downwind health threat

Saskatoon, Sask., March 6, 2002

A five-month air sampling study shows air 600 metres downwind of swine barns is as ‘fresh’ as air 2.4 kilometres upwind of a swine barn, say researchers at the Veterinary Infectious Disease Organization (VIDO) in Saskatoon. The study is important for pork producers and their neighbours concerned about potential environmental impacts and health safety issues surrounding hog production.

“The study was designed to address the question: Are there microbial products that can be detected in dust downwind from swine barns?” says Dr. Phil Willson, VIDO Program Co-ordinator – Bacteriology. “One of the reasons we initiated this study was to provide some scientific basis for addressing the concerns of people living or working near existing or proposed livestock confinement facilities.”

Specifically, the study was designed to measure the amount of airborne microbial DNA and endotoxins downwind from swine facilities. Endotoxins are pulmonary irritants that break away from the cell wall of dead Gram-negative bacteria that when inhaled, may cause coughing, phlegm, wheezing, fever and, in severe cases, chronic airway inflamation. The swine production facility at the Prairie Swine Centre’s Elstow Research Farm Inc. was used for the study. The study team also included researchers from the University of Saskatchewan Department of Agricultural and Bioresource Engineering in the College of Agriculture.

As expected, elevated concentrations of microbial DNA were found near the barn exhaust vents, Willson says. “However, at 600 metres these levels had become diluted to that of ‘fresh air.’ Statistically, the air 600 metres downwind from the barn was not different from air 2.4 kilometres upwind.”

Willson and his team chose to use the lengthy distance of 2.4 kilometres upwind as their fresh air basis to allay any concerns that the barn was influencing those samples. Air sampling began in April 2001 and was completed in August 2001.

The researchers detected more dust in the air during spring seeding and other field operations, generating small increases in endotoxin and microbial DNA levels. This is not surprising, since micro-organisms are part of nature and are found everywhere, including in soil. The researchers could not distinguish between micro-organisms from the swine barn and other environmental sources during times of soil disturbance in the vicinity of the project site, he says. “Further research would be required to make that determination, but we think that the somewhat increased microbial DNA and endotoxin levels were the result of the soil disturbance.”

While the study’s main focus was to quantify the level of microbial DNA and endotoxin in the air, researchers were also interested in identifying the organisms collected over the five months of air sampling. The results provide further good news to the industry and residents living near hog facilities.

“We isolated a number of these bacteria and sent the samples to the clinical diagnostic lab Division of Clinical Microbiology, Royal University Hospital,” he says. “They determined that, in fact, none of the bacteria were pathogens associated with airborne transmission of human respiratory disease.”

Over 80 different bacterial isolates are being analyzed to characterize species and type. “They completed the analysis on two thirds of the isolates and have determined they are relatively common types of bacteria found in the environment,” he says.

While analysis continues on the remaining bacteria isolates, the study has already shown that the airborne endotoxins and microbial DNA dispersed soon after emission from this 600-sow farrow-to-finish hog operation. “We hope this study helps people recognize that the air 600 metres downwind of a hog barn does not pose more risk of infection than fresh air.”

VIDO, a non-profit research institute wholly owned by the University of Saskatchewan, is a global leader in food animal and poultry vaccine research for infectious diseases. It operates with substantial support from the Province of Alberta and the Province of Saskatchewan. Sask Pork, Alberta Pork, Manitoba Pork and Saskatchewan Agriculture Development Fund (ADF) provide core swine research funding. Saskatchewan ADF, Livestock Environmental Initiative and Sask Pork provided funding for the project.

For more information, contact:

Stuart Bond
Associate Director, Marketing and Business Development
Veterinary Infectious Disease Organization
Phone: (306) 966-7474
Fax: (306) 966-7478