Evaluating the risks of airborne pathogens from manure irrigation

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Manure irrigation, which is the application of liquid animal manure by irrigation, is increasing. However, the risk of airborne pathogen transmission from manure to humans during spray irrigation is not well-understood. To determine how pathogens can spread using manure irrigation, LIDE measured air concentrations and risk of illness due to exposure to pathogens in the irrigation spray.

Photo showing traveling-gun manure irrigation system at a Wisconsin farm

Traveling-gun manure irrigation system at a Wisconsin farm.

Manure irrigation, which is the application of liquid animal manure by traveling gun or center pivot irrigation, is increasing in Wisconsin and other states.  However, the risk of airborne pathogen transmission from manure to humans during spray irrigation is not well-understood.

To determine how pathogens can spread using manure irrigation, LIDE measured air concentrations of manure-borne microorganisms during 21 full-scale manure irrigation events on three Wisconsin dairy farms. Samples were collected at multiple downwind distances – typically up to 700 feet – and analyzed using both quantitative polymerase chain reaction (qPCR) and bacterial cultures.

The measured concentrations of manure-borne microorganism in air were then used with pathogen dose-response curves and information related to the length and intensity of human exposure to manure irrigation to conduct a quantitative microbial risk assessment (QMRA). The QMRA resulted in predictions of the risk of human illness due to exposure to pathogens in the irrigation spray, which can be used by decision-makers to inform selection of risk mitigation policies.

 

 

 

 

Photo of LIDE scientists collecting an air sample for pathogen testing

Two LIDE scientists collect an air sample that will be cultured for bacterial pathogens.

LIDE’s role:

  • Developed a study design and sampling strategy for meeting policy-maker's information needs
  • Fostered positive working relationships with the producers who provided field-sampling opportunities
  • Collected airborne microorganism samples and conducted culture and qPCR analysis
  • Developed additional bovine-specific qPCR assays