Detection of hepatitis E virus and other livestock-related pathogens in Iowa streams

Authors: GIVENS, CARRIE - Us Geological Survey (USGS); KOLPIN, DANA - Us Geological Survey (USGS); Borchardt, Mark; DURIS, JOSEPH - Us Geological Survey (USGS); Moorman, Thomas; Spencer, Susan

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/17/2016
Publication Date: 6/16/2016
Publication URL: https://handle.nal.usda.gov/10113/5567803
Citation: Givens, C.E., Kolpin, D.W., Borchardt, M.A., Duris, J.W., Moorman, T.B., Spencer, S.K. 2016. Detection of hepatitis E virus and other livestock-related pathogens in Iowa streams. Science of the Total Environment. 566-567:1042-1051. doi: 10.1016/j.scitotenv.2016.05-123.

Interpretive Summary: Hepatitis E virus (HEV) is an unusual gastrointestinal virus in that it has the potential to be transmitted between people, swine, and wildlife such as deer. HEV infections in people can be serious with mortality rates of 1%. HEV outbreaks have been documented in developing countries, but in the United States HEV-related illnesses are rare. HEV is common in swine herds and the virus has been detected in the liquid waste lagoons of swine farms. Swine are clinically unaffected by HEV. We investigated the occurrence of HEV in the South Fork Iowa River basin in Iowa, a region where the land use is predominantly hog farming, and whether HEV occurrence in the basin’s rivers was associated with swine manure application. We found 45% of river water samples were positive for HEV. HEV occurrence increased significantly following swine manure application in the basin with only 20% of samples positive prior to manure application and 80% of samples positive after manure application. We collected swine manure from two swine farms as well as deer fecal pellets from several locations in the basin. All fecal samples, swine and deer, were positive for HEV. We sequenced a portion of the HEV genome from all the positive samples, fecal and river water, and found the sequences were identical. This suggests the viruses are shared among the three sources we sampled, river water, swine manure, and deer. This information is important for any future assessment of the risks of exposures to HEV and other livestock pathogens in this region.

Technical Abstract: Manure application is a major source of pathogens to the environment. Through overland runoff and tile drainage, these pathogens contaminate surface water and stream bed sediment. Some of these pathogens are zoonotic that can potentially affect both animal and human health. This study examined the presence of hepatitis E virus (HEV) and other livestock-related bacterial, protozoan, and viral pathogens in surface waters within the South Fork Iowa River basin following swine manure application. Increased concentrations of fecal indicator bacteria after manure application exceed the state’s bacteria water quality criteria and suggest that swine manure contributes to diminished water quality and may pose a risk to human health. Additionally, the occurrence of numerous bacterial pathogen genes and HEV in both manure samples and in adjacent surface water post manure applications suggests a potential role for swine in spreading of zoonotic pathogens to the environment. This study detected a number of zoonotic pathogens such as Shiga-toxin producing E.coli, C. jejuni, enterococci, and S. aureus that can pose mild to serious health risks to swine, humans, and other wildlife. The spread of HEV and other zoonotic pathogens through the environment is of concern to both animal and human health. This research provides the foundational understanding required for any future assessment of the risk to environmental health from zoonotic pathogen exposures in this region. This information could be important for maintaining swine herd biosecurity and protecting the health of wildlife near swine facilities.