Rangeland Management of Waterborne Pathogens from Livestock and Wildlife

UC Cooperative Extension has put together extensive resources for training and education for ranch water quality planning for extension educators and technical trainers, which can be found here. This is also a great resource for those looking for information on the current science on rangeland water quality. In this mini-blog series, we’ll highlight some of the most recent research on rangeland water quality planning and management.

Dr. Rob Atwill, Director of Veterinary Medicine Extension at UC Davis, outlines in this video how modern science can be used to implement beneficial management practices (BMPs) that reduce the risk of waterborne infectious diseases in waters used from agricultural and rural watersheds. When developing a BMP, key questions include:

• Who sheds the pathogen?
• Is the pathogen actually infectious to humans (requires high-quality molecular tests)?
• How are pathogens reaching water (and how can we interrupt that path)?
• Can the pathogen survive long enough (and how can we accelerate its inactivation)?

Knowing the source and load of a harmful pathogen is crucial to mitigating risk. In California and across the U.S., water quality regulations are based on indicator bacteria (i.e., total coliforms, fecal coliforms, and indicator E. coli). These indicator bacteria are not generally pathogenic and are very common in humans, domestic animals, and wildlife; therefore, they are not reliable predictors of pathogens shed from livestock. Research has shown that some harmful pathogens are far more likely to be introduced to a waterway by wildlife than by cattle, and cattle generally appear to have low infection levels for pathogens harmful to humans. These technologies are in critical need of updating and we need new ways to approach monitoring, but they are the standards that are currently used at the county, state, and federal levels.

Once a manager knows the source and size of the problem, they can develop, design, and implement BMPs. For example, for fall calving operations, shortening the length of the calving season can reduce the risk of Cryptosporidium infection in the herd. Earlier calving also reduces the risk of young, infected calves shedding Cryptosporidium during the rainy season when we see greater pasture runoff. In general, management efforts to disperse animals from waterways through the use of herding, attractants (such as off-stream water sources and nutritional supplements), and fencing will minimize their time loafing near water and will reduce risk. For certain areas of concern, altering timing of grazing so that cattle fecal pats are sufficiently exposed to heat and solar rays prior to the rainy season (or irrigation) allows for natural pathogen inactivation before large run-off events. Maintaining vegetation buffers also decreases the flow of pathogens into waterways and dramatically reduces risk of waterborne contamination.

Bottom line - The key to success for implementing beneficial management practices—either on ranches, rural landscapes, or in the high country—is to match the design and efficacy of the BMP to the local conditions and the expected pathogen loads.