Author: Chip Simmons, Ph.D., Assistant Research Professor, University of North Carolina at Chapel Hill, School of Public Health, osimmons@email.unc.edu Ambient temperature will affect the survival of microbial pathogens, which in turn will affect the risks of pathogens to humans or animals that may be exposed. In general, parasites survive the longest, followed by viruses, with bacteria generally being the shortest lived in the environment. All classes of pathogens generally survive for longer periods of time under cooler conditions (i.e., spring and fall) as opposed to warmer conditions (i.e., summer). Freezing temperatures (i.e., winter) can either enhance or detract from microbial survival, depending on the class and type of pathogen. Examples would include the bacteria and viruses that generally survive and remain infectious following a freeze/thaw, while other organisms, like oocysts of the parasite Cryptosporidium parvum, may not survive freezing. Other environmental, management, and host-related factors also play important roles in determining risks to humans, which include particle association of the pathogens (i.e., in a cow patty, attached to soils, etc.), the pathogen suspension media (i.e., water, wastewater slurry, air, etc.), relative humidity, environmental damage sustained by the pathogens prior to host exposure, and other pathogen factors. Additionally, when determining risks to an exposed population, we must consider host factors, such as the infectious dose of the organism, availability and exposure of a susceptible host population, and immune status of the potential host population. Given these factors, if a waste management system is marginally effective (i.e., 1 log10 or 90% microbial reduction) and there are relatively high numbers of microbial pathogens in the initial waste slurry, it is important to control host exposure pathways, such as environmental transport or exposures to the “treated” wastes.

Browse related Faqs by tag: horses, animal manure management, pathogen, temperature