Animal Waste, Water Quality and Human Health

Zoonotic waterborne pathogens in livestock 137such as organic acids, sodium nitrate and chlorate may be more effective than anysingle agent alone (Byrd et al. 2001, 2003; Jung et al. 2003).Zinc oxide in diets of weanling pigs helps maintain the stability of the intestinalmicroflora, making the gut less susceptible to colonisation by pathogens, either bycompeting for the same niche or by suppressing pathogen growth (Katouli et al.1999). Zinc and copper are both widely used supplements; more recently therehas been interest in essential oils and spice extracts as growth promotingalternatives to antibiotics (Pasteiner 2006).4.6 CONTROL POINT 4: TREATMENT OF ANIMALWASTES TO REDUCE ZOONOTIC PATHOGENSAs we noted in Chapter 3, certain zoonotic pathogens can survive for monthsand perhaps even years in moist excreta in the environment. It is alsoimportant to remember that excreta from young animals may contain highlevels of certain zoonotic pathogens and should be an important focus ofon-farm waste treatment efforts. For example, given the high levels of Crypto.parvum oocysts in young calf faeces, careful management of these excretashould substantially reduce off-site discharges of this pathogen (Miller et al.2008). Reducing the levels of these pathogens in animal excreta is one of themost important steps in the control of waterborne zoonoses that arise fromlivestock. Composting and anaerobic digestion at high temperatures are veryeffective procedures in reducing the levels of zoonotic pathogens in livestockexcreta. Depending on the excreta treatment system, the equipment and landdevoted to process this material can be expensive and are not commonly used,but even simple methods such as drying in the sun or passive stacking ofmanure solids can reduce levels of pathogens.Woodchip corrals are outside enclosures, bedded with large woodchips forover-wintering cattle and sheep. As the dung and urine is washed through thewoodchips it appears to be digested by microbes so that reasonably clean waterenters the soil.In developing countries alternative systems such as biogas and vermiculturehave been promoted with some success. In the small systems that predominatein developing countries, manure is a valued resource used for fertiliser, fuel, andbuilding material. While this means that waste build-up is rarely a problem italso results in high levels of human exposure to manure. The problem can becompounded by culture. For example, many Hindu dairy farmers regard cowmanure as sacred and innocuous, reducing their motivation to protect themselvesfrom contact with it.