Aims: To determine the prevalence and levels of zoonotic agents in livestock wastes. Methods and Results: A proportionally weighted survey was undertaken and livestock waste samples analysed quantitatively for Escherichia coli O157, pathogenic Listeria, Salmonella, Campylobacter, Giardia and Cryptosporidium. A significant proportion of wastes contained at least one zoonotic agent. Relationships were found between dry matter content and the presence and levels of some zoonotic agents. Conclusions: British livestock wastes contain measurable levels of the zoonotic agents that cause most cases of gastroenteritis in the UK. Significance and Impact of the Study: Animal wastes are disposed of by spreading to agricultural land used for the production of crops and livestock grazing. As British wastes are contaminated with significant levels of zoonotic agents, the practice may represent a way for pathogens to travel further up the food chain.

Survey results describing the levels and prevalences of zoonotic agents in 1,549 livestock waste samples were analyzed for significance with livestock husbandry and farm waste management practices. Statistical analyses of survey data showed that livestock groups containing calves of <3 months of age, piglets, or lambs had higher prevalences and levels of Campylobacter spp. and Escherichia coli O157 in their wastes. Younger calves that were still receiving milk, however, had significantly lower levels and prevalence of E. coli O157. Furthermore, when wastes contained any form of bedding, they had lowered prevalences and levels of both pathogenic Listeria spp. and Campylobacter spp. Livestock wastes generated by stock consuming a diet composed principally of grass were less likely to harbor E. coli O157 or Salmonella spp. Stocking density did not appear to influence either the levels or prevalences of bacterial pathogens. Significant seasonal differences in prevalences were detected in cattle wastes; Listeria spp. were more likely to be isolated in March to June, and E. coli O157 was more likely to be found in May and June. Factors such as livestock diet and age also had significant influence on the levels and prevalences of some zoonotic agents in livestock wastes. A number of the correlations identified could be used as the basis of a best-practice disposal document for farmers, thereby lowering the microbiological risks associated with applying manures of contaminated livestock to land.

In response to reports that the contamination of food can occur during the on-farm primary phase of food production, we report data that describes a possible cost-effective intervention measure. The effect of time before soil incorporation of livestock wastes spread to land on the rate of decline of zoonotic agents present in the waste was investigated. Fresh livestock wastes were inoculated with laboratory-cultured Salmonella, Listeria, and Campylobacter spp. and Escherichia coli O157 before they were spead onto soil. Incorporation of the spread wastes was either immediate, delayed for 1 week, or did not occur at all. Bacterial decline was monitored over time and found to be significantly more rapid for all waste types when they were left on the soil surface. There were no significant differences in initial bacterial decline rates when wastes were spread in summer or winter. Our results indicate that not incorporating contaminated livestock wastes into soil is a potential intervention measure that may help to limit the spread of zoonotic agents further up the food chain. The implications of these findings are discussed in relation to current advice for livestock waste disposal.Food can become contaminated with pathogenic microorganisms at all stages of manufacture and processing (13). However, there is a recognized potential for the on-farm transfer of pathogens to food during primary production (32). Livestock infected with zoonotic agents can excrete pathogens into their feces, and animal wastes have been implicated as a source of infection in a number of cases of human food-borne illness (2, 7). Since livestock wastes are routinely disposed of by spreading to agricultural land used for food production, the practice of waste spreading is an obvious consideration for any integrated pathogen-spread prevention-control strategy (5,17,18).Over the last decade, there has been an increase in the awareness of British farmers on the best practices for storage and disposal of livestock wastes (33). The publication of specific management guidance (26, 27) was driven largely by the need to control chemical pollution from wastes, including nitrate contamination of watercourses and airborne ammonia emissions (35). The effects of these chemical pollutants are immediate and obvious and overshadow more subtle environmental damage such as the dissemination of bacterial pathogens. Evaluation of current guidance, which has been targeted toward the control of chemical pollutants, suggested that it may increase the length of time that pathogens present in the waste could survive in the environment (18). Of particular concern is a move toward immediate solid waste incorporation and band spreading or direct injection of liquid wastes into soil. Such practices are likely to decrease the rate of waste drying, the levels of UV irradiation, and the daily range of temperatures experienced by pathogens present in the waste, potentially extending their survival (6). However, there is currently no experimentally derived information that sup...

Fecal wastes from a variety of farmed livestock were inoculated with livestock isolates of Escherichia coli O157, Listeria monocytogenes, Salmonella, Campylobacter jejuni, and Cryptosporidium parvum oocysts at levels representative of the levels found in naturally contaminated wastes. The wastes were subsequently spread onto a grass pasture, and the decline of each of the zoonotic agents was monitored over time. There were no significant differences among the decimal reduction times for the bacterial pathogens. The mean bacterial decimal reduction time was 1.94 days. A range of times between 8 and 31 days for a 1-log reduction in C. parvum levels was obtained, demonstrating that the protozoans were significantly more hardy than the bacteria. Oocyst recovery was more efficient from wastes with lower dry matter contents. The levels of most of the zoonotic agents had declined to below detectable levels by 64 days. However, for some waste types, 128 days was required for the complete decline of L. monocytogenes levels. We were unable to find significant differences between the rates of pathogen decline in liquid (slurry) and solid (farmyard manure) wastes, although concerns have been raised that increased slurry generation as a consequence of more intensive farming practices could lead to increased survival of zoonotic agents in the environment.

Aim: To measure the decline rates of zoonotic agents introduced into liquid livestock wastes in on-farm storage tanks. Methods and Results: Salmonella spp., Escherichia coli O157, Campylobacter jejuni, Listeria monocytogenes and Cryptosporidium parvum, propagated in laboratory-controlled conditions, were inoculated into 35 000-l volumes of fresh livestock wastes (pig slurries, cattle slurries and dirty waters). D-values for bacteria were six to 44 days, and for C. parvum were 133 to 345 days. Campylobacter jejuni declined significantly more rapidly than the other bacterial pathogens, while E. coli O157 declined significantly more slowly. On average, bacterial declines were not affected by the season of waste deposition and storage or by the dry matter content of the wastes, but were more rapid in dirty waters than in pig slurries. The physiciochemical composition of wastes in each category varied significantly. Conclusions: Zoonotic agents can survive for several months during storage of liquid livestock wastes. Livestock wastes should be batch-stored and not subjected to continuous additions. Significance and Impact of the Study: This study indicates that batches of liquid livestock waste, if contaminated with bacterial pathogens, should be stored for 6 months to reduce contamination levels. Alternative strategies for reducing C. parvum levels in liquid livestock wastes should be explored.