Animal Waste, Water Quality and Human Health

Zoonotic waterborne pathogens in livestock 121pathogens. For poultry pathogens such as Salm. serovar Gallinarum, avianMycoplasma and leukosis virus, specific pathogen-free flocks have beenestablished on the elite and grandparent level. Efforts have also been made toprevent poultry from passing not only faeces-associated, but egg-associatedpathogens such as Salmonella from moving down the production pyramid.Of course, zoonotic pathogen control programmes for the creation of specificpathogen-free animals must be cost-effective and require diagnostic proceduresable to detect all infected animals to be culled eg. serological procedures ratherthan microbial culture or detection methods have been found to be cost-effectivein the Danish Salmonella control programme in swine (Wegener et al. 2003).4.3.2 Biosecurity-raising livestock in a disease-free bubblePathogens enter livestock holdings by numerous routes: biosecurity managementpractices are designed to prevent the spread of disease by minimizing themovement of organisms and their living vectors (wild birds, rodents, flies, etc.)and inanimate vehicles (clothing, vehicles, feed, etc.) onto and within farmoperations. Biosecurity systems are easiest to develop and implement forintensively farmed poultry flocks and swine herds, where controlling theenvironment is necessary for profitable production as well as zoonoses control.Specially designed barns can provide physical isolation of breeder andproduction animals (White et al. 1997). These systems can be designed to keeppathogens out by limiting entry of other animals of the same and of differentspecies. Common practices include rodent, wild bird, and insect controlprocedures, and requiring human handlers to use a disinfectant boot bath, oreven shower in and shower out of barns and farms. Other strategies include themaintenance of closed-herds or at least limiting the entry of new animals intothe herd until they have been treated and/or undergone pathogen testing and/ora quarantine period has passed. In production facilities, animals of one age-classshould be housed together and an “all in, all out” policy is recommendedtogether with thorough cleaning and disinfection of the facility before it isrestocked. Biosecurity systems such as these are reported to reduce the risk ofpoultry shedding Campylobacter in their faeces (Gibbens et al. 2001). It is alsolikely that manure from animals raised with high levels of biosecurity present alower risk of food and water contamination. Organic systems often allow greaterinteraction with the external environment and it has been reported that Swedishorganic free-range chickens have much higher levels of Campylobacter thanchickens raised under conventional barn systems (Engvall 2001), providingsupporting evidence of the effectiveness of reducing contact with theenvironment in reducing pathogen load.