1.2 SOURCES OF MICROBIAL CONTAMINATIONThe microbiological quality of raw products is primarily dictated by the conditions under which they are grown, transported, stored, and treated prior to the actual canning process.1.2.1 Animals and FishThe sources and dissemination of microbial contamination in animals prior to slaughter are affected by the conditions that prevail during breeding, transport, and holding prior to slaughter, as well as those during and after slaughter. The role of breeding conditions in the contamination has been reported by various authors (Oosterom, 1979, for hogs; Le Turdu et al., 1980; Payne and Scudamere, 1977, for poultry). For example, 10 foodbome illness outbreaks were traced to the ingestion of turkey meat from one breeding flock contaminated by the same lysotype 2 strain of S. enteritidis. Animal feed, particularly that containing raw material of animal origin, has been implicated in the Salmonella infection of animals. While some studies have shown a direct relationship between the contamination of feed raw materials and the infection of animals, it has more frequently not been possible to observe the presence of the same serotype in the feed and the animals. This is a common occurrence in this type of investigation because it is extremely difficult to obtain samples of both the implicated feed and its raw materials. In addition, certain serotypes, such as S. typhimurium, multiply more easily in the intestine, while others, like S. seftenberg, are more thermally resistant and may survive processing. Animal intestines can be selective, as can the laboratory techniques used. Despite these difficulties to establish this vector, a number of cases can be cited where different serovars introduced via the intermediary of feed raw materials have been the source of public health problems: S. agona in fish meal in Peru, and France, and food poisonings in Great Britain and United States.The role of the environment cannot be disregarded. To minimize contamination, hygienic conditions must be maintained during rearing, especially in intensive rearing. Once a particular bacteria has been introduced, it can be rapidly disseminated via fecally contaminated water, feed, or by infected animals. Once it has been introduced into the animal environment, buildings, and so on, it is very difficult to suppress, let alone eliminate. Lahellec et al. (1986) showed that the presence of Salmonella in the hen house at the time the chicks are introduced can be the most important source of poultry contamination. Snoeyenbos et. al. (1969) showed that Salmonella contamination can persist even after periods of nonuse followed by cleaning and disinfection and result in the infection of subsequent flocks. Jack and Harper (1969) showed that cattle that graze in meadows fertilized with manure can become infected. The extent of the infection will depend upon the persistence and numbers of the microorganism, and the time interval between fertilization and pasturing. Crosscontamination between animals can be increased by an augmentation of those conditions favorable to this process.
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