Salmonellae are ubiquitous microorganisms commonly found in the digestive tracts of a broad range of animals, including mammals (especially rodents), birds and insects. Salmonellae multiply by binary fission and can survive and multiply in the environment, outside the host. This bacterial growth, if aided by ideal temperature conditions may take alarming proportions, reaching such high bacterial counts that could cause symptoms in an infected host.

Salmonella enterica enterica, serovars enteritidis and typhimurium, although rarely seen to cause disease in chickens, are some of the most often reported serotypes of Salmonella associated with human cases. Another feature of these strains is the capacity to persist “silently” inside the host, which will carry these microorganisms in its organs until a stress condition may re-activate their multiplication and shedding. Salmonellae can persist in the chicken’s organs and be shed on the eggs.

Human illnesses caused by Salmonella are usually associated with ingesting food or drink contaminated with Salmonella. Those could be caused by transmission to foodstuffs due to poor hygiene or by utilisation of Salmonella-contaminated meat or eggs.