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Chapter 1
1.2. History of typhoidal Salmonella
Salmonellosis has been a human health problem for centuries. In 1880, Carl
Eberth first discovered the “typhoid bacilli” through pathological
examination of a contaminated spleen. This was followed by the successful
isolation and cultivation the “Bacillus typhosus”, now referred to as
Salmonella enterica serovar Typhi, by Georg Gaffky in 1884. The decline in
cases of typhoid fever in the developed world over the last century
correlates with the increase in treatment of drinking water, pasteurization
of dairy products and the introduction of measures to avoid contact with
faecal waste in the food chain [3]. Typhoid fever is no longer endemic in
developed countries, however infection with other serovars of Salmonella
enterica often referred to collectively as non-typhoid Salmonella (NTS)
remains a major public health challenge.
1.3. Non typhoidal Salmonella
There are over 2,600 serovars of non typhoidal Salmonella. It is estimated
that 90% of the Salmonella cases reported are accounted for by 30
serovars. In 2010, S. Typhimurium and S. Enteritidis accounted for 45% and
22% of the salmonellosis cases reported in Ireland [4]. It is estimated that
between 90-95% of non typhoid salmonellosis arises from consumption of
contaminated food-stuffs including poultry and other meat products [5].
Therefore vaccination of live animal carriers may result in a reduction of
the pathogen in the meat post slaughter. The introduction of a vaccination
programme for animals against commonly associated serovars such as S.
Enteritidis in poultry has proven successful in the past [6].
However, there are drawbacks to the use of a vaccination programme.
Firstly some animals may be healthy carriers or asymptomatic therefore
vaccination needs to encompass all animals in a herd to be successful. This
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