Abstract:
A retrospective study that involves the analysis of laboratory diagnostic data collected
during the period 1996–2006 was conducted. A total of 3417 Salmonella isolations involving
183 different serotypes was recorded from 1999–2006, inclusive, at the Onderstepoort
Veterinary Institute, Agricultural Research Council, South Africa. The most common
serotypes were Salmonella enterica subspecies enterica serovar Typhimurium (917 incidents),
Salmonella enterica subspecies enterica serovar Dublin (248 incidents), Salmonella enterica subspecies
enterica serovar Enteritidis (232 incidents), Salmonella enterica subspecies enterica
serovar Muenchen (164 incidents), Salmonella enterica subspecies enterica serovar Heidelberg
(118 incidents) and Salmonella enterica subspecies enterica serovar Chester (113 incidents).
The number of recorded Salmonella isolations over the period 1996 to 2006 varies
considerably from year to year. The peak of 693 isolations was recorded in 1997, and the
lowest, 108 incidents, in 2001. Of the total incidents recorded during the period of survey,
2410 (70.5 %) occurred in poultry and other birds, 641 (18.75 %) occurred in cattle, 255 (7.46)
in pigs and 111 (3.24 %) in sheep. Despite the large number of serotypes isolated (183),
52 % of incidents were due to only 6 serotypes in decreasing order of prevalence:
S. Typhimurium, S. Dublin, S. Enteritidis, S. Muenchen, S. Heidelberg and S. Chester.
Serovar Typhimurium was the most common serotype and was detected in all animal
species sampled, with, 65%(598) of the incidents occurring in poultry and 20%(187) occurring
in cattle. Of the total of 248 incidents of S. Dublin serotype, 95.6 % (237) of incidents
occurred in cattle and of the 232 isolates of S. Enteritidis, 223 (96%) originated from poultry.
Serovar Choleraesuis was identified in 16 isolates from pigs. The following 4 serotypes were
each recorded in more than 50 incidents: S. Hadar (102), S. Schwarzengrund (99), S.
Mbandaka (94) and S. Sandiego (73). The trends of annual incidence of Salmonella infection
in cattle, sheep, pigs, poultry and other birds during the 11-year period and the distribution
of the main serotypes in individual species of animals from 1996–2006 are discussed.
