Retrospective study on the incidence of Salmonella isolations in animals in South Africa, 1996 to 2006

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.