Related Fowl Typhoid outbreaks and vaccines in Southern Africa
A new study discusses the genomic analysis of Salmonella gallinarum strains causing fowl typhoid fever outbreaks in Southern Africa. The study found that the SG9R vaccine strain is closely related to the outbreak strains, indicating that the vaccine may be the cause to these infections.
In conclusion, all the field isolates from a recent spate of fowl typhoid outbreaks in South Africa and Eswatini were closely related to the SG9R vaccine strains in use, and since nowild-type strains were identified, reversion to virulence of thevaccine is the most likely cause of these outbreaks. Van Immerseel et al. (1) similarly reported that these mutations were the likely cause of the reversion to virulence observed in Belgium.
Hence, in situations where epidemiologically feasible, it is advisable to discontinue the use of live SG9R vaccines and transition to safer alternatives like the Salmonella enteritidis live vaccine (2,3).
1. Van Immerseel F, Studholme D, Eeckhaut V, Heyndrickx M, Dewulf J, DewaeleI, et al. Salmonella Gallinarum field isolates from laying hens are related to the vaccine strain SG9R. Vaccine. (2013) 31:4940–5.
2. Chacana PA, Terzolo HR. Protection conferred by a live Salmonella Enteritidis vaccine against fowl typhoid in laying hens. Avian diseases. 2006 Jun 1;50(2):280-3.
3. Li P, Guo L, Luan Y, Zhao W, Cui L, Hao G, Sun S. Research Note: Effect of a live Salmonella Enteritidis vaccine against Salmonella Pullorum infection in breeder chickens. Poultry Science. 2023 Feb 1;102(2):102308.
