Development of an effective vaccination protocol to produce Salmonella-free layer fock

Abstract

Salmonella infections are of prime importance in the layer chicken industry and pose a significant public health threat. Production of export quality poultry products requires Salmonella-free certification. We developed and applied a vaccination schedule based on a commercial live attenuated Salmonella enterica serovar Gallinarum biovar Gallinarum (S. Gallinarum) vaccine in a layer flock. A flock of 1000 ISA Brown chickens has vaccinated with a lyophilized fowl typhoid live vaccine at definite time intervals. Isolation of Salmonella spp. in cloacal swabs and detection of serum antibody responses were performed using serum plate agglutination (SPA) test and ELISA. At the time of vaccination (16 weeks (w) of age), 50% of the tested birds carried Salmonella spp. in feces. Following booster immunization at 18 w, 21 w, and then every 12 weeks interval, the shedding of Salmonella decreased significantly over time with 40% at 21 w, 10% at 30 w, and 5% each at 42 and 54 w, and no shedding was detected at 66 and 78 w. Biochemical analysis of 32 Salmonella isolates revealed 15.6% (n=5) Salmonella enterica serovar Gallinarum biovar Pullorum (S. Pullorum), 37.5% (n=12) Salmonella Gallinarum, and 46.9% (n=15) paratyphoid causing Salmonella. Of note, the Salmonella spp. detected after 21 w of age belonged to the paratyphoid group. The decreased shedding of bacteria paralleled with increased antibody responses. The antibody level at vaccination (20% positive rate at 16 w) increased over time with a 50% positive rate at 18 w, 80% at 42 w, 90% at 54 w, and 100% at 66 w and 78 w by serum plate agglutination (SPA) test. Similarly, the serum antibody levels of chickens were also measured using ELISA and were similar to the SPA test. In conclusion, the vaccine schedule developed in this study confirmed a high seroconversion and prevented Salmonella shedding in feces. Therefore, a three-month interval vaccination protocol from the pre-laying stage to the last stage of laying is recommended to prevent Salmonella infections in laying flocks.

Fowl typhoid live lyophilized vaccine applied at 3-month intervals protected layer chickens from Salmonella gallinarum infection and prevented cloacal shedding

“…Among the different terms of reference for exports of poultry products, Salmonella -free meat and eggs are inevitable. Reviewing the available literature (vaccination at day 1 and boosting at 6, 10, 14 weeks) [ 23 , 24 ] and from our pilot experiments, a protective and cost-effective (in terms of vaccine and labor costs) Salmonella vaccination at 3 months interval up to the last stage of laying was designed [ 25 ]. This 3-month interval protocol showed desired effects of protection by the challenging dose of Salmonella, and it was cost-effective due to the long interval of vaccination [ 25 , 26 ].…”

“…One of the most prominent transmission mechanisms of poultry Salmonellae transmission is transovarian infection, which leads to the infection of the eggs and the chicks [ 39 ]. Moreover, contamination of eggs with zoonotic Salmonellae such as S. enteritidis and S. typhimurium has been recorded and is of great concern for public health and international trade restrictions [ 25 , 40 ]. The vaccine schedule employed in this study significantly reduced the shedding of Salmonella spp.…”

Non-Antibiotics Strategies to Control Salmonella Infection in Poultry

“…The poultry industry usually implements strategies of surveillance and biosecurity at international, national, and farm levels to prevent Salmonella spread [ 119 , 120 , 121 , 122 ]. Among the health management protocols, vaccination represents the most efficient and cost-effective method to reduce the impact of clinical disease, maintain herd immunity, decrease the shedding and reduce both horizontal and vertical transmission of Salmonella in poultry flocks [ 19 , 123 , 124 , 125 , 126 ]. Additionally, poultry vaccination provides safer food products for consumers reducing the likelihood of food poisoning in humans [ 30 , 125 , 127 , 128 ].…”

“…The control of Salmonella in the poultry industry has relied heavily on live and inactivated vaccines [ 123 , 125 , 126 , 127 ]. However, over the last 30 years, advances in immunology, molecular biology, and recombinant DNA technology have allowed the identification and manipulation of the microbial components against which it is generated protective immunity, which has allowed to develop of vaccines that provide broader protection against multiple Salmonella serotypes [ 124 , 148 ].…”