Protection of chickens against fowl typhoid using field vaccine programs formulated with the live attenuated strain Salmonella Gallinarum ΔcobSΔcbiA

Abstract

Salmonella enterica serovar Gallinarum biovar Gallinarum (SG) is a host-specific bacteria that causes the fowl typhoid (FT). This disease is highly pathogenic to commercial chickens, specially brown layers and breeders, causing acute septicemia followed by high morbidity and mortality. Vaccination is extensively adopted in the fields as a biosafety tool for prevention of isolated infections and outbreaks in commercial poultry flocks. The present study evaluated the use of an attenuated SG with deletions on genes cobS and cbiA (SGΔcobSΔcbiA) as a live vaccine, using vaccination schemes adjusted for field conditions. To this end, brown layers were used in two different experiments, to evaluate the long-term protection, necessary in the fields. The vaccination scheme on the first experiment consisted of two doses, the first at 4 th week-of-age and the booster dose at 8 th week-of-age with challenge at 16 th week-of-age with wild SG strain. On the second experiment, the vaccination was carried out by different routes using three doses of the live vaccine, at 4 th , 8 th and 12 th weeks-of-age, and the challenge was done at 20 th weeks-of-age. After the challenge, the mortality was recorded during 28 days, and the egg production (experiment 2) was evaluated and compared with the group of unvaccinated layers. In both experiments, the mortality was significantly reduced, and the egg production was not affected in vaccinated layer-hens. In summary, this study shows the efficacy and the protection of different vaccination schemes against FT that can be applied under field conditions in commercial poultry farms.

Альтернативні Методи Профілактики Інфекційних Хвороб Птиці

“…However, this creates risks of reducing the adaptation capabilities of the poultry organism to environmental and technological factors. To increase the productivity of poultry based on the improvement of feed conversion, feed additives with antibiotics have been widely used, which is currently prohibited by national and international legislation (Penha et al, 2018;Rothrock et al, 2019;Shi et al, 2019;Gadde et al, 2017). It should be noted that the effectiveness of measures to combat and eliminate infectious diseases is based on the use of antibacterial drugs, which creates risks of the spread of resistant strains of bacteria and is becoming an increasingly serious problem today.…”