Impact of acidified water on live Salmonella vaccine in chickens exposed to S. Heidelberg

According to the results of research conducted by Manuel Da Costa, DVM, PhD, associate director, Zoetis, acidified drinking water does not affect the efficacy of a live vaccine against Salmonella Typhimurium (ST) in chickens exposed to Salmonella Heidelberg.

Vaccination of broilers with a live ST vaccine is a strategy that producers use to reduce the level of Salmonella spp. in their processing. But some producers also acidify the water during the first few days of chick life to reduce loading and early colonization of chicks. Salmonella spp.

Dr. Da Costa and his colleagues wanted to determine if acidifying the water might interfere with TS vaccination. To do this, they experimented with 360 newborn chicks that were vaccinated by aerosol with a live ST vaccine just at hatching, then dividing them between two isolated rooms, each equipped with two compartments.

Within each department, chicks from one of them received drinking water acidified with a sulfuric acid product for the first 12 days, while those from the other did not. The target pH for the acidified water was 3.3.

Exposure to the pathogen

At 3 and 6 days of age, the researchers randomly selected 10 birds from each department to sample with cecal swabs their intake of the vaccine using specific real-time PCR (polymerase chain reaction).

At 13 days of age, all birds in the study received one dose of live vaccine against Salmonella by oral probe. Then, at 28 days of age, half of the birds in each department were orally exposed to Salmonella Heidelberg, while the remaining unvaccinated were indirectly exposed to the pathogen by mixing with them.

At 38 days of age, samples from the ceca, liver and spleen of all remaining birds were analyzed for the presence of Salmonella spp, evaluating the prevalence through enrichment and loads by most probable numbers. The researchers also swabbed for the evaluation of Salmonella spp. in the four departments.

In general, loads Salmonella they were insignificant and there were no statistical differences in the recovery of the organism between the birds that received or not the acidified water, nor between those that had been exposed directly or indirectly, by being mixed with the others.

According to Da Costa, “when we looked at the results after the exposure, it was interesting to see that the overall burden of Salmonella It was very low.” Only one of the 470 samples was positive in MPN (direct plate) tests for Salmonella, despite the fact that the colonization levels of the exposure used selective enrichment were high. In addition, all swab samples were negative for
Salmonelladice.

Da Costa recognized that the low burden of Salmonella spp. cannot be fully attributed to the vaccine as the study did not have a true unvaccinated control group. However, their conclusion is that the results indicate that acidification of the water during the first 12 days of chick life, with a pH of 3.3, does not appear to interfere with the activity of the ST vaccine.

Fig. 1. Levels of positivity to Salmonella spp in ceca and liver/spleen tissue after exposure to S. Heildelberg.

Inf. Zoetis, 1-2-2022

Hang tags: #SA762 • salmonella