Abstract
Since the occurrence of swine salmonellosis has increased over time and control strategies other than biosecurity are highly recommended, the present study aimed to evaluate the efficacy of vaccination with Salmonella Choleraesuis and Salmonella Typhimurium bacterins in pigs. Two experimental groups were formed: G1, animals immunized with two doses of a commercial vaccine (n = 20); G2, control group (n = 20). After vaccination, all pigs were orally challenged (D0) with 108 CFU of Salmonella Typhimurium and evaluated for 40 days. Every 10 days after D0, five piglets from each experimental group were euthanized and submitted to the necroscopic examination, when organ samples were collected. Blood samples and rectal swabs were collected before the first dose of the vaccine (D−42), before the second dose (D−21), before the challenge (D0), and thereafter, every three days until D39. Blood count, serum IgG measurement by ELISA, and the excretion of Salmonella Typhimurium in feces were evaluated. While the results from blood count and serum IgG concentration did not differ, the detection and excretion of Salmonella between G1 and G2 differed (p < 0.05). Therefore, it was observed that this vaccine partially protected the animals against experimental infection with Salmonella Typhimurium, reducing the excretion of bacteria in feces.
Highlights
Salmonella infection in pigs was first reported in 1886 by Salmon and Smith whenSalmonella Choleraesuis was associated with hog cholera [1], and since more than 2600 serovars of Salmonella have been reported, affecting a wide range of animals, including humans [2]
A significant difference was observed in the percentage of piglets with diarrhea (G1: 35.0% and group 2 (G2): 65.0%)
46 episodes of diarrhea were observed in animals from group 1 (G1) (20.9%; 46/220), with 32 mild cases and 14 moderate cases
Summary
Salmonella Choleraesuis was associated with hog cholera [1], and since more than 2600 serovars of Salmonella have been reported, affecting a wide range of animals, including humans [2]. From the 2637 serovars belonging to the Salmonella enterica species, at least 1576 are classified as Salmonella enterica subsp. Typhimurium (ST), the most important serovars in pig production worldwide [2,3]. Salmonella Typhimurium, a non-host-specific Salmonella, recently became the most common serovar isolated from pigs in Europe, the United States, and Brazil [4,5,6,7], and it is one of the main causes of human salmonellosis around the world, characterized by a selflimiting gastroenteritis syndrome, with diarrhea as the main symptom [8,9]. The clinical signs in pigs infected with ST course with the development of enterocolitis, beginning with watery diarrhea (with or without blood) that lasts 3 to 7 days, followed by dehydration and a decrease in feed intake; mortality is usually low [3]
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