Salmonella enterica serovar Dublin infection in dairy cattle: a case study on the management of an outbreak in Veneto Region

Chiara Tommasoni; Eliana Schiavon; Anastasia Lisuzzo; Matteo Gianesella; Marianna Merenda; Patrizio Coin; Tommaso Patregnani; Sebastiana Tola; Salvatore Catania; Antonio Barberio

Chiara Tommasoni University of Padova, MAPS Department
Eliana Schiavon
Anastasia Lisuzzo
Matteo Gianesella
Marianna Merenda
Patrizio Coin
Tommaso Patregnani
Sebastiana Tola
Salvatore Catania
Antonio Barberio

Keywords: Salmonella Dublin; Cattle; Autogenous vaccine.

Abstract

Salmonella enterica subsp. enterica serovar Dublin (S. Dublin), is a serovar adapted to cattle, causing both intestinal and systemic infections. The introduction of the bacterium leads to serious economic losses due to abortions, high mortality in calves and persistent infections, also representing a major health problem as zoonotic agent. The aim of this study was to describe an outbreak of S. Dublin on an Italian dairy cattle farm and to assess the effectiveness of the management protocol prepared by the Istituto Zooprofilattico Sperimentale delle Venezie (IZSVe).
S. Dublin was diagnosed on a cattle farm in Northeastern Italy following the conferral at the IZSVe of a newborn calf that died from enteric syndrome. At the autoptic exam pathological findings were observed in gut, liver, pericardium, lungs, joints, lymph nodes and abomasum. Considering the pathogenesis of S. Dublin, authors decided to apply a protocol prepared by the IZSVe based both on direct and indirect prophylaxis. Particularly, an autogenous vaccine against S. Dublin prepared by the Istituto Zooprofilattico Sperimentale della Sardegna (IZS Sardegna) was administered.
Screening tests were performed on fecal and milk samples (bulk tank milk) and on environmental swabs from lactating and dry cows’ boxes.
A pre and post-vaccination screening in 3-times (T0, T1, T2) was performed on serum, feces and milk to assess the immunization of cows and the effectiveness of the protocol itself. The first sampling took place 1-day prior immunization, the second and the third 2 and 11 months later respectively.
Serological examination identified 25%, 100% and 73% positive animals at T0, T1 and T2 respectively. No fecal sample in all time-points was found positive. After vaccination only 1 milk sample turned out positive.
Considering the pathogenesis of S. Dublin, the negativity of the bacteriological exams suggests a positive effect of the protocol in the reduction of clinical cases, circulation of the etiological agent and biocontainment of the infection.