Salmonella organisms are an important cause of disease in humans and other animals. In dairy cattle, a variety of diseases has been attributed to Salmonella infections, including acute diarrhea in neonates, multi-systemic illness in adults, and invasive septicemia in animals of all ages.1 In some situations on commercial dairy operations, salmonellosis can adversely impact profitability and appropriate control measures are warranted. Moreover, salmonellosis (regardless of whether it is clinically apparent) may result in foodborne exposure of humans to Salmonella organisms through milk or via meat products from animals sent to slaughter because of poor productivity.1
The prevalence of Salmonella infection on dairy operations can be relatively high even without clinical evidence of salmonellosis. Investigators detected Salmonella spp on 30 of 96 (31.3%) dairy operations in a multistate project in which samples were collected at a single time point.2 In another study3 in which investigators used 129 dairies located in Minnesota, Wisconsin, Michigan, and New York, Salmonella organisms were recovered at least once from 120 (93.0%) operations. In that study,3 fecal and environmental samples were collected at each dairy at 2-month intervals during a 14-month period. Results of these studies illustrate that Salmonella spp are quite prevalent in dairy herds and that Salmonella organisms can be intermittently shed into the environment.
Control of Salmonella infection in dairy cattle could be important for animal health and productivity as well as for the impact on exposure of humans. Effective control of salmonellosis in commercial dairies involves sanitation; biosecurity; and, if possible, increasing the animal- and herd-level immunity to salmonellosis. Unfortunately, biosecurity is often less than ideal in modern, large-scale dairy production because frequent entry of replacement heifers or cows is common and because these animals may be a source of Salmonella organisms.4 Consequently, methods to improve immunity may be of more practical value than is biosecurity for control of Salmonella infections in large-scale dairy herds.
Some proteins on the outer surface of bacteria (such as Salmonella enterica) have antigenic properties and can be exploited through vaccine technology to induce effective immunity. The SRP proteins are critical for iron acquisition and are highly conserved among and within species of bacteria.5 A novel vaccine containing specific SRP proteins derived from Salmonella enterica serovar Newport has been conditionally approved to aid in the control of disease and fecal shedding caused by infection with Salmonella Newport. The premise for the vaccine is that inactivation of SRP proteins via antibody binding will restrict the ability of Salmonella Newport to acquire iron from the environment, which will place it at a disadvantage in the microbial consortia within the gastrointestinal tract. Although the authors are not aware of any peer-reviewed studies to support the effectiveness of this vaccine, many dairy producers have adopted the routine use of this vaccine to aid efforts to control salmonellosis.a Therefore, the objective of the study reported here was to determine the effects of vaccination with a Salmonella Newport SRP vaccine on milk production, SCC, and shedding of Salmonella organisms in female dairy cattle.
Dairy Herd Improvement Association
Somatic cell count
Siderophore receptor and porin
Sandstrom JD, Epitopix LLC, Willmar, Minn: Personal communication, 2007.
Salmonella Newport bacterial extract, Conditional license, Siderophore receptors and porins, provided by Agrilabs Inc, St Joseph, Mo.
Provided by Agrilabs Inc, St Joseph, Mo.
Posilac, Monsanto Co, St Louis, Mo.
FloMaster Pro, Alfa Laval Agri, Kansas City, Mo.
Whirl-Pak, Nasco, Fort Atkinson, Wis.
Epitopix LLC, Willmar, Minn.
Immulon II HB coated 96-well plates, Dynatech Corp, Chantilly, Va.
Tween 20, Sigma Chemical Co, St Louis, Mo.
BioTek Elx-800, BioTek Instruments Inc, Winooski, Vt.
Somacount 500, Bentley Instruments, Chaska, Minn.
SAS, version 9.1.3, SAS Institute Inc, Cary, NC.
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