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United States Department of Agriculture

Agricultural Research Service

Title: Salmonellosis Outbreak and Subsequent Subclinical Infection in a Nebraska Beef Herd Attributable to Clonal Salmonella Isolates of Identical Pfge Genotype But Variable Serologic Phenotype

item Keen, James
item Snell, Robert - BURWELL VET. HOSPITAL
item He, Yongsheng - UNIVERSAL HLTH WATCH, INC
item Laegreid, William

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: October 7, 1997
Publication Date: N/A

Technical Abstract: An outbreak of clinical salmonellosis in a 150 head beef cow-calf herd in the Nebraska sandhills was identified by the sudden death of several cows in summer 1996. Over the following year (8/96 to 8/97), no additional clinical cases of salmonellosis occurred and feces and sera from all cows and calves were collected quarterly. Feces were cultured for Salmonella and sera were tested for anti-Salmonella antibodies by blocking ELISA using anti-Salmonella monoclonal antibodies. Initially, a majority of cows and calves were fecal-culture Salmonella positive. Four Salmonella serovars were isolated from the herd including two serogroup B [S. typhimurium (ST) and S. typhimurium copenhagen (STC)], and two serogroup C1 [S. thompson, and S. oranienburg]. Most cows and calves were infected with ST or STC, and many cattle were infected with both ST and STC at a given sampling time. Fecal prevalence rapidly decreased during winter until only a single cow was fecal-positive by 1/97. Pulse-field gel electrophoresis (PFGE) patterns of all ST and STC isolates from the herd were identical; PFGE patterns from the C1 isolates were different from each other and from the ST/STC. These data suggest that the outbreak and subclinical infections were likely attributable to a single genotype ST-STC clone with the capability (by an unidentified mechanism) to vary its O-antigenic factors and thereby vary its serotype between ST and STC.

Last Modified: 4/22/2015
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