Submitted to: Joint Meeting of the ADSA, AMSA, ASAS and PSA
Publication Type: Abstract only
Publication Acceptance Date: 2/28/2006
Publication Date: 7/9/2006
Citation: Van Kessel, J.S., Karns, J.S., Wolfgang, D.R., Hovingh, E., Schukken, Y. 2006. A long term, sub-clinical, outbreak of Salmonella enterica subsp. enterica Cerro in a Pennsylvania dairy herd. Joint Meeting of the ADSA, AMSA, ASAS and PSA, Minneapolis, MN, July 9-13, 2006. Interpretive Summary:
Technical Abstract: Salmonella is a prominent foodborne pathogen in the US and dairy cattle have frequently been identified as reservoirs for this organism. Here we describe a long term outbreak of Salmonella enterica subsp. enterica Cerro that was detected in a Pennsylvania dairy herd during routine monitoring as part of a longitudinal study of several dairy herds. An initial analysis of individual fecal grab samples from the milking herd indicated a very low prevalence of Salmonella (1/102) and Salmonella was not detected in 10 environmental samples. In a subsequent sampling six months later, Salmonella was isolated from 43.5% (47/108) of the cows and 40% of collected environmental samples (10/25). The Salmonella isolated in the first sampling was serovar Typhimurium var. Copenhagen, however isolates from the second herd sampling were serovars Cerro (91.5%) and Kentucky (8.5%). Sporadic environmental sampling between these initial complete milking herd samplings yielded serotypes Kentucky, Typhimurium var. Copenhagen, and Cerro and clinical salmonellosis was observed in several cows shedding Typhimurium var. Copenhagen. The herd was sampled nine additional times over the next 14 months and fecal prevalence of Salmonella ranged from 8.4% to 89%. Prevalence remained high (58 to 69%) over the following eight months, showed evidence of decline over the next three months, and then increased again to 89%. Cerro was the only serotype isolated during this period. Bulk milk was cultured weekly during this 22 month period and Salmonella was isolated from 5.3% (5/94) of milk samples. For the last 14 months of the study, milk filters were also cultured for Salmonella on a weekly basis and 65% (37/57) of the filters tested positive. There were no significant health or production concerns in the herd during this outbreak. Based on these observations we conclude that sub-clinical Salmonella enterica subsp. enterica Cerro infection can be persistent in a milking herd.