A sero-epidemiological study of Haemophilus somnus infection in dairy cattle.

摘要

Five repeated cross-sectional serological surveys of 790 dairy cattle in 4 dairy herds (3 of Holstein and 1 of Holstein and Guernsey cattle) between December 1985 and February 1987 in California were used to investigate changes in the seroprevalenceof H. somnus with respect to some demographic and disease variables. The demographic variables included age (heifers or cows) and farm (2 herds were from the Central and 2 were from the Northern Valleys of California). The serological status of cattle as either negative or positive against H. somnus, Campylobacter fetus and Leptospira hardjo were determined using ELISA. At first sampling, but not in the other samplings, cows were about twice as likely to be H. somnus seropositive as heifers. At samplings 1 and 3, but not at 2 and 5, cattle in herds of the Central Valley were less likely to be infected. In contrast, at sampling 4, the cattle in those herds were about 7 times more likely to be H. somnus seropositive. C. fetus-positive cattle were about3 times more likely to be H. somnus seropositive at sampling 1 only. There was no significant relationship between H. somnus and L. hardjo seropositivity.