To evaluate herd-level risk factors for seropositive status of cattle to 1 or more bluetongue viruses. 110 herds of cattle in Nebraska, North Dakota, and South Dakota. Blood samples were collected before and after the vector season. Samples were tested for antibodies against bluetongue virus by use of a commercially available competitive ELISA. Factors evaluated included descriptors of geographic location and management practices. Trapping of insect vectors was conducted to evaluate vector status on a subset of 57 operations. A multivariable logistic regression model was constructed to evaluate associations. For the full data set, altitude and latitude were associated with risk of having seropositive cattle (an increase in altitude was associated with an increase in risk, and a more northerly location was associated with a decrease in risk of a premise having seropositive cattle). Import of cattle from selected states was associated with an increase in risk of having seropositive cattle. From the subset of herds with data on vector trapping, altitude and latitude were associated with risk of having seropositive cattle, similar to that for the full model. However, commingling with cattle from other herds was associated with a decrease in risk of seropositivity. Findings reported here may be useful in generating additional hypotheses regarding the ecologic characteristics of bluetongue viruses and other vector-borne diseases of livestock. Sentinel surveillance programs are useful for documenting regionalization zones for diseases, which can be beneficial when securing international markets for animals and animal products.

The effect of a novel bovine mastitis trivalent vaccine, containing Staphylococcus aureus capsular polysaccharide type 5 (T5), 8 (T8), and 336 (T336), on lymphocyte subpopulations, antibody production, and neutrophil phagocytosis was evaluated. Twenty pregnant heifers were immunized with either the trivalent alone, trivalent emulsified in Freund's incomplete adjuvant (FICA), trivalent in aluminum hydroxide, or adjuvant only (FICA). Immunization was done 30 d before the expected calving date followed by 2 boosts in a 2-week interval. Compared to FICA, serum antigen-specific immunoglobulin (Ig)G1 and IgG2 were significantly increased in all the vaccinated groups before parturition and sustained until 3 wk postpartum. In comparison with the trivalent alone, formulation with either adjuvant enhanced production of IgG2, but not IgG1. Immune sera, which contained the highest amount of antibodies, slightly increased neutrophil phagocytosis to the 3 serotypes of killed S. aureus, but most of the differences were not significant due to large variation between the cows. The percentage of CD4+ lymphocyte was significantly higher in vaccinated groups than that of FICA 4 wk after the primary immunization. In comparison with FICA, cows inoculated with trivalent vaccine and adjuvants had an increased percentage of CD8+ lymphocytes at 2 time points, 2 wk before and after calving. Our results indicated that the whole cell trivalent vaccine, with or without adjuvants, is able to elicit antibody responses specific to the 3 capsular polysaccharide antigens. The increase of T8-specific IgG2 was more noticeable when the vaccine was emulsified with adjuvants.