Massey Documents by Type

Permanent URI for this communityhttps://mro.massey.ac.nz/handle/10179/294

Browse

Filters

2022 - 20252

Settings

Start date: 2022Subject: search.filters.subject.serology

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Patterns of Mycoplasma bovis antibodies in cows and calves in Swedish dairy herds, and testing strategies to detect seropositive herds
    (Elsevier Inc on behalf of the American Dairy Science Association®, 2025-10-01) Hurri E; Compton CWR; Alvåsen K; Tråvén M
    Mycoplasma bovis causes severe diseases among cattle. Sweden has a favorable situation for control of this disease, with a low prevalence of M. bovis infected and seropositive herds detected only in the southern parts of the country. To prevent the spread of the infection, analyzing antibody levels is a cost-effective method to determine herd pathogen exposure status. In this study, our aims were to monitor the antibody dynamics in infected herds over time using IDvet ELISA, to both evaluate risk-based sampling and investigate the effect of M. bovis exposure on health and production. We visited and sampled 35 dairy herds, 31 of which were sampled at least 2 times and 26 sampled 4 times and followed for 2 yr. The patterns of herd seroprevalence varied depending on the status before the herd's entry into the study and remained relatively stable at the herd level, although antibody status could differ among age groups. Overall, herds with high exposure prevalence (75%–100% positive cows, n = 13/26), and herds with low exposure prevalence (<25% positive cows, n = 5/26), maintained their exposure status throughout the study. The changes in status observed within the herds, both among calves and cows, included transitions from positive to negative, as well as from negative to positive. In 5 herds, the calf group transitioned from positive to negative, while in 1 herd, the reverse occurred. Three herds exhibited an increase in antibody levels; in 2 of these herds, the cows transitioned from negative to positive, and in 1 herd with positive cows, the calves shifted from negative to positive. A cost-effective test strategy to find likely infected herds involved sampling bulk tank milk and cows with a high SCC, which gave a 90% probability of locating infected herds by the second sampling. Milk production was reduced by 404 kg (1.3 L/d, P = 0.012) in cows positive for M. bovis antibodies. Therefore, controlling the spread of M. bovis infection will likely have a positive effect on reducing income loss for dairy herds in Sweden.
  • Thumbnail Image
    Item
    Performance of the StaphGold ELISA test in determining subclinical Staphylococcus aureus infections in dairy cows using a Gaussian mixture model
    (John Wiley and Sons Ltd, 2022-07-20) Yang DA; Laven RA
    BACKGROUND: A novel ELISA test has been developed to detect antigen-specific IgG in early and late lactation cows in New Zealand. OBJECTIVES: This study was to evaluate the discriminatory ability of the ELISA based on the detection of S. aureus-specific IgG as a screening test. METHODS: The ELISA was used for the composite milk samples taken during routine herd testing in 2018-2019 milking season in New Zealand. In the absence of a gold standard test, the diagnostic specificity and sensitivity was estimated using a Gaussian mixture model. RESULTS: The ELISA test had a high accuracy (AUC = 0.98) to detect antigen-specific IgG in early and late lactation cows with high somatic cell count due to either subsequent to or contemporaneous with the S. aureus invasion. Using an S/P ratio = 0.3 as the cut-off value, the ELISA test has sensitivity of 0.9 and specificity of 0.95, while the sensitivity increased to 0.94 at a cost of a decreased specificity of 0.9 at a lower cut-off value 0.26. CONCLUSIONS: The integration of the ELISA test as a screening tool into specific control programs may be useful to reduce the spread of S. aureus infections, to aid with treatment decisions, and to establish a correct milking order.