Reference, proceedings for oral presentation.
Krogh, K.*, Petersen, M.B., and Nielsen, L.R. Interpretation of Mycoplasma bovis tests in bulk tank and DHI-samples
from cattle herds. World Buiatrics Conference, Cairns, Australia, August 2014.
Interpretation of Mycoplasma bovis tests in bulk tank and DHI-samples from cattle herds
Kaspar Krogh, ksk@vfl.dk*1, Mette Bisgaard Petersen2 and Liza Rosenbaum Nielsen2.
1
Knowledge Centre for Agriculture, Cattle, Agro Food Park 15, DK-8200 Aarhus N, Denmark.
University of Copenhagen, Faculty of Health and Medical Sciences, Groennegaardsvej 8, DK-1870 Frederiksberg C, Denmark
*E mail: ksk@vfl.dk
2
Objectives
Mycoplasma bovis (M. bovis) is a bacterial infection that causes disease in cattle (e.g. mastitis, pneumonia,
otitis and arthritis). During an outbreak in cattle herds many animals may become affected and morbidity can
be high leading to both compromised animal welfare and severe economic losses. Because M. bovisassociated disease tends to be chronic and responds poorly to treatment, costs per case are typically high
relative to other pathogens. There appears to be an increase in clinical outbreaks and associated losses
attributed to recent spread of M. bovis amongst Danish cattle farms, and it also appears to be an emerging
disease in other european as well as non-european countries. A lager study funded by the Danish Milk and
Cattle Levy funds has been initiated in which diagnostic methods and the epidemiology of the infection are
being investigated in a field study of 40 dairy herds from 2013 to end of 2015. The objective of an on-going
part of the study is to characterize how individual antibody obtained using a M. bovis specific ELISA (MYCOPLASMA BOVIS ELISA KIT, Bio-X Diagnostics, Site du Complexe des postes 49, rue J. Wauters, 5580
Jemelle, Belgium) with a cut-off-value at 37 ODC% levels in milk corresponds to levels in blood, to investigate relationships between individual positivity in either PCR or ELISA and how share of the within-herd
prevalence of PCR-positive animals affects the BTM PCR-test results in Danish M. bovis-PCR-positive dairy
herds. At lastly to determine what the prognostic value of a PCR-reaction is at herd and animal level.
Materials and Methods
BTM-samples has been collected weekly for 13 weeks prior to at the date of sampling of individuals and will
be collected 3 weeks after individual sampling (DHI) of 200 randomly selected cows within the herd (herd
size 200 – 600 cows). Individual sampling will include both milk and blood samples. All milk samples will be
tested in parallel with PCR and ELISA. At the same time individual blood samples from the same animals will
be tested with ELISA to evaluate correlation between ELISA values from milk and blood.
Results
The prevalence of M. bovis-PCR-positive bulk tank milk (BTM) samples from Danish dairy herds has been
found to be low (1.7%, 2.0% and 1.6% in 2011, 2012 and 2013, respectively). However, these prevalences
might not reflect the true herd level prevalence due to bias caused by unknown diagnostic test performance,
and it is not yet known if or how herds can be appropriately categorised in a surveillance and control programme. A pilot study in two large dairy herds revealed that a high proportion (up to 55%) of cows can be M.
bovis-PCR-positive on individual milk-samples collected during periods with clinical disease. Results from the
on-going study will be presented.
Conclusions
Results will indicate whether antibody levels obtained from blood and milk corresponds acceptably, one cow
with a strongly positive PCR-reaction in individual milk tests, or a larger proportion of animals are needed to
attain a positive BTM-reaction. The results will be useful for further planning of surveillance and control efforts. An efficient control- or eradicationprogram will depend on profound knowledge of the epidemiology of
M. bovis-related disease as well as the performance of relevant surveillance methods.