Association of immune responses of Zebu and Holstein-Friesian cattle and resistance to mycobacteria in a BCG challenge model
Mycobacterium bovis is the main causative agent of bovine tuberculosis (BTB) in cattle and it is also responsible for a proportion of human TB cases. The annual cost of BTB worldwide is estimated at US$3 billion. Zebu cattle are considered to be more resistant to some infectious diseases than Holstein-Friesian (HF) cattle, including BTB. However, epidemiological studies do not necessarily take into account usage differences of the two types of cattle. It could be argued that HF cattle suffer
... ater metabolic stress due to their mainly dairy use, whereas Zebu cattle are mainly used for beef production. However, in experiments comparing Zebu and European cattle, the number of animals has been too small to draw statistically robust conclusions on the differences in the level of resistance between these breeds of cattle. Here, we used a recently developed vaccination-and-BCG challenge model to compare the ability of naïve and vaccinated Zebu and HF cattle to control/kill mycobacteria. Young male cattle of both breeds with similar ages were housed in the same accommodation for the duration of the experiment; after correcting for multiple comparison, we found that there was a trend for vaccinated HF cattle to have lower cfu numbers than non-vaccinated HF cattle (ρ = 0.057). No such trend was observed between vaccinated and non-vaccinated Zebu cattle (ρ = 0.560); similarly, no difference was observed between naïve HF and Zebu (ρ = 0.862) cattle. In contrast, evaluation of antigen-specific IFNγ secretion indicated that Zebu and HF cattle differed in their response to mycobacteria. Thus, under the conditions used in this work, the data indicate that there are no differences between Zebu and HF cattle. Further experiments, using larger numbers of animals may be required to determine whether Zebu and HF cattle differ in their susceptibility to infection with M. bovis.