Of 18 crias with given date of birth, four 6 to 9-months-old crias and their dams were SBV seropositive. Maternal SBV-antibodies in calves born from SBV seropositive dams had ceased 6 months after their birth (Elbers et al., 2014), but maternal BTV-8 BMH-21 were still detected in a few 7-month-old crias (Schulz, 2012). Therefore, the detection of maternally derived SBV antibodies in some crias in this study cannot be excluded and might cause a slight bias of the study results. Another possible reason for SBV seropositive results in the crias might be that SAC foetuses were naturally infected with SBV in the second part of gestation, when the foetuses have become immunocompetent (Bayrou et al., 2014 and Wernike et al., 2014).
In killer T cells study, age was the only risk factor identified for SBV-infection. Other factors associated with SBV-infection in ruminant livestock such as milk yield or return-to-service (Beer et al., 2013, Veldhuis et al., 2014a and Veldhuis et al., 2014b) were not included in the questionnaire, because these parameters are hardly available for SAC (Gauly, 2011a).
In killer T cells study, age was the only risk factor identified for SBV-infection. Other factors associated with SBV-infection in ruminant livestock such as milk yield or return-to-service (Beer et al., 2013, Veldhuis et al., 2014a and Veldhuis et al., 2014b) were not included in the questionnaire, because these parameters are hardly available for SAC (Gauly, 2011a).