Different infection parameters between dairy cows and calves after an infection with foot-and-mouth disease virus

Clinical observations of a foot-and-mouth disease (FMD) virus infection in dairy cows and calves were different. This raised the question whether they would also differ with respect to virus excretion and transmission. Data were available from transmission experiments carried out with groups of dairy cows and calves. Half of each group was inoculated with FMDV O/NED/2001; the other half contact-exposed to inoculated animals. Virus excretion, clinical signs and antibody response were measured and virus transmission was quantified. Infected calves showed mild clinical signs which did not affect general health or appetite, and not all contact calves became infected. Dairy cows, on the other hand, showed severe FMD lesions resulting in clinical mastitis, severe lameness and decreased feed intake. Also fever was observed for three consecutive days. All contact cows became infected and showed the same severity of clinical signs. The total and mean daily virus excretion differed significantly between cows and calves (P<0.05). Possibly, virus replication and clinical manifestation are associated, but the underlying mechanism of these differences needs to be elucidated. We did not observe a significant difference in virus transmission between calves and cows.