Monitoring health status of post-weaning piglets during oral vaccination against Enterotoxigenic Escherichia coli F4/F18 using salivary biomarkers

Colibacillosis negatively affects the growth of weaned piglets at a critical time in immune development, and other pathogens may also be present. Vaccination against Escherichia coli is a significant challenge, making it essential to develop various salivary biomarkers that allow for the non-invasive assessment of inflammation, health status, and immune status. A total of 137 saliva samples were studied from piglets (healthy and diseased) belonging to two groups (unvaccinated-CONTROL and vaccinated-VAC), at 2-, 4-, and 7-weeks post-vaccination against enterotoxigenic E. coli F4/F18. Morbidity, mortality, salivary pathogens (Mesomycoplasma hyopneumoniae, Mesomycoplasma hyorhinis, Streptococcus suis, porcine circovirus type 2 - PCV-2, Clostridium perfringens, porcine reproductive and respiratory syndrome virus - PRRSv and Influenza A) and salivary biomarkers were analysed: acute phase proteins (Haptoglobin - Hp and C-reactive protein - CRP), inflammation (Calgranulin C - S100A12 and enzyme adenosine deaminase - ADA), immune response (Immunoglobulin G - IgG) and oxidative status. Survival rate and body weight were numerically higher in the VAC group, although without statistically significant differences. Salivary biomarkers showed higher IgG and S100A12 values in the CONTROL in comparison to VAC. The biomarkers CRP, Hp, and ADA were higher in diseased piglets from both groups. The VAC group showed numerically lower positivity for the pathogens M. hyorhinis and M. hyopneumoniae. In general, diseased piglets from both groups were more positive for M. hyorhinis, PRRSv, PCV-2, and C. perfringens. Piglets vaccinated against ETEC F4/F18 exhibited a numerically better body condition and lower mortality, a reduced inflammatory response with lower values of CRP, ADA, S100A12, and IgG, and a lower incidence of Mesomycoplasma.