Administration of granulocyte-colony stimulating factor (G-CSF) to pigs results in a longer mean survival time after exposure to Streptococcus suis.

The use of immunomodulators is a promising alternative to the use of antibiotics for therapeutic, prophylactic, and metaphylactic use to prevent and combat infectious disease. Previously we demonstrated a replication-defective adenovirus vector that expresses porcine granulocyte colony-stimulating factor (G-CSF) elicited a sustained neutrophilia, lasting nearly 3 weeks, which may be beneficial to prevent bacterial diseases during times of peak incidence. In a pilot study using the vectored G-CSF with a Caesarian-derived, colostrum-deprived (CDCD) pig model of Streptococcus suis disease, only 1 of 4 pigs given G-CSF developed disease, while 3 of 4 non-treated pigs developed Streptococcal disease. In a subsequent study using a larger number of pigs, although there was no difference in overall survival, there was a longer mean survival time in G-CSF treated pigs. S. suis infection is more severe in CDCD pigs than conventionally raised pigs, consequently results in the field may be superior to the ones reported in this study. Although there were positive effects from the use of G-CSF in this study, further research is needed to determine if improved clinical outcomes could be achieved under field conditions and whether the use of G-CSF in pigs to induce a sustained increase in circulating neutrophil numbers may be useful as an adjunct to antibiotics to diminish the severity of Streptococcal disease, especially during times of stress and pathogen exposure such as post-weaning.