Enzootic pneumonia in sheep: ewe and lamb immune response after Mannheimia haemolytica vaccine administration under field condition in Italy

Abstract

Mannheimia haemolytica related pneumonia is characterized by high morbidity and mortality in lambs and thus is a common cause of important economic losses in sheep industry due to reduction in lamb growing and decreased carcass value. Due to the frequency of the disease, vaccination is a very common practice in Italy but the extent and duration of colostral protection in Sarda lambs born from vaccinated dams is not known.  In this study, the extent and length of colostral antibody protection in Sarda lambs born from M. haemolytica-vaccinated ewes was evaluated in field condition. The in-field trial took place in two different farms in Sardinia region (Italy). A total of forty-five adult healthy pregnant Sarda sheep were enrolled for the study (24 from the first flock and 21 from the second flock). Each flock in each farm was divided in two groups: unvaccinated control group (10 sheep from the first flock and 8 from the second flock) and vaccinated sheep (14 from the first flock and 13 from the second flock).  A total of forty-five (45) lambs born from both vaccinated (n=27) and unvaccinated (n=18) dams were included in the study. Colostrum was collected from all the dams within 6-12 hours after lambing. Serum samples were taken from all the lambs included in the study at 48 hours, 15, 30, 45, 60 days after parturition. Antibody responses following vaccinations were detected by ELISA tests. In the trial, antibody titers both on serum of ewes and lambs and colostrum were comparatively examined and important differences were observed in vaccinated pregnant ewes where serum titers developed after vaccination resulted two times higher than in the unvaccinated group; within the lamb groups, an increase of serum ELISA titers was found in lambs born from vaccinated ewes until 60 days after birth. Colostral titers didn’t show any significant difference. In conclusion, when the control group and the trial group were compared, vaccinating the lambs belonged to vaccinated dams showed significant differences concerning antibody responses against M. haemolytica.