Vaccination of ewes and lambs against parainfluenza3 to prevent lamb pneumonia

The purpose of this experiment was to test the effectiveness of vaccination against parainfluenza3 (PI3) to prevent pneumonia in lambs in a flock in which over 9%of 2657 lambs born alive in the previous 2 years had died of Mannheimia (Pasteurella) haemolytica pneumonia. The experiment was carried out using 176 Dorset ewes and their 1/4 East Friesian lambs born from 15 March to 8 April 2002. One week before the start of the lambing season, 90 ewes were vaccinated with 1ml of TSV-2®, a modified live bovine rhinotracheitis-parainfluenza3 vaccine, administered intranasally. Alternate litters of lambs within vaccinated (149 lambs) and control (137 lambs) ewe groups received 0.5 ml of TSV-2®. Death and treatment data through 66 days of age were analyzed by binary logistic regression with a model that included main effects of ewe or lamb vaccination and the two-way interaction. To account for losses of animals by death or sale, a survival analysis model was used to analyze time from birth to death through 220 days of age. Of 157 lambs delivered by vaccinated ewes, 5.1% were delivered dead, while 8.1% of 149 lambs were delivered dead to control ewes. Total deaths of lambs born alive were fewer and deaths due to pneumonia or unknown causes were fewer in the vaccinated than in the control groups, although the effect of vaccination was not statistically significant. Through 66 days of age when the first lamb was sold, only 10 lambs, or 3.5% of those born alive, died of pneumonia with about equal proportions in the four ewe and lamb vaccination groups. Through 220 days of age, more control lambs died, but the survival analysis found no statistically significant differences among vaccination groups in total death loss nor in the proportion treated, dying, or both due to pneumonia. Among a group of 34 slaughtered lambs distributed across the vaccine treatments, 27 had lung damage evident of pneumonia even though only one lamb had been treated for pneumonia. Thus, although overall deaths were non-significantly higher in control lambs, vaccination against PI3 did not appear to reduce the incidence of pneumonia in this flock. © 2007 Elsevier B.V. All rights reserved.