Dam vaccination for the prevention of neonatal diarrhea caused by enterotoxigenic E. coli in calves-a systematic review and meta-analysis

Diarrhea in neonatal calves caused by enterotoxigenic <i>Escherichia coli</i> (ETEC) is a disease that negatively affects the welfare and production of cattle. We present a review of all literature published in 1950 and later, evaluating vaccine effectiveness and efficacy in protecting calves from diarrhea and death from infection with ETEC by vaccinating dams during gestation. Of 3677 citations identified, 61 were eligible for full text review. Data was extracted from 22 citations and separated into 3 subgroups: field trials, heterologous challenge trials, and homologous challenge trials. Field trials showed no evidence to support that vaccinating dams decreased the rate of death or diarrhea in calves under 14 days of age, but due to a limited number and quality of field trials that met our inclusion criteria, it is difficult to draw general conclusions from this finding. However, in both homologous and heterologous challenge trials, vaccines helped prevent death in study calves. The outcome diarrhea was eliminated from analysis in challenge trials due to unexplained statistical heterogeneity which may be caused by a variety of definitions for diarrhea. Very few studies included information on randomization, blinding, or funding sources. Based on funnel plots, some indication for publication bias exists for heterologous challenge trials, however, a sensitivity analysis using the trim and fill method did not change results. There is evidence for the efficacy of ETEC vaccination of dams in the prevention of neonatal calf death.