Antimicrobial drugs used in the prevention and control of protozoal and bacterial calf diarrhea: A scoping review.

This scoping review examined the scientific literature on antimicrobial use (AMU) for preventing and controlling calf diarrhea. Secondary aims included describing health assessment methods and exploring the feasibility of meta-analyses to assess antimicrobial drug (AMs) efficacy. Following a registered protocol, four electronic databases were searched (initial search 2019; last update 2023). Eligibility criteria required controlled trials evaluating AMU for diarrhea prevention and control in calves ≤ 6 months, with efficacy assessed through health outcomes and/or fecal pathogen shedding. The search yielded 4486 references. After deduplication, two reviewers screened titles (n = 3259), abstracts (n = 341), and full texts (n = 106), resulting in the inclusion of 43 articles encompassing 62 trials. Pathogens associated with diarrhea included Eimeria spp. (41.9 %), Cryptosporidium spp. (40.3 %), Salmonella spp. (8.1 %), and Escherichia coli (3.2 %). High variability and frequent incomplete reporting of trial methodologies were observed. The most frequently assessed AMs were diclazuril, toltrazuril, and lasalocid for Eimeria, and halofuginone, chlortetracycline, and oxytetracycline for Cryptosporidium, Salmonella, and E. coli, respectively. Fecal consistency (93.5 %) and stool blood (48.4 %) were the most commonly evaluated fecal traits, while microscopy-based quantitative (50 %) and semi-quantitative (48.4 %) tests were frequently used for fecal pathogen shedding. Results suggest that meta-analyses could be performed to evaluate AM efficacy for diarrhea associated with Cryptosporidium and Eimeria. Future research should assess the efficacy of AMs approved by regulatory agencies, refine diagnostic methods for evaluating diarrhea etiology, validate health assessment techniques, and compare the efficacy of management practices in preventing and controlling calf diarrhea.