Table 15.

Overview of arguments leading to the consensus distributions for the eight selected control options. Next to the arguments for low and high effectiveness and some general comments, the table shows the largest range of quantitative estimates as given in this opinion, the source of these estimates (i.e. the PAF analysis, the concentration model or literature data), and the relative risk reduction estimates obtained by EKE

Control option	Arguments for low effectiveness	Arguments for high effectiveness	General comment	Largest range of quantitative estimates (%)a	Source of quantitative estimates	Median consensus (90% Probability interval) (%)
Vaccination	Doubts about inconsistencies in field conditions after upscaling Despite many efforts, there is no vaccine (proven to be effective in practice) currently available	Model results confirm large potential of vaccination The results are more consistent than for feed or water additives	It is generally agreed that the wide distribution reflects existing uncertainty and differences in judgement between experts	9–92	Concentration model	27 (4–74)
Feed and water additives	Doubts about inconsistencies under field conditions; very little evidence of reproducibility Publication bias: negative results are not published	Some additives show a large effect When effective, the risk reduction achieved is large	Unclear which specific additive is chosen Large variability between additives and studies	0–80	Concentration model	24 (4–60)
Discontinued thinning	Discontinued thinning will not reduce prevalence under poor biosecurity conditions	Data suggest that flocks are rarely Campylobacter negative after thinning (Koolman et al., 2014) It is very difficult to maintain high biosecurity during thinning; undermines the motivation to, and effect of, carrying out good biosecurity	Different experiences in different countries Differences between countries will be large Unclear how often thinning is currently applied in EU MSs; CAMCON project found that majority of flocks (> 80%) were thinned in large producer countries: ES, UK and PL	2–25	EFSA Opinion 2011; van Wagenberg et al. (2016)	18 (5–65)
Employing few and well‐trained staff	Training and/or certification alone does not mean that good biosecurity is consistently implemented	Key for good overall biosecurity Good biosecurity and husbandry are reliant on people knowing what they are doing and why	Main peak reflects PAF results	2.7–38.8	PAF analysis	16 (5–45)
Avoiding drinkers that allow standing water	Not clear why nipple drinkers are associated with lower prevalence of Campylobacter in the flock	Standing water may facilitate cross‐infection between birds using the same drinker. Drinker cups are quickly contaminated with bedding materials and possibly feed providing a niche in which Campylobacter may survive and cross‐infect other birds Cups on drinkers may allow spillage onto the bedding resulting in a higher moisture content that supports Campylobacter survival	Experts agreed on average (linear pool) of distributions based on individual judgements, without detailed discussion	0–78.5	PAF analysis	15 (4–53)
Addition of disinfectants to drinking water	The birds may dislike the odour or taste of the water resulting in lower effectiveness	Prevents water acting as a source of Campylobacter Effective way of administering anti‐Campylobacter agents ensuring all birds are treated	Experts agreed on average (linear pool) of distributions based on individual judgements, without detailed discussion	0.6–54.9	PAF analysis	14 (3–36)
Hygienic anterooms at broiler house entrance	Requires motivation on the part of the farmers	A key part of any biosecurity system ensuring Campylobacter are not transmitted form a contaminated farmyard into the broiler house Easy to implement	Experts agreed on average (linear pool) of distributions based on individual judgements, without detailed discussion	0–31.9	PAF analysis	12 (3–50)
Designated tools per broiler house	Will not be effective as stand‐alone measure Sharing tools indicates poor overall biosecurity	There is evidence that it is effective, although the effect is small		1–16	CAMCON project	7 (1–18)

^aAs presented in the opinion.