Control of VTEC O157 and Campylobacter jejuni/coli on cattle farms : Effective interventions and implementation

Abstract

Verocytotoxogenic E. coli O157 (VTEC O157) and Campylobacter jejuni/coli are zoonotic pathogens of public health importance, which are commonly carried and shed by cattle. Control at farm level needed isto limit shedding and contamination of the environment and the human food chain. On- farm risk factors for shedding of both bacteria were identified. Cross-sectional studies revealed that VTEC O157 shedding was associated with low frequency of assessing the wetness of bedding, animals housed in large groups and wet bedding in enclosures. For Campylobacter indoor housing, presence of milking cows, less frequent emptying and cleaning of water troughs and drinking private water supply water increased the risk of shedding. A longitudinal study observed that groups of VTEC O157 and Campylobacter shedding animals were only intermittently positive and that indoor housing increased the risk of shedding both organisms, where frequent cleaning of water troughs and drinking water from public water supplies were associated with reduced shedding of Campylobacter. A randomised controlled trial (RCT) was conducted to assess the impact of removal of risk factors on VTEC O157. Dry bedding, stable rearing groups, a closed herd policy and no contact with cattle from other herds significantly reduced VTEC O157 on farms over a period of 4.5 months. When these results were collated with the risk factor studies, a 5-point zoonotic control plan was generated: frequent emptying and cleaning of water troughs, dry bedding in enclosures, maintain stable rearing groups, apply a closed herd policy and avoid direct contact between cattle from different herds. To encourage uptake of the zoonotic control plan, the likelihood of implementation on farms was investigated. A total of 1.5 years after the end of the RCT, ineffective measures were continued by 55% of farmers, where only 19% adopted new effective practices due to evidence of effect. Implementation of all practices had financial costs, but ineffective practices provided no disease-controlling benefits, but a perception of improved animal welfare. This observation showed that some farmers were willing to adopt practices without financial gains, if other benefits were perceived. To investigate motivators for implementation, theories from social sciences, behavioural economics and human medicine were combined with the knowledge of livestock farming. This generated a theoretical conceptual framework: a “pathway to disease control”-model, which was validated using field data. The “pathway to disease control”-model was used to identify and explain motivational factors for implementation of zoonotic control on English and Welsh cattle farms. In general, attitudes towards zoonotic control were positive, but intent to control was inhibited in approximately half the farmers by non-supportive social norms and/or a lack of belief in self-efficacy. The remaining farmers showed a gradual intent to control, but had not implemented any structured control program due to external barriers including lack of knowledge and cultural and economic pressure from both society and industry. The farmers with no intent to adopt control measures identified their private veterinarian as the preferred motivator, whereas consumer-demand and financial rewards or penalties were significantly more likely to be preferred by farmers who intended to control.