The use of item response theory models to evaluate scales designed to measure knowledge of, and attitudes toward, antibiotic use and resistance in Swedish dairy producers

Understanding Vietnamese chicken farmers' knowledge and practices related to antimicrobial resistance using an item response theory approach

Introduction

Antimicrobial resistance (AMR) poses a threat to animal and human health, as well as food security and nutrition. Development of AMR is accelerated by over- and misuse of antimicrobials as seen in many livestock systems, including poultry production. In Vietnam, high AMR levels have been reported previously within poultry production, a sector which is dominated by small-scale farming, even though it is intensifying. This study focuses on understanding small- and medium-scale chicken farmers' knowledge and practices related to AMR by applying an item response theory (IRT) approach, which has several advantages over simpler statistical methods.

Methods

Farmers representing 305 farms in Thai Nguyen province were interviewed from November 2021 to January 2022, using a structured questionnaire. Results generated with IRT were used in regression models to find associations between farm characteristics, and knowledge and practice levels.

Results

Descriptive results showed that almost all farmers could buy veterinary drugs without prescription in the local community, that only one third of the farmers received veterinary professional advice or services, and that the majority of farmers gave antibiotics as a disease preventive measure. Regression analysis showed that multiple farm characteristics were significantly associated to farmers' knowledge and practice scores.

Conclusion

The study highlights the complexity when tailoring interventions to move towards more medically rational antibiotic use at farms in a setting with high access to over-the-counter veterinary drugs and low access to veterinary services, since many on-farm factors relevant for the specific context need to be considered.

Methods to develop and evaluate attitudinal scales to measure farmer perceptions: Using sheep scab as an example

There is limited information on the attitudes and opinions of British sheep farmers when preventing and managing sheep scab in their flocks. Attitudes are examples of latent traits, which are not directly observable. They must be measured indirectly which can be achieved using measurement scales. Attitudinal measurement scales are used frequently in research, but are seldom evaluated prior to use, particularly in veterinary research. Therefore, the aim of this study was to identify and assess latent traits which influence the control of sheep scab with the use of exploratory factor analysis, and then further evaluate these factors with the use of item response theory to determine how they perform as scales. An online survey was completed by 726 British sheep farmers during October 2021 (725 useable responses), which included a section with 37 belief statements related to the opinions and attitudes of sheep farmers around the management of sheep scab. These belief statements were developed and adapted from previous research. During the analysis, they were subjected to exploratory factor analysis, which suggested that the scales performed reasonably well. The scales were then evaluated further by item response theory. The graded response models for each attitudinal scale were assessed by graphical evaluation. They demonstrated that the scales were able to distinguish those respondents with low perceptions of control, responsibility, and trust, and those who had high perceptions of luck. This study provides insights into some of the factors influencing the management of sheep scab, and how well these scales perform. Additionally, it further highlights the importance of evaluating attitudinal scales for use in research, and that exploratory factor analysis alone does not provide enough information on how well they perform.

Design and analysis of a structured questionnaire to assess the probability of elimination of Rhipicephalus microplus from farms in a subtropical area

In areas in which R. microplus may be eliminated from farms, it is essential to evaluate the infestation situation and the biosecurity measures available when deciding whether or not to undertake an elimination effort. Multiple questionnaires have been developed to evaluate the cattle tick situation on farms, however, the validity of those questionnaires has not been evaluated. This study aimed to develop a standardized and validated questionnaire to estimate the likelihood of cattle tick elimination from farms. A list of items (topics) to be covered was sent to 25 experts for their evaluation, with 11 responding. Based on the selected items, thirty-five closed questions were developed and evaluated through a cognitive interview process with 8 veterinarians and 5 farmers. Subsequently, a focus group evaluation was carried out with 30 farmers and a pretest of the revised questionnaire was performed with 94 farmers. A test, re-test evaluation was carried out in a subset of the pretest respondents after two-weeks. The questionnaire took approximately 10 min to complete. The ability of the questionnaire to reliably produce a score reflecting the expected probability of a farm eliminating ticks was evaluated through the use of a two-parameter logistic item-response theory model. A subset of questions related to a unidimensional latent variable were identified. This set of items appeared to have good ability to predict which farms were more likely to achieve the elimination, although the evaluation of that predictive ability was beyond the scope of this work.