Bovine cysticercosis is caused by the larval stage of the human tapeworm Taenia saginata. Cattle become infected through the accidental ingestion of food or water which has been contaminated with human faeces. After 8-10 weeks the larvae will establish in the muscles and develop into cysts.
The presence of Taenia sanginata cysts in cattle is determined during post mortem meat inspection and enforced through Regulation (EC) No 854/2004. Carcasses with visible cysts are either downgraded or condemned depending on the amount and type of visible cysts.
In Britain, positive cases detected during post mortem inspection are recorded in the FSA national meat inspection database, but without additional information on animal or farm characteristics. Farm characteristics, such as water source, type of production and geographic location are likely to influence the likelihood of Cysticercus bovis infection.
Farm characteristics could, therefore, be used to classify farms according to their ‘a priory’ risk of the animals raised in them having cysticercosis; and this classification could be the basis for different, more targeted, types of inspection.
To achieve the aim of compiling and summarizing relevant evidence that could eventually result in more targeted meat inspection activities for Cysticercus bovis, the following steps were carried out:
- Existing published evidence was identified, appraised and summarised. This included published scientific literature and grey literature.
- Existing data on disease presentation in UK farms was explored. This was based on post mortem meat inspection and information provided on the agricultural census.
- Information on farm level risk factors from case and control farms, by means of a postal questionnaire and elicit expert opinion, was gathered.
All of these sources of information were used to establish farm categories with different risk profiles with respect to Cyscticercus bovis infection.
The Food Standards Agency contracted the Royal Veterinary College and Safe Food Solutions to carry out project FS517002, with the aim of gathering evidence that could inform more targeted and cost effective inspection activities, for the detection of Cystiercus bovis infection in UK cattle at slaughter. This report outlines the methods, results and conclusions of the epidemiological research. Additionally, it makes a proposal for a ‘classification tool’ whereby meat inspection activities can be targeted at cattle with a higher risk of C. bovis infection at slaughter.
The project initiated with a systematic review of published evidence to identify previously defined risk factors for C. bovis infection in cattle, in addition to previous research outcomes on the design and implementation of more targeted meat inspection of cattle for C. bovis infection.
Using available cattle slaughter records and accompanying movement history data, three analytical approaches were employed in order to detect risk factors associated with C. bovis infection. The first analysis showed limited evidence of association between farm characteristics and risk of C. bovis infection. The second analysis showed that animals with a history of being on a ‘high risk’ farm (featured in the movement history of a previously infected animal) have four times higher odds of being found as positive for C. bovis at meat inspection. The final analysis showed that male cattle slaughtered at between 0-20 months of age were less likely to be infected with C. bovis.
Simulation modelling was then used to demonstrate the utility of a classification tool to direct inspection to high risk animals, which could lead to an 18.5% reduction in the total number of cattle undergoing meat inspection for C. bovis, whilst at the same time increasing the proportion of infected carcases detected at inspection from 15%, in the current situation, to 21%.