Quantitative risk assessment for human Taenia saginata infection from consumption of Australian beef

Abstract

Humans are the primary host of the tapeworm Taenia saginata, and the tapeworm eggs are passed in human faeces. Viable eggs can be ingested by cattle and form cysts (Taenia saginata cysticercus, more commonly known as Cysticercus bovis) in their muscles. While cysts become non-viable over time, the life cycle is completed if viable cysts are ingested by humans in raw or undercooked beef. In Australia, T. saginata is not endemic in the human population and cattle are generally not grazed on pastures that have been irrigated with sewage. Nevertheless, all cattle are inspected post-mortem for lesions, including incisions of the heart and masseters, despite the lack of sensitivity of inspection when infections are light.A Quantitative Risk Assessment (QRA) model was adapted and updated to quantify the risk of human T. saginata infection from consumption of Australian beef domestically and in key export markets. The model was used to investigate the effect of reducing current post-mortem inspection (PMI) protocols by removing the need to incise the masseters, or by removing all incisions, for low risk cattle.The results of the QRA indicate that the risk of human T. saginata infection from consumption of Australian beef is very low—a median 0.37 (95% Credibility Interval: 0.03–10.5) and 0.27 (0.01–3.8) cases per 1 billion (109) portions consumed in the domestic and top 5 export markets (USA, Japan, Korea, China and Canada), or equivalently 0.56 (0.04–15.8) and 0.97 (0.05–13.4) illness per year, respectively. Moving to reduced PMI, which only includes incisions of the heart, was estimated to result in a negligible increase in risk, equivalent to one additional infection every 12.5 and 33.3 years in the domestic and all export markets, respectively. Further reduction in PMI requirements, i.e. visual only PMI, was estimated to result in a small increase in risk to 0.7 (0.05–19.0) and 1.1 (0.06–16.5) illness per year—a median increase of about one additional case in domestic and export markets each per seven years.The evidence present in this QRA demonstrates that alternative post-mortem inspection procedures for C. bovis achieve equivalent food safety outcomes to the current domestic standard.