Inactivation of Trichinella muscle larvae at different time-temperature heating profiles simulating home-cooking.

Background: Trichinellosis is caused by consumption of raw or undercooked meat containing infective Trichinella muscle larvae (ML). Only few studies on heat-inactivation of Trichinella ML are available in literature and more validated data concerning heat inactivation is needed to improve the risk estimation.

Objective And Methods: The aim of the present study was to evaluate the two in vitro methods "staining" and "morphological examination" as proxies for Trichinella ML heat inactivation in comparison with the mouse bioassay method to get more insight in the relationship between heat, heating time and inactivation of Trichinella ML. The second aim was to evaluate whether these methods could replace the bioassay in the light of ongoing animal use reduction in lifescience research. Tubes containing quantified live Trichinella ML were exposed to heat profiles ranging from 40 to 80 °C. Subsequently, inactivation was evaluated using both methylene blue staining and morphological examination, which was validated by bioassay. Results were used to model Trichinella inactivation.

Results: Trichinella muscle larvae exposed to 60 °C or higher for 12-12.5 min were not infective to mice. We found that morphological examination was more consistent with the bioassay than methylene blue staining. Modelled inactivation fitted experimental data consistently. Moreover, this study shows that larval Trichinella morphology may be used in situations where bioassays are not possible or prohibited.

Conclusions: The relationship between heat and inactivation of larvae obtained from this study could be used in Trichinella QMRA models to improve quantification of the risk of Trichinella infection.