Effect of some physical factors on the viability of third-stage Gnathostoma binucleatum larvae.

To diminish the risk of transmission to humans of advanced third-stage larvae (A3L) of Gnathostoma binucleatum in fish foods, we evaluated the effects of some physical factors on larval viability. A3L protected within fish meatballs were subjected to freezing, refrigeration, boiling, dry heat, and immersion in lemon juice. By freezing, larvae were killed in 48 h, by refrigeration after 30 days, by boiling in 4 min, and by broiling for 60 min. By lemon juice immersion (pH 2.5), encysted larvae were killed after 5 days and nonencysted larvae in 7 h. Results show that freezing fish at -10 to -20°C for 48 h, or cooking fish by frying, boiling, or broiling, will prevent transmission of G. binucleatum. Furthermore, results dispel the popular myth that lemon juice kills encysted larvae in fish.