The Infectivity of Frozen Gnathostoma spinigerum Encysted Larvae in Mice

Abstract

Abstract

The infectivity of encysted larvae of Gnathostoma spinigerum in mice, after being frozen in the freezer of a household refrigerator (-2 to -4 ^oC), was evaluated. The larvae used in the experiment, which were obtained from laboratory-infected rats and mice, were 6 months old. Those recovered from naturally infected eels were of unknown age. Each group of larvae was placed in a blockglass containing physiological saline, kept in the freezer for 1, 6, 12, 18, 24, 30, 36 or 48 hours, and fed to clean mice, 5 larvae per mouse. Both the 6-month-old and the unknownage encysted larvae lost their infectivity completely after being frozen for 48 hours. When the larvae were rolled up inside the mice flesh and frozen at the same temperature for 48 hours, they could still infect clean mice, with an infectivity of 20.0%. It was concluded that although G. spinigerum encysted larvae could survive several days in the freezer of a household refrigerator they lost their infectivity only after 1-2 days. However, the mimetic infected meat containing encysted larvae resisted this freezing temperature for at least 48 hours.

Keywords : G. spinigerum, infectivity, frozen, encysted larvae, mice, eels