Effect of temperature on the survival of Alaria alata mesocercariae

Abstract

Recent findings of Alaria alata mesocercariae in wild boars and other animals in Europe reinforced the concern about the public health risk posed by this parasite especially if the game meat is insufficiently heated during preparation. Cooking and freezing are effective methods for the inactivation of parasites in meat whereas refrigeration is considered as an essential part of the Good Hygiene Practice. Additionally, microwave dielectric heating may represent an equally effective tool for parasite inactivation. Therefore, isolated vital mesocercariae were examined with respect to their resilience against heating, refrigeration, freezing, and microwave heating. A. alata mesocercariae stored in Ringer's solution do not survive heating temperatures that exceed 60.0 °C. Similarly, exposure to microwave heating ensured an inactivation of all parasite developmental stages after 90 s of treatment. In contrast, the parasites' tolerance towards cold is far higher as the mesocercariae survived refrigeration temperatures (4.0 ± 2 °C) in Ringer's solution for up to 13 days. An effective inactivation by cold is therefore only guaranteed if the infested game meat is frozen to a core temperature of -13.7 °C for a minimum of 2 h at least. Game meat should be handled with the same or even higher caution than meat of husbandry animals since wild animals may be infected with parasites or other zoonotic agents that are not common in livestock. It is therefore of crucial importance that appropriate temperature time protocols are used for the reliable inactivation of these zoonotic agents.

Alaria alata in Terms of Risks to Consumers’ Health

“…Freezing is recommended for inactivating many parasites, including Trichinella or Toxoplasma [ 69 ]. Gonzales-Fuentes et al (2015) pointed out that freezing game meat to an internal temperature of at most −13.7 °C inactivates mesocercariae [ 70 ]. The survival of the larvae of A. alata at the temperatures in refrigerators (4 to 8 °C) is very high, even during long-term storage; therefore, the potential risk for consumers remains high [ 58 ].…”

Prevalence of Alaria infection in companion animals in north central Oklahoma from 2006 through 2015 and detection in wildlife

“…The discovery of A alata mesocercariae in wild pigs from Europe over the past decade during mandatory testing for Trichinella larvae suggests that wild pig products, particularly those consumed raw or undercooked, could be a potential source of alariosis for humans. 1,6,[14][15][16][17][18][19] Identification of optimal methods for detection of infected carcasses and establishing risk factors for human exposure have led to several studies 17,36,37,[39][40][41] on the effects of tissue digestion solutions, sodium chloride and ethanol concentrations, simulated gastric solutions, curing processes, and temperatures on the viability and tenacity of A alata mesocercariae. In a 2% sodium chloride solution, mesocercariae were viable for up to 21 days but died within 24 hours in a 3% sodium chloride solution.…”

A Review on Alaria alata, Toxoplasma gondii and Sarcocystis spp. in Mammalian Game Meat Consumed in Europe: Epidemiology, Risk Management and Future Directions

“…Heat treatment is reported as the most effective method for the inactivation of A. alata mesocercariae in wild boar meat. Heating at 72 • C for 2 min is recommended by the German Federal Institute for Risk Assessment [9], and, in other studies, DMS did not survive heating temperatures over 60.0 • C nor exposure to microwave heating after 90 s of treatment [69]. In contrast, tolerance towards cold temperatures appears to be higher: mesocercariae survived refrigeration temperatures for 5 days in a French trial [70], up to 13 days in another study [69], and motile mesocercariae were recovered from chilled carcasses even 20 days post mortem [71].…”

“…Heating at 72 • C for 2 min is recommended by the German Federal Institute for Risk Assessment [9], and, in other studies, DMS did not survive heating temperatures over 60.0 • C nor exposure to microwave heating after 90 s of treatment [69]. In contrast, tolerance towards cold temperatures appears to be higher: mesocercariae survived refrigeration temperatures for 5 days in a French trial [70], up to 13 days in another study [69], and motile mesocercariae were recovered from chilled carcasses even 20 days post mortem [71]. An effective inactivation by cold is only guaranteed if the infected game meat is frozen to a core temperature of −13.7 • C for a minimum of 2 h [69].…”

“…In contrast, tolerance towards cold temperatures appears to be higher: mesocercariae survived refrigeration temperatures for 5 days in a French trial [70], up to 13 days in another study [69], and motile mesocercariae were recovered from chilled carcasses even 20 days post mortem [71]. An effective inactivation by cold is only guaranteed if the infected game meat is frozen to a core temperature of −13.7 • C for a minimum of 2 h [69].…”