TRICHINELLOSIS: RUSSIA (SIBERIA)
22 Nov 2002
Smoked bear meat suspected behind outbreak of trichinellosis in Siberia. A trichinosis epidemic has broken out in Siberia, with 71 people affected in Khakassia and Kemerovo so far, Russian health officials report. Among those diagnosed with the disease are 21 children under 14 years of age. All the patients have been hospitalized, and their condition is evaluated as serious, yet stable. According to the officials, the mass contamination has presumably been triggered by consumption of smoked meat of a bear infested with trichinae. Investigation has now been launched to identify the actual causes of the epidemic.
ProMed: Trichinella spp. are found worldwide in many carnivores and are prevalent in Russia. Undercooked wild boar is a well-known source of infection, but other sources including domestic pigs need to be excluded.
TRICHINELLOSIS: RUSSIA (SIBERIA) – Follow-up Report
1383 cases (2 fatal) were reported during 1995 to 1997. Trichinella pseudospiralis is found in sylvatic animals (raccoon dog, corsac fox, tiger cat, tawny eagle, and rook) in remote regions (Caucasus, Kazakhstan). An outbreak of approximately 30 cases of human infection has been reported in Kamchatka; local domestic pigs and brown rats were found infected at the time. As many as 61 persons may have been infected by bear meat in Zima (Siberia) during an outbreak in 1997, with additional cases in Sayansk, Angarsk, and Irkutsk. In Samara in 1998, 9 persons developed the disease after ingestion of barbecued badger meat.
A. Tyler Zerwekh
24 Nov 2002
It may be helpful to know that freezing meat at minus 15 degrees C effectively kills the parasite [easy to do in Siberia! - Mod. JW]
This interested responder would like to point out that the method of cooking [the infected bear meat was] "smoking." Albeit one of the finer grilling culinations, smoking poses a public health risk because of the low temperatures involved with the process.
MPH Environmental Health & Safety
Biosafety Division University of Texas Health Science Center
Houston, TX, USA
B. Allen B. Clarkson
02 Dec 2002
Regarding the comment in the previous posting in this thread (see reference below), "It may be helpful to know that freezing meat at minus 15 degrees C effectively kills the parasite [easy to do in Siberia! - Mod.JW]":
Trichinella transmitted in very cold climates is not killed by the same low temperature exposure that kills this parasite transmitted in moderate climates. Since posts on ProMED-mail are considered authoritative by many, a correction should be made. The fact that the moderator accepted the comment makes this all the more important.
Allen B Clarkson
Jr PhD Associate Professor Department of Medical and Molecular Parasitology
New York University School of Medicine
New York, NY 10010
C. Dr Edoardo Pozio
Concerning the trichinellosis outbreak in Siberia [associated with] the consumption of bear meat and the comment of Dr JT Zerwekh, it is very important to know that freezing game meat of carnivores (for example, brown bear, polar bear, arctic fox, red fox, wolf, raccoon dog, lynx, walrus) at -15 degrees C does not kill larvae of Trichinella nativa present in these animals. Larvae of this Trichinella species in muscle tissue survive to freezing at -18 degrees C up to 5 years! In arctic and subarctic regions of Europe, Asia, and North America, the only choice to kill larvae of Trichinella present in muscles of carnivorous mammals is by heating at +60 degrees C or at higher temperatures with a time related to the thickness of the meat.
Furthermore, it is important to keep in mind that muscle larvae of Trichinella britovi (a species present in carnivore mammals and sometimes in wild boars and domestic pigs of temperate regions of Europe and Asia) also survive to freezing for a long period of time.
The following references can be useful to study in depth this subject: 1. Gamble HR, et al. Vet Parasitol 2000; 93: 393-408. 2. Dick TA, Pozio E. Trichinella spp. and trichinellosis. In: WM Samuel, MJ Pybus, Kocan AA (editors). Parasitic diseases of wild mammals, 2nd edition. Ames: Iowa State University Press, 2001: 380-96. 3. Pozio E. Vet Parasitol 2000: 93: 241-62. 4. Pozio E. Vet Parasitol 2001; 98: 133-48.
Dr Edoardo Pozio President of the International Commission on Trichinellosis Laboratory of Parasitology Istituto Superiore di Sanita Rome, Italy Tel.+39 06 4990 2304 Fax +39 06 4938 7065 firstname.lastname@example.org
ProMed: We thank Dr Pozio for his authoritative statement. The paper by CM Kapel and colleagues (J Parasitol 1999; 85(1): 144-7) referred to in a previous posting describes survival of Trichinella nativa for at least 4 months at -18 C in meat from a carnivore host, and survival for shorter periods of T. nativa at -30 C is well known. As only Trichinella nativa and not Trichinella spiralis has been described from Siberia, freezing the meat at -15 C or other temperatures in normal household freezers will not inactivate trichinella in Siberia. - Mod.EP