CDC Report - Two Outbreaks of Trichinosis Linked to Consumption of Walrus Meat

If you ever have the opportunity to eat walrus meat, make sure it is cooked well.  There were two recent outbreaks of trichinosis or trichinellosis (five cases each) in Alaska that were associated with consumption of walrus meat.  The disease is caused by the parasite trichinella and is acquired when the larvae of the worm in ingested when consuming contaminated meat of animals including bear, cougar, wild boar and walruses.  Domestic pigs were once a source, but not really any more since controls were put in place by the industry to improve farming conditions.

Initial infection leads to nausea, diarrhea, vomiting, fatigue, fever, and abdominal discomfort. This is followed within a few weeks by headaches, fevers, chills, cough, swelling of the face and eyes, aching joints and muscle pains, as the larvae get into the blood stream and start to encyst into the muscles.. "If the infection is heavy, patients may experience difficulty coordinating movements, and have heart and breathing problems. In severe cases, death can occur."

Cooking wild meat to an internal temperature of 160ºF will take care of the issue.  Canning wild meat is another alternative to consider.

CDC - MMWR
https://www.cdc.gov/mmwr/volumes/66/wr/mm6626a3.htm?s_cid=mm6626a3_e
Two Outbreaks of Trichinellosis Linked to Consumption of Walrus Meat — Alaska, 2016–2017

Trichinellosis Surveillance in the United States, 2008 - 2012 - Summary of CDC Report

CDC issued a surveillance report on cases of Trichinellosis.  This is a quick summary.

 

Trichinellosis is a parasitic disease caused by Trichinella, a nematode. It had been traditionally associated with undercooked pork, but more recently it is more associated with wild game.  [Prior to improvements in pig husbandry in 1940's and 1950's, it was estimated that over 15% of people in the US had been infected by Trichinella.]

 

From the report:

"Trichinella infection in human hosts can be divided into an intestinal (enteral) phase and a muscular (parenteral) phase, with clinical manifestations ranging from asymptomatic infection to fatal disease, depending on the number of larvae ingested. After ingestion, larvae are released into the intestinal mucosa and subsequently migrate to the blood vessels, from which they spread throughout the body before reaching the skeletal muscles."

 During the initial phase, within the first few days of infection, symptoms can range from asymptomatic to severe gastrointestinal distress.  As the parasite migrates to the muscle and embeds itself, the person can have fever, muscle pain, and swelling.  Death can occur in cases where this is inflammation of the heart, brain, or lung tissue as well as due to respiratory failure from a high level of infection of encysted worms in the diaphragm muscle [it gets so many encysted worms that the muscle can't work...tell me that isn't a miserable way to buy the farm].

 

During the reporting period, 2008-2012, there were 84 confirmed cases.

• 22 cases were linked with pork products, including 10 with commercial pork products, 6 with wild boar, and 1 with home-raised swine, and 5 unspecified.
• 41 cases were linked to bear meat
• 2 cases with deer meat
• 2 with ground meat
• 17 cases unknown
• From 51 cases that were further investigated, 24 reported eating raw or undercooked meat [for the other cases, as we know, people hate to admit being stupid...who wants to admit eating bear tartare, or drinking the fresh blood of their hunted bear prey...yeah, you know that guy].

So the number of cases has continued to decline thanks to commercial pork practices and better cooking practices by the consumer, but vigilance is still needed, especially with wild game.  Consumers of pork and game must follow proper cooking or freezing methods to destroy the parasite.

USDA's Updated Trichinella Fact Sheet

USDA recently updated its webpage on Trichinella, and this provides a nice reference on the topic.  I thought it would be good to post this as well as an op-ed column in the NY Times on Trichinella in free range pigs (2009). In the 1930s, there were hundreds of cases per year that were reported (although it was not a reportable illness in many states).  An estimate made from autopsies indicated that the level in the US population may have been as high as 12% (ref below).  In the past decade, there have only been a handful of cases, mostly related to wild game, specifically bear.  Much of this is due to industry practices and veterinary inspections. While there are some that refuted the NY Times piece based upon the lack of Trichinella cases related to free range pigs, in theory, it seems that if pigs are allowed to free range, there is potentially a higher risk of these pigs encountering this parasite (through the eating on infected rats or the feces of infected animals.)

While the mortality rate is low, symptoms of trichinosis can range from mild to severe.

“Nausea, diarrhea, vomiting, fatigue, fever, and abdominal discomfort are the first symptoms of trichinosis. Headaches, fevers, chills, cough, eye swelling, aching joints and muscle pains, itchy skin, diarrhea, or constipation follow the first symptoms. If the infection is heavy, patients may experience difficulty coordinating movements, and have heart and breathing problems. In severe cases, death can occur.  The acute phase occurs after the mature warm lays eggs in the small intestine and these eggs hatch into larvae which enter the bloodstream and travel to muscle tissue within the body, such as the diaphragm.  There they become encysted.

USDA’s review of Trichinella

A Focus on Trichinella -- Updated Version

http://fsrio.nal.usda.gov/nal_web/fsrio/fsheet.php?id=230

A primer on trichinosis from CDC

http://www.cdc.gov/ncidod/dpd/parasites/trichinosis/factsht_trichinosis.htm

A 1938 survey of trichinosis in the US

http://www.jstor.org/stable/4582479

2009 NY Times Op-Ed on free range pigs and Trichinella

http://www.nytimes.com/2009/04/10/opinion/10mcwilliams.html?_r=1&scp=1&sq=free-range%20trichinosis&st=cse