Trichinosis (also known as trichinellosis or trichiniasis) is a parasitic disease caused by roundworms.
Infection was once a very common issue and though outbreaks still occur among wild animals, trichinosis is now rare in factory-farm raised meat throughout the US. Successful trichinae control programs implemented by the U.S. pork industry have nearly eliminated the disease in domestic swine raised in confinement, but hogs raised outdoors in close contact with rodents and other wildlife have an increased chance of acquiring a trichinella infection.
Note: Chickens are innately resistant to trichinella spirals, according to a study.
Trichinosis is a concern for raw fed dogs because it can be contracted by eating infected raw meat. Bears and wild hogs are the most common carriers. Untested domestic pigs and hogs raised by small farmers and homesteaders are also a potential risk to raw fed dogs.
Note: Cooking infected pork kills the parasite, making the meat safe for human consumption.
Watch: Steve Rinella Talks About Contracting Trichinosis
Trichinella Facts
• T. spiralis: Mostly found in swine, but also found in many wild, warm-blooded carnivores and omnivores.
• T. britovi: This is the second most common species to infect humans by way of wild boar and domesticated pigs. Found in Europe, Asia and northern and western Africa.
• T. native: Has a high resistance to freezing, is found in the Arctic and subarctic regions in polar bears, Arctic foxes, walruses and other wild game.
• T. pseudospiralis: Infects birds and mammals. Has infected humans and is a nonencapsulated species.
• T. papuae: Infects mammals and reptiles (crocodiles, humans, and pigs). Found in Papua New Guinea and Thailand. Also nonencapsulated.
• T. nelson: Found in eastern Africa.
• T. murrelli: infects humans, especially from black bear meat and infects wild carnivores in North America.
• T. zimbabwensis: Can infect mammals and possibly humans. This nonencapsulated species was found in reptiles of Africa.
How does the infection spread?
Carnivores and omnivores become infected when they eat infected raw meat. For example, wild hogs (and domestic) will eat anything from mice and rats, to bear carcasses and snakes. All of these infected animals will infect a hog.
Raw fed dogs can then become infected when they eat raw infected meat. This is why even feeding untested hog meat is unsafe.
Note: Because trichinella testing is required on pork inspected by the USDA, there is low risk in feeding commercially raised pork, though some choose not to take the risk at all.
What are the symptoms of infection?
Trichinosis can have misleading symptoms. Depending upon the number of larvae ingested, an infection can range from mild to severe. Mild infections usually involve upset stomach, diarrhea and vomiting. With more severe infections there may be muscular pain, fever, headache, exhaustion, sore eyes and throat, hemorrhages under the skin, difficulty breathing and in the most severe cases the infection can result in death.
There are two main phases of infection: enteral (affecting the intestines) and parenteral (outside the intestines).
In the stomach, the larvae are exposed to stomach acid which releases them from their cysts. They then start invading the wall of the small intestine, where they develop into adult worms.
During the second phase, the larva infects muscle tissue. Once the larvae have established in muscle cells (usually by 3 to 4 weeks after infection) treatment may not completely get rid of the infection or symptoms.
What about freezing wild/untested hog meat?
Freezing is only usually effective for T. spiralis, since other species (such as T. native) are freeze resistant or can survive long-term freezing.
Freezing experiments performed by the USDA on the survival of T. spiralis in pork.
• Predicted times required to kill trichinae were 8 minutes at -20° C (-4° F), 64 minutes at -15° C (5° F), and 4 days at -10° C (14° F).
• Trichinae were killed instantaneously at -23.3° C (-10° F).
• The U.S. Department of Agriculture’s Code of Federal Regulations, requires that pork intended for use in processed products be frozen at -17.8° C (0° F) for 106 hours, at -20.6° C (-5° F) for 82 hours, at -23.3° C (-10° F) for 63 hours, at -26.1° C
• (-15° F) for 48 hours, at -28.9° C (-20° F) for 35 hours, at -31.7° C (-25° F) for 22 hours, at
• -34.5° C (-30° F) for 8 hours, and at -37.2° C (-35° F) for 0.5 hours. These extended times take into account the amount of time required for temperature to equalize within the meat along with a margin of safety.
Concerns:
There are a few issues for raw feeders to consider here.
Yes, freezing has been shown to effectively kill certain strains of the parasite, but as mentioned above, not all strains can be killed by freezing.
Secondly, the average freezer doesn’t reach some of these extreme temperatures or doesn’t reach them quickly enough. There’s a possibility that freezing in a home freezer may not be effective on T. spiralis 100% of the time.
Lastly, testing samples can be much smaller than the average cut of meat. So that begs the question “How small do the cuts have to be for freezing to be effective?”
One study found that freezing cuts of pork less than 6 inches thick for 20 days at 5 °F (−15 °C) or three days at −4 °F (−20 °C) kills T. spiralis larval. However, this has not been found to kill other trichinosis larval worm species and T. spiralis isn’t the only strain found in the United States.
Conclusion:
It’s a big risk to feed untested raw pork to your raw fed dog. The safest and healthiest thing you can do for your dog(s) is refraining from feeding meat from wild carnivores and omnivores and untested domestic meat. The last thing you want is for your dog(s) to become infected and suffer, when a trichinella infection was preventable.
Sources:
http://cmr.asm.org/content/22/1/127
https://www.aphis.usda.gov/vs/trichinae/docs/fact_sheet.htm
http://www.usda.com/
thanks for the info it was quite helpful and well organized. Thanks for not being to wordy and verbose. Brevity is bliss for blogs. I am a dog owner living on Maui and hunt wild pigs and deer. I was not sure of the Trich issue but I think it is good not to risk it. Our dog Malu does try well on the raw food diet and it does get pretty expensive here to get organic clean sources of chicken and beef. Thanks again
Kevin