Just how safe is it to eat meat these days? Have modern processing procedures eliminated a lot of the risk, or are there certain meats that we should still stay away from. Perhaps the ancient religions of Judaism, Muslim, and others were wise to mark certain meats, such as pork, as “unclean” and forbidden. Could trichinosis have something to do with it? Let’s see what we can find out.
What is Trichinosis?
Trichinosis, also known as trichinellosis or trichiniasis, is a type of parasitic roundworm disease that is contracted by humans when we eat certain types of undercooked meat from animals infected with trichinosis. The roundworm that causes trichinosis is a nematode called Trichinella spiralis. Trichinosis gets its name from the Greek word trichina, which is translated “hairlike,” and is also the name for a single worm of the species.
The most common carriers of trichinosis are meat eating wild animals (carnivores) and pigs. Bears, foxes, walruses, rodents, and horses are the most likely sources of contamination to humans. Trichinosis can only be contracted by eating the larvae of Trichinella spiralis in animal flesh. Pigs are often exposed by eating garbage containing uncooked meat. Due to more strict regulation of swine production in recent years in the United States, commercially raised hogs here are less likely to be infected with trichinosis than they used to be. The biggest source of trichinosis exposure in the U.S. is the consumption of improperly prepared bear meat. There are typically an average of about 50 cases of trichinosis reported in the United States annually. However, pigs are still fed raw garbage in many underdeveloped countries, and trichinella roundworms and their corresponding infections in humans are much more common in these parts of the world. The World Health Organization reported recently that up to 50% of the swine in Eastern Europe might be infected. Other common sources of exposure include dogs in Africa and Asia; pork sausage, wild boar, and horsemeat in parts of Europe; and walruses and bears in Northern Canada.
Basically, how the process of human contamination works is this:
- A meat-eating animal such as a bear or a hog consumes animal flesh that contains worms in the larval (second) stage of life. The prey that this animal ate originally had the adult worms living in its intestinal lining. The adult worms mate, the male dies, and the female goes on to bear offspring.
- Trichinella spiralis is unique in the fact that the embryonic or larval (second) stage of their life cycle takes place within the uterus of the female, rather than after birth. Thus, as mama worm gives birth in the intestinal lining of her host, she actually produces babies that are already in the larval stage. This unique design makes it much easier for the species to survive and proliferate. From mating to birth only takes about one week.
- These newly born larvae—typically about 1500 from each female—begin a journey that starts in the blood stream of the host, and eventually ends in the muscles of the skeletal system and heart (striated muscle). Those that cannot find a home in striated muscle usually die off.
- At this point, the larvae will go through a process called encysting. They will grow to about one millimeter in length, coil their bodies, and create a “cocoon” for themselves called a “cyst.” In these cysts, the larvae can hibernate for up to 10 years within the muscle flesh of their host.
- Enter the hungry family that is about to sit down to some nice bear steaks that the hunting party has just taken. “I’ll take mine rare please…” Big mistake. What the diners do not know is that the game they are about to eat may have up to thousands of invisible hitchhikers in the form of trichina cysts. If the meat is undercooked, the cysts will survive and be ingested into the intestinal tract of the person.
- At this point, the digestive juices will do their job on the meat, and the cysts will be broken down, allowing the larvae to find a new home in the intestinal tract of the diner where they will mature and mate.
- The process then begins to repeat itself. The offspring will journey through the circulatory system to the heart and muscle, where they will be encysted in the human host’s striated muscles. The new host is not likely to be eaten, but he or she will contract the illness called trichinosis.
What Are the Symptoms of Trichinosis?
Symptoms of this parasitic illness are greatly dependent on the level of infestation the individual is experiencing. This level of infestation can be measured and classified based on the number of cysts in the contaminated meat the patient has eaten. This number is called the “worm burden.” Those with a low worm burden may have no symptoms, and in fact never even know that they have been infected. Folks with a moderate or high worm burden will experience symptoms that will vary depending on the stage of development of the trichina worms.
- Initial symptoms usually appear one or two days after eating the contaminated meat, when the worms have broken out of their cysts and found a new home in your intestinal lining. These typically include:
- Stomach cramps
- Fatigue and malaise
- Usually within a week after eating the meat, the larvae will begin their journey through the bloodstream and into the muscle tissue. At this point, especially for those with a high worm burden, the symptoms can become more intense and pronounced, including:
- Sore and tender muscles (myositis). The muscles most often affected are those of the face, eyes, jaw, neck, biceps, lower back, and diaphragm (between the abdominal and chest cavities, involved in breathing).
- Fever, sometimes very high
- Swelling, especially in the face and/or around the eyes
- Greater fatigue
- Conjunctivitis (pink eye)
- Super sensitivity to light
- Increased abdominal pain
- Increased diarrhea
- Bleeding into parts of the eyes (whites and retinas), and into the nail beds.
These symptoms may last for months, and will vary as the process of infestation continues. Most patients will experience the worst symptoms about three weeks after ingesting the meat, but recovery from trichinosis is very slow, and some folks take 6 months or more to shake off the fatigue and feel back to normal.
Are There Possible Complications From Trichinosis?
Serious complications are relatively rare. However, in instances of heavy infestation, or if a person has other health problems that may cause his or her immune system to be compromised, the larvae can migrate to and infest vital organs of the body, and produce potentially dangerous systemic infections. A small number (about 1%) of trichinosis cases are fatal due to these complications. They include:
- Myocarditis: Inflammation of the heart muscle. If trichina larvae embed in the heart, it is a very serious situation.
- Encephalitis: Inflammation of the brain tissue. Next to the heart, the brain is the second most serious location for complications of trichinosis.
- Meningitis: Inflammation of the lining of the brain.
- Nephritis: Inflammation of the kidneys.
- Pneuomonitis: Inflammation of the lungs.
- Sinusitis: Inflammation of the sinuses.
How is Trichinosis Diagnosed?
Other than a visual identification of the characteristic symptoms such as facial swelling and muscle inflammation and pain, there are more definitive tests available to help with the diagnosis of trichinosis:
- Blood tests: A general blood test can detect abnormally high levels of a certain type of white blood cell (eosinophils) that is associated with trichinosis. Beyond that, there is a more specific test called the bentonite flocculation (BF) test that can actually detect the presence of larvae in the blood if the trichina cycle is in the right phase.
- A muscle biopsy can also be taken and analyzed in the lab for trichina parasites. This must be done three to four weeks after the ingestion of the suspected meat in order for the timing to be right for trichina to be in the muscle tissue.
What Treatments Are Available for Trichinosis?
There is no medication that can eliminate the larvae that are encysted and embedded into your muscles. The only option is to wait until they die. However, there are several drugs available that can kill the intestinal worms and larvae before they enter the blood stream. These are called anthelminthics (anti-worm) medications, and they are effective if given soon enough after the contaminated meat was eaten (within 24 hours is best). As with any drug, there are side effects you should be aware of and concerned about. Anything that is toxic to trichina worms will also be toxic to people to some degree. Most cases of trichinosis are not serious, and will run their course without intervention. A good parasite cleanse would be recommended if you know you have been exposed. I would save the use of these drugs for special circumstances such as people who have compromised immune systems or other extenuating health issues.
The best course of action is to prevent trichinosis before it ever becomes an issue. Here are some tips:
- One option is to not eat meat, or at least not the kinds that are potential carriers of trichinosis, such as pork and certain species of wild game. There are many resources available these days that will help you to eat a balanced, healthy, meatless diet with lots of variety, if you should choose to go that direction.
- If you do eat meat, make sure that it is thoroughly cooked to an internal temperature of 140 F.
- Freezing pork and some other meats properly can kill trichinosis worms and larvae. They should be frozen for a minimum of 20 days at 5 F or 3 days at 4 F. Keep in mind that if the cuts are more than 6’’ thick, freezing might not be totally effective to kill all the trichinosis parasites.
- Beware that freezing does not kill trichina parasites in bear meat and many other wild game meats. The only way to be sure these meats are safe it to properly cook them.