This is a problem found worldwide (though obviously not in countries where pork is not eaten), though it is becoming much less common in the US, as regulations make it very hard for any commercial pork to get the infection in the US.
The adult Trichinella spiralis live in the intestinal mucosa of pigs. The larva hatch within the intestine, then migrate to columnar epithelial cells (as in those commonly found in skeletal muscles). Here they wait patiently for the pig to get eaten, where they can be released from the muscle tissue. They can become encapsulated in muscle tissue and remain dormant there for a very long time - sometimes several months!
Prey and carrion are reservoir hosts. In the past, the most common way to get this infestation was through uncooked pork, but now it is more commonly associated with wild pigs or bears, or even polar bears.
When humans eat the infected pork muscle tissue (yum), the larva travel to the gut, where they become adults. These then begin producing tons of little baby Trichinella spiralis, which migrate through the intestinal wall in search of muscle tissue. These larva are quite small - they actually move THROUGH the cells, rather than between them like most larva that travel through body systems. Unfortunately, this means that the cells they do pass through die. This can be quite a problem if they are moving through places like the brain or the lungs in search of their preferred muscle tissue. Peri-orbital edema is also characteristic of this infection.
In cases where the worm load is small, problems rarely present. However, in cases of high worm burden, the cellular death and subsequent eosiniphilic (allergic) reactions can be quite severe. In the brain, this can cause meningitis, or brain damage due to damaged tissue. Once the larva reaches its preferred skeletal muscle cell, it goes through an interesting process to make what is called a nurse cell, which I'll detail in the next post. These cells can live in the muscle for years. However, once it gets to this stage, there is really no point in treating the infection, as they aren't causing any problems. They do sometimes show up on unrelated muscle biopsies though, causing a big surprise for whoever's analyzing the tissue!
Photo Credit: trichinella.org
Treatment is given to halt the production of larva in the gut, to stop the tissue death caused by migrating larva. Corticosteroids can also be given, to lessen the eosiniphilic reaction caused by the migration of the larva.
This problem presents as gastro-intestinal pain., and may mimic food poisoning. There can be some muscular pain, caused by the migrating larva and the dying cells. It can also present as myositis, facial edema, fever, and/or peripheral eosiniphilia. Myocarditis can occur in severe infections. It can cause death.
Diagnosis is most often serological, meaning it is done with blood serum in the lab. Antibodies can be detected approximately 12 days after infection. Larva can also be found in biopsied muscle, but by that point it is often beyond the point of treatment. On the plus side, if the person has survived to that point, they're not likely to die from it!
Photo Credit: trichinella.org
This is why my grandmother always overcooked meat!
ReplyDeleteDescribing baby larvae in the stomach made them sound almost cute...
I like to anthropomorphize my worms :) Cause they're adorable and just want to love you! By burrowing through your bodily organs!
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