The New York Times has launched what I can only assume is an inadvertent pro-vegetarian campaign. Last week an article featured pictures of cattle, shoulder to shoulder in a pen, up to their cattle knees in "mud", accompanying an article about beef consumption in the US. You could almost smell the repugnant odor, especially if you've ever driven by one of these vast cattle pens. Even at 50mph/80kph, the smell is mind-alteringly revolting, capable of singeing the hair off the inside of your nostrils.
Today the paper provides lurid details from the investigation of a neurological illness that affects workers of hog manufacturing plants, especially one in Austin, Minnesota. (Denise Grady, "A Medical Mystery Unfolds in Minnesota")
The Center for Disease Control (CDC) in Atlanta reports that at least 12 people at the Austin, Minnesota plant have been affected with symptoms ranging from weakness on both sides of the body that gets worse over time, mild pain, numbness, tingling and heaviness in their legs and feet, to acute paralysis. While the illness generally resolves and some workers were affected for only 8 days, others were affected up to 213 days.
Investigators on the case recognize common symptoms between workers, and although they don't yet know the exact cause, they're making progress. The Washington Post described how the translator who accompanied the patients recognized common symptoms between some of her clients. Once several victims were identified, investigators learned that the majority of the affected workers had harvested brains from the swine.This is a stomach churning job that the journalists seem lucky enough to not have actually witnessed, since reporters are not allowed in the plant. We try not to revel in the details that follow, but queasy readers, be forewarned.
When the state epidemiologist toured the plant with the owner, they observed workers at the "head table", whose job was to remove the brain and skeletal muscle from the swine. Brains were removed with an air hose in a process that called "blowing brains". After studying workers from various stations at the plant, the CDC found that 7 of the 10 head table workers in their study were affected by the disease. These workers didn't wear long sleeves or face shields. Possibly as a result they inhaled aerosolized brains or head muscle from the spray that caused their symptoms. Once the plant owners realized that the illness was related to brain blowing, say all the news stories, they stopped the process.
The interesting part of the story to some people may be the gross-out factor, but to doctors and scientists it's the question of what causes the disease. It wasn't clear from the first patients that the symptoms were work related, since many of the symptoms are common to other diseases. Tests for various parasites, viruses and bacteria came back negative. More testing revealed that the patients had what doctor's think is a new disease, progressive inflammatory neuropathy (PIN) 1. This label distinguished the condition from doctors' original assessment earlier last year of chronic inflammatory demyelinating polyneuropathy (CIDP), a rare, but known disease.
Doctors ran tests for inflammation, and "electrodiagnostic tests" of the nervous system, such as measurements of nerve conductivity. One of the things that showed up is evidence of axonal and peripheral nerve cell demyelination. Myelin covers the axon part of the nerve cell and allows small electric impulses, the action potential, to be conducted very quickly through the nerve cell. Healthy myelinated nerves transmit signals to and from the spine to the periphery of the body.2
Doctors hypothesize that the patients' immune systems became unable to distinguish foreign proteins of the pigs that they inadvertently ingested, from their own body's proteins. In this autoimmune ("auto"- self) response, the immune system attacks the body's own proteins, perhaps in the myelin. When the myelin is damaged, as with different autoimmune disorders such as Multiple Sclerosis (which also effects the central nervous system 3), or in Guillain-Barre Syndrome, the nerve signals don't transmit properly, causing numbness or tingling, numbness, foot droop, or more severe symptoms.
One avenue of research scientists are following according to the NYT is comparing the pig to human myelin DNA sequence to understand the extent of the similarities. Researchers hope to gain knowledge about what exactly happens in the immune system to cause the neuropathy. The goal is to identify agents that trigger the immune response.
The workers respond to treatment differently, as would be expected from the disparate disease pathology. Some workers responded to steroid treatment. Other workers responded to intravenous immunoglobulin (IVIG) treatment. IVIG treatment uses donated IgG immunoglobin products from the plasma of pooled blood from many donors, either to boost the antibodies in an immune compromised individual, or as in these cases, to suppress the autoimmune response and control inflammation. Some have recovered quickly, while others have a longer road ahead.
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1When news outlets say, "CDC is calling the condition progressive inflammatory neuropathy". The term is not too complicated to understand. Doctors observe that the symptoms get worse over time, progress, "progressive". Tests show evidence of "inflammation"2. Disease of the nerves is "neuropathy" -- in this case of the peripheral nerves. Thus, "progressive Inflammatory Neuropathy".
2The nervous system is amazing, an you can see this every time you move by understanding a little bit about the neuromuscular system. Complex and intricate physiology allows you score a goal or dip your toe in the water and recognize it as cool, or warm, as the nervous system communicates that back to the brain. To briefly summarize the process, which you can find in more thorough detail elsewhere, when you kick the ball, the thought originates in the CNS -- through the motor cortex of your brain, then as a nerve impulse transmitted down your spinal cord. At that point the somatic nervous system transmits the signal from the spine to the muscles of your foot and leg. At the muscle, a biochemical reaction at the site where the nerve cell meets the muscle cell triggers muscle contraction. Think of this happening for all the muscles, in the exact right order, when athletes pass a football, or perform an uneven parallel bar routine, or swim.
3 In the body there is the peripheral nervous system (PNS), and the central nervous system (CNS). The CNS is the brain and spinal cord, and the peripheral nervous system consists of the somatic and autonomic nervous systems. The somatic nervous system innervates skeletal muscle, skin, and sense organs.
----------------------------------------------The Jungle is Upton Sinclair's book about meatpacking conditions in the early 20th century.
Acronym Required wrote other posts about livestock related diseases that were infectious, which PIN is not. We wrote about BSE (mad-cow disease), caused by an infectious agent called a prion, in "Cow Rendering - Ingenuity Gone Mad", and "The Companions of Mad Cows". We've also covered the bacterial infection of Streptoccocus suis in Chinese pigs, and the Coxsackie virus in Britain's Foot-and-Mouth Disease. We wrote several posts on the H5N1 virus known as avian flu.
