Random Nature #147

Losing Control:  Quality Pork Processors, Inc. (QPP) has a plant in Austin MN which employs over 1,200 people in the slaughter of 17,000 hogs per day for Hormel.  Over the last year, it's become apparent that there is a cluster of a rare disease at the plant...chronic inflammatory demyelinating polyneuropathy (CIDP). 

The pathologic hallmark of the disease is loss of the myelin sheath (the fatty covering that wraps around and protects nerve fibers) of the peripheral nerves.

Chronic inflammatory demyelinating polyneuropathy is disease believed to be due to immune cells, cells which normally protect the body, but are now attacking the nerves in the body. As a result, the affected nerves fail to respond, or respond only weakly, to stimuli causing numbing, tingling, pain, progressive muscle weakness, loss of deep tendon reflexes (areflexia), fatigue, and abnormal sensations. The likelihood of progression of the disease is high.

CIDP, which typically strikes 0.8-1.9 people per 100,000, is not infectious.  Eleven workers at the plant have suffered similar symptoms, but it hasn't just been CIDP. 

Doug Schultz, a spokesman for the Health Department, said Wednesday that five people have been diagnosed with chronic inflammatory demyelinating polyneuropathy (CIDP); two have Guillain-Barre syndrome (GBS); and the rest either haven't been diagnosed or have been diagnosed with something else.

Both GBS and CIDP cause the body's immune system to attack itself, says the Web site for the National Institute of Neurological Disorders and Stroke.

The two conditions are related and both generally happen after some type of trigger.

Guillain-Barre syndrome is acute inflammatory demyelinating polyneuropathy...more on it in a moment. 

So, what triggered these diseases and is anybody else at risk?  Well, since the problem hasn't struck the state's other pork processing plants, one would figure it must be something specific to the QPP plant.

MDH said it is investigating a number of possible exposures in the plant, including toxins, infections, tissue from pigs and others. The 11 employees who became ill worked in an area where either swine heads or organs are processed. MDH said no illnesses have been associated with the cold side of the plant where the pork is processed. None of the cases had apparent associations outside of the workplace.

Thus, health officials say no one is at risk from the pork products.  How have things improved for the workers?   

Brains:  Few slaughterhouses process pig brains.  Until recently, the QPP plant did (for export), and it had an unusual means of harvesting them.

In a rapid-fire process that is noisy, smelly and bloody, severed pigs' heads are cut up at the head table at a rate of more than 1,100 an hour. Workers slice off the cheek and snout meat, then insert a nozzle in the head and blast air inside until the light pink mush that is the brain tissue squirts out from the base of the skull.

Kruse, whose job was to remove meat from the back of the animals' heads, said she doesn't recall any spray or mist from the de-braining. The head-table workers were protected by safety glasses, helmets, gloves and belly guards, but none wore anything over their mouths or noses, she said.

Kruse is a QPP worker who may never recover from her ongoing bout with CIDP.

The working theory from two Mayo Clinic neurologists treating the workers: Exposure to pig brain tissue scattered by the compressed air triggered the illnesses.

...

Compressed air could turn some brain matter into a mist that could be inhaled by workers, said Mike Doyle, a microbiologist who heads the University of Georgia's Center for Food Safety. Or the workers may have come into contact with something dangerous and then touched their noses or mouths, he said.

Scientists have yet to figure out if there is something in the brain matter that could be causing the symptoms.

Yet, production at the plant continues. 

"We've stopped harvesting brain product with compressed air," Wadding said in an interview, adding the company also has added face shields on helmets and covered workers' exposed arms in the part of the plant that processes swine heads and organs. Only workers in that part of the plant have developed and been treated for symptoms.

"These are all just precautionary measures. We have no idea if we are the cause or what we are protecting them from. The Health Department recommended these steps, so we implemented them and will continue to do so," said Wadding.

Because the state came up with precautions that the plant is following, is QPP thus protected from being sued should more of its workers fall prey to the disease?

Chronic Versus Acute:  Guillain-Barre syndrome, while not common, occurs more frequently than CIDP. 

Since the eradication of polio in most parts of the world, Guillain-Barre syndrome (GBS) has become the most common cause of acute flaccid paralysis. GBS is an autoimmune disorder of the peripheral nervous system characterized by weakness, usually symmetrical, evolving over a period of several days or more. Since laboratories began to isolate Campylobacter species from stool specimens some 20 years ago, there have been many reports of GBS following Campylobacter infection. Only during the past few years has strong evidence supporting this association developed.

GBS first came to prominence related to the swine flu vaccine in the mid-70s...though it's still debated whether the vaccine actually triggered GBS. 

Campylobacteriosis is a common type of diarrhea (sometimes bloody) which is often accompanied by cramps and sometimes fever.  It's caused by the spiral- or comma-shaped bacteria noted below.

Species within the genus, Campylobacter, have emerged over the last three decades as significant clinical pathogens, particularly of human public health concern, where the majority of acute bacterial enteritis in the Western world is due to these organisms. Of particular concern are the species, C. jejuni and C. coli, which are responsible for most of these gastrointestinal-related infections.

Because there are a number of types of diarrhea, it takes a stool sample to positively identify campylobacteriosis.  Thus, no doubt the illness is underdiagnosed.  How do people become infected by these bacteria?

- Campylobacters are widely distributed and occur in most warm-blooded domestic, production and wild animals. They are prevalent in food animals such as poultry, cattle, pigs, sheep, ostriches and shellfish; and in pets, including cats and dogs.

- The main route of transmission is generally believed to be foodborne, via undercooked meats and meat products, as well as raw or contaminated milk. The ingestion of contaminated water or ice is also a recognized source of infection.

- Campylobacteriosis is considered to be a zoonosis, a disease transmitted to humans from animals or animal products. In animals, campylobacters seldom cause disease.

It's yet another illness we get via the fecal-oral route, so remember good hygiene.  Cooking kills the bacteria.  Fortunately they don't tolerate drying, and most are killed when frozen.  But if they sicken us... 

Most people who get campylobacteriosis recover completely within 2 to 5 days, although sometimes recovery can take up to 10 days. Rarely, some long-term consequences can result from a Campylobacter infection. Some people may have arthritis following campylobacteriosis; others may develop a rare disease that affects the nerves of the body beginning several weeks after the diarrheal illness. This disease, called Guillain-Barre syndrome, occurs when a person's immune system is "triggered" to attack the body's own nerves, and can lead to paralysis that lasts several weeks and usually requires intensive care. It is estimated that approximately one in every 1000 reported campylobacteriosis cases leads to Guillain-Barre syndrome. As many as 40% of Guillain-Barre syndrome cases in this country may be triggered by campylobacteriosis.

The culprit in most of those GBS cases is C. jejuni.  Testing for antibodies from the immune response can help determine if the symptoms are from GBS or a variant known as Miller/Fisher syndrome.  CIDP is less understood. 

At the Farm and Elsewhere:  It might be easier to list the places where Campylobacter bacteria aren't found.

Poultry appear to be the main reservoir of Campylobacter jejuni. In the UK, up to 100 percent of chickens, turkeys and waterfowls have been shown to harbour this organism. In one study in New Zealand, Hudson isolated Campylobacter from 56.6 percent of chickens. Other studies have suggested that wild animals such as sparrows, rodents and flies carry these organisms in their intestine. Campylobacters may be spread from the wild animal reservoirs to the environment and transmitted to other animals and humans.

In New Zealand, Savill isolated Campylobacter jejuni from shallow groundwater (75 percent), river water (60 percent), drinking water (37.5 percent) and roof water (29.2 percent). These results suggest that water also could act as a significant reservoir for human campylobacteriosis.

Few studies have been carried out to isolate C. jejuni from flies, both experimentally as well as in the natural setting. From a sample of 32 houseflies exposed to a liquid suspension of C. jejuni, the organism was recovered from the feet and ventral surface of the body of 20 percent of the flies and from the viscera of 70 percent. Rosef and Kapperud isolated C. jejuni from flies with a carrier rate of 50.7 percent from a chicken farm and 43.2 percent from a pig farm...

And in New Zealand, there was a Campylobacter isolation rate of 51.7 percent in cats.  I could go on, but you get the point. And of course, Campylobacter didn't necessarily trigger anything at the QPP plant. 

Triggers:  It's not just Campylobacter that fools the body into an immune response which causes nerve disorders.

Two-thirds of GBS cases are associated with prior acute infection of several bacterial species and viruses. Campylobacter jejuni, cytomegalovirus, Epstein-Barr virus, Mycoplasma pneumoniae, Haemophilus influenzae, and Varicella-zoster virus have been found in patient serum after the onset of GBS. The most commonly proposed mechanism for the development of autoimmune disease is molecular mimicry. Molecular mimicry refers to the situation where the pathogen and host share nearly identical antigens, which induces an antibody and T cell immune response that is cross reactive.

Cytomegalovirus, also known as human herpesvirus type 5, is something most people catch (and retain for life) and don't know they've had (previous blog here).  In a few, it causes symptoms resembling infectious mononucleosis.  Epstein-Barr virus, also known as human herpesvirus type 4, causes genuine infectious mono. Varicella-zoster virus, also known as human herpesvirus type 3, causes chicken pox and shingles.

Mycoplasma pneumoniae, as one might guess from the name, is one of several bacteria that causes pneumonia.  Haemophilus influenzae was once mistakenly thought to cause the common flu.  The several strains of this species cause things like lower respiratory tract infections, conjunctivitis, epiglotittis (a dangerous windpipe infection), and acute bacterial meningitis.

Meanwhile with CIDP, there are a few instances of it being associated with hepatitis C and a few with multiple sclerosis.  I hope that health authorities can determine what's behind the QPP cases.