Wednesday, February 7, 2018

Typhoid, Pellagra

I have a morbid fascination with diseases that are (mostly) no longer threats to humans, maybe because it's comforting to realize we have made at least some progress on our well-being. A couple of recent articles covered two examples.

A Washington Post story, Scientists find possible cause for mystery epidemic that wiped out Mexico 500 years ago, describes evidence of Salmonella enterica, which causes typhoid fever, in Mexico not long after the European invasion. While I generally know that huge percentages of North America's indigenous people were killed by European diseases, I've always heard more about that within the current boundaries of the U.S. What I learned from this story is that 80 percent of people in what we now call Mexico were killed in just three years (1545–1548), and that half of the remaining population were killed 30 years later (1576–1578). The total number of people killed is estimated between 5 and 15 million in the first wave alone.

So that's 90 percent of the country. Imagine a disease that delivered that much death in such a concentrated area and short period today. The 1918 influenza epidemic killed about 20 million worldwide, out of a much larger population base. The black death in northern Europe is thought to have killed something like half the population, and we're still talking about it.

Why aren't the deaths of these Mexican indigenous people something we all know about? The answer is obvious, and sickening: because it's assumed to be the natural order of things, God showing who his chosen people were, part of Manifest Destiny. It's always good to revisit Jared Diamond's 1992 article, The arrow of disease, which examines why Europeans brought disease with them but North Americans didn't send diseases to Europe. (That article led him to write the book Guns, Germs and Steel.)

It wasn't about destiny or divine intervention: it was the result of geography and human actions over time.

The other article I recently saw is from the most recent issue of Discover magazine (and is not posted online yet). It tells of a disease that sickened 3 million people across the American South between 1900 and 1940, killing 100,000. After weakness and a swollen tongue, the disease would progress to dermatitis, diarrhea, dementia, and death. It was named pellagra, the word for rough or dry skin in Italian, another country where it had been reported in previous centuries. It was not common in the U.S., though, until after 1900.

There were two theories on the disease's cause: an infectious agent (like so many other diseases that had recently been tackled through germ theory) or a dietary reason, specifically corn.

A New York doctor named Joseph Goldberger was put in charge of fighting pellagra for the U.S. Public Health Service in 1914. He realized right away that health care workers were not catching the disease from the afflicted, and so quickly ruled out infection as a cause. Corn was a good candidate, though, because
The grain had only recently become a popular foodstuff. As "King Cotton" and textile mills came to dominate the South's post-Civil War economy, many families converted all their farmland to cotton. They stopped planting vegetables and keeping livestock. As a result, many poor Southerners now ate almost exclusively what was called the Three Ms: low-quality meat, molasses, and meal (industrially refined cornmeal)—the same cheap gruel often served at orphanages and asylums.
Goldberger fed the children at a Mississippi orphanage "a diet such as that enjoyed by well-to-do people" and found the pellagra rate fell rapidly. He then fed a Three M diet to a dozen healthy prisoners in a state penitentiary (!) and found that over six months, half of them developed the disease.

My favorite part of the article (eww):
To bolster his case against the germ theorists, in 1916 Goldberger conducted what he called filth parties. He tried to infect himself, his wife, and other volunteers with pellagra by injecting and ingesting the skin scales, urine, feces, blood and saliva from pellagra patients. No one got pellagra.
Since there was no support for food aid to improve the diets of the poor (of course not!), Goldberger eventually settled on supplementation through brewer's yeast, which was cheap and available.

Goldberger died in 1929 before knowing exactly what was lacking in the diets of pellagrans. In 1937 Red Cross researchers identified niacin, or B3, and pellagra is now one of the well-known but uncommon dietary deficiency diseases, like scurvy or rickets.

But I didn't know how it was figured out or what lengths people went to understand it.


A couple of earlier posts on public health and epidemiology:

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