written by Tara Haelle

This news is about a week old now, but I’m still catching up and didn’t want to skip it. First, I have a confession to make. I never actually read a single one of the Little House on the Prairie books. Somehow, despite being an avid little reader, I never picked them up (though I did devour the entire Nancy Drew library). But I did grow up watching the show, so I’m very familiar with Laura, Mary and the rest of the characters I fondly remember. In fact, bizarrely enough, it was my confusion over a “Little House on the Prairie” episode – in which a character is raped by a mime in the woods – that led to “the sex talk” from my mom. I asked my dad what had happened, and he told me, “Ask your mother.” Though that strange episode (clip here) obviously sticks in my mind, I still recall snippets of other ones, with Laura from her youth up through her years as a schoolteacher, and the family’s Christmases. And I remember Laura’s sister Mary, who tragically went blind when she was 14 in 1879 from scarlet fever. Or so we were told.

In fact, though, it probably wasn’t scarlet fever after all, even though that disease was rampant, between 1840 and 1883, which includes the time of the Ingalls girls’ childhood. The more likely culprit of Mary’s blindness was determined by three doctors and a researcher from the University of Michigan and the University of Utah who did a bit of looking into the tale. They published their findings in Pediatrics last week, based on their research of local newspapers, school enrollment information, Laura’s other writings and what we know of disease from that era.

Scarlet fever was considered one of the top four causes of blindness until at least 1910 even though doctors don’t understand how the fever might cause blindness. It also killed anywhere from 15 to 30 percent of those who fell ill with it. But there were three other top causes of blindness then: measles, meningitis and “other diseases of the head.” And the evidence from primary sources points to one of these instead.

Before writing the Little House on the Prairie books, Laura wrote a memoir in 1930 called “Pioneer Girl,” in which she mentions scarlet fever afflicting her family in the winter of 1872. She later writes that Mary wasn’t well throughout the winter of 1878-79, and then she fell very ill in April with delirium, fever and a “pain in her head.” Laura never mentions scarlet fever here, but she describes seeing Mary with “one side of her face drawn out of shape,” which her mother attributes to a stroke. It is then that Mary’s vision starts going downhill. Her blindness baffled the local doctor, so he asked another physician, who said the nerves of her eyes “were dying” from a sickness with a “long name” that “was the result of the measles,” Laura wrote. Laura also wrote about Mary’s illness again decades later in a 1937 letter to her daughter, when she mentions spinal meningitis, then crosses it out and calls Mary’s illness “some sort of spinal illness.”

“Spinal illness” shows up again in Mary’s school records from the Iowa College for the Blind, where she went from 1881 to 1889. The records also note “brain fever” as the cause of Mary’s blindness. Brain fever was also a common term at the time for meningoencephalitis, an inflammation of both the central nervous system and the brain. Ruling out a couple of other possibilities based on primary source accounts, meningoencephalitis is what the Pediatrics research concluded Mary probably had.

“Meningoencephalitis is the most likely cause of Mary’s illness and subsequent blindness,” the authors wrote, noting that it’s known to cause inflammation of the optic nerve in a way that could cause gradual blindness. “It explains not only her fever and headache, but also Mary’s ‘stroke’ from direct infection or post-infectious inflammation of the facial nerve that left one side of her face paralyzed.”

There are two types of meningoencephalitis: bacterial and viral. The researchers said it probably wasn’t bacterial because Mary was a smart, straight-A student and the bacterial form can cause brain damage. But a number of different viruses can cause the viral form of the inflammatory disease. It could have been a mosquito-carried virus, such as dengue fever or yellow fever, which are called arboviruses. Or, it could have been one of the respiratory-related viruses called enteroviruses, the best known of which is polio. Or, it could have been Epstein-Barr, or even herpes. What the viral meningoencephalitis probably wasn’t caused by, however, was the measles, which Mary had had two years earlier. Though there is not enough evidence to determine which of these viruses led to the meningoencephalitis that probably caused Mary’s blindness, it appears pretty clear that scarlet fever was not involved at all.

So why did Laura change the cause of Mary’s blindness to scarlet fever in her series? The researchers speculate that it may have been an attempt to make it easier for kids to understand, or her editors may have wanted to use a more familiar sounding disease, especially since scarlet fever was, historically, a pretty awful and a very common disease during that time. “Mary’s story illustrates how tales of disease are woven into our culture, reinforced by recollections of a 19th century scourge on children,” they wrote.

So what does that mean for us today? Well, as a mom, I’m grateful scarlet fever isn’t around anymore. The rates began dropping rapidly in the early 1900s for unknown reasons, before antibiotics were ever used for it. I’m also glad most of the serious mosquito illnesses like dengue fever are no longer endemic to the U.S. (at least until recently) due to eradication measures. But I’m especially glad that polio, and even measles – though it wasn’t the likely culprit here – are no longer common in this country. Polio is nearly gone, yellow fever only exists in a few parts of the world and measles is now very rare – all due to vaccines. It’s easy to forget how devastating the “usual childhood diseases” of the 19th and early 20th centuries were to families. Sanitation improvements have helped tremendously. So have antibiotics and other medical advances. And so have vaccines.