Little House on the Prairie was first aired on NBC in 1974

If you watched Little House on the Prairie, which first aired on NBC in 1974, you might remember the story of Mary Ingalls. The television show was based on the classic book of the same name, drawn from the real-life experiences of Laura Ingalls Wilder, Mary’s younger sister.

As part of the story, Laura describes how Mary lost her sight as a teenager after contracting scarlet fever. Iowa paediatrician Dr Beth Tarini became intrigued by the story while studying medicine and spent more than 10 years researching letters written by Laura, local newspaper accounts of Mary's illness and epidemiological data on blindness and infectious disease in the late 19th century.

Mary Ingalls

In Wilder’s unpublished memoir, Pioneer Girl, there is no reference to Mary having scarlet fever the year she went blind (1879), although it mentions Mary having scarlet fever when she was much younger (1872). Looking at epidemiological data from the time, Dr Tarini and her team discovered most cases of blindness attributed to scarlet fever were temporary. She also found newspaper accounts of Mary's illness describing "severe headaches" and that one side of her face was partially paralysed. A reference to “some sort of spinal sickness” and a visit to a Chicago specialist was also mentioned in letters Laura wrote to her daughter Rose, before her book By the Shores of Silver Lake was published. The pupils’ register of the Iowa College for the Blind, which Mary attended from 1881 to 1889, corroborates Laura’s mention of spinal sickness, listing Mary’s cause of blindness as “brain fever”, which was the term used at the time for meningoencephalitis.

So, why did Laura pin the cause of her sister's blindness on scarlet fever? It’s likely because Laura and her editors thought scarlet fever would be more relatable to her readers at the time, wrote Dr Tarini in Paediatrics, especially as it appears in other books from the same period, including Little Women and Frankenstein.