First up, this article will be discussing phthiriasis, a disease that may or may not exist, rather than pthiriasis, the pubic crab lice that definitely do. Now that we have that confusion out of the way, on with the horror show.
Imagine this: you notice cysts starting to spring up all over your body. Then one day, whether you can't resist a scratch or you just catch yourself on a door frame, you open up the cyst and swarms of insects come pouring out of your rotting flesh. Your body slowly gets eaten away by these insects, until you die, more insect than human. Accounts of this strange grim disease have endured through history and across cultures. But does it really exist?
Aristotle mentioned phthiriasis in the History of Animals in 350 BCE, describing carnivorous insects that "live on the juices of living flesh" as generated out of the flesh of animals. "When lice are coming there is a kind of small eruption visible, unaccompanied by any discharge of purulent matter; and if you prick an animal in this condition at the spot of eruption, the lice jump out," he wrote.
Other accounts, such as that by Diodorus Siculus centuries later around 50 BCE, describe winged insects emerging from the bodies of North African people who ate locusts, eating away at their flesh before they emerged through holes in the skin.
One thing many accounts tend to have in common, aside from making the reader itchy, is that when they mention afflicted individuals they tend to be those thought morally corrupt. Several accounts attribute the death of the Roman dictator Sulla to phthiriasis, including Plutarch and Pliny the Elder. According to Plutarch, the tyrant's flesh turned entirely to lice. He hired workers to wipe away the pests, but they kept coming and consuming his flesh.
"Were not his victims more fortunate at the time when dying, whom we pity today when Sulla is universally hated?" Pliny wrote. "Come, was not the close of his life more cruel than the calamity of all the victims of his proscriptions, when his body ate itself away and bred its own torments?"
The tales, as Dr Jan Bondeson wrote in a 1998 paper, Phthiriasis: the riddle of the lousy disease, often depict the disease as a punishment from gods against people who have done wrong. In an account by Lactantius (c. 250-325 CE), known to be pious, an emperor that refused to acknowledge the Christian god was said to have been eaten away down to the bone by vermin, while his torso became mummified, and his eyes burst out his sockets.
These tales continued for centuries, right up until the 1730s when they stopped entirely for just over 70 years. Doctors began to question the disease's existence, particularly the claims that flesh could spontaneously generate lice from within. Entomologists had their back, being skeptical of the ability of lice to live and breed beneath the skin, without oxygen to keep them alive.
According to Bondeson, a German skeptic by the name of Dr Husemann reviewed historical accounts of the disease in 1856 and concluded it never existed at all. Nevertheless, it continued to be referenced among doctors well up until around the 1870s, after which there have been no cases at all.
So, does it exist? Well, the answer to that is a definitive... maybe, but not in the way that it was described in ancient times.
According to Bondeson's paper, in 1940, Professor A. C. Oudemans studied a subspecies of Harpyrynchus mites called H. tabescentium that made him inclined to think the disease existed. The mites are capable of burrowing underneath the skin and live in clusters beneath it. When the hazelnut-sized insect-tumor is cut, the insects pour out with minimal other liquids. Due to the size of the clusters, they can go on to kill their host, making Oudemans and others believe that the species could have caused the disease, if it existed.
The only problem with this is that the mites have been documented well in birds, but not a single case of infestation has been found in humans. Couple this with the fact that no good descriptions or illustrations of the disease have been found, and that in ancient times it was largely only described as happening to bad people as a divine punishment, most historians and medics believe that it likely didn't exist at all.
Other explanations include that the ancient accounts were describing scabies or infestations found in open wounds.