Catastrophic Caterpillar Cilium
The Caterpillar, or the Blue Caterpillar, or Absolem (if you believe he has a name) is a fictional character from the novel, Alice’s Adventures in Wonderland, by Lewis Carroll. Alice doesn’t immediately like him when they first meet, because he talks in riddles and asks challenging questions. However, the Caterpillar does teach Alice how to grow and shrink by eating pieces of the mushroom upon which he sits. Absolem appears five times in the Disney movie based on the novel, first outside Wonderland on the shoulder of Hamish Ascot, who is proposing to Alice. He is next seen in the world below when consulted by the White Rabbit and friends regarding Alice’s true identity; he appears this time in a thick cloud of hookah smoke, which he blows at Alice. The Caterpillar is seen again when Alice arrives at the White Queen’s castle, and once more to remind Alice of her prior visit to Wonderland. It is hard to recognize him the last time he appears because he has left Wonderland, transformed into a butterfly and perches on Alice’s shoulder as she sets off for China.
However, not all caterpillars provide wisdom for a journey through a fantasy land. In April 2018, London was invaded by toxic oak processionary moth (OPM) caterpillars that apparently hitchhiked into the United Kingdom on Dutch lumber used for construction projects. This army of long-haired larvae is causing a rash of violent illnesses among people and animals that include contact dermatitis (ICD-10-CM code L24.89, Irritant contact dermatitis due to other agents), asthma attacks (J45.901, Unspecified asthma with exacerbation), sore throat (J02.9, Acute pharyngitis, unspecified), eye pain (H57.13, Ocular pain, bilateral), vomiting (R11.10, Vomiting, unspecified) and fevers (R50.9, Fever, unspecified). Although the speed of the reaction is typically slower than a bee sting, the outbreak is so intense that health officials have issued a serious warning: Beware of white-haired caterpillars.
The invading army’s weapon consists of a deadly urticating protein called thaumetopoein, which is located primarily in the caterpillar’s hairs. Each insect has approximately 63,000 individual hairs, which they drop as they trudge along in their search for food. And once released from the caterpillar, the hairs can also become airborne, spreading the toxin to a wider area. In addition, the larvae can voluntarily shed their hairs as a defense mechanism if they feel threatened and a great deal of hair is left in the communal nests. ICD-10-CM code T63.431A [Toxic effect of venom of caterpillars, accidental (unintentional), initial encounter] would be added to the symptom codes for the affected individual. The place of service would typically be Y92.821, Forest as the place of occurrence of the external cause.
To make matters worse, the toxic protein remains active for as long as 5 years after leaving the caterpillar, a gift that keeps on giving. Over 600 individual sites near London are being treated by the Forestry Commission, by trapping the not-deadly-at-all moths to prevent breeding and initiating an extensive biopesticide campaign to eliminate the caterpillars. Although the current outbreak should be short-lived, moths of a certain age become pesticide-resistant. This means that London may have to brace for a sequel to the invasion next spring when new caterpillars hatch from eggs left on oak trees.
In addition to their danger to humans, the caterpillars feed exclusively on oak leaves and large populations can strip trees bare, leaving them weakened and vulnerable to other threats. The caterpillars build unique white, silken webbed nests on the trunks and branches of oak trees in the early summer, and also leave white silky trails when they travel. OPM caterpillars generally traverse the ground in a nose-to-tail single file procession, from one oak tree to another. Large groups of moving larvae may travel in an arrow-head pattern, with one leader and several rows of followers in procession. Residents and visitors are being cautioned to avoid touching the caterpillars or their nests, and not to follow the hair-laden trails. According to Alice’s Adventures in Wonderland:
She stretched herself up on tiptoe, and peeped over the edge of the mushroom, and her eyes immediately met those of a large caterpillar, that was sitting on the top with its arms folded, quietly smoking a long hookah, and taking not the smallest notice of her or of anything else.
It was fine for Alice to start a conversation with a wise Blue Caterpillar in the fantasy world of Wonderland. However, anyone encountering a white-haired OPM caterpillar, on a mushroom or anywhere else, shouldn’t dally in the vicinity – just keep walking and hope that those deadly hairs don’t get in the way!