Stylostome

Stylostome is a feeding structure formed in host tissue by certain parasitic larval mites, most notably trombiculid mites (chiggers). When a larva attaches to a vertebrate host, it injects saliva containing digestive enzymes that macerate host cells. The host tissue responds by forming a tubular projection that extends toward the feeding site. This conduit, called the stylostome, serves as a pathway for the larva to withdraw liquefied tissue and fluids.

Formation and appearance: The stylostome penetrates the epidermis or superficial dermis and can resemble a finger-like tube or a short hollow cone. It is composed of host tissue that has reorganized around the mite’s feeding canal and may be surrounded by localized inflammatory cells, including eosinophils and macrophages. The larva feeds for a period before disengaging and dropping off.

Clinical and diagnostic relevance: In humans, chigger bites produce intense itching and dermatitis, often at sites where clothing fibers press on the skin. Histologically, stylostomes may be identified as remnants of the feeding tube within the dermal tissue. Recognition of stylostomes can aid in the diagnosis of chigger infestations in both human and veterinary pathology.

Etymology and taxonomy: The term stylostome derives from Greek stoma ‘mouth’ with stylos ‘column or stake,’ reflecting the tube-like feeding structure. Stylostomes are most commonly described in trombiculid mite larvae; they are a characteristic feature in studies of chigger parasitism.