Chigger Bites

“Chigger” is the common name for species of the Trombiculid family of mites. Bites from the larva of these mites can cause local pruritus and irritation, formally known as trombiculiasis or trombiculosis. The reaction is usually mild and self-limited, but the bites may rarely transmit disease or result in a bacterial superinfection. While there are many species of parasitic mites in a variety of habitats all over the world, the species most commonly referred to as chiggers include Eutrombicula alfreddugesi in the south of the United States, Trombicula autumnalis in Europe, and species of the Leptotrombidium genus in Asia and Oceania. The larvae of these species feed on the skin of a variety of animals, including humans. Adult mites burrow into the soil and feed on detritus while the larvae of these species accumulate on the edges of leaves and grass before hitching on to a passing host. They then migrate to a preferred feeding site, attach themselves to the host’s skin, and secrete proteolytic enzymes to digest host epidermal cells. This provokes an inflammatory reaction with surrounding erythema, a variable degree of swelling, and intense pruritus. They are easily dislodged by scratching. They rarely remain attached to humans for more than 48 hours, but the intense pruritus, inflammation, and localized allergic response may last for weeks afterward. Rarely, the light-red to orange colored larva, measuring 0.15 to 0.3 mm in length, may be identified on the skin. More typically, the diagnosis of trombiculiasis will depend on exposure to trombiculid habitat, the pattern of the lesions, and exclusion of other possible diagnoses.