Among the trombiculid chiggers including the scrub click here typhus-transmitting Leptotrombidium species, only the larvae are human and animal ectoparasites. The larger chigger nymphs and adults are free-living and feed on small insects and their eggs. All trombiculid
larvae exhibit a unique method of feeding on hosts and transmitting salivary secretions, which may contain O tsutsugamushi, the causative agent of scrub typhus, in endemic regions. Larvae pierce the skin with sharp mouthparts and infuse tissue-dissolving saliva to fill a pool of lymph, other body fluids, and dissolved epithelial cells to aspirate from (Figure 1). The repeated injection of saliva into bite wounds incites a host reaction forming a straw-like hollow tube, the hypostome (stylostome), which extends downwards firmly anchoring the mite into the host’s skin. 1 All of the non-infectious chigger larvae can cause scrub itch or trombidiosis with the American chigger mite, Eutrombicula alfreddugesi, being the most common culprit in the United States; the European autumn harvest mite, Neotrombicula autumnalis, the most common culprit in Europe; and the Asian chigger, Eutrombicula sarcina, the most common culprit in Asia (Table 1). Initially painless, chigger bites will cluster where clothing is tight against the skin, especially on the genitalia, thighs,
buttocks, Docetaxel flanks, waists, and ankles. SPTLC1 Localized itching and discomfort ensue when the larvae withdraw their mouthparts and depart after feeding for 3 to 6 hours for most non-infectious chiggers. Although some trombiculid larvae remain attached to and feeding on human hosts for up to a month, the larval vectors of scrub typhus feed
for 2 to 10 days before dropping to the ground engorged, and ready to mature into free-ranging nymphs. Forcibly removing feeding chiggers often decapitates larvae leaving mouthparts embedded to cause further inflammation. 1 Several untested strategies for removing feeding, engorged chiggers intact have included painting chigger bite sites with colloidion, clear fingernail polish, or Liquid Skin, then drying the sites with a hair dryer and peeling the coated and dried chiggers off the skin intact. Localized intense itching will often be followed by prurigo, an eruption of intensely pruritic erythematous papules by 10 to 12 hours, followed by crusting and healing by 24 to 48 hours. 1 Treatment of mild infestations is supportive with soap and water cleansing, warm water soaks, and topical local anesthetics and antihistamines. Prurigo should be treated specifically with topical corticosteroids, with oral corticosteroids indicated for severe cases. Impetigo and other secondary infections are potential complications that would necessitate antibiotic treatment. Tetanus prophylaxis is recommended, if indicated.