OBSERVATION Multiple Pruritic Papules From Lone Star Tick Larvae Bites Emily J. Fisher, MD; Jun Mo, MD; Anne W. Lucky, MD Background: Ticks are the second most common vec- was treated with permethrin cream and the lesions re- tors of human infectious diseases in the world. In addi- solved over the following 3 weeks without sequelae. The tion to their role as vectors, ticks and their larvae can also organism was later identified as the larva of Amblyomma produce primary skin manifestations. Infestation by the species, the lone star tick. larvae of ticks is not commonly recognized, with only 3 cases reported in the literature. The presence of mul- Conclusions: Multiple pruritic papules can pose a di- tiple lesions and partially burrowed 6-legged tick larvae agnostic challenge. The patient described herein had an can present a diagnostic challenge for clinicians. unusually large number of pruritic papules as well as tick larvae present on her skin. Recognition of lone star tick Observation: We describe a 51-year-old healthy woman larvae as a cause of multiple bites may be helpful in simi- who presented to our clinic with multiple erythematous lar cases. papules and partially burrowed organisms 5 days after exposure to a wooded area in southern Kentucky. She Arch Dermatol. 2006;142:491-494 ATIENTS WITH MULTIPLE PRU- acteristic clinical and diagnostic features of ritic papules that appear to be infestation by larvae of Amblyomma species bitespresentachallengetothe and may help clinicians make similar di- clinician. We present a case of agnoses in the future. a healthy 51-year-old woman whowasbittenbymultiplelarvaeofthetick, P REPORT OF A CASE Amblyomma species, most likely A ameri- canum or the lone star tick. Ticks have been recognizedashumanparasitesforthousands A 51-year-old white woman presented with of years and are the second most common multiple, diffuse, intensely pruritic pap- vector of human infectious disease after ules and papulovesicles (Figure 1). Five mosquitos.1 Their role in the transmission days prior to her presentation, the pa- of several human infectious diseases has tient was boating on a lake in southern Kentucky. On 2 occasions, she had dis- For editorial comment robed in a wooded area near the lake, leav- ing her clothes on the ground for several see page 497 minutes before redressing. One day after the second time she undressed, the pa- been known since the beginning of the 20th tient noted the onset of an erythematous century.1 In particular, Amblyomma species pruritic rash that progressed with addi- have been identified as the vector for tional lesions over the next few days. several human diseases including Rocky She visited several physicians in the fol- Mountain spotted fever, Q fever, ehrlichio- lowing days who variously diagnosed infes- sis, tularemia, and African tick bite fever tationswith“no-see-ums”(forwhichshewas Author Affiliations: Division of via salivary secretions. In addition to being prescribed cetirizine hydrochloride [Zyrtec; Pediatric Dermatology vectors for human diseases, ticks can cause Pfizer US, New York, NY] and a 5-day course (Drs Fisher and Lucky) and severalprimarydermatologicmanifestations of prednisone), bedbugs, and finally pubic Department of Pathology including erythematous papules, skin hem- lice (for which she was given a prescription (Dr Mo), Cincinnati Children’s Hospital Medical Center, and orrhages, papular urticaria, diffuse derma- of 5% permethrin cream). Despite numer- Department of Dermatology, titis, necrotic ulcers, prurigo, erythema ousshowersandscrubs,therashprogressed, The University of Cincinnati migrans–like rash, and patchy alopecia, but and the patient began to note the presence School of Medicine (Drs Fisher reports of primary infestations are rare.2-5 of tiny dark “bugs” attached to her skin in and Lucky), Cincinnati, Ohio. The present report summarizes the char- the centers of many of the papules. (REPRINTED) ARCH DERMATOL/ VOL 142, APR 2006 WWW.ARCHDERMATOL.COM 491 ©2006 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 09/24/2021 Figure 1. Multiple erythematous papules on a 51-year-old woman seen 5 days after her exposure to wooded area. Figure 3. Amblyomma species, microscopic view, showing 6-legged larval A B form. COMMENT Ticks are obligate blood-sucking arthropods that para- sitize every class of vertebrate in almost every region of the world. They are currently considered to be second only to mosquitoes as vectors of human infectious dis- eases in the world.1 The life cycle of most hard ticks requires 2 years for completion and includes the egg, the 6-legged larva or Figure 2. Organism partially burrowed in the skin. A, The organism appears “seed tick,” the 8-legged immature nymph, and the as a dark spot. B, Close-up view of the organism on the skin, later identified 8-legged reproductively mature adult. All stages except as Amblyomma species larva, the lone star tick. the egg require a blood meal for morphogenesis.6,7 The larvae emerge from eggs deposited on the ground and then She presented to our dermatology clinic for further crawl up grasses and other low vegetation where they can recommendations before using the permethrin cream. In easily attach to passing animals or humans.2 The tick clings the clinic, we found hundreds of red, blanching papules to hair or clothing, waits until the host is at rest, moves and papulovesicles on her trunk and extremities, espe- to an appropriate exposed area of the host’s body, and cially in areas that had been under her clothing. On close then bites. inspection, we found dark, 1-mm organisms in the cen- It appears that this patient must have undressed near ter of many of the papules. Under magnification, these a nest of newly hatched tick larvae that were attracted to were determined to be bugs of unknown type whose heads her clothing and attached themselves before transfer- were partially burrowed under the skin (Figure 2). Sev- ring to her skin when she redressed. Ticks inject an an- eral of the organisms were removed with forceps and vi- esthetic similar to lidocaine, which usually makes their sualized in mineral oil under the microscope; they were bites painless. A tick may spend up to 24 hours on the rotund, 6-legged organisms (Figure 3). host before biting and then feed for 2 hours to 7 days be- The patient was instructed to complete a single overnight fore dropping off.8 After completion of a blood meal at 1 application of 5% permethrin cream and try to scrub off the site, the larva typically drops to the ground where it molts organisms the next morning. The initial diagnosis was in- to become a nymph.3 The larval and nymphal stages are festation by chigger mites, but because of the unusual na- so small they often are not seen until they have fully en- ture of the presentation, including the large size and num- gorged with blood. This may account for the patient not ber of organisms and the fact that the organisms were still noticing the ticks until the fourth or fifth day of her in- attached and burrowed, this diagnosis was questioned. festation. Sample organisms were sent for definitive identifica- For most tick-borne diseases, it appears that the tick tion to the C. Wayne Ellett Plant and Pest Diagnostic Cen- must remain attached for 24 to 48 hours before disease ter of Ohio State University, Columbus, and found to be transmission occurs.9 Among the 13 genera of Ixodidae, the larvae of Amblyomma species, most likely A ameri- 3 are known to transmit disease to humans in the United canum, the lone star tick. The patient’s pruritus began States: Amblyomma, Dermacentor, and Ixodes.7 All stages to resolve approximately 2 days after application of the of Amblyomma except the egg are capable of transmit- permethrin cream, and the erythematous papules gradu- ting disease.2,3 ally resolved over the next 3 weeks. She has not had any Amblyomma americanum is the most common spe- further complications. cies of Amblyomma found in the United States. It is named (REPRINTED) ARCH DERMATOL/ VOL 142, APR 2006 WWW.ARCHDERMATOL.COM 492 ©2006 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 09/24/2021 the lone star tick due to the prominent white dot on the NH). In a study comparing these 3 tools with tweezers, back of the adult female and is abundant in the south cen- it was found that all of these tools were more effective tral and southeastern United States. Amblyomma ameri- than tweezers in removing nymph-stage ticks.14 canum and Amblyomma cajennense ticks will feed on small There are no data to indicate that prophylactic treat- or large mammals during any stage of their life cycle and ment with antibiotics after a tick bite reduces the risk of are commonly found on white-tailed deer.2,10 They are disease transmission in all cases. A recent randomized known to transmit several human diseases including ehrli- trial showed that a single 200-mg dose of doxycycline chiosis (Ehrlichia chaffeensis) in the mid-Atlantic, south administered within 72 hours after a recognized Ixodes central, southeastern, and western (California) states; tu- scapularis bite had an efficacy of 87% in preventing ery- laremia (Francisella tularensis) in the southeastern and thema migrans. The number needed to treat to prevent south central states; and, less commonly, Rocky Moun- 1 case of erythema migrans was 36 among people with tain spotted fever (Rickettsia rickettsi) and Q fever (Coxi- any I scapularis bite and 12 among people with bites from ella burnetii). Amblyomma americanum is a rare cause of engorged nymphal I scapularis.15 The possible effects of tick paralysis.6 In the past several years, A americanum prophylactic treatment on other infections transmitted has been shown to be the vector for an erythema migrans– by deer ticks and on strains of Borrelia in Europe and like rash illness termed “southern tick-associated rash ill- Asia, as well as its use to prevent Lyme disease in chil- ness” (STARI) caused by Borrelia lonestari.11-13 dren, have not been evaluated.