K Ectoparasitic Diseases

Introduction to Ectoparasitic 291 Diseases James H. Diaz

Ectoparasites infest the skin and its appendages, such as the hair and miscellaneous , and 7 mites. Most of the dermatoses sebaceous glands, and most external orifices, especially the ears, nares, originated in the United Kingdom (n = 46; 63%), and were caused by and orbits. Like endoparasites, ectoparasites may be obligatory parasites, tick bites (n = 18), principally Ixodes ricinus (the common sheep tick), programmed to feed on human hosts to complete their life cycles, or an important European vector of Lyme disease and neuroborreliosis. facultative parasites, preferring to feed on nonhuman hosts, infesting Myiasis cases predominated in returning travelers (n = 18; 67%), humans only as accidental or dead-end hosts. Over the past 2 decades, principally furuncular myiasis from larval infestation by Cordylobia there have been several reports of significant outbreaks of ectoparasitic anthropophaga (n = 9), the tumbu , or Dermatobia hominis (n = 4), diseases, principally myiasis, scabies, and tungiasis, both in indigenous the human botfly. Among the arthropod dermatoses caused by miscel- populations and in travelers returning from developing nations and laneous , most were pediculosis pubis caused by infestation even exclusive tropical beach resorts.1,2 Many common ectoparasites, with Phthirus pubis, the pubic louse (n = 7), or hemorrhagic, bullous such as head lice and scabies mites, are also developing increasing bite groupings caused by Cimex lectularius, the common bedbug (n = resistance to medical therapies, including the safest topical insecticides.3–6 3). The authors concluded that exotic ectoparasitic infestations, par- Other ectoparasites, such as the New World human botfly, Dermatobia ticularly myiasis, predominated in returning travelers from Africa and hominis, and the jigger or chigoe flea, Tunga penetrans, are resistant to Latin America; pubic lice were domestic, likely sexually transmitted, systemic and topical antiparasitics and can be treated only surgically. infestations; and bedbug infestations were domestically and internation- Ectoparasitic diseases have reemerged as unusual, but not uncommon, ally acquired, often from exposure to fomites, including bedding and infectious diseases worldwide, especially in high-risk populations. luggage. Indigenous populations of ectoparasite-endemic tropical nations often have recurrent infestations and superinfestations that can result in severe MECHANISMS OF disfigurement from facial cavitary myiasis or permanent disability from ECTOPARASITE-BORNE tungiasis-associated autoamputations. DISEASES AND INJURIES The a rarthropodthropod ectopa ectoparasitesrasites ca cann t hrthreatenea human health directly by TAXONOMY OF ECTOPARASITES burrowing into and feeding, dwelling, and reproducing in human skin The p hphylumylum Ar Arthropodathropoda i sis t hthee l alargestrgest p hphylumylum o fof th the kingdom and orifices (mites, fleas, ), or by blood or tissue juice sucking (fleas, and includes the subphylum Crustacea and the classes Insecta and lice, mites, ticks). The arthropod ectoparasites can also threaten human Arachnida. All the medically important ectoparasites, including fleas, health indirectly by infectious disease transmission (fleas, mites, ticks). flies, lice, mites, and ticks, are members of the phylum Arthropoda and Ticks are the most versatile ectoparasitic arthropods and can transmit have chitinous exoskeletons, segmented bodies, and jointed appendages. a variety of infectious diseases (viral, bacterial, and protozoan) and Fleas, flies, and lice are six-legged members of the class Insecta, which even inject paralytic toxins (tick paralysis) during their prolonged blood also includes the mosquitoes and true bugs (order Hemiptera). Mites, meals. Unlike other ectoparasites, ticks can be infective as males and including chigger and scabies mites, and ticks are the eight-legged females at birth (by transovarial pathogen transmission) and throughout members of the class Arachnida, subclass Acari. The arthropod ecto- all stages of their development (by transstadial pathogen transmission). parasites of medical importance are stratified yb taxonomic classes and The most commonly encountered arthropod ectoparasites, excluding distinguishing external anatomic characteristics in Table 291.1. ticks, and the major clinical manifestations of their infestations are featured in Table 291.2. The tick-borne pathogens and the clinical EPIDEMIOLOGY OF manifestations of their infections are featured in Chapter 296, Tables ECTOPARASITIC DISEASES 296.1 through 296.8. EctoparasiticEctoparasitic diseasesdiseases shareshare mmanyany of ththe general characteristics of emerging infectious diseases. Commonly shared characteristics of CONCLUSIONS ectoparasitoses and emerging infectious diseases include the following: RecentRecent epidemiologicepidemiologic evidencee now supports the endemicity of several (1) origination as zoonoses, with disease establishment dependent on ectoparasitic diseases and their arthropod vectors (Table 291.3) and arthropod vector competency; (2) introduction into new, susceptible host human and animal reservoir hosts throughout the developing world populations; (3) infection by endemic agents given selective advantages by and in many parts of the developed world, including Europe and the changing ecologic or socioeconomic conditions; and (4) recent movement United States. Ectoparasitic diseases have also reemerged in regions from rural to urban endemic areas, often following migrating human where they were once effectively controlled. Ectoparasitic diseases will host populations seeking better economic opportunities.7–9 continue to reemerge in the developed world for several reasons, including To assess the potential combined impact of increasing international the following: (1) the globalization of trade and commerce with ecto- travel and the relaxation of quarantine regulations for imported parasites and their human and animal hosts traveling worldwide on in the United Kingdom on arthropod-induced ectoparasitic dermatoses, airplanes and container ships; (2) mass movements of populations from McGarry and colleagues analyzed 73 specimens removed from rural to urban areas and from developing to developed nations; (3) the symptomatic patients and submitted to their laboratory for identification worldwide legitimate and illegal trade of exotic animals and animal at the Liverpool School of Tropical Medicine during the years 1994 to hides and skins; (3) the accidental and intentional introduction of exotic 2000.10 Of the 73 specimens identified, there were 27 ticks, 24 flies, 15 animal species into new regions with welcoming ecosystems; (4) the 3479 3480

TABLE 291.1 Taxonomy of Arthropods (Phylum Arthropoda) of Major Medical Importancea NO. OF LEGS, NO. OF BODY SEGMENTS, s COMMON NAMES OTHER IDENTIFYING ANATOMIC FEATURES ent

g Phylum Arthopoda, Class Insecta Order Diptera, family Culicidae Mosquitoes Six, three, wings ic A g Order Diptera Fliesa Six, three, wings

tiolo Order Hemiptera True bugs (e.g., bedbugs, reduviid bugs) Six, three, ± wings E Order Hymenoptera Ants, bees, wasps Six, three, ± wings Order Phthiraptera Licea Six, three, no wings Order Siphonaptera Fleasa Six, three, no wings Phylum Arthropoda, Class Arachnida Subclass Acari Mites and ticksa Eight, one globose body, no distinct headsb, no wings Order Araneae Spiders Eight, two, no wings Order Scorpiones Scorpions Eight, two, abdomens with terminal stingers aThe arthropod ectoparasites of major medical importance by taxonomic order and distinctive anatomic features. ectious Diseases and Their b f Mouthparts visible dorsally only in ixodid (hard) ticks. In I

TABLE 291.2 Common Arthropod Ectoparasites (Excluding Ticks) and Clinical Manifestations

Part II of Ectoparasitoses REPRESENTATIVE SPECIES OF COMMON NAMES OF MAJOR CLINICAL INFESTING ARTHROPOD INFESTING ARTHROPOD MANIFESTATIONS OF ECTOPARASITES ECTOPARASITE GEOGRAPHIC DISTRIBUTION ECTOPARASITOSES Class Insecta, Order Phthiraptera, Lice Suborder Anoplura Pediculus humanus corporis Body louse Worldwide Pediculosis corporis Pediculus humanus capitis Head louse Worldwide Pediculosis capitis, trench fever (Bartonella quintana) Phthirus pubis Crab (pubic) louse Worldwide Pediculosis pubis (phthiriasis) Order Diptera Flies Family Screwworms Auchmeromyia senegalensis Congo floor-maggot fly Sub-Saharan Africa, Cape Verde Larvae are nocturnal blood feeders, no myiasis Islands (tissue invasion); wound (cutaneous) myiasis Callitroga americana American screwworm North and Central America Cavitary (invasive) myiasis Chrysomyia bezziana Old World screwworm Tropical Africa, Asia, Indonesia Cavitary (invasive) myiasis Cochliomyia hominivorax New World screwworm Central and South America Furuncular myiasis Cordylobia anthropophaga Tumbu (mango) fly Africa Furuncular myiasis Family Oestridae Botflies Cuterebra spp. Rodent botfly North and Central America Furuncular myiasis Dermatobia hominis Human botfly Central and South America Furuncular myiasis Order Siphonaptera Fleas Ctenocephalides spp. Cat (C. felis) and dog fleas Worldwide Bite groupings (mechanical vectors of dog and (C. canis) rat tapeworms, less efficient bubonic plague vectors) Pulex irritans Human flea Worldwide Bite groupings (efficient plague vector in Chilean Andes) Tunga penetrans Chigoe (jigger) flea Central and South America, Africa Tungiasis Europe, Asia Xenopsylla cheopis Oriental rat flea Africa, Americas Most efficient bubonic plague vector Class Arachnida Spiders, mites, ticks Worldwide Subclass Acari Mites and ticks Sarcoptes scabiei Itch (scabies) mite Worldwide Scabies, crusted (Norwegian) scabies Eutrombicula alfreddugesi Common chigger (redbug chigger) Worldwide Chiggers Leptotrombidium akamushi Japanese-Asian rodent chigger Japan, India, Australia Potential scrub typhus (Tsutsugamushi disease) vector Leptotrombidium deliensis Indian-Asian rodent chigger Eurasia-Eastern Asia, Southeast Asia, Potential scrub typhus (Tsutsugamushi disease) India, Australia, Indo-Pacific Islands vector

increasing frequency of pyrethroid-resistant strains of ectoparasites, health consequences.13 Formerly felt to be susceptible to the safest especially head lice and scabies mites; and (5) the growing populations pyrethroid pesticides and incapable of transmitting infectious diseases, of susceptible, and often immunocompromised, human hosts living in head lice have acquired the capability to harbor B. quintana like body long-term care facilities and in crowded and impoverished periurban lice and potentially to transmit trench fever to new naïve host populations. communities.11,12 The eradication of pyrethroid-resistant head lice infestations in homeless The isolation of the trench-fever pathogen, Bartonella quintana, in persons in crowded shelters and children in schools will require the head lice from homeless persons in the United States illustrates how use of more powerful pesticides with potential for adverse effects, such well socioeconomic factors, human behavioral trends, and vector as carbaryl, lindane, and malathion; or the use of new, safer alternatives, adaptations can support ectoparasite persistence with significant public such as oral and topical ivermectin-containing pediculicides.11 3481

TABLE 291.3 Selected Infectious Diseases Transmitted by Arthropods Infectious Disease Vector Cha Anaplasmosis (human granulocytotropic) Hard ticks p

Arbovirus diseases (including yellow fever, dengue fever, encephalitis) Mosquitoes and ticks ter 291 Babesiosis Hard ticks Boutonneuse fever (tick bite fever; Rickettsia conorii) Hard ticks Introduction to Ectoparasitic Diseases Cat scratch disease, cat scratch fever (Bartonella henselae) Cat fleas Chagas disease (American trypanosomiasis) Triatomine (kissing) bugs Colorado tick fever Hard ticks Ehrlichiosis, monocytotropic (Ehrlichia chaffeensis) and granulocytic (Ehrlichia ewingii) Hard ticks Endemic relapsing fever (Borrelia duttonii) Soft ticks Epidemic relapsing fever (Borrelia recurrentis) Human body lice Epidemic typhus (Rickettsia prowazekii) Human body lice Filariasis (Wuchereria bancrofti, Brugia malayi) Mosquitoes Leishmaniasis (Leishmania spp.) Lutzomyia sand fly in the Americas, phlebotomid flies elsewhere Loiasis (Loa loa) Tabanid flies Lyme disease (Borrelia burgdorferi) Hard ticks Malaria (Plasmodium spp.) Mosquitoes Murine typhus (Rickettsia mooseri) Rat fleas, lice Onchocerciasis (Onchocerca volvulus) Black flies Plague (Yersinia pestis) Rat fleas Q fever (Coxiella burnetii) Hard ticks, fleas Rickettsialpox (Rickettsia akari) Mouse mites Rocky Mountain spotted fever (Rickettsia rickettsii) Hard ticks Scrub typhus (Rickettsia tsutsugamushi) Mites (chiggers) Trench fever (Bartonella quintana) Body lice, potentially head lice Trypanosomiasis, African sleeping sickness Glossina (tsetse) flies West Nile fever Mosquitoes

Key References 6. Chosidow O. Scabies. N Engl J Med. 2006;354:1718–1727. amplification reaction. Pest Manag Sci. 2010;66: 10. McGarry JW, McCall PJ, Welby S. Arthropod dermatoses 1031–1040. The complete reference list is available online at Expert Consult. acquired in the UK and overseas. Lancet. 2001;357: 13. Bonilla DL, Kabeya H, Henn J, et al. Bartonella Quintana 4. Meinking TL, Serrano L, Hard B, et al. Comparative in 2105–2106. in body lice and head lice from homeless persons, San vitro pediculicidal efficacy of treatments in a resistant head 12. Hogdon HE, Yoon KS, Previte DJ, et al. Determination of Francisco, California, USA. Emerg Infect Dis. 2009;15: lice population in the United States. Arch Dermatol. knockdown resistance allele frequencies in global human 912–915. 2002;138:220–224. head louse populations using serial invasive signal Chapter 291 Introduction to Ectoparasitic Diseases . e1 1. 8 uintana 4 Q s in :1031–1040 3 k

66 . ris s g

. 2010; l. Determination of of Determination l. . i a c 0:210–220. S 6 al. Bartonella Bartonella al. Lancet t e poisonin S. Arthropod dermatoses d y Emerg Infect Di Infect Emerg . 2008;1 Soc Pest Manag d pesticide-resistant ectoparasitic pesticide-resistant 6. g . 5 increase pestici y 91 – a State Me a State l J JW, McCall PJ, Welb PJ, McCall JW, 912 y 5: 357:2105–210 1 ren. ren. ; ; uired in the UK and overseas. overseas. in the UK and uired ld ections ma ections i q f ead louse populations using serial invasive signal serial using invasive ead populations louse rancisco, California, USA. rancisco, 001 h n San persons, homeless n body head lice from lice and McGarr Hogdon HE, Yoon KS, Previte DJ, et DJ, Previte KS, HE, Yoon Hogdon Diaz JH. Increasin Bonilla DL, Kabeya H, Henn J, e J, H, Henn Kabeya Bonilla DL, amplification reaction. amplification 2 i h i F 2009 knockdown resistance allele frequencies in global human in global human allele frequencies resistance knockdown ac c . 10. 12. 11 13. g

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A . J En 5–974 N 6 ect Dis ect f our AG, O AG, our b 119:9 ; cabies. cabies. S . O 2007 merg In 7. . cle, resistance, and safet and resistance, cle, E 2 . y 7 ics r 47 er DH, Bar er DH, 3 –1 ogy. – 8 l lk 3 1 arano N, Arguin PM, Pappaioanou M. Impact o M. Impact PM, Pappaioanou N, Arguin arano a cFee RB. Global infections: avian influenza and other and influenza avian infections: Global RB. cFee hosidow hosidow ebwohl M, Clark L, Levitt J. J. L, Levitt M, Clark ebwohl ediat 4 7 W M M L C on life c life on zoonotic and vector-borne diseases: and ecological vector-borne and zoonotic factors. epidemiological 3 1 globalization and animal trade on infectious disease infectious trade on animal and globalization eco significant emerging pathogens. pathogens. emerging significant P . . . . 7 8 9 5 6. 50. 6 arva

. l l 45–1 6 utaneous :1 . 6 C 34 ; rop Med Int Int Med rop al. al. T t . y Arch Dermato al. Comparative in Comparative al. 2002 . e to control zoonotic control e to t d g Travel Med J o F Jr, e o F Jr, j . y meier H. Cutaneous meier H. Cutaneous l J Me ld g of treatments in a resistant head in a resistant treatments of y iasis in international travelers iasis in international . N En g e N, Fe k 910 . iasis: the challen 7– . g 90 , Menc 7: J ces

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e Brazil: an airport surve an Brazil: . lb g e 14:374–380 r ; k rans and tun and rans g itro pediculicidal efficac itro Meinkin Roberts R Heu M, Arau Gomide J, Heukelbach ectoparasitoses associated with povert with associated ectoparasitoses mi exitin v 2007 2002;138:220–224 larva mi lice population in the United States. in the United lice population Health efe . 4. 3. 1 2. R