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tvpjournal.com | March/April 2015 | TodAy's VeTerinAry PrAcTice PArAsiTe ProTocoLs For yoUr PrAcTice Peer reviewed 63 for treatment of P caninum, but macrocyclic lactones (ivermectin, selamectin, moxidectin, and milbemycin oxime) are reportedly effective. 8 TICKS (METASTIGMATIDS) only about 10 of the approximately 850 known tick species have varying degrees of medical importance in the U.s. These include members of the tick families Argasidae (soft ticks) and ixodidae (hard ticks), the latter of which are further divided into 2 subfamilies, with distinct biologic features that affect feeding behavior and vector competence. Table 2 briefy describes some of the tick-borne diseases and zoonoses that affect dogs in the U.s. Argasidae (Soft Ticks) soft-bodied ticks lack a sclerotinized dorsal scutum and are further characterized by mouthparts that originate on the ventral surface, though these mouthparts may extend beyond the anterior to become visible from the dorsal surface (Figure 2, page 64). Larval and nymphal stages of the one-host spinose ear tick—Otobius megnini—infest mammalian ear canals, including those of dogs and people. These ticks are not known to be a vector for pathogens but can cause a painful form of otoacariasis. Members of another argasid genus, Ornithodoros, live in dwellings or bedding areas of their hosts, taking multiple short blood meals over the course of several months to several years. Ornithodoros species have not been demonstrated to parasitize dogs in the U.s.; however, they are known to TabLe 2. t ick-Borne diseases of dogs & Cats in the U.s. disease pathoGen pathoGen tYpe knoWn/pUtatiVe V eCtor(s) ZoonotiC disease ? American canine hepatozoonosis Hepatozoon americanum Protozoan (Apicomplexa) Amblyomma maculatum No Canine babesiosis Babesia vogeli Babesia gibsoni Protozoan (Apicomplexa) Rhipicephalus sanguineus No Canine hepatozoonosis Hepatozoon canis Protozoan (Apicomplexa) Rhipicephalus sanguineus No Cyclic thrombocytopenia (anaplasmosis) Anaplasma platys Rickettsiales (Anaplasmataceae) Rhipicephalus sanguineus No Feline cytauxzoonosis Cytauxzoon felis Protozoan (Apicomplexa) Dermacentor variabilis Amblyomma americanum No granulocytic anaplasmosis Anaplasma phagocytophilum Rickettsiales (Anaplasmataceae) Genus Ixodes Yes granulocytic ehrlichiosis Ehrlichia ewingii Rickettsiales (Anaplasmataceae) Amblyomma americanum Yes Human babesiosis* Babesia microti (and others) Protozoan (Apicomplexa) Ixodes scapularis Yes Lyme borreliosis Borrelia burgdorferi Spirochete Genus Ixodes Yes Monocytic ehrlichiosis Ehrlichia canis Rickettsiales Rickettsiales (Anaplasmataceae) Rhipicephalus sanguineus Dermacentor variabilis No Ehrlichia chaffeensis Amblyomma americanum Yes Ehrlichia muris–like agent Ixodes scapularis Yes rocky Mountain spotted fever Rickettsia rickettsii Rickettsiales (Rickettsiaceae) Dermacentor variabilis Rhipicephalus sanguineus Yes * With the exception of human babesiosis, etiologic agents of the zoonotic diseases in this table are reported to naturally infect dogs in the U.S. Among European dogs, a Babesia microti-like parasite has been reported; among dogs in the western U.S., the zoonotic agent Babesia conradae was reported. 9