ClinQuiz: Ectoparasites - Answer 3A

Correct. The organism depicted in Figure 3B is a morula of Ehrlichia ewingii, which is transmitted to dogs by lone star ticks (Figure 3A). The organisms are morphologically identical to Anaplasma phagocytophilum, which is transmitted by black-legged ticks, or deer ticks (Ixodes species).7,8 Patients usually respond to doxycycline within two or three days.9 However, infections can recrudesce; 28 days of treatment is recommended to better eliminate chronic infections.10

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