Clinical features. The clinical features of the tick-borne typhus diseases (Table 9.3) are very similar and usually milder than those of Rocky Mountain spotted fever. Fatal cases are rare. The initial lesion develops at the site of the tick bite with an erythematous papule, which vesiculates and develops an overlying eschar, also called 'tache noir' (Figure 9.6) and local lymphadenopathy. Fever and headache develop and after about 5 days a widespread exan-them evolves, which usually involves the palms and soles. This is an erythematous maculopapular eruption but may become haemorrhagic.
Reservoir: house mice, rodents. Distribution: USA, Russia, Africa.
Clinical features. Rickettsialpox is a mild self-limiting disease. The initial skin lesion, which develops at the site of the mite bite after 7-10 days, is a 1-1.5 cm painless erythematous papule. Central vesiculation subsequently develops and becomes covered with a black eschar. This lesion heals slowly to leave a scar. Regional lymph nodes may be enlarged. Fever develops 3-7 days after the initial lesions and a widespread exanthem evolves. The rash has a widespread distribution and is maculopapular and vesicular in nature. Palms and soles are usually spared. The eruption heals without scarring.
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