A previously healthy 39-year-old presented with fever, weakness,
and muscle pain, which began about 6 days after his return from a
3-week safari in Africa. The patient reported being bitten by a
tick during the safari.
Physical examination revealed a temperature of 38.2°C, one 0.5
cm eschar on the trunk (figure 1) and non-itchy rashes on his lower
limbs (figure 2).
Figure 1 Eschar on the trunk.
Figure 2 Rashes on lower limbs.
Which of the following is the most likely diagnosis?