The chigger bite is painless and may become noticed as a transient localized itch. Bites
are often found on the groin, axillae, genetalia or neck (4). An eschar is often seen in
humans at the site of the chigger bite. The illness begins rather suddenly with shaking
chills, fever, severe headache, infection of the mucous membrane lining the eyes (the
conjunctiva), and swelling of the lymph nodes. A spotted rash on the trunk may be
present. Eschars are rare in patients in countries of South-East Asia and indigenous
persons of typhus-endemic areas commonly have less severe illness, often without rash
or eschar (13). Whether this is due to past exposure to the organism, or to other factors,
is unknown. Symptoms may include muscle and gastrointestinal pains. More virulent
strains of O. tsutsugamushi can cause haemorrhaging and intravascular coagulation.
Complications may include atypical pneumonia, overwhelming pneumonia with
adult respiratory distress syndrome (ARDS)–like presentation, myocarditis, and
disseminated intravascular coagulation (DIC). Patients with scrub typhus often exhibit
leucopenia.
Acute scrub typhus appears to improve viral loads in patients with HIV. This
interaction is currently unexplained (29). Clinical scrub typhus is not known to occur
naturally in animals.