All about Indian tick typhus

·         Indian tick typhus is a disease of the spotted fever group of Rickettsiae caused by Rickettsia conorrii subsp indica.

·         In India, the Indian tick typhus is prevalent in hilly forest areas. Infection has been seroepidemiologically reported from various parts of the country such as Nagpur, Jabalpur, Jammu and Kashmir, Kanpur, Sagar, Pune, Lucknow, Bangalore and Kangra.

·         The brown dog tick (Rhipicephalus sanguineus is the reservoir of infection and is infective at all stages of its life. Infection in nature is maintained by transovarian and trans-stadial passage. The rickettsiae can be transmitted to dogs, rodents. Man is an accident host and acquires the infection by the bite of infected tick.

·         The incubation period is usually 3 to 7 days.

·         The patient will give a history of a recent tick bite.

·         Clinically, the infection presents as acute onset of moderate to high grade fever, which may persist for 2-3 weeks, malaise, headache, deep muscle pain. A maculopapular rash appears on the 3rd day of fever. Unlike the rash in other rickettsial diseases, in Indian tick typhus, the rash is first seen on the extremities (ankles and wrists), moves centripetally and involves the rest of the body.

·         Unlike other spotted fever group, the maculopapular rash in Indian tick typhus is frequently purpuric, absence of inoculation eschar at the site of the bite (eschar if present, is always single) and absence of lymphadenopathy.

·         Diagnosis is based on Weil-Felix test, 4-fold rise in agglutinin titer in paired sera or single titer of more than equal to 1:320 is considered diagnostic for infection.

·         Doxycycline is the drug of choice

·         Prevention: Avoid known tick-infested areas. People exposed to risk infection should  do daily inspection of the body for ticks, disinfection of dogs.