Diseases & National Health Programme
All are true about scrub typhus except
|A||Mite is a vector|
|B||Adult mite feeds on vertebral host|
|C||Caused by tsutsugumushi|
|D||Tetracycline is treatment|
a. The causative agent of scrub typhus is Rickettsia tsutsugamushi. There are several serologically distinct strains.
b. RESERVOIR: The true reservoir of infection is the trombiculid mite (Leptotrombidium delinese and L. akamushi). The infection is maintained in nature transovarially from one generation of mite to the next. The nymphal and adult stages of the mite are free-living in the soil; they do not feed on vertebrate hosts. It is the larva (chigger) that feed on vertebrate hosts and picks up the rickettsiae. The larval stage serves both as a reservoir, through ovarian transmission, and as a vector for infecting humans and rodents.
Mode of transmission –
a. By the bite of infected larval mites. The transmission cycle may be depicted as below:
b. Mite → Rats and mice → Mite → Rats and mice;
c. Mite → Rats and mice → Mite → Man;
d. The disease is not directly transmitted from person to person.
e. Incubation period - Usually 10 to 12 days; varies from 6 to 21 days
Clinical features –
- Scrub typhus .resembles epidemic typhus clinically. The onset is acute with chills and fever (104°-105° F), headache, malaise, prostration and a macular rash appearing around the 5th day of illness. Generalized lymphadenopathy and lymphocytosis are common. One typical feature is the punched-out ulcer covered with a blackened scab (eschar) which indicates the location of the mite bite. The pyrexia falls by lysis in the 3rd week in untreated cases. The Weil Felix reaction is strongly positive with the Proteus strain OXK.
Treatment: Tetracycline is the drug of choice