Scrub typhus is cause by

Ans. a (Rickettsia tsutsugamushi) (Ref Ananthanarayan, Microbiology, 8thfp. 408, 410; Park 20th/263)# Scrub typhus is caused by R. tsusugamushi.# The vector is trombiculide mite.# The microbes are transmitted transovarially in mites.SCRUB TYPHUS (CHIGGER-BORNE TYPHUS)# Causative agent is R. tsutsugamushi.# Important reservoir is trombiculoid mite.# The nymphal and the adult stages of mite are free living in the soil.# They do not feed on vertebrate host.# Larva (chigger) feeds on vertebral host and picks up the rickettsiae.# Infection is maintained in nature transovarially from one generation of mite to next.# Larval stage serves both as reservoir, through ovarian transmission, and as a vector for infecting humans and rodents.# Tertacycline is the only drug of choice.# Sulfonamides should not be given.DiseaseCausative agentsVectorReservoirWF reactionCommentsEpidemicR. prowazekiLouseHuman+++ OX19# Red louse diseasetyphus # Transmitted by Pediculosis corporis and capitis.# Centrifugal rash 5 days after fever# Reactivation leads to Brill-Zinsser diseaseEndemic (Murine) typhusR. typhi (mooseri)Rat fleaRodent+++ OX19# Tunica reaction +# Rash on 4th day of feverScrub typhusR. tsutsugamushiMite (Chiggers)Rodent+++OXK# Punched-out ulcers with eschar# Erythematous rash on 5th day of fever# Lymphadenopathy (Zoonotic tetrad)Indian tick typhusR. conoriiTickRodent Dogs-# Fever boutounneuse# Tachenoir escharRMSFR. ricketssiTickRodent Dogs+++OX19, 2# Most severe ricketssial disease# Rash on wrist, palm and sole 3rd day of fever# Indirect immunofluo-roscence +.Rickettsial poxR. akariMiteMice-# Most mild disease# Eschar seenQ-feverCoxiella burnetti Cattle, sheep and goats-# No rash or local reaction.# No arthropod vector# Vaccine availableTrench feverRochalimaea quintanaLouseHuman-# Only rickettsia that can be culturedEherlichiosisE. senetsu, canlsTick bite--# No eschar/ rash# "Morules" diagnostic.