Scrub typhus

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Scrub typhus


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Scrub typhus:

Dr.T.V.Rao MD Scrub typhus Dr.T.V.Rao MD 1

Scrub typhus :

Scrub typhus or Bush typhus is a form of typhus caused by the intracellular parasite Orientia tsutsugamushi, a Gram-negative α- proteobacterium of family Rickettsiaceae first isolated and identified in 1930 in Japan Scrub typhus Dr.T.V.Rao MD 2

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Incidence of Scrub typhus:

Incidence of Scrub typhus The precise incidence of the disease is unknown, as diagnostic facilities are not available in much of its large native range which spans vast regions of equatorial jungle to the sub-tropics. In rural Thailand and in Laos, murine and scrub typhus accounts for around a quarter of all adults presenting to hospital with fever and negative blood cultures The incidence in Japan has fallen over the past few decades, probably due to land development driven decreasing exposure, and many prefectures report fewer than 50 cases per year. Dr.T.V.Rao MD 4

Scrub Typhus:

Scrub Typhus Scrub typhus caused by Orientia tsutsugamushi Mild to fatal 6-18 days after bite of Mite An Escher is formed at the site of bite With enlargement of Lymph nodes, Interstitial pneumonitis ,lymphadenopathy,spleenomegaly Encephalitis, Respiratory failure, circulatory failure Dr.T.V.Rao MD 5

Rickettsia tsutsugamushi.:

Rickettsia tsutsugamushi. Causative agent is Rickettsia tsutsugamushi . Found in areas where they harbour the infected chiggers particularly areas of heavy scrub vegetation's. Dr.T.V.Rao MD 6

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RESERVOIR: Trombiculid mite which feeds on small mammals. MODE OF TRANSMISSION: By bite of infected larval mites. Infection occurs during wet season when the mites lay their eggs. It is the larva (chigger) that feeds on vertebrate hosts. TRANSMISSION CYCLE MITE------RATS AND MICE-----MITE----RATS AND MICE MAN Dr.T.V.Rao MD 7


SCRUB TYPHUS Etiology: Orientia tsutsugamushi Resembles Epidemic typhus except for the ESCHAR generalized lymphadenopathy & lymphocytosis cardiac & cerebral involvement may be severe Dr.T.V.Rao MD 8


Epidemiology Source of infection-------- Rat Route of transmission---- -Trombiculid mites Susceptible population---- All susceptible Epidemic features---------- Tsutsugamushi triangle Dr.T.V.Rao MD 9

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Mode of Transmission :

Mode of Transmission Mite Rats & Mice Humans Mite     No direct person to person transmission Mite Islands (Accidental host) Dr.T.V.Rao MD 11


Chigger reservoir Larval stage vector Dr.T.V.Rao MD 12

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An important vector-borne disease, first described in 1899 in Japan . D uring World War II, this disease killed t housands of soldiers who were stationed in rural or jungle areas of the Pacific theatre. Scrub Typhus The disease occurred and threatened people throughout Asia & Australia. The range stretches from the Far-east to the Middle-east ( from Japan and Korea, Southeast Asia, Pakistan, India, to Arab countries and Turkey ). There are approx. 1 million cases each year world-wide, & over 1 billion people at risk. Dr.T.V.Rao MD 13

Clinical Features:

Clinical Features Incubation period : 1-3 wks. ( usually6-21 days) Fever(104-105°F) with chills,malaise,conjunctival Irritation. Maculopapular rash Lymphadenopathy,Lymphocytosis Headache, Cough, Myalgia Gastrointestinal symptoms Typical “ Eschar formation” ( 5 th day of illness) Dr.T.V.Rao MD 14

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Pathogen: Orientia tsutsugamushi Rickettsial bacteria Vector: Leptotrombidium Chigger-Mite An acute febrile, rickettsial disease caused by a gram-negative, rod-shaped (cocco-bacillus) bacterium, known as Orientia (Rickettsia) tsutsugamushi. Scrub Typhus : A Rickettsial Disease O. tsutsugamushi is transmitted to vertebrate hosts (rodents-primary host & humans-secondary or accidental host) by the bite of larval mites (chiggers) of the genus Leptotrombidium , e. g. L. deliense, L. dimphalum, etc. Dr.T.V.Rao MD 16

Scrub typhus:

Scrub typhus Dr.T.V.Rao MD 17


Eschar Probability: Higher than 60%. Location: Axillary fossa, inguinal region, perianal region, scrotum, buttocks and the thigh. Appearance: an ulcer surrounded by a red areola, is often covered by a dark scab. The most specific manifestation of scrub typhus . Dr.T.V.Rao MD 18

Clinical Manifestation:

Clinical Manifestation Incubation period is 4~21 Sudden onset with a fever 1st week, systemic toxic symptoms 2nd week, get worse, complication 3th week, conv alesce Dr.T.V.Rao MD 19

Complications :

Complications Pneumonitis Hepatitis Myocarditis Meningoencephalitis Disseminated intravascular coagulation Multi organ failure Dr.T.V.Rao MD 20


Eschar Probability: Higher than 60%. Location: Axillary fossa, inguinal region, perianal region, scrotum, buttocks and the thigh. Appearance: an ulcer surrounded by a red areola, is often covered by a dark scab. The most specific manifestation of scrub typhus . Dr.T.V.Rao MD 21


Investigations Weil- feilx test positive- proteus strain oxk Indirect immunofluorescence. PCR for Orientia tsutsugamushi from blood of feverish patients. Some studies have used PCR (polymerase chain reaction) on specimens obtained from eschars . Dr.T.V.Rao MD 22

Diagnosis of Scrub typhus :

Diagnosis of Scrub typhus The cheapest and most easily available serological test is the Weil-Felix test, but this is notoriously unreliable . The gold standard is indirect immunofluorescence , but the main limitation of this method is the availability of fluorescent microscopes, which are not often available in resource-poor settings where scrub typhus is endemic. Indirect immunoperoxidase (IIP) is a modification of the standard IFA method that can be used with a light microscope , and the results of these tests are comparable to those from IFA. Dr.T.V.Rao MD 23

Management :

Management Drug of choice : Tetracycline Doxycycline orally or Chloramphenicol in more severe cases. Azithromycin has been used in resistant cases and may be better than doxycycline - especially in children and pregnant women. Dr.T.V.Rao MD 24

Treatment :

Treatment The drug most commonly used is doxycycline; but chloramphenicol is an alternative. Strains that are resistant to doxycycline and to chloramphenicol are common in northern Thailand.Rifampin and azithromycin are alternatives. Azithromycin is an alternative in children and pregnant women with scrub typhus , and when doxycycline-resistance is suspected. Ciprofloxacin cannot be used safely in pregnancy and is associated with stillbirths and miscarriage. Combination therapy with doxycycline and rifampicin is not recommended due to possible antagonism . Dr.T.V.Rao MD 25

Prevention :

Prevention Vector control : Application of insecticides eg : lindane or chlordane to ground and vegetation. Environmental control Personal protection Dr.T.V.Rao MD 26

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Programme Created by Dr.T.V.Rao MD for Medical and Paramedical Students in the Developing World Email Dr.T.V.Rao MD 27

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