Etiology First isolated from patient by Japanese in 1930. Named O tsutsugamushi in 1995. Obligate intracellular Giemsa-positive. 0.3 ～ 0.6um×0.5 ～ 1.5um, about the size of bacteria a cross immunity with proteus OXk Sensitive to Chloramphenicol and tetracycline
Pathogenesis and pathology Inoculation Invade Local lymph node Spread by Blood stream Invade Vascular endothelium Papule maculoppular eschar ulcer Enlargement of local lymph node General symptoms of intoxication General organ hyperaemia. Systemic lyphadenopath
Clinical Manifestation Incubation period is 4~21 Sudden onset with a fever 1st week, systemic toxic symptoms 2nd week, get worse,complication 3th week, convalesce
Specifc features 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.
Specifc features Maculopapular rashes Onset: Appear at the end of the 1st week, lasts 3~7d. Location: Chest, abdomen, whole trunk, or upper and lower limbs. rarely involves the face, palms and soles..
Specifc features － Lymphadenopathy Regional lymphadenopathy: occur at the end of the 1st week. localize: the draining lymph node around the primary eschar characterized by tenderness and enlargement Generalized lymphadenopathy: appears 2-3 days later.
Laboratory Examinations Blood routine: Leukopenia Normal of WBC, Elevation with some complications. Biochemical examination Injure of liver fuction
Laboratory Examinations －－ Serologic examination Weil-felix: Can be positive as early as 4th day after onset. >1:160 or increase 4 times during the course. Easy for operation but poor for specialization. IFA: Almost the gold standard. Positive at the end of the 1st week. Last for years. IIP: Comparable to those from IFA. More available.
Laboratory Examinations －－ Pathogenic examination Culture: Mouse is usual experimental animal. spleen and liver are stain with Gimsa. PCR: Detect the orientia DNA Not routinely available
Diagnosis Epidemiology data ： Visit the endemic area during the past 3weeks. working, camping or sitting on grass Clinical manifestation ： Eschar,regional lyphadenopathy, fever, maculopapular rash, leukopenia, failed therapy with common antibiotic drug. Laboratory examination ： Weil-felix reaction with titers beyond 1:160 or fourfold rise during the course of disease.
Differential Diagnoses Epedemic typhus: occur in winter and spring, bite by louse, Weil-felix with OX19 is positive. Typhus: Slow onset, persistent high fever, mental apath, bradycardia, digestive symptoms, rose rash, no eschar, widal test positive. Blood culture of typhus bacillus is positive. Leptospirosis: Tenderness of calf muscle, microsopic demonstration
Treatment Sensitive antibiotics decrease fatality from 40% to 2%. － General treatment Enough bed rest, rich vitamin and plenty of water. Intensive nursing care and prevent complication
Treatment － Pathogen treatment Chloramphenicol : 2g per day for adult, or 25mg/kg of bw per day for children. Doxycycline: 0.2g per day for adult. Roxithromycin: 0.6g per day for adult, 2~3mg/kg/d for child Azithromycin,tetracycline are also sensitive. Half dose for 7- 10 days after defervescence
Treatment Strains resistant to doxycycline and chloramphenicol Combination therapy with doxycycline and rifampicin should be used
Prevention Source of infection: Rat Routes of transmission: Trombiculid mite Protect succeptibility: Avoid being bitten No effective vaccine against scrub typhus
Summary Scrub typhus is caused by orientia tsutsugamushi. People acquire oriential infection when being bitten by larva of trombiculid mite. The clinical manifestation can be characterized by fever, eschar, regional lymphadenopathy, maculopapular rash and leukopenia. (Typical eschar is a scrub typhus marker.) Organism of scrub typhus is sensitive to chloramphenical and tetracycline.