Scrub typhus is an acute infectious illness caused by the bacteria Orientia tsutsugamushi, which is transmitted to humans through bites from trombiculid mites. It is endemic in parts of Asia and the Pacific. Symptoms include high fever, headache, rash and eschar at the site of the mite bite. Diagnosis is made through serologic tests detecting antibodies or PCR. Treatment is with doxycycline or azithromycin. Preventive measures include protective clothing, insect repellents and vector control. With treatment, prognosis is good, but mortality can be high without treatment or if complications develop.

1. SCRUB TYPHUS
Prepared by
Dr. Anil Giri
MPH First Year
KIST Medical College & Teaching Hospital

2. DEFINITION
Scrub typhus is an acute, febrile,
infectious illness that is caused by
Orientia tsutsugamushi
(an obligate (absolute/compel)
Intracellular gram-negative bacteria).

3. Scrub means low shrub & grasses that
harbors the vector (trombiculid mites
also called chiggers).
However, this term is not entirely accurate, in
that scrub typhus can also be prevalent in
areas such as sandy beaches, mountain,
deserts and rain forests.

4. COMMON TROPICAL INFECTIOUS DISEASES
 Rickettsioses:
Scrub typhus
 Orientia tsutsugamushi
 Vector: Trombiculid mite (chigger)
Leptothrombidium spp.
Murine typhus
 Rickettsia typhi
 Vector: Xenopsylla cheopsis
 Enteric fever
 Typhoid fever
 Paratyphoid fever
 Nontyphoidal salmonellosis Tuberculosis
 Malaria Dengue infection
 Helminthic infection Infective diarrhea
 Leptospirosis Melioidosis

5. HISTORY OF DISEASES:-
 Scrub typhus is one of the tropical rickettsial
diseases.
 This was first described in China in 313 AD.
 Bacteria was first isolated in Japan in 1930 AD.
 Orientia is genus of bacteria in family Rickettsiaceae.
 US cases have been imported from regions of the
“tsutsugamushi triangle,” which extends from
northern Japan and eastern Russia in the north to
northern Australia in the south and to Pakistan and
Afghanistan in the west, where the disease is
endemic.

7.  Western medicine became especially interested in
scrub typhus during military campaigns fought in
East Asia. During World War II, 18,000 cases were
observed in Allied/suppoter troops stationed in rural
or jungle areas of the Pacific theatre. Scrub typhus
was the second or third most common infection
reported in US troops stationed in Vietnam and still
infects troops in the region.
 Currently, it is estimated that about 1 million cases
of scrub typhus occur annually and that as many as
1 billion people living in endemic areas may
have been infected by O.tsutsugamushi at some
time.

8. EPIDEMIOLOGY:-
 Scrub typhus is endemic in regions of eastern Asia
and the southwestern Pacific (Korea to Australia)
and from Japan to India and Pakistan.
 It is generally a disease of rural villages and
suburban areas and is normally not encountered
in the cities.
Age-, sex-, and race-related demographics
 People of all ages are affected equally by scrub
typhus. Men and women are affected with equal
frequency. No race-related differences in incidence
have been documented.

9. IN NEPAL
 Aug 2015 after 3 months of Earthquake, case noted
in:- Chitwan, Lalitpur, Dhading,
Sankhuwasabha, Bhojpur, Dhankuta, Siraha,
Kailali & Ramechap.
 A total of 101 confirmed scrub typhus cases
were reported from 16 districts in 2015. Out of
them, eight cases died, accounting for a crude
case fatality rate of 8%.
 By the end of August 2016, more than 500
confirmed cases and six additional deaths were
reported from the various districts of the
country.
 2016—831 cases of scrub typhus were reported in 47
districts and 14 people died by the end of that year.

10. From 2015 to 2017,
1239 scrub typhus cases were
confirmed with the largest outbreak
occurring in 2016 with 831 (67.1%)
cases.
The case fatality rate was 5.7% in 2015
which declined to 1.1% in 2017.
A nationwide outbreak of scrub typhus
was declared as the cases were
detected in 52 out of the 75 districts of
Nepal.
Seasonal trend was observed with a
peak during August and September.

11. a total of 1,999 people were
infected with the disease; in
2020,
In 2021, the number declined
to 1,026.
Over 260 people have been infected
with the disease since the start of
2022 till May 12, 2022.

12. SUSPECTED CASE

13. ETIOLOGY
 Scrub typhus is caused by Orientia
tsutsugamushi, an obligate intracellular gram-
negative bacterium that lives primarily in mites
Trombicula genus
Leptotrombidium(genus) akamushi(Sp)
Leptotrombidium deliense .
 This organism is found throughout the mite’s body but is
present in the greatest number in the salivary
glands.

15. NOT TO CONFUSE WITH:

16. MODE OF TRANSMISSION:-
 Scrub typhus is often acquired during occupational
or agricultural exposures because active rice fields
are an important reservoir for transmission.
 Taking a rest directly on the grass,
 working in short sleeves,
 working with bare hands, and
 squatting to defecate or urinate posed the highest
risks.

18. Pathophysiology:-
 When the mite feeds on rodents (eg, rats,
moles/छुचुन्द्रो, and field mice, which are the
secondary reservoirs for bacteria) or humans,
the parasites are transmitted to the host.
 Wild rats serve as the natural reservoir for the chiggers
(and represent a risk factor for human infection), but they
are rarely infected with O tsutsugamushi.
 Only larval Leptotrombidium mites (chiggers) transmit the
disease.
 Orientia is also transmitted transovarially in mites and can
unbalance the sex ratio of offspring in favor of females, further
propagating infection.

24. SIGNS AND SYMPTOMS
 History:
 Travelling to scrub typhus endemic area.
 Chigger bite (often painless and unnoticed)
 Incubation period of 6-20 days (average, 10 days)

25. SYMPTOMS:-
 High fever (40-40.5°C [104-105°F]), occurring
more than 98% of the time,
 Headaches,
 Shaking chills,
 Red eye,
 Anorexia, abdominal pain, nausea, vomitting
 General apathy, regional lymphadenopathy
 Cough, difficulty in breathing
 Centrifugal (center to periphery) macular rash on
the trunk. In adults, the eschar is often truncal,
whereas children may have lesions in the
perineum.

27. Rash; a small, painless, gradually enlarging papule, which
leads to an area of central necrosis and is followed by
eschar formation in centrifugal (central to peripheral)
pattern.

30. PHYSICAL FINDINGS:-
 Tender regional or generalized lymphadenopathy,
occurring in 40-97% of cases
 Enlargement of the spleen,
 Altered consciousness.
 If acute hearing loss is present (as may be the case
in as many as one third of patients, according to
some reports), it strongly points toward scrub
typhus.

32. COMPLICATIONS:-
 Central nervous system (encephalitis), pulmonary
(ARDS) or cardiac involvement.
 Rarely, acute renal failure, shock and disseminated
intravascular coagulation (DIC) .
 If the patient does not receive treatment, symptoms
may last for more than 2 weeks; with treatment, the
patient recovers within 36 hours.

34. DIAGNOSIS
Laboratory studies in patients with scrub typhus
may reveal the following:
 Early lymphopenia with late lymphocytosis
 Decreased CD4:CD8 lymphocyte ratio
 Thrombocytopenia
 Elevated transaminase (SGOT, SGPT) levels (75-
95% of patients)
 Chest radiography may reveal pneumonitis,
especially in the lower lung fields.

35. Laboratory studies of choice are serologic
tests for antibodies, including the
following:
 Indirect immunoperoxidase test
 Indirect fluorescent antibody test
 Dot immunoassay
 Rapid immunochromatographic tests for detection
of IgM and IgG
 Polymerase chain reaction (PCR) assay
 Rapid diagnostic reagent for scrub typhus
 Weil-Felix OX-K strain agglutination reaction

36. ELECTRON MICROSCOPIC
VIEW

38. MANAGEMENT:-
 Antibiotic therapy.
Drug of choice:-
 Capsule Doxycycline (Tetracycline) 100mg twice
daily for 7-10 days. Provided free by Nepal
government.
For Pregnant & Children:-
 Tablet or Syrup Azithromycin (Macrolides) 10mg per
kg per day for 5 days.
Others:-
Rifampicin 600-900mg per day for 7 days.
Clarithromycin 500mg per day for 10 days.
Ciprofloxacin 500mg twice daily for 10days.

40. SUPPORTIVE TREATMENT:-
 Normal diet & rest.
 Inpatient care may be necessary for patients with
severe scrub typhus. In such cases, meticulous
supportive management is necessary to abort
progression to DIC or circulatory collapse.

41. PREVENTIVE MEASURES
in endemic areas include the following:
 Protective clothing:- Wearing a long-sleeved
shirt while working, keeping work clothes off the
grass, and always using a mat to rest outdoors
showed protective associations.
 Insect repellents
 Short-term vector reduction using
environmental insecticides and vegetation
control.

43. CHEMOPROPHYLAXIS REGIMENS:-
 A single dose of doxycycline given weekly, started
before exposure and continued for 6 weeks after
exposure.
 No effective vaccine is available.

44. PROGNOSIS:-
Prognosis varies and depends on the
severity of illness, which relates to the
different strains of O tsutsugamushi,
as well as to host factors.
In patients who are not treated,
mortality ranges from 1% to 60%,
depending on the patient’s age, the
geographic area, and the particular
strain responsible for the infection.

45.  With appropriate antibiotic treatment,
mortality from scrub typhus is quite rare,
and the recovery period is short and usually
without complications.
 However, mortality is still approximately
15% in some areas as a consequence of
missed or delayed diagnosis.[31] If severe
complications such as acute respiratory
distress syndrome (ARDS) arise, mortality
may still be high.

47. REFERENCES
 https://nhrc.gov.np/wp-
content/uploads/2017/11/Final_Scrub.pdf
 https://bmcinfectdis.biomedcentral.com/articles/10.1
186/s12879-021-05866-6
 https://tkpo.st/3LcXvVE
 https://kathmandupost.com/health/2022/05/12/scru
b-typhus-a-neglected-disease-emerging-as-new-
health-challenge

48. DR. ANIL GIRI
MPH FIRST YEAR
KIST MEDICAL COLLEGE & TEACHING HOSPITAL