Abstract Korea, China, Philippines, Australia, India, Pakistan,

Abstract

Scrub typhus, a vector borne zoonotic disease, has
become the leading cause of treatable febrile illness in endemic geographies. Morbidity and mortality are high
among the elderly with underlying disease, in rural areas. Fatal complications are rare among healthy adults in the metropolitan
areas, with timely treated. In the occupational sector, scrub typhus hardly occurs among carpenters assembling pallets using manufactured wood. The author
presents here, a fatal case, probably complicated by scrub typhus myocarditis. Despite
of uncertainty on cause of death, this unusual work related death was
compensated by the Korea Workers’ Compensation &
Welfare Service (KCOMWEL). This might be a
warning signal of re-emerging infectious diseases to re-emphasize preventive
strategy in every sector of public health including occupational and
environmental hygiene.

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Introduction

Mite-borne Scrub typhus, an endemic typhus, is geographically distributed across 13 million square
kilometer of the tsutsugamushi triangle including Japan, Korea, China,
Philippines, Australia, India, Pakistan, Tibet, Afghanistan, and the USSR.1
A median incidence of 4.6/100,000, mortality rate of 6.0% among those untreated
and 1.4% among those treated has been reported in the tsutsugamushi triangle.(1)
Scrub typhus invades the blood vessels in the host’s body, causing
widespread perivasculitis
in the organs.2-4 This results in
various complications; 2-8
pneumonitis
and meningoencephalitis are relatively common, whereas myocarditis
is unusual, subclinical and has been rarely reported. 9-12

Carpentry-related
occupational diseases might be
related to
exposure of multiple hazards such as carbon monoxide,
volatile organic compounds, noise, wood dust and ergonomic factors. Occupational
scrub typhus rarely occurs among carpenters assembling pallets using manufactured wood. The
author reports here, an unusual case of a carpenter with delayed complication
of fatal myocarditis, approved for survivors’
benefit from KCOMWEL. This is the
first carpentry related occupational death by scrub typhus in Korea.

 

Case report

The widow signed the
informed consents to report this case, and permission number from IRB, of the
author’s institute, is EMC 2016-05-005.

A 56 year-old man, with no significant medical history except a surgery for a left clavicular fracture in 2000, visited the emergency unit on Nov 2nd,
2015.
His pulse rate and
body temperature were 130/min and 39.1°C, respectively. The physical
examination revealed a 1´1
cm necrotic skin lesion with erythematous rim in the
right axilla, with several erythematous maculopapular
rashes on his trunk, right side of the neck,
and on both arms.
The chest X-ray revealed left pleural thickening. ECG showed sinus
tachycardia (Heart Rate
124/min) with left ventricular hypertrophy. Other investigations were AST 228 IU/L, ALT 130 IU/L, CK 1204 IU/L, CRP 6.34 mg/dL; an
immunochromatographic assay for scrub typhus was positive, and immunofluorescent antibody IgG titer against O.
tsutsugamushi was
1:1280.

His general condition improved after 3 days of treatment with intravenous azithromycin. On the 5th day, he complained of dyspnea.
Vital
signs were stable, but the chest X-ray revealed haziness on lower lobes, bilaterally. An echocardiogram revealed
severe left ventricular systolic dysfunction; the left ventricular
ejection fraction was 13% with global
hypokinesia and left atrial/ventricular dilatation. A chest
computed tomography scan confirmed bilateral pleural effusion, and a
cardiac
magnetic resonance imaging revealed dilated cardiomyopathy. A coronary computed tomography angiography showed no evidence of coronary atherosclerosis, with
intact coronary arteries; ischemic heart disease was thus ruled
out. The
patient was diagnosed as scrub typhus–induced myocarditis according to the diagnostic
criteria for clinically suspected myocarditis of the European Society of Cardiology
Working Group on Myocardial and Pericardial Diseases. 13

The patient showed symptomatic improvement
on the 7th day of treatment at the cardiology unit and was discharged
with scheduled outpatient follow-up. Until the follow up on 24th Nov, there was
no symptom of aggravation. However, more than 2
months later, on 2nd Feb, 2016, he presented
with aggravating
dyspnea, of abrupt onset
9 hours
before admission. Vital
signs showed blood pressure 80/60
mmHg, pulse rate 132/min, respiratory rate 31/min and body temperature 37°C. Arterial
blood gas analysis revealed severe metabolic acidosis; blood pH was 7.18, PaCO2
13.0 mmHg, PaO2 114.0 mmHg, HCO3-4.9 mmEq/L, and base excess -20.7 mmEq/L.
Furthermore, N?terminal pro-brain natriuretic peptide and D-dimer levels were
elevated to 27157 pg/mL
and 1.62 µg/dL,
respectively. The white blood cell count was 1290/?L, implying leucopenia and C-reactive
peptide was 15.43 mg/dL. The blood chemistry showed an
electrolyte imbalance, with serum
Na+ 120
mEq/L, serum Cl- 89 mEq/L. Estimated GFR was 29 mL/min/1.73 m2 . Liver
enzymes were elevated as AST 188
IU/L, ALT 169
IU/L, and g–GTP 65 IU/L. Chest X-ray revealed no significant findings. Septic shock and multi-organ failure were
suspected in unknown origin. However,
no suspected infectious agent was found on laboratory investigation. The
patient died next day and there was no
chance to perform further investigation for the cause of death.

On the medical records, an insect
bite was reported at his workplace on 26th Oct, 2015. No outdoor activities such as gardening/farming, landscaping or traveling to rural area were reported for the past couple of months. He had been assembling
pallets using processed wood and pneumatic
nail guns for 2 years. Total number of workers was two, including
an employer. Wild logs and recycled wastes were piled up in the small yards of other companies
adjacent to his workplace (Figure 1). The
surroundings had poor hygiene; insect vectors and rats
could easily infiltrate to his plant (Figure 2). In the questionnaire, his employer
described he could see rats in the workplace.

 

Discussion

  The incidence of scrub typhus is positively correlated with the physical environment (temperature, precipitation, climate change) and human activities.14-16 Nationwide  surveillance
of chigger mite, the vector of scrub typhus, reported a significant increase in
the  number per captured rat from 86.0
(2005~2007) to 137.8 (2011~2013).17 Nationwide
 surveillance of scrub typhus, initiated
in 1994, reported over 1000 cases from 1998, over  6000 cases from 2005, over 10,000 cases in
2013.  The prevalence from 2001 to 2013 was highest in females (62.84%), 60-69
year old group (19.4%), and in the months of October/November (75.3%).12

Scrub typhus had been known to affect mainly rural
populations, but nationwide surveillance has revealed a sharp increase among
metropolitan populations. Comparing the change in prevalence across major
cities from 2003 to 2012, lowest average prevalence rate in Seoul increased
0.54 to 3.75, medium rate in Daejeon 2.03 to 33.86 and highest rate in Ulsan
2.81 to 59.73, respectively.16 

Korean Center for Disease Control (KCDC) started reporting deaths complicated by scrub typhus since 2011, and 75 deaths have been
reported until 2016.18 Mortality rate from scrub typhus was
reported highest in 2013 (0.22%) overall. Most of the deaths were seen in
people above 70 years of age(73.9%), those with eschar positive(91.3%), and
those with underlying diseases(73.9%), (% from total mortality group),
respectively.12 Sepsis(56.5%) was the most prevalent complication
followed by pneumonitis, Acute Respiratory Distress Syndrome, and Acute Renal Failure.12
Care in the ICU and higher acute physiology and chronic health evaluation
(APACHE) II score can be independent predictive factors of mortality.8
However, fatal myocarditis complicated by scrub typhus has been rarely reported;
the known cases include a 85 years-old woman with underlying hypertension,
diabetes and angina in Korea,19 and two children in Thailand.20

According to the data of 1,062 work related infectious
disease cases compiled by KCOMWEL during 2006~2011, the most common cause was
scrub typhus (567, 53.4%), followed by tuberculosis (227, 21.4%), viral
hepatitis (55, 5.2%), and viral influenza (53, 5.0%). Unskilled laborers,
including short-term contract workers (unemployed) in public sectors, were most
vulnerable to scrub typhus, followed by health care professionals. 21

Despite no significant underlying disease, availability
of timely diagnosis and proper treatment corresponding to the symptoms, and being
relatively young to develop fatal complications, the infection in this case progressed
to an unusually delayed type of fatal myocarditis/ cardiomyopathy, combined
with sepsis of unknown origin and multi-organ failure. From complete remission
of infection to complication of sudden fever/death, the latent period was
slightly over 2 months. Chung et al.22 reported persistence
of O. tsutsugamushi
for several months after recovery in six cases. Watt
et al.23
presented the possibility of scrub typhus reactivation triggered by
leptospirosis. Last hospitalization after
9 hours fever  was too short to investigate
the cause of death. No other co-morbidity condition or infectious agent was found
for the septic shock and death, except previous myocarditis complicated by scrub
typhus.

Considering,
that the
scrub typhus transmission in urban areas is steadily increasing in the endemic areas,14-16,24 this case serves as a warning for the risk of morbidity
and mortality among other occupations. Basic concepts of health/hygiene protection at
worksite should be re-emphasized; safety and
hygiene as well as education of the target population by healthcare
professionals is necessary to reduce morbidity and mortality from scrub typhus
in endemic geographies.

 

Disclaimer statements

The authors are
the sole contributors

No Funding

No Conflict of
Interest

 

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