Vol.2, No.7, 427-431 (2013) Case Reports in Clinical Medicine
Copyright © 2013 SciRes. OPEN ACCESS
Strongyloides stercoralis in an immunocompetent
adult: An unexpected cause of weight lost
Lia Marques1*, André Rodrigues1, Elisa Vedes2, Dores Marques1
1Serviço de Medicina III, Hospital de Pulido Valente, Centro Hospitalar Lisboa Norte, Lisboa;
*Corresponding Author: marques.lia@gmail.com
2Unidade de Cuidados Intensivos do Hospital da Luz, Lisboa
Received ************* 2013
Copyright © 2013 Lia Marques et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
S trongyloides stercoralis infect s at least 100 mil-
lion humans worldwide each year, but its preva-
lence is underestimated. It is endemic in hot and
humid climates as well as resource poor coun-
tries with inadequate sanitary conditions. The
rise of international travel and immigration has a
positive impact in strongyloidiasis. Due to its
unique auto infection life-cycle, Strongyloides
may lead to chronic infections remaining unde-
tected for decades. Strongyloidiasis is most of-
ten asymptomatic but it has a wide ra nge o f c lin i-
cal presentations. The two most severe forms of
strongyloidiasis are hyperinfection and dissemi-
nated syndromes. These occur most often in pa-
tients with impaired cell mediated immunity. A
42-year-old immunocompetent man presented
with chronic watery diarrhea, malaise, upper ab-
dominal pain, anorexia and weight lost. Strongy-
loides stercoralis was identified in stool sam-
ples and duodenal biopsy. The patient was suc-
cessfully treated with albendazole. The authors
report a case of strongyloidiasis hyperinfection
in an immunocompetent host 20 years away
from an endemic area and make a literature re-
Keyw ords: Strongyloides st er corali s;
Immunocompetent; Hyperinfection
Strongyloides stercoralis (S. stercoralis) is an intesti-
nal nematode endemic in tropical and subtropical coun-
tries and in the Southeastern United States [1-5]. The
helminth is also present in some restricted areas of the
European Union such as northern Italy, rural Romania or
southeastern Spain [4]. S. stercoralis affects 30 - 100 mil-
lion people worldwide [4,6,7], but this current estimate
dates back to review articles published between 1989 and
1996 [2,8]. Recen t pu blication s state that strongyloidiasis
remains an underestimated public health problem [1,4,9,
10]. A 10-year multicenter surveillance program per-
formed in Spain and published in 2013, highlights the
high prevalence of S. stercoralis cases imported by im-
migrants, most being asymptomatic and with eosinophilia
Strongyloidiasis is caused by the female nematode S.
stercoralis. It’s life cycle is comprised of 2 parts: a free-
living cycle outside of the host as rhabditiform larvae
and a parasitic life cycle as infective filariform larvae [5,
11-14]. During the free-living cycle in the soil, Strongy-
loides transform from rhabditiform larvae into infective
filariform larvae, which penetrate the human skin and
proceed into the submucosa, then into the venous circu-
lation, and then toward the right heart and lungs [5,11-
14]. During the pulmonary maturation process, Strongy-
loides larvae induce alveolar capillary bleeding and po-
tent eosinophilic inflammation, resulting in eosinophilic
pneumonitis [5,11-14]. From the alveoli, the larvae mi-
grate up the pulmonary tree and trachea, reaching the
larynx, were they are swallowed and travel to the stom-
ach and small bowel [5,11,13]. Inside the GI tract, Stron-
gyloides larvae mature into adult female worms that em-
bed themselves in the mucosa of the small bowel and
produce eggs via parthenogenesis. Within the intestinal
lumen, the eggs hatch into non infective rhabditiform
larvae, which are excreted, along with stool, into the en-
vironment [5,11]. Some larvae, however, re-enter the
blood stream through the bowel wall and migrate through
lungs, it reenters the host via enteral circulation (endo-
autoinfection) or perianal skin (exoautoinfection) by-
passing the soil cycle [1,4,5,11-14]. Thus, parasites can
remain in the human body for th e remainder of the ho st’s
L. Marques et al. / Case Reports in Clinical Medicine 2 (2013) 427-431
Copyright © 2013 SciRes. OPEN ACCESS
life. This ability for auto infectio n implies that infestation
can be life-long and extremely heavy [1,4,5,15].
Strongyloidiasis is generally benign and asymptomatic,
eosinophilia and larvae in stool may be the only indica-
tors of infection, but eosinophilia is not obligatory [1,5,
16]. In immunocompromised host, it can cause substan-
tial intestinal disease and can disseminate widely to ex-
tra-intestinal sites, this clinical form of the infection be-
ing called hyperinfection syndrome [1,4,5]. Hyperinfec-
tion means accelerated auto infection characterized by
development or enhanced GI and pulmonary symptoms
with increased numbers of larvae seen in stool or sputum,
restricted to the organ of auto infective cycle [1,5]. Typi-
cally, hyperinfection syndrome occurs in patients from
endemic areas of S. stercoralis who receive immunosup-
pressive therapy. The diagnosis in such patients may be
difficult because of a lower incidence of eosinophilia. Dis-
seminated disease is defined by the presence of parasites
outside of the traditional life cycle (i.e. , in organs other
than the skin, GI tract, or lungs) [1,5,15,18,19]. Involve-
ment of brain, heart, gall bladder, and kidney has been
reported [1,6]. Although hyperinfection syndrome can
occur in any host, disseminated disease occurs mainly in
immunocompromised individuals [5,14,18].
In immunocompetent hosts, Strongyloides typically cause
a low-grade chronic infection, which has been seen even
up to 40 years after exposure [1,19]. Most patients are
completely asymptomatic. Some have mild gastroin-tes-
tinal, cutaneous, or pulmonary symptoms with or with-
out fever. These symptoms may be acute or they may
wax and wane chronically before spontaneous resolution.
Gastrointestinal presentations include diarrhea and ab-
dominal discomfort, nausea, anorexia, weight loss caused
by gastritis, or enteritis with ulceration. Patients also can
have occult gastrointestinal blood loss or fat and vitamin
B12 malabsorption [20]. Pulmonary symptoms include
cough and dyspnea, sometimes associated with wheezing,
caused by larval migration through the lungs, or eosino-
philic pneumonia [20]. The pathognomonic rash of Strongy-
loides infection is larva currens that likely represents an
allergic response to migrating larvae [20 ].
The clinical presentation of hyperinfection syndrome
is similar to that of classic strongylo idiasis [5]. However,
due to increased parasite turnaround and dissemination,
patients with hyperinfection syndrome and disseminated
disease often have catastrophic clinical manifestations
such as shock, disseminated intravascular coagulation,
meningitis, renal failure, and /or respiratory failu re [5 ,12 ].
Mortality with hyperinfection can be up to 87% in the
immunosu p pressed patients [20].
The diagnosis of S. stercoralis is often delayed due to
the presence of sub clinical or poorly symptomatic cases,
the usually low parasite load and irregular larvae output
and the lack of a gold standard diagnostic test [4]. Diag-
nosis is based on detection of larvae in the stool or spu-
tum. The sensitivity of a single examination is on ly 25 to
30%, but increases to 70% to 85% with three consecutive
stool samples using the agar plate method of larval de-
tection [5,20-23]. Detection of larvae in the duodenal
aspirates is more sensitive and hence should be consid-
ered when there is a clinical suspicion of hyperinfection
[24]. In the past years serological and immunological
stool tests have been developed in order to improve di-
agnostic sensibility in immunocompromised and post
transplant patients [24-26]. S. stercoralis serological as-
says can simplify the diagnosis and overcome the poor
sensitivity of single stoo l exams, but its specificity is less
well defined [27]. Problems of cross-reactivity seem to
arise especially in areas where other nematodes are also
endemic. New and promising tools such as serological
methods based on recombinant antigens or PCR are also
available in some referral centers. However, the optimal
diagnostic strategy, both for epidemiolo gical surveys and
for individual diagnosis and screening, has yet to be de-
fined [28,29].
Str o ng ylo id e s i nf ec ti on is treated with the aim to erad i-
cate strongyloidiasis. In chronic infection, ivermectin
(200 mg/kg orally, once daily) for 1 - 2 days or albenda-
zole (400 mg orally, twice daily) for 7 days is sufficient.
A number of randomized clinical trials have been carried
out, showing that ivermectin is the drug of choice, and a
single dose is highly effective (over 90%) [9,28,29].
However, drug efficacy may have been overestimated, as
faecal-based methods alone have been used to assess
cure in almost all studies. Multiple doses may be neces-
sary to obtain the goal of eradication in a patient, and the
current indications by Wold Health Organization refer to
a schedule of two consecutive d ays as a possible alterna-
tive to the single dose [28].
In recent years there has been an increasing number of
papers concerning strongyloidiasis in medical literature,
mainly case reports in immunocompromised and post
transplant patients, but also some reports of strongyloi-
diasis in immunocompetent patients and with atypical
presentations [1,17,20]. The actuality of this re emerg-
ing infection justifies the present case report of stron-
gyloidiasis in an immunocompetent otherwise healthy
A 42-year-old man was admitted to our hospital with
chief complaints of chronic diarrhea for the previous
three months. He had a history of passing watery and
foul smelling stool. He complained of upper abdominal
pain, anorexia and weight lost (4 kilograms over three
months). He was natural from Guinea Bissau, and had
lived in Portugal for the past 20 years, during this time
L. Marques et al. / Case Reports in Clinical Medicine 2 (2013) 427-431
Copyright © 2013 SciRes. OPEN ACCESS
he hadn’t return Guinea Bissau. He had been recently
medicated with proton pump inhibitor (omeprazole) after
a normal upper endoscopy that was performed for upper
abdominal pain in the previous mouth. From the past
medical history only to point alcoholic habits of 46 g/
ethanol/day. The patient denied other symptoms namely
vomits or fever. He had no history of tick exposure, con-
tact with sickness, or recent travel.
Physical examination revealed a weight of 59.6 kg
(body mass index of 18 Kg/m2), dehydration, abdominal
examination was notable for diffuse pain and tenderness.
Anal exam was not possible due to painful anal fissure
and systemic examination findings were normal. There
was no lymphadenopathy, clubbing, skin lesions and/or
pedal edema.
His laboratory investigations were as follows: Total
leucocyte count: 13,050 × 109/L with normal differential,
reactive C protein mildly elevated (2.8 mg/dL), no throm-
bocytopenia and no anemia, mild renal impairment (urea
30.70 mmol/L; Creatinine 141.44 mmol/L), hyponatre-
mia (127 mmol/L), hypokalemia (2.7 mmol/L). Chest roen-
togram (Figure 1) has shown left hilar opacity sugges-
tive of lymph node enlargement. Abdomen ultrasound
was normal.
During the hospital stating the patient remained apy-
retic, with liquid diarrhea (5 to 6 passages of liquid
brown stools without blood or mucus). The investiga-
tions revealed: Serology for human immunodeficiency
virus and acute h ep atitis A, B, and C infection were nega-
tive, thyroid function was in the normal range, erythro-
cyte sedimentation rate 103 mm in 1 h. Stool fat content
was in the normal range. Colonoscopy wasn’t performed
due to painf ul ana l fissure.
The pa tie nt u nd erw ent upp er endoscopy revealing mild
esophagitis and duodenitis with nematodes most sugges-
tive of S. stercoralis visualized within the crypts. To in-
vestigate consumptive symptoms and clarify the x-ray
abn ormality a computer tomography (CT) was performed
and showed (Figure 2): pulmonary micro nodules the
Figure 1. Chest roentogram—left hilar opacity suggestive of
lymph node enlargement.
left inferior lobe and the right superior lobe suggesting
inflammatory or infectious focus; lymph node enlarge-
ment in the left hilar area; intestinal distension without
enlargement of abdominal lymph nodes. Bronchial Fi-
broscopy revealed generalized inflammatory signs. Bron-
choalveolar lavage analysis was negative for mycobacte-
rias, bacteria and neoplastic cells. Bacteriological and
mycobacterium stool and blood analysis were negative.
Serial stool samples were collected and subsequently re-
vealed many S. stercoralis larvae. Treatment with oral
albendazole (400 mg twice daily) was initiated and the
patient completed a 7 day regime with good clinical and
laboratory responses. Three months after hospital dis-
charge the patient was reevaluated and remained asymp-
tomatic, diarrhea subsided and he had a 10 Kilograms
weight gain. Serial stool analysis was obtained and consis-
tently negative for ova and parasites.
The presented case represents a S. stercoralis infection
in an immunocompetent adult. In our patient, stool sam-
ples were positive possibly because of a high parasitic
burden. The chest roentogram and CT findings may be
attributed to the pulmonary phase of the parasite life cir-
cle. In fact, chest radiography can reveal diffuse alveolar
or diffuse interstitial infiltrates, segmental alveolar infil-
trates, or pleural effusions [20]. Endoscopic findings also
support the diagnosis. The endoscopic manifestations of
strongyloidiasis are broad, ranging from normal appear-
ing mucosa to ulcerative and catarrhal duodenitis [5].
Patients with a clinical and histopathologic diagnosis of
“idiopathic” eosinophilic gastroenteritis should also be
thoroughly evaluated for Strongyloides because larvae
may not always be apparent on initial evaluation, and
therapy with corticosteroids may lead to fatal hyperin-
Figure 2. Computerized tomography imagery with pulmonary
micro nodules the left inferior lobe and the right superior lobe
suggesting inflammatory or infectious focus; lymph node en-
largement in the left hilar area; intestinal distension without
enlargement of abdominal lymph nodes.
L. Marques et al. / Case Reports in Clinical Medicine 2 (2013) 427-431
Copyright © 2013 SciRes. OPEN ACCESS
fection if the diagnosis of strongyloidiasis is missed [5].
Thus, evaluation should include several stool examina-
tions and upper endoscopy procedures with duodenal
biopsies. Multiple biopsy specimens should be taken to
increase the histopathologic yield, even if the duodenal
mucosa does not manifest any major abnormalities [5].
In this patient there was no eosinophilia, but it is pre-
sent in 50% to 80% of patients with mild infection. In
contrast, a low eosinophil count occurs in patients with
hyperinfection and disseminated disease [20,30], as seems
to be the present case.
Low socioeconomic status, alcoholism, white race,
and male gender have been associated with higher preva-
lence of Strongyloides stool positivity [31]. The patient
had all of these factors and was original from an endemic
region (Guinea Bissau) and was probably a chronic host
for S. stercoralis acquired before his immigration to Por-
tugal, 20 years earlier. It is postulated that the steady
immigrant influx to the European Union has increased
the number of infected carriers with S. stercoralis [4].
But presently there is no data on portuguese epidemiol-
ogy for S. stercoralis, thus epidemiological studies are
needed. To support this need there is widespread agree-
ment in the scientific community that its prevalence is
largely underesti mated [1,10,19].
The clinical manifestation of hyperinfection syndrome
varies widely and the onset may be acute or insidious.
There is no quantitative definition, but it is characterized
by an increase in gastrointestinal or pulmonary symp-
toms with an increased larval load in th e stool or sputum.
GI syndrome manifestations include watery diarrhea,
weight loss, vomiting, and occasional bleeding. Usually
symptoms of pulmonary strongyloidiasis include cough,
dyspnea, wheezing, pulmonary hemorrhage, and pleural
effusion [30]. A recent report was however able to iden-
tify through questionnaires and stool evaluations that
individuals infected by S. stercora lis were more likely to
complain of stomach ache [32,33]. This patient presented
with an insidious form of disease, but his clinical mani-
festations fit the hyperinfection syndrome diagnosis.
Strongyloidiasis is commonly reported in immuno-
compromised patients; however, our patient was immu-
nocompetent as his HIV status was negative, the history
of alcoholism may have induced some imunosupression
contributing to susceptibility to hyperinfection. The pa-
tient responded well to albendazole therapy and there
were no Strongyloides larv ae in the stool wh en examined
after therapy. That and his favorab le clinical evo lu tion all
support the diagnosis.
The present patient was unusual in that he was other-
wise healthy and immunocompetent who presented with
pulmonary and gastrointestinal symptoms of strongy-
loidiasis hyperinfection syndrome. He had risk factors
for strongyloidiasis: he was natural from an endemic area
and had heavy alcohol consumption. The authors high-
light the importance of correctly diagnose and treat strongy-
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