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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_182_библиотеки_им_акад_М_И_Перельмана.pdf
A
Adults can survive in human host for 5 years
Display nocturnal periodicity with peak presence in
bloodstream between 10 p.m. and 2 a.m.
Culture
There is no role for culture in diagnosis of filarial
worms
Endosymbiosis
Filaria nematodes have an endosymbiotic relationship
with Wolbachia species bacteria
Death of the Wolbachia bacteria leads to infertility in
the nematode
Helminthic Parasitic Infections: Nematodes
MICROSCOPIC PATHOLOGY
Histologic Features
Intact male and female adult filariae can be seen in
lymphatics, skin nodules, or pleural fluid
Granulomatous reaction around dead and dying
filariae
Calcified and lamellated granulomatous reaction
Acute lymphangitis and chronic lymphatic dilatation
and fibrosis
Polypoid endolymphangitis
Eosinophilic lymphadenitis (Meyers-Kouwenaar
syndrome)
Cytologic Features
Microfilaria may appear as coiled structures sheath,
visible nuclei, and caudal space
Fragments of adult worms may be present depending
on type of sampling
Differentiation of Filarial Parasites
Blood/fluid smear light microscopy can be used to
differentiate the species
Filaria are visible on Giemsa stain
W. bancrofti does not have nuclei in its tail and is
sheathed
B. malayi has terminal and subterminal nuclei in its
tail and is sheathed
Mansonella species are unsheathed
M. perstans has paired nuclei down to end of tail
M. ozzardi has a single row of nuclei that end before
tail
M. streptocerca has as single row of nuclei that extend
to end of tail
HUMAN FILARIASIS
DIFFERENTIAL DIAGNOSIS
Bacterial or Fungal Lymphadenitis
Presence of bacteria on Gram or silver stain; presence
of fungal forms on silver stain
Edema Secondary to Nephrotic Syndrome,
Congestive Heart Failure, Cirrhosis
Correlation with clinical history
Hydrocele
Diagnosed with transillumination
Microscopically seen as loose connective tissue with
mesothelial lining
Chronic hydrocele may have inflammation and
fibrosis
Malignancy of Scrotum, Testis, or Kidney
Clinical correlation, serum tumor markers, histological
diagnosis
Nonfilarial Elephantiasis (Podoconiosis)
Ascending and asymmetric
Can begin as foot pain, plantar edema, and rigidity of
toes
Rarely involves groin
Not caused by filarial reaction; rather, caused by a
reaction to mineral components in volcanic clay
Nonfilarial Lymphedema (Milroy Disease)
Edema with dilated lymphatic spaces
Lower limb edema present at birth or develops in early
infancy
Onchocerciasis (M. streptocerca)
Onchocerca microfilaria have a single row of nuclei that
do not extend to end of tail or head
DIAGNOSTIC CHECKLIST
Clinically Relevant Pathologic Features
Blood is drawn at night for maximum parasite yield on
peripheral smear
Exposure history is very important for entering
filariasis into differential diagnosis
Pathologic Interpretation Pearls
Speciation may be difficult on worm cross section
especially if worm is dead
ANCILLARY TESTS
ntigen Detection
Circulating filarial antigen can be detected using
monoclonal antibodies raised against related species of
nematodes
V
PCR
Large-scale prevalence studies are carried out using
PCR
SELECTED REFERENCES
1. Handa U et al: Diagnosis of filariasis on cytology: a series of
24 cases. Trop Doct. 44(2):92-5, 2014
2. Marcos LA et al: Testicular swelling due to lymphatic
filariasis after brief travel to Haiti. Am J Trop Med Hyg.
91(1):89-91, 2014
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Microscopic Features
p
d
Helminthic Parasitic Infections: Nematodes
HUMAN FILARIASIS
(Left) Cross sections of
male W. bancrofti are seen
in dilated spermatic cord
lymph vessels. (Courtesy
Franz von Lichtenberg
Collection of Infectious
Disease Pathology, BWH.)
(Right) The filaria become
lodged in lymphatics due
to intense inflammation
occluding the lymphatic
lumina. (Courtesy Franz von
Lichtenberg Collection of
Infectious Disease Pathology,
BWH.)
(Left) Degenerating W.
bancrofti are present in
an inguinal lymph node
hilus, surrounded by a
large granuloma. (Courtesy
Franz von Lichtenberg
Collection of Infectious
Disease Pathology, BWH.)
(Right) A granuloma is
resent in the spermatic
cord, which contains a
necrotic filarial remnant.
The differential diagnosis
includes TB. (Courtesy
Franz von Lichtenberg
Collection of Infectious
Disease Pathology, BWH.)
(Left) Inflamed pelvic
lymphatics contain W.
bancrofti. Note the rim
of inflammatory cells
and reactive thickening
of lymphatic walls .
(Courtesy Franz von
Lichtenberg Collection of
Infectious Disease Pathology,
BWH.) (Right) Pelvic
lymphatics contain calcified
W. bancrofti. Note the paire
uteri remnants . (Courtesy
Franz von Lichtenberg
Collection of Infectious
Disease Pathology, BWH.)
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Helminthic Parasitic Infections: Nematodes
ONCHOCERCIASIS
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1
Numerous hyperpigmented papules , lichenified
plaques , and nodules diffusely involve the lower
leg of a patient who recently returned from Africa. (From
DP: Nonneoplastic Derm.)
TERMINOLOGY
Synonyms
River blindness
Definitions
From Greek "Onkos" (barbed) + "kerkos" (tail)
ETIOLOGY/PATHOGENESIS
Infectious Agents
Onchocerca volvulus: Nematode transmitted by biting
blackflies of genus Simulium
Onchocerca lupi: Extremely rare infection (can occur in
United States)
Blackflies inhabit shores of rapidly flowing streams
CLINICAL ISSUES
Epidemiology
25 million people are infected with O. volvulus
worldwide
31 countries contain > 99% of cases
Common in Africa, Middle East, and South and
Central America
O. volvulus has a 5-stage life cycle, in which blackfly
acts as obligate intermediate host
Humans are sole definitive host
Infection occurs when blackfly introduces O.
volvulus larva into host
Larva develops into adult female worm and sheds
hundreds of microfilariae that migrate into skin
and eyes of host
Presentation
One of the leading causes of blindness in developing
world
Multisystem disease occurs
A large unilateral right inguinal mass, composed of
enlarged lymph nodes, hernia, and worm(s), involves
folds of inelastic, atrophic skin and results in "hanging
groin." (From DP: Nonneoplastic Derm.)
Skin
Acute stage: Diffuse dermatitis with intense
pruritus, ulceration, and bleeding
Chronic stage: Hypopigmented "leopard skin" or
atrophic "lizard skin" lesion
May also present as unilateral papular eruption
with focal involvement (known as "sowda" in
Yemen and Sudan)
Subcutaneous nodules over bony prominences
(adult worms)
Ocular
Photophobia, conjunctivitis, and blindness
Systemic
Fatigue, fever, and femoral/inguinal lymphadenitis
Most symptoms of onchocerciasis are caused by bodily
response to dead or dying larvae
Laboratory Tests
Serology, PCR, ELISA, and skin snip test
Ocular infection can be diagnosed with a slit-lamp
examination of anterior part of eye where larvae are
visible
Treatment
Ivermectin, doxycycline
Prognosis
Chronic and recurrent inflammation of eyes can lead
to blindness
No vaccine or medication to prevent infection with O.
volvulus
MICROSCOPIC PATHOLOGY
Histologic Features
Skin
Hyperkeratosis, acanthosis, and elongated rete ridges
of epidermis
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ONCHOCERCIASIS
Terminology
Agent: Onchocerca volvulus transmitted by biting
blackflies of genus Simulium
Clinical Issues
One of the leading causes of blindness in developing
world (2nd to cataracts)
Top Differential Diagnoses
Mansonella streptocerca
Dermal edema, chronic lymphocytic and
eosinophilic inflammation, dilated lymphatics, and
microfilariae of O. volvulus (5-9 m wide, 220-360
m long)
Anterior end of microfilaria has a long cephalic
space (7-13 m long); anterior nuclei are adjacent to
each other
Posterior end (9-15 m long) has long caudal space
and tapers to fine point
Onchocercoma: Fibrotic nodules formed by bundles
of adult worms encased by lymphocytes and
macrophages
Adult worm has external ridges on longitudinal
sectioning with 2 underlying striae per ridge
Cytologic Features
Unsheathed microfilaria can be seen on skin snips or
touch preps
DIFFERENTIAL DIAGNOSIS
Other Human Filariasis
Mansonella streptocerca
Microfilariae are smaller in diameter (2.5-4 m)
Anterior end cephalic space is shorter and coiled in a
"shepherd’s crook" configuration
Blunt tail with terminal round nuclei
Dirofilaria immitis
Forms nodules (usually in lung) with no
microfilariae
Key Facts
Food allergies and vitamin A deficiency
Tumors (mesenchymal, metastatic)
Diagnostic Checklist
Microfilariae of O. volvulus live in dermal collagen,
are unsheathed, have long cephalic space at anterior
end, and their posterior ends taper to fine points with
long caudal spaces
Food Allergies and Vitamin A Deficiency
Can cause diffuse dermatitis mimicking onchocerciasis
Careful clinical history and absence of organism easily
differentiate from onchocerciasis
Tumors (Mesenchymal, Metastatic)
Biopsy lacks microfilariae and shows tumor cells
DIAGNOSTIC CHECKLIST
Pathologic Interpretation Pearls
Microfilariae of O. volvulus live in dermal collagen, are
unsheathed, have long cephalic space at anterior end,
and their posterior end tapers to fine point with long
caudal space
SELECTED REFERENCES
1. Awadzi K et al: A randomized, single-ascending-dose,
2. Centers for Disease Control and Prevention (CDC):
3. Murdoch ME: Onchodermatitis. Curr Opin Infect Dis.
4. Stingl P: Onchocerciasis: developments in diagnosis,
5. Okulicz JF et al: Cutaneous onchocercoma. Int J Dermatol.
Helminthic Parasitic Infections: Nematodes
ivermectin-controlled, double-blind study of moxidectin
in Onchocerca volvulus infection. PLoS Negl Trop Dis.
8(6):e2953, 2014
Progress toward elimination of onchocerciasis in the
Americas - 1993-2012. MMWR Morb Mortal Wkly Rep.
62(20):405-8, 2013
23(2):124-31, 2010
treatment and control. Int J Dermatol. 48(4):393-6, 2009
43(3):170-2, 2004
IMAGE GALLERY
(Left) An H&E-stained nodule from a patient demonstrates an adult worm in cross section , which contains microfilariae . (Center) Skin
with onchocercal dermatitis shows elongation of the rete ridges, dermal edema, dilation of vessels, chronic inflammatory cells, and microfilariae.
(Right) An unsheathed microfilariae in the skin shows the anterior (long cephalic space and paired nuclei) and posterior end (long caudal
space tapering to a fine point) .
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Helminthic Parasitic Infections: Nematodes
STRONGYLOIDIASIS
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Adult worms and rhabdoid larvae living in jejunal crypts
cause mild eosinophilia and chronic inflammation.
TERMINOLOGY
Definitions
Infectious disease caused by Strongyloides stercoralis
nematode
From Greek "strongylos" (round) + "eidos" (form)
ETIOLOGY/PATHOGENESIS
Infectious Agents
Strongyloides stercoralis is an intestinal nematode that
infects humans through contact with soil containing
larvae
Larvae directly penetrate skin, migrate through
bloodstream to lungs, mature, and reside in small
intestine as adults
CLINICAL ISSUES
Epidemiology
Common in tropics, subtropics, and warm regions;
affects ~ 30100 million people worldwide
Unique life cycle compared to other nematodes due to
ability of noninfective larvae to mature directly into
infective filariform larvae in host, which can cause
"autoinfection"
Presentation
Asymptomatic
Acute infection shows cutaneous reaction "ground
itch" as larvae penetrate skin, most commonly in foot
Chronic infection larvae can migrate intradermally,
which results in intense itchy red tracts, usually in
perianal area
Larvae migration can cause respiratory symptoms,
e.g., dry cough
Section shows the larval form of the intestinal
Strongyloides (strongyloidiasis) .
Loeffler syndrome: Fever, dyspnea, wheeze,
pulmonary infiltrates with blood eosinophilia may
be seen (rare)
Migration of larvae to gastrointestinal system can
cause abdominal pain, diarrhea, vomiting, and
anorexia
Up to 75% of people with chronic form have mild
peripheral eosinophilia or elevated IgE levels
Upper thighs larva migration (larvae currens) is
pathognomic for strongyloidiasis
Hyperinfection syndrome and disseminated
strongyloidiasis occurs in immunosuppressed patients
Infection with human T-cell leukemia/lymphoma
virus type I (HTLV-I) is also a major risk factor for
strongyloides hyperinfection syndrome along with
organ transplant and prolonged steroid therapy
Serological testing prior to start of steroid therapy is
strongly suggested for any patient with remote risk
Laboratory Tests
Gold standard for diagnosis: Serial stool examination;
presence of rhabditiform larvae is diagnostic
Stool concentration techniques, such as Baermann
technique and modified agar plate method, can be
used to improve sensitivity
Duodenal aspirates for morphological identification of
organism
Serological testing for antibodies
For patients with potential exposure who are being
placed on immunosuppression, serology should be
used to determine pretreatment requirements
Treatment
Ivermectin or albendazole
Prognosis
Acute symptomatic disease resolves with treatment
Chronic disease with dissemination and
immunosuppression (hyperinfection) has high
mortality (80%)
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STRONGYLOIDIASIS
Terminology
Infectious disease caused by Strongyloides stercoralis
nematode
Clinical Issues
Common in tropics, subtropics, and warm regions;
affects ~ 30100 million people worldwide
Gold standard for the diagnosis of Strongyloides is
serial stool examination
Key Facts
Microscopic Pathology
Duodenal or jejunal biopsy may reveal parasites in
mucosa, eosinophilic infiltration in lamina propria,
or granulomatous reaction
Top Differential Diagnoses
Schistosomiasis (Katayama fever), amebiasis,
balantidiasis, infections by Ancylostoma duodenale, or
Necator americanus
Ulcerative colitis and polyarteritis nodosa
Helminthic Parasitic Infections: Nematodes
MACROSCOPIC FEATURES
Endoscopic Features
Because of small size of adults and larvae as well as
localization within cells of small intestinal crypts,
worms are not visualized during endoscopy but may
produce discrete lesions (red, raised lesions), which are
biopsied for diagnosis
MICROSCOPIC PATHOLOGY
Histologic Features
Duodenal or jejunal biopsy may reveal parasites
in mucosa, and eosinophilic infiltration in lamina
propria with granulomatous reaction
Hyperinfection
Larvae may be found in many tissues and
fluids including sputum, bronchial washings,
cerebrospinal fluid, urine
Cytologic Features
Larvae can be seen by a simple wet mount in fluid
from a bronchoalveolar lavage (BAL) or in other body
fluids during hyperinfection
DIFFERENTIAL DIAGNOSIS
Other Parasitic Conditions
Schistosomiasis (Katayama fever), amebiasis,
balantidiasis, infections by Ancylostoma duodenale, or
Necator americanus
Negative biopsy &/or serology/stool exam can
differentiate strongyloidiasis from other parasitic
infections
Ulcerative Colitis
Mimics Strongyloides colitis, but obtaining travel and
residence history is important
Biopsy shows absence of larva or eggs with low
eosinophilic infiltrates
Polyarteritis Nodosa
Involvement of capillaries and venules in addition to
arteriolar involvement seen in polyarteritis nodosa is a
major point of distinction
SELECTED REFERENCES
1. Pichard DC et al: Rapid development of migratory,
linear, and serpiginous lesions in association with
immunosuppression. J Am Acad Dermatol. 70(6):1130-4,
2014
2. Coster LO: Parasitic infections in solid organ transplant
recipients. Infect Dis Clin North Am. 27(2):395-427, 2013
3. Greaves D et al: Strongyloides stercoralis infection. BMJ.
347:f4610, 2013
IMAGE GALLERY
(Left) Histologic evaluation revealed a chronic inflammation in the submucosa, along with eosinophils, consistent with Strongyloides. (Center)
Medium-power view of the same case shows the adult form of Strongyloides stercoralis larvae in the duodenal glands . (Right) H&E highpower view of duodenal biopsy shows that numerous larvae with pointed tails are present within the crypts , consistent with Strongyloides.
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Helminthic Parasitic Infections: Nematodes
TRICHURIASIS
The long thin "head" of the Trichuris worm burrows
in between intestinal epithelial cells, causing stimulation
of nerves and the feeling of a full colon, which leads to
chronic pushing and prolapse.
TERMINOLOGY
Synonyms
Whipworm infection
Definitions
Greek: "Tricho" (hair) + "oura" (tail)
ETIOLOGY/PATHOGENESIS
Environmental Exposure
Eggs are found and mature in soil in warm climates
with ingestion through poor hygiene or lack of clean
water
Infectious Agents
Trichuris trichiura
Nematode parasite found in human large intestine
Genetic Predisposition
Susceptibility may be through genes on chromosomes
9 and 18 (not fully characterized)
Trichuris Therapy
T. trichiura infection
Crohn disease and ulcerative colitis have responded
with remission to iatrogenic infection with
whipworm
Trichuris promotes (via Th2 cytokines and IL-22)
goblet cell hyperplasia and mucus production
Trichuris suis infection (zoonosis)
Immunomodulatory therapy for multiple sclerosis,
inflammatory bowel disease, seasonal allergic
rhinitis, specific allergens
Cross section shows an adult female Trichuris worm in
the bowel, containing numerous eggs in this resection.
CLINICAL ISSUES
Epidemiology
Global prevalence: 17% with 800 million infections at
any given time
Specific community prevalence can be 30-40% and
as high as 80% in subgroups (school-aged children)
Presentation
Vast majority of patients are asymptomatic
Symptomatic presentations have a range of
manifestations
Mild abdominal pain
Rectal prolapse (young children)
Dysentery-like syndrome with mucoid diarrhea,
rectal prolapse, and anemia
Endoscopic Findings
Worms are large and easily seen on endoscopy
(single or multiple) but may mimic polyps (local
inflammation)
Laboratory Tests
Stool examination for ova and parasites reveals eggs
In pregnant women and some other populations,
anemia is related to intensity of egg burden
Treatment
Albendazole and mebendazole are first-line therapy
Prognosis
Chronic infection in childhood can lead to growth
stunting and mental delays
MICROBIOLOGY
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Parasite Characteristics
Large nematodes (up to 4 cm in length) that primarily
reside in cecum and ascending colon
Heavy infestation in rectum leads to rectal prolapse
TRICHURIASIS
Helminthic Parasitic Infections: Nematodes
Etiology
Trichuris trichiura: Eggs in soil in warm climates, poor
hygiene, or lack of clean water
Clinical Issues
Global prevalence of 17% with 800 million infections
Microscopic Pathology
Colonic mucosa may be benign, show active colitis or
hyperplasia of goblet cells (polyp-like hyperplasia)
Life Cycle
Eggs are excreted by host into environment where
they mature to infective forms over 3 weeks
Ingested eggs hatch, molt, and develop in small
intestine
Worms move to large intestine and mature to adult
worms, penetrate wall with their thin forebodies, and
copulate
Females lay up to 20,000 eggs per day and adult
worms survive in colon for usually 1 year, but up to 5
years
Females begin producing eggs ~ 65 days after
infection
MACROSCOPIC FEATURES
Colonic Resection
Either as a rare indication or more likely when found
incidentally, worms are visible as 1-2 x 0.3 cm white
worms adherent to mucosa colonic hyperemia and
hyperplasia
Key Facts
Top Differential Diagnoses
Hookworm infection
Strongyloidiasis
Capillariasis
In colonic resections, intact or fragmented posterior
end of worm may be present in lumen with eggs in
cross section
DIFFERENTIAL DIAGNOSIS
Hookworm Infection
Hookworms are attached directly to mucosa via
cutting plates without burrowing, and they produce
little (if any) inflammatory response
Strongyloidiasis
Strongyloides stercoralis are very small (not grossly
visible) and produce raised red patches that
microscopically show collections of eosinophils with
adult and larval forms within mucosal wall (between
intestinal epithelial cells
Capillariasis
Capillaria philippinensis are small nematodes (< 5
mm) that produce eggs similar to Trichuris and a lifethreatening dysentery-like syndrome
Anterior head of worm between intestinal epithelial
cells
Posterior end of worm in lumen with eggs in cross
section
MICROSCOPIC PATHOLOGY
Histologic Features
Colonic mucosa may be benign or show active colitis
or hyperplasia of goblet cells (polyp-like hyperplasia)
Fragments of anterior head of worm are seen burrowed
between intestinal epithelial cells
SELECTED REFERENCES
1. Phuphisut O et al: Triplex polymerase chain reaction assay
for detection of major soil-transmitted helminths, Ascaris
lumbricoides, Trichuris trichiura, Necator americanus, in
fecal samples. Southeast Asian J Trop Med Public Health.
45(2):267-75, 2014
MICROSCOPIC FEATURES
(Left) Multiple cross sections of the adult Trichuris worm are shown in the lumen or burrowed in intestinal cells. Note the lack of
inflammatory response. (Center) Scattered eggs
a distinctive ovoid shape ("rugby ball" or "American football") with bilateral mucus plugs
in human infection capillariasis.
of Trichuris are seen in the adherent stool contents. (Right) The eggs of Trichuris species have
. They are only morphologically similar to the eggs
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Helminthic Parasitic Infections: Nematodes
ZOONOTIC NEMATODE INFECTIONS
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Cross section of a dead Anisakis worm within a large
eosinophilic granuloma was found incidentally as a
mass during gastrectomy.
TERMINOLOGY
Manifestations
Ancylostomiasis
Angiostrongyliasis
Anisakiasis
Baylisascariasis
Dirofilariasis
Gnathostomiasis
Toxocariasis
Trichinellosis
ETIOLOGY/PATHOGENESIS
Environmental Exposure
Animal exposures: Cutaneous larva migrans,
toxocariasis, gnathostomiasis, baylisascariasis
Mosquito/animal exposure: Dirofilariasis, North
American Brugia
Undercooked meat/fish or raw vegetables:
Trichinellosis, anisakiasis, angiostrongyliasis
Infectious Agents
Nematodes in which life cycle is normally completed
outside of humans
Incidentally infect humans
Lead to tissue pathology (masses, lesions)
Ancylostoma caninum, Ancylostoma braziliense, and
other species (mammal hookworms causing cutaneous
larva migrans)
Angiostrongylus cantonensis (rat lung worm) and
Angiostrongylus (Parastrongylus) costaricensis
Anisakis simplex and Pseudoterranova decipiens (cod
worm)
Baylisascaris procyonis (raccoon lung worm)
Dirofilaria immitis, Dirofilaria repens, Dirofilaria
ursi, Dirofilaria tenuis (dog, dog, bear, and raccoon
heartworm)
A subcutaneous mass was removed from a patient. The
mass consisted entirely of a large dead worm, which had
microfilarial forms within its body, consistent with a
nematode.
Gnathostoma spinigerum and Gnathostoma hispidum
(larva migrans profundus)
North American Brugia (species unclassified)
Toxocara canis and Toxocara cati (larva migrans)
Trichinella spiralis, Trichinella pseudospiralis, Trichinella
nativa, Trichinella nelsoni, Trichinella britovi, and
Trichinella papuae (trichinellosis)
CLINICAL ISSUES
Presentation
Burrowing skin eruptions
Cutaneous larva migrans (CLM) (2 cm/day) from
Ancylostoma
Red, indurated, haphazard burrows
Usually on lower extremities or any surface in
contact with ground
Larva migrans profundus (LMP) (1 cm/hour) from
Gnathostoma
Begins with abdominal pain, fever, anorexia,
vomiting
Proceeds with migration to intermittent, painful,
itchy skin lesions, which turns to edema when
migration subsides
May migrate to any part of body and cause
symptoms due to specific organ involvement
Eosinophilic meningitis (Angiostrongylus is most
common cause)
Toxocariasis and baylisascariasis
Visceral larva migrans (VLM)
Severe reaction to migrating larvae with organ-
specific manifestations
Covert toxocariasis (CT)
Chronic exposure with fever, abdominal pain,
headache, cough (wheezing), sleep disturbances,
hepatomegaly, lymphadenitis
Ocular larva migrans (OLM)
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ZOONOTIC NEMATODE INFECTIONS
Etiology
Direct animal exposures: Cutaneous larva migrans,
toxocariasis, gnathostomiasis, baylisascariasis
Mosquito exposure: Dirofilariasis, North American
Brugia
Undercooked meat/fish/vegetables: Trichinellosis,
anisakiasis, angiostrongyliasis
Clinical Issues
Eosinophilic meningitis (Angiostrongylus is most
common cause)
Ocular larva migrans (OLM)
Solitary mass in lung (D. immitis)
Masses in stomach/duodenum (Anisakis,
Pseudoterranova)
Solitary mass in lymph node (North American Brugia)
Single worm, single eye involved with erythema,
white/fixed pupil, retinal damage, orbital
inflammation, and strabismus
Granulomatous nodules of eye may also be D.
tenuis
Other organ involvement with Baylisascaris can
occur due to wandering nature and continued
growth of worm, including neurological
involvement
Solitary mass in lung (D. immitis)
Rarely, Ascaris lumbricoides, human hookworm,
and S. stercoralis may arrest in pulmonary stage and
cause pneumonitis (eosinophilic) or granulomatous
lesions
Solitary mass in skin/subcutaneous tissues (D. repens,
D. ursi, D. tenuis)
Solitary mass in lymph node (North American Brugia)
Masses in stomach/duodenum (Anisakis,
Pseudoterranova) or small/large bowel (Angiostrongylus
costaricensis)
Acute anisakiasis is a syndrome of immediate
nausea, vomiting, and abdominal pain following
ingestion of live worms from raw fish
Systemic manifestations of trichinellosis
Initial infection can present with diarrhea,
abdominal pain, and vomiting
Release of larvae (1 week after infection) can lead
to tissue edema, conjunctivitis, fever, myalgias,
splinter hemorrhages, rashes, and have peripheral
eosinophilia
Life-threatening symptoms include myocarditis,
meningitis/meningoencephalitis, and pneumonitis
Laboratory Tests
Serological tests for antihelminthic antibodies can
be helpful in confirming suspected clinical diagnosis
but are available at limited number of reference
laboratories
Stool examination for ova and parasites may be
positive in larva currens but negative in all other
entities
Key Facts
Cutaneous larva migrans (CLM) (2 cm/day) from
Ancylostoma
Larva migrans profundus (LMP) (1 cm/hour) from
Gnathostoma
Larva currens (LC) (10 cm/day) from Strongyloides
stercoralis
Visceral larva migrans (VLM)
Microscopic Pathology
Eosinophilic granulomatous inflammation with
central degenerated dead nematode structures
Cross sections of living larvae or adult worms with
variable neutrophilic/eosinophilic inflammation and
necrosis
Treatment
CLM: Albendazole, ivermectin, or thiabendazole
LMP: Albendazole &/or surgical intervention if
possible (accessible)
LC: Ivermectin
VLM: Albendazole with corticosteroids
OLM: Albendazole &/or surgical intervention
Trichinellosis: Albendazole/mebendazole
Prognosis
Vast majority of nematode zoonoses are asymptomatic
or resolve completely with treatment
VLM and trichinellosis, when severe, can lead to
mortality if not properly treated
MICROBIOLOGY
Parasite Characteristics
Ancylostoma: Migrating larvae up to 1 mm with
bilateral double alae (wing-like projections on side of
body)
Angiostrongylus: 11-12 mm immature adults with
dome-like lateral chords
Anisakis/Pseudoterranova: 3rd- and 4th-stage larvae
are 15-45 mm, have Y-shaped lateral chords, and a
muscular trefoil-shaped esophagus
Baylisascaris: Grow from 20 mm to 1.5 cm over time;
smaller, thinner excretory columns and bilateral single
alae
Dirofilaria: 150-300 m in diameter with large, broad
lateral chords, and slender, paired muscle bundles;
worms are often degenerated and inflamed
Gnathostoma: 5-12.5 mm in length, 3rd-stage larva,
head and cuticle with rows of spines, large lateral
cords occupying most of body lumen
Toxocara: 400 m x 20 m with large excretory
columns and bilateral single alae
Trichinella: 1.5-4.0 mm x 50-150 m (adults), while
encysted larvae are 1 mm in length and curled
Helminthic Parasitic Infections: Nematodes
Size of worm, location, and internal and external
structures are key to speciation
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