Helminths-KP-BMC.pptx

Worms and More Worms:
The World of Helminths
Dr.Hamisi Mkindi

What are helminths?
• Complex and fascinating organisms
• Infect about 1.5 billion people, or 24% of the world’s population
• Belong to 4 phyla:
• Nematoda (roundworms)
• Platyhelminthes (flatworms)
• Acanthocephala (spiny-headed worms)
• Nematophora (hairworms)
1. World Health Organization. Soil-transmitted
helminth infections [Internet]. 2022
2. Despommier et al. Parasitic Diseases. Seventh
Edition.

Pathogenic Helminths (to Humans)
|---Platyhelminthes phylum---| |---Nematoda phylum---|
(flatworms) (roundworms)
Trematodes Cestodes Nematodes
(flukes) (tapeworms)
Male and female adults of
Schistosoma mansoni
Taenia saginata adult
worm
Ascaris lumbricoides adult
worm
1. Images: CDC-–DPDx
Edition.

Major helminths around the world
Trematodes
Blood flukes
S. haematobium
S. japonicum
S. mansoni
Liver flukes
Clonorchis sinensis
Fasciola hepatica
Opisthorchis viverrini
Lung flukes
Paragonimus westermani
Intestinal flukes
Fasciolopsis buski
Metagonimus yokogawai
Cestodes
Intestinal tapeworms
Diphyllobothrium latum
Hymenolepis nana
Taenia saginata
Taenia solium
Larval cysts
Echinococcus granulosus
Echinococcus multilocularis
Taenia solium
Nematodes
Intestinal
Ancylostoma duodenale
Ascaris lumbricoides
Capillaria philippinensis
Enterobius vermicularis
Necator americanus
Strongyloides stercoralis
Trichuris trichiura
Tissue invasive
Angiostrongylus cantonensis
Anisakis simplex
Baylisascaris procyonis
Brugia malayi
Gnathostoma spinigerum
Loa loa
Onchocerca volvulus
Toxocara canis
Trichinella spiralis
Wuchereria bancrofti
Edition.
2. Hotez et al, J Clin Invest 2008

How helminths differ from other pathogens
• Lifespan—up to years
• Eukaryotic, multicellular
• Sometimes have complex lifecycles
• Immune dysregulation--shifting host immune system away from Th1
and inducing Th2 responses (eosinophilia and IgE)
• Do not multiply within host (exceptions: Strongyloides, Capillaria,
Hymenolepis)
Edition.

Global prevalence and distribution
Hotez et al, J Clin Invest 2008

Question # 1:
A 37 year-old woman originally from rural Tanzania undergoes a speculum exam
during routine screening. She has also been complaining of recurrent crampy lower
abdominal and suprapubic pain for the past 3 months. On exam, there are “sandy
patches” and papules at the cervix. Biopsy of these areas reveal an egg with
surrounding granulomatous inflammation.

Trematodes
Blood flukes
S. haematobium
S. japonicum
S. mansoni
Liver flukes
Clonorchis sinensis
Fasciola hepatica
Lung flukes
Intestinal flukes
Fasciolopsis buski
Cestodes
Hymenolepis nana
Taenia saginata
Taenia solium
Larval cysts
Taenia solium
Nematodes
Intestinal
Necator americanus
Trichuris trichiura
Tissue invasive
Anisakis simplex
Brugia malayi
Loa loa
Onchocerca volvulus
Toxocara canis
Edition.

History of schistosomes (1 of 2)
• Dr. Bilharz described S.
haematobium serving in the
German army and stationed in
Egypt
• Made the connection between
hematuria and S. haematobium
• Before this—paleoparasitologists
have found S. haematobium
eggs in Egyptian mummies from
1250 BCE.
• Advent of “manhood” or “rite of
passage” for young Egyptian boys
to have bloody urine as they
became men, similar to female
menstruation
Theodor Maximilian Bilharz, M.D. (1825–1862) 1. Despommier et al. Parasitic
Diseases. Seventh Edition.

History of schistosomes (2 or 2)
• Scottish physician who discovered S.
mansoni (+ other parasites, including
extensive work on lymphatic filariasis)
while stationed on the island of
Formosa (modern-day Taiwan)
Patrick Manson, M.D. (1844–1922)
1. Despommier et al. Parasitic

Global distribution of Schistosoma species
1. Weerakoon et al. Clinical Microbiology
Reviews, 2015.

Life cycle of
schistosomes
Intermediate snail hosts
(genera):
Biomphalaria--S. mansoni
Oncomelania--S. japonicum
Bulinus--S. haematobium, S.
intercalatum, S. guineensis
Neotricula aperta—S. mekongi
1. CDC-–DPDx
Edition.

Acute schistosomiasis
• Cercarial dermatitis or
swimmer’s itch
• Urticarial skin plaques or papules
that occur in response to re-
exposure to cercariae in a person
previously sensitized
• Can be seen with exposure to both
human and avian schistosomes
• Katayama fever or snail fever
(described in 1847 in the
Katayama district of Japan)
• Occurs in previously unexposed
hosts and at onset of egg-laying
phase (3-8 weeks)
• Fevers, myalgias, abd pain,
diarrhea, headache, urticaria
• May see eosinophilia, increased
AST, alkaline phosphatase
1. Despommier et al. Parasitic Diseases. Seventh Edition.
2. https://stacks.cdc.gov/view/cdc/18143

Chronic schistosomiasis
S. mansoni, S. japonicum
• Intestinal and hepatosplenic
disease
• Chronic abd pain, blood in stools,
colitis, hepatosplenomegaly, portal
hypertension, periportal liver fibrosis,
hematemesis
S. haematobium
• Granulomatous cystitis, bladder
fibrosis/cancer, obstructive
uropathy
• Chronic genital disease—female
genital schistosomiasis (women—
pelvic pain, post-coital bleeding,
dysmenorrhea)
• Increased risk of HIV acquisition
1. Top left photo: Neglected Tropical
Diseases Study Group, University of the
Philippines Manila--Dr Vicente Y.
Belizario, Jr., Convenor
2. Top right photo: Masong et al. PLOS GPH,
2021.
3. Norseth et al. PLOS NTD, 2014.

Schistosomiasis—Diagnosis and Treatment
• Dx:
• Examination of stool and urine for eggs (acute schisto—usually clinical diagnosis)
• Serology--useful in travelers or immigrants from endemic areas who have not been
treated in the past
• For new infections—collect serum sample 6-8 weeks after likely infection
• Not appropriate test for those repeated infected and treated—cannot distinguish resolved vs.
active infection
• Antigen test—can detect new infections, but not widely available in clinical setting
(U.S.)
• Eggs in urine/stool Kato katz thick smear/pcr assays
• Rx: praziquantel 40mg/kg stat or in 2 divided doses
1. CDC-–DPDx
Edition.

Question # 3:
A 67 year-old woman from China presents with chronic RUQ pain and significant
weight loss. On MRCP, there is marked biliary ductal dilatation with a papillary mass
concerning for cholangiocarcinoma.

Clonorchis sinensis (“Chinese Liver Fluke”)
• Earliest record of clonorchiasis dates
back to an ancient corpse in the Han
Dynasty in 278 B.C.
• James McConnell was first to report it
in the English literature in 1874 while
a resident in Calcutta
• Eggssnailsfreshwater fish--
>humans ingest metacercariae in raw
or undercooked fish
• Larvae develop in duodenumbile
ducts and can live up to 50
yearscholangitis,
cholangiocarcinoma
• Dx: stool eggs (can also see flukes on
imaging, ERCP); Rx: praziquantel
1. CDC-–DPDx
Edition.

Opisthorchis viverrini (“Southeast Asian Liver
Fluke”)
• Endemic to northern Thailand,
Vietnam, Cambodia, Laos
• Opisthorchis felineus—Russia,
Belarus, Ukraine, Italy, Germany,
Kazakhstan
• Similar life cycle to Clonorchis—
acquired from eating raw or
undercooked fish
• Can also cause pancreatitis,
cholangitis, cholangiocarcinoma
• Similar Dx and Rx to Clonorchis
1. CDC-–DPDx
Edition.

Fasciola hepatica (“sheep liver fluke”)
• Acquired by eating encysted larvae
on aquatic vegetation
• Adult flukes migrate through liver:
RUQ pain, hepatitis
• Takes residence in biliary ducts and
matures over 4 months, can induce
biliary obstruction
• Dx: stool eggs (low sensitivity
during acute stage), serology,
circulating antigen
• Rx: triclabendazole (FDA approved
in 2019)
• Note: only trematode that does not
respond well to praziquantel
1. CDC-–DPDx
Edition.

Question # 4:
• A 55 year-old man from Thailand presents for evaluation of a chronic cough of 6
months associated with occasional blood-tinged sputum. ROS is positive for
intermittent fevers and chest pain. On CT imaging of the lungs, there are
subpleural linear opacities and pleural thickening. Further history reveals that the
patient regularly eats som tam, a Thai green papaya salad typically served with
pickled crabs.
Image from:
http://www.chefseng.com/weekend-
special-spicy-papaya-salad-wblue-crab-
khaonom-koke/

Paragonimus westermani (“lung fluke”)
• Eggsmiracidium penetrates
snailsfreshwater
crabs/crustaceans-->humans
• Adult worms hatch in small intestine
and migrate to lungs to mature
• Signs + Symptoms:
• Eosinophilia, fever, cough, diarrhea
during acute migration
• Chest pain, chronic pulmonary
hemoptysis, lung infiltrates
• Dx: sputum or stool eggs
• Rx: praziquantel
Edition.

Intestinal flukes
Fasciolopsis buski (“Giant intestinal
fluke”– 2 cm x 8 cm)
• Lifecycle: eggssnailsmetacercariae
on aquatic vegetation-->humans
infected after eating veggiesadult
fluke lives in small intestine
• Symptoms: usually asymptomatic; can
cause abd pain, diarrhea, fever,
ulceration, hemorrhage
• Dx: stool eggs; Rx: praziquantel
Metagonimus yokagawi (”Minute
intestinal fluke”–2.5 mm x 0.75 mm)
• Lifecycle: eggssnailscercariae
penetrate fresh/brackish water fish
tissuehumans (+fish-eating
mammals and birds) get
infectedadults live in small
intestine
• Symptoms: abd pain, diarrhea, weight
loss
• Dx: stool eggs; Rx: praziquantel
1. CDC-–DPDx
Edition.

Trematodes (flukes): Summary
• Flat, fleshy, leaf-shaped worms
• Parasites of mollusks (typically snails are the intermediate hosts)
• Usually hermaphroditic (except schistosomes, the blood flukes, which
has male and female worms)
• Praziquantel treats all, except Fasciola hepatica which requires
triclabendazole

Question # 5:
A 26-year-old woman from Mexico is passing thin, flat, white tissue fragments in
her stools over the past month. She is otherwise healthy and does not report any
symptoms. Your micro lab confirms that these tissue fragments are indeed parts of
a helminth.

Taenia species
Taenia solium (“Pork tapeworm”)
• Acquired by eating larvae in pork—most
people are asymptomatic and may pass
proglottids (gravid parts of the worm) in stools
• Cysticercosis, including neurocysticercosis
(most common cause of seizures worldwide), is
acquired from eating food contaminated with
feces containing eggs
Taenia saginata (“Beef tapeworm”)
• Acquired by eating larvae in undercooked
beef (relatively asymptomatic, but can have
more GI symptoms—longer than T. solium)
• No risk of invasive disease (unlike above)—T.
saginata eggs only hatch in cow stomachs
• Dx: stool proglottids or eggs (not
frequently passed, plus eggs are
indistinguishable between species)
• Rx: Praziquantel for intestinal tapeworm
infection (but not for neurocysticercosis-–
different guidelines)
1. CDC-–DPDx
Edition.

Neurocysticercosis
• Can cause:
• Seizures
• Hydrocephalus
• Headaches
• Focal neurological deficits Top: brain on autopsy
showing diffuse
cystic/cavitated lesions
(https://www.cdc.gov/paras
ites/features/ncc_cme_feat
ure.html)
Bottom: CT brain showing
calcified lesions with edema
(https://radiopaedia.org/arti
cles/neurocysticercosis?lang
=us)

Neurocysticercosis Dx and Rx Guidelines
• Diagnosis:
• Definitive = tissue biopsy, multiple cystic lesions each with scolex on imaging, or retinal
cysticercus seen on fundoscopic exam
• Presumptive: suggestive lesions on imaging
• Cysticercus serology is supportive
• Treatment: (medical therapy decreases risk of future seizures, but has immediate risk of increasing brain
inflammation/seizures)
• If hydrocephalus or diffuse cerebral edema, treat with steroids and/or surgery (not with anti-parasitics)
• If no increased ICP: 1-2 viable cysts  albendazole + steroids before anti-parasitic
>2 viable cysts  albendazole + praziquantel + steroids before anti-parasitics
+ retreatment for any lesions persisting for 6 months after the end of the initial
course of therapy
• Antiepileptics for all NCC patients with seizures
1. Diagnosis and Treatment of Neurocysticercosis:
2017 Clinical Practice Guidelines by IDSA and
ASTMH

Diphyllobothrium latum (“broad fish
tapeworm”)
• Can grow to >10m (record is
25m, making it the longest
human parasite)
• Wide distribution—North
America, Scandinavia, Russia,
Baltics, etc.
• Acquired by eating raw or
undercooked fish
• Symptoms of B12 deficiency in
40% of patients
• Dx: stool proglottids or eggs; Rx:
praziquantel
1. CDC-–DPDx
Edition.

Hymenolepis nana (“dwarf tapeworm”)
• Small intestinal tapeworm (34-45mm),
mostly infects children, worldwide
prevalence of ~4% (other species—H.
diminuta; rare)
• Humans infected when they ingest eggs
from contaminated food, water, or
hands
vs. eating cysticercoid-infected insects
• Autoinfection can occur (like in
Strongyloidiasis)
• Dx: stool eggs
• Rx: praziquantel (active against adults +
cysticercoid in villus tissue)
vs. alternatives: niclosamide (only active
against adults) and nitazoxanide
1. CDC-–DPDx
Edition.

• Cestode helminth that forms hydatid
cysts (“watery vessel” containing internal
cystic fluid and daughter cysts) in humans
• Most in liver (65%), 25% in lungs (RLL), rest
can occur anywhere in body
• Distribution of disease coincides with
sheep husbandry (ingestion of eggs)
• Presentations: (60% asymptomatic, but..)
• Allergic symptoms/anaphylaxis due to cyst
rupture after trauma
• Peritonitis, cholangitis, biliary obstruction,
pneumonia due to cyst rupture in those
spaces
• Bone fracture due to bone cysts, mechanical
rupture of heart with pericardial tamponade,
hematuria/flank pain due to renal cysts
1. CDC-–DPDx
Edition.

E. granulosus - diagnosis
1. Mehta et al. Trop Parasitol, 2016.
2. CDC-–DPDx
Edition.
Radiology
(Multiloculated cyst appearing as well-defined fluid
attenuation lesion with multiple septae or daughter cysts
in a honeycomb pattern)
Microscopy
(Cyst with multiple daughter cysts)
Serology
Of patients with
hepatic cystic
echinococcosis, 30-
40% have negative
serologies
• Ability of
parasite antigens
to inhibit B cell
activity
• Those with intact
cysts may not
experience
sufficient antigen
challenge

E. granulosus - treatment
• Need to be careful to not spill cyst contents
• Anaphylaxis
• Spilled protoscoleces (larval component of hydatid cyst) can re-establish infection
• Typically treat with albendazole first (x several days) before surgery or
PAIR (Puncture, Aspiration, Injection, Re-aspiration) vs. “watchful waiting”
(e.g., single cyst without daughter cyst and pt asymptomatic)
• Surgery remains most effective treatment and can lead to complete cure
1. https://www.cdc.gov/parasites/echinococcosis/treatment.html
2. https://www.who.int/news-room/fact-sheets/detail/echinococcosis

• Fox/rodent lifecycle—disease
distribution coincides with fur
trappers
• Appearance of infiltrative, tumor-
like growth that is poorly
demarcated
• Has a semi-solid nature
• does not form large cyst or produce
protoscoleces
• grows by external budding/mets
• Similar diagnosis, typically treat
with albendazole and surgery
1. CDC-–DPDx
2. Chouhan et al. Clinical Radiology, 2019.
Edition.

Cestodes (tapeworms) Summary
• Have flat, ribbon-like bodies consisting of proglottid segments which
contain reproductive organs
• Have no digestive systems (absorb food through soft body wall)
• All except D. latum have suckers with hooklets on the scolex
• Humans acquire through oral route (fecal-oral or eating cyst-laden
food)
• Adult tapeworms do not cause significant pathology in the human
intestines (unlike adult trematode or nematode worms)
• But significant global morbidity when humans serve as intermediate hosts
(e.g., neurocysticercosis and echinococcosis)
Edition.

Question # 6:
A 40-year old woman who is originally from Kenya and worked on a farm presents
for her annual physical. She states she has been doing well except that she recently
passed a large, round, whitish worm in her stools. She denies any symptoms. She
brings the worm to your office in plastic container.
1. CDC-–DPDx

• One of the largest nematodes/soil-
transmitted helminths (STH)
• Eggs in soilingestlarvae hatch in
intestinesmigrate to liver then
lungslarvae coughed up and swallowed
into GI tractworm matures
• Symptoms
• Loeffler’s syndrome—eosinophilic pneumonitis
with transient lung infiltrates
• Abd pain, distention, or intestinal obstruction
with large worm burden
• Aberrant worm migrationcholangitis,
pancreatitis
• Asymptomatic—passing eggs or large worm in
stools
• Dx: typically stool eggs (or worm); Rx:
albendazole or mebendazole; alternative--
pyrantel pamoate 1. CDC-–DPDx
Edition.

Hookworms—Ancylostoma and Necator species
• Filariform larva penetrates
skingoes to lungs, then coughed up
and swallowed—worm matures in
intestines
• Major cause of iron-deficiency
anemia and protein loss
• Symptoms:
• urticarial rash (papulovesicular
dermatitis) vs. cutaneous larva migrans
(serpiginous lesions if worms migrate
laterally)
• transient pneumonitis
• Abd pain
• Signs + symptoms related to anemia and
protein loss, particularly in children
• Dx: stool eggs, consider clinical if CLM;
Rx: Albendazole or mebendazole
1. CDC-–DPDx
Edition.

Question # 7:
A 45-year-old American man with no known medical history presents with nearly 4 months of
profound daily diarrhea and weight loss of 35 pounds after spending 1 month in the Philippines.
Towards the end of his backpacking trip, he decided to try a “jumping salad” prepared by a street
food stall—symptoms started shortly after. Review of systems is negative for cough and other
respiratory symptoms.
On exam, the patient appears pale and nearly cachectic. His labs reveal electrolyte derangements,
anemia, low albumin, and is notable for a negative HIV 4th generation screen.
1. https://www.overseaspinoycoo
king.net/2008/06/jumping-
salad-fresh-water-shrimp-
salad.html

• Acquired by eating
raw/undercooked crustaceans and
minnows
• Intestinal capillariasis—manifests
as abdominal/GI disease
• Can become serious due to
autoinfection (embryonated eggs
hatch inside host’s intestine and
released larvae can re-invade)
• Protein-losing enteropathy may
occurcardiomyopathy, emaciation,
cachexia, death.
• Dx: stool microscopy; Rx:
Albendazole or mebendazole
1. CDC-–DPDx
Edition.

Enterobius vermicularis (pinworm)
• Ubiquitous; fecal/oral transmission;
typically present in children with peri-
anal itching (rarely appendicitis)—
humans are only host
• Dx: stool O+P not helpful—usually
employ scotch tape test—tape applied
to perianal region in early morning
and then removed for examination
under microscopy to detect eggs or
worms
• Rx: pyrantel pamoate, albendazole, or
mebendazole single dose
• Treat all family members
• Retreat in 2 weeks
• Trim fingernails, wash bedsheets,
practice good hand hygiene 1. CDC-–DPDx
Edition.

• Penetrate skin-->enter lungsmature in
intestines
• Usual manifestations: mild abd pain,
wheezing/transient infiltrates, urticarial
rash/cutaneous larva migrans
• Risk of autoinfection, hyperinfection,
disseminated strongyloidiasis
• Immunocompromised state (steroids, TNF-
inhibitors, HTLV-1, malignancy, malnutrition)
• Disseminated disease characterized by
multisystem involvement (GI—abd pain,
diarrhea; pulm—cough with lung infiltrates;
systemic—fever and hypotension due to shock
2/2 gram-negative sepsis)
• Can have bacteremia, pneumonia, meningitis,
particularly with gram-negative organisms
1. CDC-–DPDx
Edition.

Strongyloides diagnosis and treatment
• Dx:
• Stool O&P and/or serology
• In disseminated infections, can check sputum or bronchoalveolar lavage fluid
for O&P—may see larvae migrating/moving across sample
• Rx:
• ivermectin
• For at-risk groups, ideally would check serology and/or give prophylactic ivermectin if
pt’s background or clinical history (e.g., from endemic region and has unexplained
peripheral eosinophilia) fits before starting immunosuppressive drugs, such as steroids
• For disseminated infection—prolonged ivermectin (until stool/sputum
negative x 2 weeks) with abx for gram-negative infection + supportive care if
warranted
1. https://www.cdc.gov/parasites/strongyloides/h
ealth_professionals/index.html
Edition.

Trichuris trichiura (whipworm)
• 4 cm long nematode, frequently
coincident with other STH
infections (Ascaris and hookworms)
• Fecal/oral transmission
• Heavy infection may lead to loose,
frequent stools, tenesmus, blood in
stools, and rectal prolapse in
children
• Dx: stool eggs (football-shaped
with two polar plugs)
• Rx: albendazole or mebendazole
1. Despommier et al. Parasitic

Trematodes
Blood flukes
S. haematobium
S. japonicum
S. mansoni
Liver flukes
Clonorchis sinensis
Fasciola hepatica
Lung flukes
Intestinal flukes
Fasciolopsis buski
Cestodes
Hymenolepis nana
Taenia saginata
Taenia solium
Larval cysts
Taenia solium
Nematodes
Intestinal
Necator americanus
Trichuris trichiura
Tissue invasive
Anisakis simplex
Loa loa
Onchocerca volvulus
Toxocara canis
Edition.

Eosinophilic meningitis
• Angiostrongylus cantonensis (”rat lungworm”)
• Most common parasitic cause of eosinophilic meningitis worldwide (SE Asia, Pacific
basin, Caribbean)
• Typically acquired by ingestion of parasite in snails/slugs or raw vegetables vs.
contaminated water source
• Dx: CSF PCR (not widely available); Rx: supportive with steroids—unclear benefit;
anthelmintic therapy controversial
• Others:
• Baylisascaris procyonis—acquired by ingestion of eggs shed in raccoon feces (can
cause visceral/neural larva migrans, eosinophilic meningitis)
• Gnathostoma spinigerum—acquired by ingesting infective larvae in freshwater fish
(ceviche), snakes, birds (can cause VLM, subcutaneous swellings, eosinophilic
meningitis, ocular disease)
• Caveat—very simplistic way of approaching this (probably most useful for test
questions).
• Keep in mind that other nematodes can also cause eosinophilic meningitis, as well as some
species from trematodes and cestodes 1. CDC-–DPDx
Edition.

Toxocariasis
• Acquired by ingestion of eggs in animal feces (Toxocara canis—dog;
Toxocara cati—cat)—larvae hatch in intestines then migrate to liver, spleen,
lungs, brain, and/or eye
• Symptoms
• Visceral larva migrans: usually children (<5yo); fever, eosinophilia,
hepatosplenomegaly, wheezing, pneumonia
• Ocular larva migrans: often older children (5-10yo); retinal lesions appear as solid
tumor-like  unilateral vision loss
• Dx: clinical + Toxocara antibody testing (serum + intraocular ELISA)
• Rx: can be self-limiting disease; acute VLM or OLM—albendazole and
steroids
Edition.

Anisakis simplex
• Acquired by ingesting larvae in raw
or undercooked seafood
(worldwide)
• Acute abdominal symptoms of pain
and vomiting (hours), mimicking
food poisoning, gastric ulcer,
appendicitis, or IBD if larvae
penetrate gastric mucosa or pass
into small bowel
• Allergic reaction to worm
• Dx and Rx: usually endoscopic
removal of worm, but sometimes
self-resolves
1. CDC-–DPDx
Edition.
3. Madi et al. Can J Gastroenterol, 2013

• Acquired from eating meat
containing cysts (pork/boar, bear,
horse, wild game)
• Larvae released from cysts by
gastric acid, invade small bowel,
then migrate to striated muscle
• Symptoms: acute abd pain and
diarrhea, later with severe muscle
pain, periorbital edema,
eosinophilia
• Dx: serologies supportive, biopsy
definitive; Rx: albendazole +
steroids
1. CDC-–DPDx
Edition.

Filariasis
• Filariae—threadlike, tissue-
invasive roundworms that are
transmitted by insect vectors
• Caused by
• Wuchereria bancrofti
• Brugia malayi
• Loa loa
• Onchocerca volvulus Microfilaria of W. bancrofti in a thick blood smear,
stained Giemsa
1. CDC-–DPDx
Edition.

Body location of filarial infections
Brugia malayi
(lymphatic filariasis—mosquitos)
Loa loa
(Loasis--deer fly (Chrysops flies))
Onchocerca volvulus
(river blindness—black flies)
Adults
lymphatics
Subcutaneous tissues (moving)
Subcutaneous tissues (nodules)
Microfilariae
blood (night)
blood (day)
skin
1. Despommier et al. Parasitic Diseases.
Seventh Edition.
2. CDC-–DPDx

Lymphatic filariasis
• W. bancrofti and B. malayi (vector—mosquito bite)
• W. bancrofti—Sub-Saharan Africa (not southern portion),
some western Pacific Island nations, part of the Caribbean,
South America, India, Southeast Asia
• B. malayi—Southeast Asia
• Clinical disease:
• Asymptomatic
• Acute lymphadenitis—painful swelling of lymph nodes,
fever, secondary bacterial infections
• Elephantiasis—lymphedema of arms, legs, etc.
• Tropical pulmonary eosinophilia—paroxysmal
nocturnal asthma with dyspnea, fatigue, weight loss,
eosinophilia (>3,000/mm3)
• likely due to excessive immune response to
microfilariae in lung
• Dx:
• Microscopy—ID of microfilariae on blood smears at night
• Serology—ELISA with Western blot
• Antigen testing—circulating filarial antigen assay (only
Wb)
• Identification of adult worm (tissue biopsy or ultrasound
“filarial dance sign”)
• Rx:
• R/o co-infection with Loa loa first due to risk of severe
treatment adverse effects (avoid DEC in high load of Loa
loa on blood smears)
• DEC (diethylcarbamazine) or doxycycline
• Triple-drug therapy (DEC/albendazole/ivermectin) now
recommended by WHO in areas not co-endemic for Loa
loa or Onchocerca volvulus
• Lymphatic surgery, hydrocele drainage
• Lymphedema care, treatment of wounds/secondary
bacterial infections
2. CDC-–DPDx

Filarial dance sign
1. https://www.youtube.com/watch?v=g
uyP0a5k1Zw

Onchocerca volvulus
• Bite from black fly (vector)—causes
“river blindness”
• Found mainly in West and Central
Africa; foci in Yemen and Brazil-
Venezuela border
• Dermatitis, lymphadenopathy
(inguinal, head/neck), ocular
(keratitis, iritis, optic neuritis,
cataracts, blindness, etc.)
• Nodding syndrome—presents with
seizures, head nodding, periods of
unresponsiveness
• Dx:
• Microscopy—skin snips, nodulectomy
• Rx:
• ivermectin—make sure no co-infection
with Loa loa (high microfilarial levels)
• moxidectin (FDA approved in 2018)
• Both are microfilaricidal, need repeated
treatments
• Alternative: doxycycline for 6 weeks
2. https://aho.org/fact-sheets/onchocerciasis-fact-sheet/
3. https://www.thenewhumanitarian.org/ar/node/246506
4. CDC-–DPDx

Loa loa (“African eye worm”)
• Bite from deer fly (Chrysops spp—
vector)
• West and Central Africa
• Asymptomatic
• Calabar swellings (allergic rxn to
worms/dead worms)--moves
• Worm migration across eye
• Endomyocardial fibrosis, renal disease
• Encephalitis, lymphadenitis
• Serious adverse reactions when
treated with agents for other
parasitic infections
• Dx:
• Adult worm in subconjunctiva
• Microscopy—blood smears during middle
of day
• Rx:
• Microfilarial level <8000 MF/ml—DEC
(diethylcarbamazine)
• >8000 MF/ml—apheresis or albendazole
first prior to treatment with DEC
• Do not use DEC with O. volvulus co-
infection--risk of blindness and/or
worsening of skin disease
2. CDC-–DPDx
3. Bowler et al. Eye, 2011.

General treatment summary of filariasis
Brugia malayi
(lymphatic filariasis)
Loa loa
(Loasis)
Onchocerca volvulus
(river blindness)
Treatment
DEC
DEC
ivermectin
Avoid
-------
DEC and ivermectin if high microfilarial
level
DEC
Adverse effects (due to immune response and effects from dying worms)
Loa loa with high microfilarial levelsencephalopathy and death
Onchocerciasis-->blindness and severe skin inflammation
2. CDC-–DPDx

Nematodes (roundworms) summary
• Nonsegmented, round
• Has nervous, digestive, renal, and reproductive organs
• Has flexible outer coating (cuticle) with muscular layer underneath
• People get infected in a variety of ways:
• Eating eggs in fecally contaminated food/soil (Ascaris, Trichuris, Enterobius,
Toxocara, Baylisascaris)
• Direct penetration of larvae through skin (Strongyloides, hookworms)
• Eating food with infectious larvae (Angiostrongylus, Gnathostoma, Anisakis,
Capillaria, Trichinella)
• Vector (filarial nematodes)
2. CDC-–DPDx

Some key associations (simplified)
• Freshwater exposure + hematuria or hepatosplenomegalyschistosomiasis
• crab/crayfish consumption + pulm sxsParagonimus
• Seizures with calcified brain lesionsTaenia solium (egg exposure), NCC
• Chinese pt with cholangiocarcinomaClonorchis sinensis (vs. O. viverrini in Southeast Asia though less
commonly associated with cancer)
• Megaloblastic anemiaD. latum (B12 deficiency)
• Allergic reaction after abd/lung traumaEchinococcus
• Itchy feet after returning from tropicsdermatitis/ground itch from hookworm
• Gram-negative sepsis in setting of steroidsdisseminated strongyloidiasis
• Elevated CK, periorbital edema, profound peripheral eosinophiliaTrichinella
• Eosinophilic meningitis, drinking from garden house with slugs/snails around-->Angiostrongylus
• SQ nodulesO. volvulus
• Nighttime blood microfilariaelymphatic filariasis (vs. daytime blood-Loa loa and skin-O. volvulus)
• Eosinophilia, increased AST/ALT, dog exposurevisceral larva migrans from Toxocara canis
• Abdominal pain after eating sushiAnisakis

Concluding Thoughts
• Helminths are diverse and quite prevalent around the world—affecting ¼
of the world’s population
• High morbidity (e.g., developmental delays in children, loss of employment in adults,
etc.) and mortality
• Methods for eradicating helminths
• Annual (or more frequent) mass drug administration targeted towards country (i.e.,
annual praziquantel + albendazole in Tanzania), vaccine development?
• Education (hand hygiene, wash/cook food, wear protective clothing such as boots or
long sleeves)
• Water/food sanitation
• Vector/intermediate host control (e.g., snail eradication in Japan)
• WHO’s goal is to achieve and maintain elimination of STH morbidity in pre-
SAC and SAC by 2030

Thank you for the opportunity to present!
Questions/comments?

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