Lecture 69_70 - Intestinal and Tissue Dwelling Nematodes Flashcards
what are some common features of helminth infections?
Do not multiply within the host
Most infections are of low burden; rarely are there high burdens
Genetics, infection history, nutrition correlate with worm burden
Helminth parasites establish long term infections (nematodes - 1 to 3 years, river blindness – 10+ years, strongyloides – lifetime)
Helminthes – induce eosinophilia – elevated igE; skewing the patient towards a Th2 response
What are the Gastrointestinal Nematodes?
which are anthropodic ?
which are zoonoitc?
Antrhopodic Nematodes: Pinworm -- Enterobius vermicularis Hookworm -- Ancylostoma Duodenale Ascaris Lumbricoides --- Whipworm -- Trichuris Trichiura Strongyloides -- Threadworm
Zoonotic:
Trichinellosis – Trichinella spiralis
Toxocariasisi – Toxacara canis and Toxicara cati
Describe the General lifecycle of the nematode:
xxxx
Pinworm
what is it scientific name?
what is the name of the infection
what kind of nematode is it?
describe its life cycle and how it infects humans?
Enterobius vermiculiaris
Enterobiasis
Anthropotic GI nematode
Adults live in the intestine Females move to the perianal region; where she distributes very sticky eggs The human scratches eggs on hands re-innoculation; infect other people
In the Gut the eggs hatch
males and females unite
Pinworm
- geographic distribution
The most common helminthic infection in the US
common in preschool and school aged children in crowded conditions
Pinworm
- clinical features
- lab dx
Asymptomatic
Peri-anal pruritus (itching)
anorexia, irritability, abdominal pain, disturbted sleep
Labs:
Scotch tape test of the peri-anal region early in the morning
Followed by microscopic detection of eggs
Pinworm
treatment
Prevention
Treat: Pyrantel Pamoate – paralysis of the pinworm
Prevention – hygeine, laundering of bedding;
Hookworm
what is the scientific name?
what kind of nematode?
Describe the life-cycle and how it infects humans?
How long do they stay in the host?
aka – Ancylostoma duodenale and Necator americanus.
Anthropodic GI Nematode
Lifecycle:
- eggs are passed in the feces
- hatch and develop into L3 forms in favorable environmental conditions
- Humans walking with bare feet or other skin contact
- hookworm penetrates the skin
- travels to veins –> heart –> lungs
- Develop in to L4 form and become very motile
- Climbs to the esophagus
- induces cough, swallow reflex and enters the Gut
- Concentrate in the jejunum
-Develop into adults
- attach to intestinal wall with resultant blood loss
-
Eliminated by host in 1-2 years
Hookworm
who gets infected?
what is the geographical distribution
Second most common human helminthic infection (after ascariasis)
Effects children, pregnant women, malnourished persons
Hookworm
- describe the morphology and pathology
1 mm long
Female Teeth – Chitinous structures–
protrudes into the lamina propria – disrupts and sucks blood of capillaries
Hookworm
Describe the pattern of disease burden
describe immunological changes in the lungs
burden: increases over time – unlike other parasites whose peak burdens are at young ages
Immuno: makes the lung a Th2 biased environment
Ancylostoma duodenale and Necator americanus.
clinical features
Labs/diagnosis
Treatment
Clinical features:
- itch at site of skin penetration
- Iron deficiency anemia – can lead to growth and mental retardation
- diarrhea, weight loss, abd pain, cardiac complications (arrythmias)
Labs/Dx: Microscopy
Treat: light infections in most countries go untreated
Albendazole
Ascaris Lumbricoides; Ascariasis
- describe the lifecycle and how its infectious to humans
- what happens when sick, under stress or during treatment?
the largest nematode of human intestine – females up to 35 cm
- Embryonated eggs are passed in the feces
- infective eggs are swallowed -larvae hatch
- invasion of intestinal mucosa; carried in the blood to the LIVER and then the LUNGS
- Develop in the lungs for 2 weeks; penetrate the alveolar walls
- Crawl up to the esophagus
- cough and swallow
- back in the gut
- 2 more months of maturation
when host is sick: migration of the worms out of the body (nose, mouth, anus)
Ascaris Lumbricoides; Ascariasis
- epidemiology:
- how is it transmitted ?
- geographic distribution
The most common human helminthic infection (25% of the world)
World wide distribution
more so in tropical zones
Fecal oral ingestion
Ascaris Lumbricoides
- Clinical features: light vs heavy infection
- lab/dx
- Treatment
Low worm burden: Asymptomatic; flu like symptoms; coughing wheezing in lung phase
high burden: -abdominal obstruction - flu like symptoms - exclusion of the biliary tract - cough, wheezing if in lung "Ascaris Pneumonia"
Labs/Dx: microscopic identification of eggs in stool
adults worms in stool
larvae in sputum
Treatment: Albendazole, mebendazole, pyrantel pamoate
Whipworm
scientific name
Describe the lifecycle and pathogenesis
Trichuris Trichiura
- Unembryonated eggs passed with the stool
- Embryonate in the soil
- Ingested (soil contaminated hands, or food)
- hatch in the small intestine and release larvae
- Migrate to the colon
- Wrap themselves around villi -
- Burrow to the LP
- Suck blood from capillaries
- Females produce 20-30K per day
Whipworm
Epi and geopraphic distribution
3rd most common round worm of humans
Infections more frequent in tropical climates; urban areas
whipworm
Clinical features: light vs heavy
Dx/Labs
Treatment
Clinical Features:
Flatulence, lower abd pain, constipation, diarreha
Severe: dysentery, tenesmus, anemia (growth and mental retardation); Intestinal blockage; Rectal prolapse
Labs: Microscopy
Treatment: Mebendazole; albendazole
Strongyloides
aka
Describe the lifecycle and how its infectious to humans
how do they reproduce?
what is autoinfection?
aka - Threadworm
Lifecycle similar to hookworm L3 Penetrates skin Travels to lung, esophagus, gut travel to colon Develop into ONLY FEMALES
Reproduce – larave exit feces and can develop into males and females
Autoinfection – larvae themselves penetrate through the gut
Strongyloides
- Clinical features: moderate vs severe
Labs:
frequently asymptomatic
Moderate infection: sx associated with migrating larvae
rash at site of penetration
coughing and wheezing if in lungs
abd pain, N, V, Dharrhea
Severe: chronic colitis, anemia due to blood loss, diarrhea, weight loss
Labs; microscopy
Treat: ivermectin
Trichonosis –
what bug causes this?
what kind of bug is this?
describe the lifecycle and how it infects humans
Trichinella Spiralis
Zoonotic Nematode
Lifecycle mainly in rodents rodents eaten by pigs/bears Eggs hatch in intestine Larvae enter striated muscle tissue Form cyst Human eats pig or bear meat Eggs --> larvae --> skeletal muscle cysts
Trichonosis
clinical manifestations
Diagnosis
Treatment
days 1-2: GI symptoms
Facial edema, fevers, chills, arthralgias
heavy infection: CNS involvement, respiratory involvement, cardiac involvement
Dx– muscle bx of encysted larvae
Treat: Albendazole; mebendezole
Toxocariasis
what bug(s) cause(s) this?
what kind of bug is this?
describe its lifecycle and how it infects humans?
Toxacara canis and Toxicara cati
Zoonotic Nematode
Lifecycle predominantly in dogs and cats Eggs released in feces Children take eggs into mouth from contaminated soil (sand box) Eggs hatch in our intestine Larval Migrants (wander to viscera, eyes)
Toxocariasis:
What are the different clinical manifestations?
dx
Treatment
Asymptomatic
Ocular Larval Migrans:
- ocular scaring of cornea, retina — vision loss
Visceral Larval Migrans:
migrate under skin; to heart, liver, lung, brain
Dx: clinical presentation, exposure hx, antibody detection
Treat:
VLM - antiinflammatory
OLM - Mebendazole, albendazole
Lymphatic Filariasis:
- what bugs cause it?
- how does it infect humans (what is the vector)?
- describe the life cycle
Wucheria bancrofti
Brugia malayi
Female mosquito takes blood meal and introduces the L3 larvae into the host
L3 –> L4 (becomes motile)
finds way to the lymphatic system
Finds a vessel that is just afferent to a large LN
Male and females mate –
L1 larvae released to Lymph
Make it to ciruculatory system
Picked up by a mosquito
Lymphatic Filariasis:
what are the clinical manifestations?
Diagnosis?
Treatment?
Clinical Manifestations:
- inflammatory responses block lymph flow: Elephantitis
- If chronic – can become vascularized and permanent
- Febrile episodes
- Hanging Groin
- chyluria
Dx: Microfilariae by microscopy
Giemsa satin
Serology, PCR
Treat:
Diethylcarbamazine, Ivermectin
Onchocerciasis (River Blindness)
what is the bug that causes this?
What is the vector?
describe the life cycle and how its infectious to humans
Onchocerca volvulus
a tissue dwelling nematode
vector: Blackfly –
Blackfly bite transmits L3
L4 Develops into males and females
A connective tissue capsule contains the bug in the dermis
Larvae disseminate under the skin
can migrate to the eyes; repeated lesions will lead to blindness
Onchocerciasis (River Blindness)
what are the clinical manifestations?
Diagnosis?
Treatment
manifestations: Itching, eruptions, exfoliative dermatitis,
Eye: punctate keratitis, sclerosis keratitis, blindness
Skin: Loss of elastase – elephant skin
Depigmentation on top on bony prominence – leopard skin
Dx: skin bx
pretzel stage
Tx:
Ivermectin, Dierthylcarbamazine; Doxycycline
What is the signature lesion of river blindness?
Sclerotic keratitis of the cornea leading to pinholing of vision
Describe the lymphatic pathology of
§ Wuchereria bancrofti
§ Brugia malayi
§ Onchocerca volvulus
- acute lymphatic swellings
- recurrent swelling can lead to persistent elephantitis
- Hanging groin –
– Secondary nodules:
regions of swelling are immunodeficient; more susceptible to infections, including commensals
- Chyluria
what is the “parasite” of the parasite that causes filariasis?
what can it be treated with? what is the result
Wolbachia - intracellular gram negative proteobacteria of Filariasis causing agents
Treat with doxy - parasite becomes sterile
inflammatory responses to this bug is responsbile for ocular manifestations. Treat the bug, no inflamatory response
