Parasites II: helminths and Vermin Flashcards
what is the tissue response
eosinophilia
- IgE, mast cells
- eosinophils chemotactic factors
- IL-4 and IL-5
most important fatal helminth disease in humans
schistosomiasis
- S. mansoni: latin america, Africa, Middle east
- S. japonicum: Asia
- S. haematobium: Africa
death usually results from what for schistosomiasis
hepatic granulomas and fibrosis
special difference with S. haematobium
hematuria and obstruction of bladder
-predisposes to squamous cell carcinoma of bladder
Life cycle of schistosomiasis
- sporocytes in fresh water snails
- ceraria infect humans by penetrating through skin
- migrate in peripheral vasculature to portal and pelvic venous system where they develop into adult worms
what is reaction of body to egg formation?
granulomas and fibrosis
where do eggs shed for schistosomiasis?
shed in feces
-complete life cycle when hatch in water
pathogenesis of schistosomiasis
hepatic damage is due to toxic products and cell-mediated immunity
induction of what factors cause induction of IgE
IL-3, 4,5
- induction of IgE synthesis, mastocytosis, and eosinophils
- resistance to reinfection-> IgE levels
what do eggs from schistosomiasis induce?
lymphocytes to secrete fibrogenic factors with fibroblast proliferation and portal fibrosis
hallmark of schistosomiasis
hepatic fibrosis out of proportion to the parasite injury
schistosomiasis granuloma
- calcified pinhead granulomas form around the egg
- include macrophages, lymphocytes, neutrophils and eosinophils
how do these granulomas cause portal hypertension?
pipestem portal fibrosis results in portal hypertension, splenomegaly, esophageal varices and ascites
which schistosomiasis associated with bladder cancer
S. Haematobium
-squamous cell carcinoma of bladder
Liver flukes
Clonorchis siensis
- infected by eating improperly cooked fish
- live in biliary ducts
- usually asymptomatic
what can liver flukes result in
biliary hyperplasia, fibrosis, portal cirrhosis
-chronic infection-> cholangitis, cholelithiasis, pancreatitis, cholangiocarcinoma
tapeworms
Taenia saginata-> beef tape worm
taenia solium-> pork tapeworm
Taenia saginata
ingestion of undercooked beef
-NO cysticercosus (but does cause it in pig)
taenia solium
ingestion of undercooked pork with encysted cysticerci
-attach to intestinal wall with scolices, proglottids with eggs shed in feces
cysticercosus
T. solium eggs ingested-> larvae hatch-> penetrate gut wall
how to T. solium cysts get into CNS?
hematogenous dissemination
-convulsions, increased intracranial pressure, mental disturbances
what kind of cyst cause a host reaction in T. solium cysticercosus
degeneration cysts result in local inflammation and focal scarring, calcifications
Echinococcus
E. granulosus
E. multilocularis
E. granulosus
E. multilocularis
canine tapeworms
- ingestion of eggs from infected animals
- asymptomatic and chronic
E. granulosus
southwest US
- hydatid cysts may result in an anaphylactic reaction if the cysts ruptures
- DO NOT spill contents of cysts
E. multilocularis
northern US and Canada
-liver disease, usually fatal
where do Echinococcus cysts most commonly found?
hydatid cysts most commonly in liver and lungs
Enterobius vermicularis
pinworms
- most common in US
- worm of intestine
- spread by oral ingestion of eggs extruded from anus
- anal puritis
- lifespan: 2 months
Trichuris trichiura
whipworms
- common in tropics
- warm, moist areas of southern US
- symptoms depend on wormload, local hyperemia, lesions of colonic mucosa
- NOT invasive
Necator Americans/Ancylostoma duodenale
hookworms
- attach to upper levels of small intestine
- transmitted by infectious larvae, not eggs
- larvae penetrate between toes
- dissemination follows a route similar to ascaris
dissemination of ascaris, hookworms, and stronglyoides
ingestions of eggs-> bloodstream-> lungs-> invasion by filariform larvae-> esophagus-> adult forms reside in intestines
hookworm pathology
small, itchy papule where they penetrate the skin
- mild pneumonitis may result from traveling thru the lungs
- most significant symptoms and signs occur from ingestion of blood of host leading to blood loss (.2ml/worm/day)
strongyloides stercoralis
- distribution parallels hookworms, similar life cycle
- entry of filaria through skin
- Appalachia, SE US
- cat/dogs as reservoirs
manifestations of strongyloides stercoralis
usually mild
-in IC’s, hyperinfection may result with severe penumonitis and duodenitis
most common parasite of humans after pinworms
Ascaris lumbricoides
Ascaris lumbricoides
tropics and subtropics
- large worms
- live unattached in lumen of small intestine
signs and symptoms of Ascaris lumbricoides
eosinophilic pneumonitis of lung including dyspnea, dry cough, fever, eosinophilia
- colicky epigastric or periumbilical pain
- malnutrition
greatest danger related to Ascaris lumbricoides
results from abdominal migration in body including blockage of biliary ducts
-obstruction of small intestine may also occur
small intestine parasites
giardia
hookworm
stryongyloides
ascaris
Trichinella spiralis
- ingestion of improperly cooked pork
- larvae penetrate tissue-> disseminate hematogenously-> encyst in muscle cells
- muscle cells involved: diaphragm, EOM, laryngeal, deltoid, gastrocnemius, intercostal muscles
- eosinophilia, fever, myalgias, periorbital edema
how does Trichinella spiralis cause eosinophilic infiltrate in lungs?
trapped larvae in lungs
how can Trichinella spiralis cause heart failure
patchy interstitial myocarditis with eosinophilia and giant cells resulting in scarring, heart failure
Larval Migrans syndromes (LMS)
- zoonotic disease: nonhuman hookworms cannot complete life cycle in humans
- LMS: intense eosinophilic inflammatory reaction by host
- treatment: decrease inflammatory reaction: steroids and antihistamines
cutaneous larval migrans
Ancylostoma
- creeping eruption: associated with hookworms of dog, cat
- causes intensely pruritis skin lesions
- plumbers, construction workers, duck hunters, others exposed to infected soil
visceral larval migrans
Toxocara canis, T. cati
- dog/cats infected-> dissemination through body
- usually S-L
- puppies-> give to children
- hepatomegaly, hypereosinophilia, hypergammaglobulinemia, history of geophagia
neural larval migrans
Balisascaris
- -wildlife
- infections of raccoons
- children of poor hygiene and geophagia
- disease depends on # of organisms and re-infections
- CNS disease: results in eosinophilic meningoencephalitis
- larvae not lost in stools, diagnosis by tissue
lymphatic filariasis
wuchereria bancrofti
- subSaharan africa, L.A. and SE asia
- mosquitos
- larvae develop in lymphatic channels-> chronic damage to lymphatics (T cell mediated)-> granulomas around adult parasites
- can result in lymphatic dilatation and lymphedema is terms elephantiasis when in lower limb
- scrotum, penis, vulva, leg or arm
Filariasis
- infected larvae transmitted by infected biting arthropods during blood meal
- larvae migrate to appropriate site of host’s body-> develop into micro-filariae producing adults
- adults dwell in various human tissue-> can live there for several years
- microfilariae infect biting arthropods
river blindness
onchocerca volvulus
- filarial nematode: transmitted by blackflies
- MAJOR cause of blindness in Africa: punctate keraitis, damage to retinal (cross reaction between parasite antigen and retinal pigment epithelial cells)
- chronic pruritic dermatitis, sub, cut. dermal nodules (onchocercoma)
head lice
pediculus humanus capitis
body lice
pediculus humanus humanus
crab louse
Pthirus pubis
scabies
sarcoptes scabei
chiggers
larvae of prostigmata (mites)
Fleas
human (Pulex irritans) or rat (xenopsylla cheopis)
body lice and head lice vectors for
louse borne typhus: rickettsia prowazeki
trench fever: rochalimaea quintana
louse-borne relapsing fever: Borrellia recurrentis
crab louse characteristics
STD
Blue spots
-.2-.3 cm in diameter, irregular outline, painless, do not disappear on pressure, deeper tissue
-appear after hours after crab lice has bitten and last for days
-poisonous saliva injected by crab louse (similar to melanoderma caused by body louse)
scabies characteristics
close contact spread
- burrow in skin but never beyond stratum corneum
- intense pruritic lesions: mediated by IgE, mast cells, E
- re-occur every 28 days after locally laid eggs hatch
- other races cause in animals: just itchy in humans
chigger bites
(mites)
- take up residence in hair follicles
- inject digestive enzymes that rupture cells, causing an intense local inflammatory response
rhinosporidiosis
Mesomycetozoea
- aquatic protistan
- india, Sri. Lanka, Texas, SW US
- traumatic inoculation of organism from water source
- causes granulomatous of mucous membranes resulting in polyp formation
- infections of nose, nasopharynx, conjunctiva
