Vector Borne Helminth Infections and Schistosomiasis Flashcards Preview

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Flashcards in Vector Borne Helminth Infections and Schistosomiasis Deck (37)
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Nematoda, Cestoda, and trematoda

Roundworms, tapeworms, flukes


Themes in helminth infections

Long ter mand chronic
ANy type of host
All life cycle stages can cause symptoms
Host response is responsble for symtoms


Host responses to helminths

Lots of morbidity but little mortality
Th2 like response
IgE with eosinophilia and mast cell responses


Wuchereria bancrofti and brugia malayi vector and dz

mosquito and lymphatic filariasis


Loa loa
Onchocerca volvulus
Dirofilaria immitis

Vectors and dz

Crysops fly - loasis
Simulium fly - river blindness
Mosquito - canine heartworm


Lymphatic filariasis transmission

Any kind of mosquito...anopheles, culex, aedes
Anopheles and culex bite at night while aedes bites in day


Lymphatic filariasis infeciton process

MF (microfilariae) develop in the mosquito and migrate outside of the surface of the proboscis...migrate in from the skin to the blood to the lymph tissue

Live 5-10 years and are viviparous (no egges)


Timing and release of MF

Synchronized with biting habits...anopheles and culex in lymph nodes release MF at night

Some people develop elephantitis, most do not


Pregression of lymphatic filariasis

Larvae mature in lymph nodes for 6 months to a year...migrate to lymph nodes in lower extremities like legs, groin, genitalia...can remain paired for 5-40 years...fever may be present and then recurrent lymphedema due to worms lodged in lymphatic system

If adult worms die, huge immune response that results in formation of granulomas that become fibrotic, blocking vessels and causing localized damage



Giant swelling of organs or tissues triggered by lymph entering the tissue causing prolif of tissue and skin in localized manner


Men can get ____ with lymphatic filariasis

Orchitis with hydrocele (enlargement of the scrotum)


Tx of lymphatic filariasis

Focus on controlling MF grwoth
Piperizine derivatives (diethylcarbamazine DEC) is a prophlyactic for mass tx...paralyzes MF and then cleared by liver...potential allergic side effects cause anaphylaxis in some cases

Ivermectin/mebendazole can work


Strategies to control filarial dz

Control of contact with vectors
Detect with periodic blood smears
Periodic admin of DEC to both symptomatic and asymptomatic patients


Loa loa

Transmitted by chrysops biting fly
Slow developing dz


Loa loa life cycle

MF enter fly bite during blood meal...develop into adults (1-4 years)...migrate through tissue and release worms and MF do NOT elicit a significant immune response of cause severe pathology in loa loa


Migration of loa loa

Occurs subcutaneously
Generally painless but can be felt on bridge of nose, conjunctiva and eyelid
Calabar swelling can occur - severe angioedema
Liver worms elicit minor pathology than dead
Dead elicit huge eosinophilic response


Ocular involvement of loa loa

Cause ocular filariasis - release MF which interfere with cornea and retina

Must be removed surgically


Detection, tx, and periods of loa loa

Detect MF, highest levels are midday...can detect ocular with slit lamp

DEC kills MF and immature stages but not adults (be careful with dose)...ivermectin and mebendazole can also be used

Adult worms must be removed during transit through eye

Incubation - 2-12 months
Prepatent - 6 mos -4 years
Patent - 4-17 years


Onchocerca volvulus

Transmitted by simulium of black flies
Only females
Transmit 3rd stage larvae (L3) or MF
Repeated infections can cause progressive blindness


Progression of onchocerca volvulus

MF migrate through skin maturing for about a year...slow migration results in nodules...worms mate and produce MF which migrate to skin and eye...MF taken back up by simulium flies


Symptoms of onchocerca volvulus

Cutaneous - papular dermatitis (craw craw), thickening of skin (sowda), changes in pigmentation...also elephantiasis

Ocular - mostly from dead MF...keratitis...chroioretian ldamage in anterior chamber of the eye...inflam damage to optic nerve and retina


Diagnosis and tx of onchocerca

Skin snips from nodules
Slit lamp of anterior chamber
Sclerocorneal punch biopsy
Rarely detectable in blood

DEC (could worsen cutaneous symptoms), Ivermectin, surgery



Leaf or oval shaped
Blind alimentary canal
Locomotion by muscle movement
Adults pair for life
Use snails as IM hosts


Schistosomiasis stages

Eggs are released in partially matured state...mature in bodies of water and release miracidia...miracidia infect snail and form sporocyst within which thousands of cercariae are formed...cercariae are released from snail to water and infect the human...mature in humans to adults and form mating pairs


Schistosomiasis structure and cause of pathology

Female in the gynocophorous canal of the male
Eggs responsbile for pathology caused by worms


Life cycle of schistosomiais in humans

Cercariae burrow in skin or swallowed...intesstinal migrate to mesenteric veins...urinary migrate to pelvic veins...eggs are shed


At site of infection

Maculopapular rash in hours-week


Intestinal schistosomiasis

Acute - takes 14-84 days
Fever, headache, hepatomegaly, bloody diarrhea, S mansoni can have resp syndromes
Symptoms coincide with depositon of eggs


Chronic intestinal schistosomiasis

Immune response to eggs and granuloma formation
Force eggs into the lumen of the boewel
Maximal granuloma at intestine and following portal circulation, the liver
Hypogastric pain with blood in the stool, diarrhea and constipation...colon cancer symptoms
Liver fibrosis promoting hepatomegaly...postal hypertension, anemia, and ascites due to liver damage


Urogenital schistosomiasis

Initial symptom in hematouria
Increased proteourea
Granulomas in the bladder
Obstruction of ureters
Renal colic and failure
Women can get female genital schistosomiasis as ulcertive, hypertrophic lesions on the vulva and perineum (also from intestinal)


Pulmonary schisto

Escape of eggs to lungs leads to pulmonary hypertension and cardiac hypertrophy


CNS shisto

S japaniocum can impair blood flow


Childhood schisto

Anemia, growth and reatardation


Intestinal schisto vs. urinary times

Intestinal has patent period of 25 years, uro only 25 weeks


Tx of schisto

Praziquantel and tetrahydroquinolones


Microbilharzaria variglandis

Cercarial dermatitis caused by schisto in lakes and ponds
Dead end host
Rash, itching, localized edema
Topical corticosteroids and antihistamines


other flukes