Microbiology: Nematodes

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Cause: Anisakiasis

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is herring worm, infection of GI

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Epidemoilogy: Anisakiasis

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marine mammals as reservoir and definitive hosts

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life cycle: Anisakiasis

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1) eggs released in feces and crustaceans (1st hosts) eat larvae
2) saltwater fish or squid (second int. hosts) eat infected crustaceans and larvae encyst in muscles
3) marine mammals eat infected fish and adult worms in organs of abdominal cavity
4) humans eat raw fish, larvae dont develop into adults

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pathogensis: Anisakiasis

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laravae produce obstruction and inflammation at sites of invasion that develop into eusinophilic granulomas

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Tx: Anisakiasis

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mebendazole with surgical removal

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cause: Ancylostomiasis

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Ancylostoma duodenale and Necator americanus are human hookworms

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life cycle: Ancylostomiasis

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1) Adult worms live in SI of humans
2) Rhabditiform larvae hatch from eggs and develop into infectious filariform larvae on ground
3) infected larvae penetrate skin of humans, go to lungs, coughed and swallowed- adult worms in SI

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Pathogenesis: Ancylostomiasis

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adult worms suck blood from SI producing iron deficiency anemia

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Tx: Ancylostomiasis

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Mebendazole

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Cause: Ascariasis

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Ascaris lumbricoides is human roundworm, 1billion people carry

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can form ball and block intestine,

curly tail

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Ascariasis

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life cycle: Ascariasis

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1) adult worms live in SI of humans and eggs pass out with feces in soil
2) humans ingest, larvae hatch in stomach and penetrate SI
3) larvae further develop in lungs, coughed and swallowed and become adult worms in SI

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Pathogenesis: Ascariasis

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intestinal disturbances,
-trapped larvae in lungs and liver produce immune response and allergies

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Symptoms: Ascariasis

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Lofflers syndrome (eosinophilia in lung tissue)

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Tx: Ascariasis

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Mebendazole

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cause: Enterobiasis

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human pinworm

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Epidemiology: Enterobiasis

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group infection, whole family needs treatment

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life cycle: Enterobiasis

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1) lives in LI,
2) adult females migrate out at night lay eggs
3) humans ingest eggs from fecal material
4) eggs become infective, hatch in SI and develop into adults in LI

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Pathogenesis/Sx: Enterobiasis

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-appendicitis and pelvic peritoneal granulomas
-anal pruritus

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Dx: Enterobiasis

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transparent tape to anal area in morning and observed for elongated thin shelled eggs with well developed embryos and flat-side

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Tx: Enterobiasis

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Albendazole

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life cycle: Strongyloidiasis

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1) parthenogenic adult female worms live in SI
2) produce larvated eggs that have rhabditiform larvae- pass out with feces and develop into filariform larvae
3) filariform larvae penetrates skin of humans go to lungs, cough and swallow- to SI
4) autoinfection is due to filariform larvae in intestine and then penetrating skin of anal area

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Pathogensis: Strongyloidiasis

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-sloughing of patches in intestinal mucosa
-hyperinfection- or autoinfection: larvae invade lungs, GI tract, lymph nodes

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Sx: Strongyloidiasis

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serpinginous macular eruptions on skin with itching and rashes or urticaria q

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Tx:Strongyloidiasis

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Ivermectin + retreatment

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cause: Trichuriasis

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human whipworm

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Epidemiology: Trichuriasis

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humans only

Louisiana

feces is fertilizer

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Life cycle: Trichuriasis

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1) Adult worms live in large intestine where they release eggs which mature in soil
2) ingest food or contaminated water and larvae hatch in the small intestine and develop into adult worms in large intestine (years of life)

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pathogenesis: Trichuriasis

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adult worms and eggs produce inflammation of mucosal lining of cecum and eggs get trapped in appendix- appendicitis

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Sx: Trichuriasis

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malnourishment, anemia, colon infection symptoms

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Dx: Trichuriasis

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Barrel shaped polar plugged eggs

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Tx: Trichuriasis

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Mebendazole

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Cause: cutaneous larva migrans

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ancylostoma braziliense and ancylostoma caninum cat and dog hookworms

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pathogenesis: cutaneous larva migrans

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larvae penetrate skin and wander around dermis of humans but never enter blood stream (like shistasome dermatitis)

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Sx: cutaneous larva migrans

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-serpinginous tunnels,
-quick onset,
-vesicles and bullae at sight of entry,
-tunnels dry and crusted leaving dead tissue

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Dx: cutaneous larva migrans

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history of exposure

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Tx: cutaneous larva migrans

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albendazole

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life cycle: cutaneous larva migrans

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1) adult worms in SI of dogs and cats- eggs out in feces
2) larvae hatch out of eggs and develop into filariform larvae on soil
3) larvae penetrate skin on contact and humans are dead end hosts (like shistosome dermatitis)

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cause: Neural larva migrans

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Baylisascaris procyonis, racoon roundworm

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epidemiology: Neural larva migrans

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racoons are definitive hosts, humans are dead end hosts, non human animals- intermediate

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life cycle: Neural larva migrans

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1) adult worms live in SI of racoons- eggs in feces out into ground
2) mammals ingest eggs and larvae encyst
3) racoons eat infective larvae when feeding and adult worms go to SI

1) humans ingest eggs larvae migrate to nervous system- humans are dead end hosts

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Dx: Neural larva migrans

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Clinical history of eating dirt contaminated racoon feces,

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Tx: Neural larva migrans

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Thiabendazole and steroids

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Cause: Visceral larva migrans

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Toxocara canis, Toxocara cati, eggs wander in viscera

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Epidemiology: Visceral larva migrans

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-dogs and cats are reservoirs
-transmitted by eating raw infected tissue of chickens sheep or cattle

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life cycle: Visceral larva migrans

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1) adult worms are found in SI of dogs/cats eggs released-ground
2) eggs ingested by dogs cats, larvae to lungs cough/swallow adults in SI
3) humans (accidental host) larvae enter bloodstream and migrate extensively through visceral organs (dont mature into adults)

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pathogenesis: Visceral larva migrans

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-migrating larvae produce allergies
-damage depends on # of eggs

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Sx: Visceral larva migrans

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Loss of vision

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Tx: Visceral larva migrans

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Ivermectin and steroids

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Trichinella Spiralis: cause of Trichinosis- larvae is?

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larvae is round and coiled

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Life cycle: Trichinosis

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1) adult worms live in SI
2) larvae are released directly into bloodstream when female inserts ends into mucosa and forms cysts
3) humans ingest undercooked infected meat- larvae excyst and form adult worms in SI

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Pathogensis: Trichinosis

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Larvae and adult worms burrow in intestinal mucosa producing inflammation, toxic effects and hypersensitivity

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Symptoms: Trichinosis

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malaise abdominal pain, 1 to 5 days, cough, intensive muscle pain, congestive heart failure, 7 to 14 days post infection

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Dx: Trichinosis

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Encysted larvae in muscle tissue

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Tx: Trichinosis

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-Thiabendazole is effectve in intestinal stage
-Mebendazole in muscular stage

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Cause: Filiarsis

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Wuchereria bancrofti and Brugai Malayi

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Epidemiology: Filiarsis

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tropical areas of the world

W. bancrofti- humans only
B. Malayi- humans and non-humans

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Life cycle Filiarsis

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1) Uninfected mosquito ingest microfilariae and are vectors
2) microfilariae are passed from infected mosquitoes (mansonia) into bloodstream and develop into adult worms after migration into lymphatic system of humans

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Pathogensis: Filiarsis

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slow movement of lymph fluid- elephantiasis

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Tx: Filiarsis

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Diethylcarbamazine

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Cause: Dirofiliariasis

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dog heartworm

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Life cycle: Dirofiliariasis

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1) adult worms live in hearts of dogs
2) Microfilariae are released into bloodstream, nocturnally where they are picked up by mosquitoes during a blood meal
3) mosquitoes inject into other dogs or humans (in humans non threatening)
4) larvae develop into adult worms in heart in dogs

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Pathogenesis: Dirofiliariasis

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microfilariae are trapped in skin or lung tissues and produce allergic reactions

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Sx: Dirofiliariasis

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Coin shaped lesions

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Tx: Dirofiliariasis

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Surgical removal and Ivermectin

Front 66

Cause: Dracunculiasis

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guinea worm, firy serpeant bc it burns when sore opens

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Epidemiology Dracunculiasis

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Africa and Asia, humans only as reservoir

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Life cycle: Dracunculiasis

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1) adult worms live in connective tissue underneath skin of humans
2) larvae are released when skin comes into contact with water
3) Cyclops or water flea ingest larvae and larvae develop into infective form
4) when humans drink water containing flea, larvae break out of fleas, penetrate mucosa of stomach and migrate through blood to sites under skin where they are adult worms

Front 69

Pathogenesis: Dracunculiasis

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adult worms release metabolites into the connective tissue and produce allergic reactions

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Sx: Dracunculiasis

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yearlong incubation period

ulcers become secondarily infected with bacteria

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Dx: Dracunculiasis

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adult female worms are found excending from subcutaneous tissue releasing larvae in water

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Tx: Dracunculiasis

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Sugery or physical removal of worm (need to get whole worm)

Tetanus immunization should be given

control by purifying water

Front 73

Cause: Loiasis

Back 73

arthropod eye worm

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Epidemiology: Loiasis

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equatorial africa, humans only

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life cycle: Loiasis

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-adult worms of Loa loa live in subcutaneous tissue of humans where they release microfilariae
-deer flies pick up microfilariae
-microfilariae develop into infectious filariform larvae and are then transmitted to a new human host during blood meal

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Pathogenesis: Loiasis

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adult worms move around in subcutaneous tissue releasing metabolites that produce inflammatory raection

worms appear under conjunctiva

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Sx: Loiasis

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-subcutaneous Calabar swellings
-worms under conjunctiva produce irritation, crawling sensation in eye

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Tx: Loiasis

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Diethylcarbamazine for tx and prophylaxis

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Epidemiology: Onchocerciasis

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Equatorial Africa, South and Central America

Humans and monkeys as reservoirs

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Life cycle: Onchocerciasis (river blindness)

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1) adult worms live in subcutaneous tissues of humans, females release microfilariae into skin
2) female black flies pick up microfilariae and larvae develop into filariform larvae
3) black flies transmit filariform larvae into humans

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Pathogenesis: Onchocerciasis

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incubation is one year or more

microfilariae cause severe pathogenic effects in eyes when they die and become enveloped in fibrous scar or onchocercoma

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Sx: Onchocerciasis

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subcutaneous worms, optic nerve damage in skin

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Dx: Onchocerciasis

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Mazzotti test: oral dose of diethylcarbamazine produces a papular erythematous rxn in affected skin along with conjunctival swelling

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Tx: Onchocerciasis

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Diethylcarbamazine