Helminths Flashcards
Worms of the intestines
Nematodes: Ascaris Pinworms Hookworms Whipworms
Cestodes: Taenia spp Echinococcus Granulosus (hydatid cysts) Diphyllobothrium latum (fish tapeworm) Hymeolepis nana
Life cycle, symptoms, transmission, and treatment of ascaris
A. lumbricoides
One of the largest and most ubiquitous worms
Life cycle:
Eggs require 2-3 weeks in soil If ingested, hatch in duodenum
If penetrate, end up in pulmonary circulation grow and molt in alveoli coughed and swallowed and hatch in intestine
Symptoms:
Pneumonitis
Sudden asthma attacks in non-asthmatics
Heavy infections of adult worms may cause intestinal obstruction
Transmission:
Ova in feces
Passage of adult ascarid
Treatment:
Albendazole/ Mebendazole (Vermox)
Life cycle, symptoms, diagnosis, and treatment of pinworm
Enterobius vermicularis
Most common helminth infection in US
Oral-fecal transmission; eggs can be in dust/clothes
Life cycle:
Gravid females migrate to perianal area to deposit eggs Don’t need intermediate host
Symptoms:
Infection is common, but sx are mild
Allergy/prurits (perianal) lose sleep
Worm can migrate to vagina and cause granuloma
Diagnosis:
Ova in cellophane tape slide preparation or sediment of saline rinse from a swap of perianal area
Treatment:
Albendazole/ Mebendazole(Vermox) Reinfection is common
Life cycle, symptoms, diagnosis, and treatment of whipworms
Trichuris trichuria
“whip” like appearance
Lifecycle:
Similar to pinworm lifecycle except eggs require 2-3 wks in soil to become infectious
Infection:
Light infection=asymp Heavy infection= abd pain with bloody or mucoid diarrhea; appendicitis;
prolapsed, edematous rectum
Diagnosis:
No eosinophilia
Treatment:
Albendazole/ Mebendazole(Vermox)
Life cycle, symptoms, diagnosis, and treatment of hookworms
Strongyloides
Similar to hookworms except that eggs hatch in intestinal mucosa and rhabditiform larvae are passed in feces
Lifecycle:
Autoinfection can result from transformation of rhabditiform to filariform in gut followed by penetration into circulation
Infection:
More in immunosuppressed i.e. AIDS patients or high dose corticosteroids autoinfection and dissemination also higher Dypsnea, abdominal pain
Diagnosis:
Larvae in feces Larvae in sputum if disease is disseminated
Treatment:
Ivermectin
Life cycle, symptoms, diagnosis, and treatment of Taenia species
Tapeworms
Anterior attachment organ=ScolexStrobila=chain of segments (proglottids) T. saginata=beeftapeworm –requires intermediate hostT. solium=porktapeworm
Life cycle:
Embryonate eggs ingested by (pig/cow)Humans eat undercooked meat scolex attaches to intestinal wall, produce strobila In pork, BUT NOT BEEF, cysticercosis can developand the human can transmit
Infections:
Often asymptomatic; abd pain, hunger, indigestion, eosinophilia Later on: can have cerebral and neurocysticerosis
Diagnosis:
Morphology is the same SO the numbers of uterine branches in the proglottids (India Ink) distinguish beef and pork species Beef=15-30Pork=7-13Al/
Treatment:
Mebendazole or Praziquantel (except if neural involvement)
Life cycle, symptoms, diagnosis, and treatment of Echinococcus granulosis
Hydatid cyst formation
From ingesting eggs from feces of animals NOT from eating animal itself
Life cycle:
Tapeworm stage only in animal (not human)
Ingest eggs → larvae migrate and form slow-growing tumor like hydatid cysts
Infections:
Liver and lung are most common site of cysts
Like slow growing tumor
Rupture of cysts can lead to secondary echinococcosis
Diagnosis
Cysts in feces
Treatment:
Surgical removal then anti-helminth drugs (Prazi)
Life cycle, symptoms, diagnosis, and treatment of Diphyllobothrium latum
Fish tapeworm
Requires 2 intermediate hosts
Rare in the US but increasing with increased consumption of raw fresh water fish
Other fishy worms
Sparganosis (spirometra mansoni): Asia, Australia
Anisakisasis: in raw fish
Life cycle:
Eggs passed in feces hatch into ciliated coracidium larvae→ then ingested by small crustaceans
Fish eat the infected crustaceans → third stage larvae develops
Human eats fish; larva grow in small intestine
Infections:
Usually asymptomatic; may produce a B12 deficiency anemia indistinguishable from pernicious anemia
Diagnosis:
Characteristic ova or proglottids in feces
Treatment:
Praziquantel
Niclosamide
Life cycle, symptoms, diagnosis, and treatment of Dracunculiasis (Guinea Worm)
Guinea worm:
From drinking contaminated water
Poised to be the next eradicated disease (led by Carter Center) after smallpox due to clean water
Life cycle:
Ingest infested water
Larvae develop in intestine → migrate thru subcutan tissue → cause ulcer, migrate thru skin
Infections:
Ulcer with worm
Diagnosis:
Clinical presentation
Treatment:
Clean water
Life cycle, symptoms, diagnosis, and treatment of Trichina
Trichinella spiralis
Used to be very common, but now only ~100 cases/yr, usually from undercooked pork or consumption of wild animals
Life cycle:
None noted
Infections:
Trichinosis: larvae in heart, muscle, brain and GI tract
Bilat periorbital edema, conjunctivits
Diagnosis:
Immunological tests or muscle biopsy in setting of symptoms and marked eosinophilia
Treatment:
No effective drugs
Life cycle, symptoms, diagnosis, and treatment of Filaria
Wuchereria bancrofti (elephantiasis)
Most common cause of lymphatic filariasis
Transmitted by mosquitoes; humans are only reservoir
Symptoms are result of Wolbachia bacteria that infect the worm → thus new treatment strategy is to get rid of this and thus get rid of worm effects
Life cycle:
Lie in lymphatic vessels for years
Embryonated eggs produce microfilarieae that reach the blood
Infections:
Most common cause of lymphatic filariasis (usu unilateral)
Agent of elephantiasis=grotesque swollen limbs and scrotum
Diagnosis:
None noted
Treatment:
Anti-helminth
Doxy/tetracycline
Life cycle, symptoms, diagnosis, and treatment of Trematodes
Schistosomes (Schistosomiasis):
S. mansoni (gut): Arabia, Africa, Caribbean, S. America
S. japonicum (gut): China, Japan, Phillipines
S. haematobium (bladder): Africa, Middle East
Life cycle:
Eggs hatch, releasing miracidia, which are ingested by snail→ released
Penetrate skin → go to bladder
Infections:
Dermatitis (“swimmer’s itch”)
Katayama fever
Chronic fibro-obstructive sequalae
Diagnosis:
Ova in urine
Distinguish types by position of spike and regions visited by patient
Treatment:
Praziquantel
Blood and deep tissue worms
Dracunculiasis (Guinea Worm) Trichina Filaria Onchocerca volvulus Trematodes/Schistosomes
