Parasites

Question 1

Ascaris lumbricoides

Answer 1

a large nematode that causes intestinal infection and very rarely obstruction. easily visible macroscopically as it is 15-30cm in length, infection is by ingestion of embryonated eggs from infected soil (SE Asia/ South America). humans = definitive hosts. lung migration –> loefflers syndrome, intestinal phase –> worm burden

Question 2

Borrelia burgdorferi

Answer 2

spriochaete that causes lymes disease. organism transmitted from rodent and ruminant hosts to man by lxodes tick (zoonosis) –> skin rash (erythema chronicum migrans) and arthritis. diagnosis by serology as difficult to grow

Question 3

cryptosporidium

Answer 3

protozoan causes severe diarrhoes in AIDS patients, known to be a sever cause of self-limiting diarrhoea (diarrhoea and mucus) in children. cysts found in water supplies (e.g. swimming pools) also carried by animals and lead to outbreaks. human-human spread = faecal oral. diagnosis by microscopy for cysts in stools. no available treatment

Question 4

echinococcus

Answer 4

platyhelminth (flatworm) –> cestode (tapeworm) genus of helminth that causes hydatid disease. commonest species is e.granulosus a tapeworm of dogs. life cycle includes small intestine of dogs and internal organs of ruminants (sheep, goats). ingestion of tapeworm ova –> worms hatch –> lungs and liver –> large fluid filled cysts. human - accidental or dead host (life cycle does not progress in them)

Question 5

entamoeba histolytica

Answer 5

protozoa –> amoeba –> sever diarrhoea (amoebic dysentery) an occasionally fluid-filled lesions in the liver (Abscess). infection = faecal-oral, by poor sanitation. direct detection of amoebic cysts in stool sample. amoebic abscesses may be diagnosed by serology.

Question 6

enterobius vermicularis

Answer 6

pin worm, threadworm. very common helminth infection transmitted by infection of ova from the faeces of infected individuals. diagnosis = detection of ova in stool or from anal sample. usually treated with anti-helminthic agent but many cases remain undiagnosed.

Question 7

giardia intestinalis

Answer 7

protozoa –> flagellate –> found at trophozoites in the upper small intestine or as cysts in faeces. major cause of diarrhoea worldwide can cause failure to thrive due to malabsorption by children. microscopy of stools for cysts or duodenal aspirates or biopsies for trophozoites. treatment = metronidazole

Question 8

helminths

Answer 8

parasitic worms –> nematodes (round) cestodes (tapeworms) and trematodes (flukes). life cycles tat include but not restricted to human hosts. definitive host = host in which sexual reproduction takes place

Question 9

hookworms

Answer 9

two species of helminths - ankylostoma duodenale ad necator americanus. like attached to small intestine –> release ova into GI tract. excretion -> ova hatch into free-living larvae. larvae penetrate the skin of the foot and migrate to the lungs –> small intestine –> site of infection. volume of blood lost as a result of hookworm infection may result in iron deficiency anaemia.

Question 10

plasmodium spp

Answer 10

protozoan organisms that cause malaria. spread by anopheline mosquitoes and diagnosed by examination of blood films.4 species: P. falciparum, P. vivax (commonest), P.malariae, P.ovale. prophyloaxis is important

Question 11

plasmodium that produces the most severe disease

Answer 11

p. falciparum is life threatening

Question 12

sarcoptes scabi

Answer 12

causes scabies. female s.scabei mites lay eggs in burrows in the skin. characteristic itch of scabies is followed by a hypersensitivity reaction to various allergens produced by the burrowing of the mites

Question 13

schistosoma

Answer 13

genus of trematode (fluke) –> shistosomiasis.free living stage involves a fresh water snail and the persistence of human worms in the human venous circulation either in the mesenteric circulation (s.mansoni, s.japonicum) or the bladder (s.mansoni). diagnosis is by detection of eggs in the stool or urine

Question 14

strongoloides stercoralis

Answer 14

nematode infection of the small intestine –> diarrhoea possibly as a result of malabsorption. unusual worm with a life cycle involving an extra-corporeal stage, autoinfection, by penetration of worm larvae trough the wall of the small intestine and subsequent migration back into the GI tract

Question 15

taenia spp

Answer 15

tapeworm genus (cestode). t.saginata (beef tapeworm) or T.solium (pork tapeworm). T.saginate = benign disease –> worm lives in the small intestine and releases ova and worm segments periodically. T.solium = serious disease –> cysts are formed in muscle and other tissue (cysticercosis)

Question 16

toxocara canis

Answer 16

round worm (nematode) of dogs. ocular infection (eg retinitis) of children is the most common human manifestation

Question 17

toxoplasma gondii

Answer 17

protozoan parasite (sporazoan) for which cats are the definitive host. humans infected via cat litter or from ingesting cysts in undercooked meat from an accidental host. primary infection often symptomless but may cause serious disease in immunosuppressed patients. contracted in pregnancy –> severe congenital infection. diagnosed by serology for IgG and IgM antibody

Question 18

trichomonas vaginalis

Answer 18

protozoan that causes vaginitis in women. no apparent symptoms in men. microscopy of wet preparation of vaginal secretions. treatment = metronidazole

Question 19

trichuris trichuria

Answer 19

nematode know as the whipworm because of its shape. inhabits the large intestine, may cause diarrhoea. diagnosis by observation of “tea tray” shaped eggs in the stool sample

Question 20

leishmania

Answer 20

protozoan parasites –> leishmaniasis. spread by the bite of sandflies. cutaneous, mucocutaneous or visceral spread. presents with ulcers