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Flashcards in Parasites Deck (27):

Main groups of parasites

- Protozoa
- Helminths (worms)
- Arthropods (lice, ticks mites)



- Microscopic, one celled organisms
- Free-living or parasitic in nature
- Able to multiply in humans
- Transmission: faecal-oral route, live in intestine. Arthropod vector, live in the blood or tissue of humans
- Malaria, amoebae, flagellates



- Nematodes, roundworms
- Cestodes, tapeworms
- Trematodes, flukes, flatworms


Malaria, species and vector

- Protozoa
- Plasmodium spp.
- Vector: Anopheles mosquito


Life cycle of malaria

- Complex
- Sporozites injected under skin by mosquito
- Travel through blood and enter liver
- Mature in liver and re-enter circulation as merozoites
- Invade red cells, multiply and lyse cells
- Sexual forms taken up by mosquito


Diagnosis, symptoms and treatment of malaria

Diagnosis: Giemsa stained blood films show infected red cells. Little rings in cells
Symptoms: Pyrexia, rigors, flu-like illness, anaemia and haemolysis
Treatment: Insecticide mosquito nets, prophylaxis


Amoebic dysentery species

- Protozoa
- Entamoeba histolytica


Life cycle of amoebic dysentery

- Trophozoite ingests red cells by throwing out pseudopodia - hot stool
- Cyst of E.histolyica: 2 nuclei and chromatoid body, typically found in formed stool


Symptoms and clinical findings of amoebic dysentery

Diarrhorea with blood/pus
Clinical findings: intestinal and extra-intestinal infections, liver abscess in late disease


Leishmaniasis species and vector

- Protozoa
- Leishmania spp.
- Vector: infection by bite from sandflies


Diagnosis and clinical findings of leishmaniasis

- Histology of biopsy material
- Clinical findings: Cutaneous or muco-cutaneous leishmaniasis, skin or mucosal ulceration
Visceral Leishmaniasis: fever, weight loss and hepato-splenomegaly


Enterobiases species and route

Helminth, roundworm
Enterobius vermicularis
Faecal-oral route


Enterobiases life cycle

Pinworms travel down to the anus at night and lay eggs
1cm, threadlike found in children


Diagnosis of enterbiases

Press adhesive tape against perianal region in the morning and ova can be seen on microscopy


Nematodes species

- Helminths
- Ascaris lumbricoides


Life cycle of nematodes

- Ingested eggs hatch in the intestine
- Larvae carries by circulation to lungs, swallowed again
- Adult worms develop in and inhabit small intestine
- Ova seen in faeces by microscopy
Have characteristic thick shell


Symptoms of nematodes

- Often asymptomatic, can get transient pulmonary symptoms
- Mass of worms may obstruct small intestine or common bile duct


Tapeworms - cestodes, species

- Flatworm
- Taenia sagniata (beef) and Taenia solium (pork)


Life cycle of cestodes

- Larvae doesn't mature to adult form in beef or pork, needs a host
- Larval cysts are in intermediate host, meat
- Definitive host of adult tapeworm is human
- If T.solium eggs are direct consumed, you can get cystericercosis and wreck brain


Diagnosis of cestodes

Ova in stools on microscopy


Echinococcus tapeworms species, route and vector

Echinococcus sp.
Vector: carried by dogs, wolves and foxes
Faecal-oral route, humans ingest eggs from dog faeces


Life cycle of echinococcus

Ingest eggs
Eggs hatch and enter circulation
Hydatid cyst forms in liver


Treatment of Hydatid cyst

Need to resect whole cyst in liver otherwise you can release the fluid inside and cause anaphylaxis


Schistosomiasis species

Flukes, trematodes
S. haematobium (bladder) - haematouria, bladder ca.
S. mansoni (intestinal)
S. japonicum (intestinal) - most severe


Life cycle of Schistosomiasis

- Swimming in freshwater
- Eggs excreted in urine or faeces
- Miracidia released in fresh water
- Intermediate host, snail
- Cercaria emerge from snails
- Migrates through lungs to liver
- Mature in liver into worms (schistosomes), migrate to mesenteric or bladder venules
- Lay eggs that cause inflammation in bladder or intestinal wall
- Acute febrile episode 4-8 weeks later


Helminth infection is often accompanied by

Eosinophilia and elevated IgE


Diagnosis of parasitic infection

- Microscopy: identification of parasites in host tissue or excreta. Observing P, C and O in faeces
- Culture rarely possible
- Blood films for malaria: thick and thin films looking for ring of plasmodium
- Serology: detection of antibodies, if the parasite is located in deep tissue sites