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Flashcards in Parasites Deck (27):
1

Main groups of parasites

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

2

Protozoa

- 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

3

Helminths

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

4

Malaria, species and vector

- Protozoa
- Plasmodium spp.
- Vector: Anopheles mosquito

5

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

6

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

7

Amoebic dysentery species

- Protozoa
- Entamoeba histolytica

8

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

9

Symptoms and clinical findings of amoebic dysentery

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

10

Leishmaniasis species and vector

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

11

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

12

Enterobiases species and route

Helminth, roundworm
Enterobius vermicularis
Faecal-oral route

13

Enterobiases life cycle

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

14

Diagnosis of enterbiases

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

15

Nematodes species

- Helminths
- Ascaris lumbricoides

16

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

17

Symptoms of nematodes

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

18

Tapeworms - cestodes, species

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

19

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

20

Diagnosis of cestodes

Ova in stools on microscopy

21

Echinococcus tapeworms species, route and vector

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

22

Life cycle of echinococcus

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

23

Treatment of Hydatid cyst

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

24

Schistosomiasis species

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

25

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

26

Helminth infection is often accompanied by

Eosinophilia and elevated IgE

27

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