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Flashcards in parasites Deck (53):
1

what is a parasite

animal or plant living in or on another and drawing nourishment from it

diagnosis of parasitic disease involves exposure history, clinical pattern of illness, ID in stool, blood, tissues, indirect evidence (serology, detection or parasitic antigens, DNA

2

what is a helminth

WORM

reproduce SEXUALLY usually within the host

pre-adult stage = OVA and LARVAE that live within or external to the host

3

what are protozoa

SMALL, UNICELLULAR organisms

have a nucleus and functioning organelles
reproduce quickly and ASEXUALLY in the host

have have a sexual phase in another host or vector

sub groups are based on motility (i.e amoeba, flagellates, ciliates, sporozoa/amicomplexa)

some protozoa have life stages alternating between proliferative stages (trophozoites) and dormant cysts

4

what are protozoa cysts

dormant phase

can survive in harsh conditions

allow the parasitic special to survive without a host

allow for transmission

5

what are protozoa trophozoites

actively feeding METABOLIC form of the protozoa

6

what are ectoparasites

insects

7

list the 3 classes of parasites

1. protozoa (one celled organisms)
2. helminths (worms)
3. ectoparasites (insects)

8

list the 3 classes of helminth

1. cestodes (tapeworms)
2. nematodes (roundworms)
3. trematodes (flatworms/flukes)

9

list the 4 classes of protozoa

1. amoeba
2. ciliates
3. flagellates
4. sporozoans

10

what is a definitive host

host of a parasite where SEXUAL reproduction of the parasite occurs

11

what is an intermediate host

animal essential to the COMPLETION of the LIFE CYCLE of the parasite

transmission requires a reservoir and route of infection

12

nematode body

UNsegmented

bilateral symmetry

fully functional digestive tract

long and cylindrical

male and female worms

13

nematode sexes

separate

have male and female worms

14

nematode infection/transmission

eggs/larvae ingestion, skin penetration, arthropod vector

15

nematode lifecycle

eggs --> several larvae stages --> adult stage

16

list 7 nematodes

1. necator americanus (hookworm)
2. Loa Loa (filaria)
3. Wucheria bancroft (filaria)
4. onchocerciasis

5. ascaris lumbricoides
6. strongyloides stertocalis
7. enterobius vermicularis

17

hookworm

nematode

necator americanus

LARVAL stage of worm penetrates SKIN --> usually through FOOT causing infection in the foot

once it penetrates the skin, it is carried through teh blood vessels

heavy infections can result in childhood anemia

SOIL TRANSMITTED helminth

18

Loa Loa (filaria)

nematode

EYE worm

adult conjunctiva migration

transient calabar swellings

diagnosis via serology, microfilaria on BLOOD SMEAR

transmitted via CHRYSOPS fly

19

Wucheria bancroft (filaria)

nematode

ELEPHANTITIS

very common in some tropical zones

early symptoms = fever, lymphadenitis, transient edema

late obstruction = chronic edema and skin changes caused by blocked lymphatics

transmitted via MOSQUITO

20

onchoceriasis (filaria)

nematode

RIVER BLINDNESS

NO blood invasion

major cause of blindness--> skin disease in Africa and Yemen

diagnosis based on serology, skin snip, nodule biopsy

transmitted with SIMULIAN fly

21

Ascaris lumbricoides

nematode

prototypical roundworm

notable for LUNG MIGRATION phase--> larvae are coughed up, swallowed and mature in gut

excreted eggs need to embryonate in specific environmental conditions in soil before becoming infective--> therefore direct person to person transmission is not possible

heavy infection may result in bowel obstruction

22

Strongyloides stertocalis

nematode

MINUTE roundworm

can replicate and completed ENTIRE LIFECYCLE within a HUMAN

infection can persist for a human lifetime

SOIL TRANSMITTED helminth and is often acquired from skin penetration

23

Enterobius vermicularis

nematode

PINWORM

very common--> causes PRUTITUS ANI in kids

fecal-oral transmission

persists due to poor hygiene

eggs can persist in local environment

24

cestode body

are TAPEWORMS

large, can be up to meters long

live attached to MUCOSA in SMALL INTESTINE of host

use SCOLEX to attach which is an attachment organ with 4 ventral suckers with or without hooks

structure = chain of segments (proglottids) + neck + scolex

25

cestode sexes

hemaphroditic

26

cestode infection/transmission

can live for decades

infection is via egg/larvae ingestion

27

name a cestode

taenia solium (pork tapeworm)

taenia saginatum is cow tapeworm
dipnyllobotherium latum is from uncooked fish
echinococcus is from sheep

28

taenia solium

cestode

pork tapeworm

causes NEUROCYSTOCERCOSIS

most medically important tapeworm infection worldwide

most common parasite of CNS

most preventable cause of EPILEPSY

results from undercooked PORK--> humans eat adult tapeworm from pork--> human excretes eggs--> if another human ingests the eggs, eggs hatch and turn into CYSTECERCI in tissues, including in the brain

parenchymal disease (cysts--> degeneration--> calcification--> seizures)

extraparenchymal disease (sub-arachnoid space, ventricles, spine)

most important clinical goal is to CONTROL INFLAMMATION

29

trematode body

flatworms/flukes

first intermediate host is SOIL
second intermediate host is FISH/SHELLFISH

dorso-ventrally flattened, unsegmented, leaf-like or cynindrical structure

30

trematode sexes

hermaphroditic

31

trematode infection/transmission

require 1 or more intermediate hosts

infect through skin penetration or larvae ingestion

32

name 2 trematodes

1. paragonimus westermani
2. schistosomiasis

33

paragonimus westermani

trematode

LUNG fluke

reservoir = wild and domestic carnivores

usually asymptomatic--> can have COUGH (often confused with TB, lung cancer)

rare cerebral disease

diagnosis through serology, sputum (eggs), eosinophilia

infection through LARVAE INGESTION

34

schistosomiasis

trematode

BLOOD fluke

cause of morbidity in Sub-Saharan Africa

acquired by swimming in freshwater lake or rivers

microscopic CERCARIAE burrow through skin and migrate to blood vessels surrounding target organs --> females lay eggs--> eggs penetrate into tissue through vessel walls --> eggs propelled into lumen --> pass in urine or stool

urogenital = S. haematobium
intestinal/hepatic = S. mansoni, S. japonicum

acute infection is usually 4 weeks post-exposure and involves fever, diarrhea, eosinophilia

continued egg-laying leads to chronic inflammation and then to cancers, cirrhosis

35

list 5 ectoparasites

1. scabies
2. head lice
3. body louse
4. trench fever (body louse)
5. bot fly (Dermatobium hominis)

36

which type of protozoa are intestinal protozoa

FLAGELLATE

i.e GIARDIA lamblia ("beaver fever")

37

which type of protozoa are extraintestinal protozoa

PLASMODIUM (malaria)

38

list 3 diseases caused by protozoa

1. malaria
2. leishmania
3. giardia lamblia

39

malaria vector

FEMALE ANOPHELES night-biting MOSQUITO

transmits through BITE

40

malaria species

P. falciparum
P. vivax
P. ovale
P. malariae
P. knowlesi

50% = falciparum

41

malaria reproduction

asexual cycle in RBCs (SHIZOGANY)

sexual reproduction in female anopheles mosquito (SPOROGANY)

42

malaria diagnosis method

thick and thin BLOOD SMEAR --> can determine species of plasmodium as well as % RBCs infected (parasitemia)

rapid antigen tests

43

what is the most important parasitic disease

malaria--> #1 cause of fever in returning travellers

44

symptoms of uncomplicated malaria

fevers
rigors
headaches
diarrhea
nausea

may be mistaken for viral infection

45

symptoms of complicated malaria

from P. FALCIPARUM

evidence of end-organ dysfunction (coma, renal failure)
mortality is 10-20% with Tx

46

P. falciparum

infection is a medical emergency
endemic in sub saharan africa
parasites induces formation of sticky "KNOBS" on RBCs which clog small vessels in brain and lungs

47

P. falciparum versus P. vivax

1. dormant liver stage?
2. disease severity?
3. relapse?
4. asymptomatic carriage?
5. Tx

1. P. falciparum NO; P. vivax YES
2. P. falciparum 5% = severe; P. vivax risk of severe disease is not established
3. P. falciparum NO; P. vivax YES
4. P. falciparum = common; P. vivax very common
5. P. falciparum = arteminisin combo therapy; P. vivax = chloroquine + 14 days primaquine

48

Leishmania vector

sandfly

49

Leishmania species

L. donovani
L. infantum
L. chagasi (chagas disease)

50

Leishmania diagnosis

skin biopsy
serology

51

Leishmania Tx

amphotericin B

topical ketoconazole

52

Leishmania clinical presentation

cause of ulcerated papule

subclinical infection is most common

HIV coinfection = reactivation

fever, lymphadenopathy, hepatomegaly, progressive MASSIVE SPLENOMEGALY

53

giardia lamblia

intestinal protozoa (flagellate)

most common GI intestinal protozoal infection in world

fecal oral transmission

may be asymptomatic

causes GI symptoms by EFFACEMENT OF VILLI via inciting inflammation at the intestinal brush border

this means that dietary FATS are absorbed poorly and result in "GREASY" STOOLS that FLOAT in the toilet

NEVER INVASIVE on its own, and will NOT cause bloody diarrhea