6/7 - Parasitology and the Pathogenesis of Parasitic infections

Question 1

what is a parasite?

Answer 1

an organism that lives on/ in a host organism - gets its food from/ at the expense of its host

Question 2

what are the three main classes ofparasitesthat can cause disease in humans?

Answer 2

protozoa
helminths
ectoparasites

Question 3

what are protozoa?

Answer 3

microscopic, single-celled organisms that can be free-living or parasitic in nature

• multiply in humans, cause severe infections

Question 4

how can protozoa be transmitted?

Answer 4

faecal-oral or by arthropod vector

protozoa living in the human intestine - transmitted by faecal-oral route

protozoa living in blood/ tissues - transmitted by an arthropod vector

Question 5

four different types of protozoa?

Answer 5

amoeba
flagellates
ciliates
sporozoan

Question 6

examples of medically important protozoa infections?

Answer 6

Trypanosoma cruzi
Leishmania spp.
Toxoplasma gondii
Malaria

Question 7

what are helminths?

Answer 7

large, multicellular organisms (worms) generally visible to the naked eye in their adult stages

can’t multiply in humans in their adult form

Question 8

what are the three main helminth groups?

Answer 8

Nematodes (roundworms)
Trematodes (flukes)
Cestodes (tapeworms)

Question 9

types of medically important helminths

Answer 9

soil-transmitted parasites
filarial parasites
trematodes
cestodes

Question 10

types and examples of medically important helminths

Answer 10

soil-transmitted helminths - e.g. Hookworm, Enterobius vermicularis

filarial parasites - e.g. Loa loa, Onchocerca volvulus

trematodes - e.g. Schistosoma mansoni/haematobium/japonicum

cestodes - e.g. Taenia saginata/ solium

others - e.g. Toxocara canis

Question 11

what type of parasite is Onchocerca?

Answer 11

filarial parasite - roundworm

Question 12

what type of parasite is the Schistosoma genus?

Answer 12

trematodes - flatworms

Question 13

what are ectoparasites?

Answer 13

blood-sucking arthropods such as ticks, fleas, lice, and mites

they attach or burrow into the skin and remain there for relatively long periods of time

Question 14

types and examples of medically important ectoparasites?

Answer 14

ticks - hard or soft
lice - e.g. pediculus humanus humanus
mites - e.g. scabies
flies - e.g. botflies

Question 15

what are the two types of parasite hosts?

Answer 15

intermediate – host in which larval or asexual stages develop

definitive – host in which adult or sexual stage occurs

Question 16

what are the two types of parasite vector?

Answer 16

mechanical when there’s no parasite development in the vector

biological when some stages of life cycle occur

Question 17

describe/ give examples for some factors that determine (distribution of) parasitic infections

Answer 17

geographical location - highest in Asia and Africa, lowest in Western countries like Europe, America

faecal-oral transmission routes affected by access to clean water and hygiene

parasite food transmission - affected by regulatory controls for food safety and surveillance

the complexity of parasitic life cycles - e.g. if they need intermediate or definitive hosts

education, income, availability of cheap and effective treatments, environmental sanitisation

Question 18

name two diseases caused by protozoa

Answer 18

Chagas disease
leishmania - visceral/ cutaneous

Question 19

name two diseases caused by helminths

Answer 19

schistosomiasis
onchocerciasis

Question 20

name three different ectoparasites that cause diseases

Answer 20

ticks
lice
botflies