parasitology

Question 1

what is a parasite

Answer 1

organism that lives on or in a host organism and gets its food from or at the expense of its host

3 main classes of parasites:

1. protozoa
2. helminths
3. ectoparasites

Question 2

what are protozoa

Answer 2

microscopic, single celled organisms that can be free living or parasitic
able to multiply in humans allowing serious infections to develop from single organism

transmission = protozoa living in human intestine can be transmitted by fecal oral route

on protozoa living in blood or tissues are transmitted by an arthropod vector

Question 3

types of protozoa

Answer 3

amoeba
flagellates
cilitates
sporozoa

Question 4

medically important protozoa infections

Answer 4

entamoeba hystolytica 
giardia lamblia 
trichmomonas vaginalis 
malaria 
toxoplasma gondii 
cryptosporidium = causes diarrhoea

Question 5

what are helminths? nomatodes

Answer 5

large multicellular organism, visible to naked eye in adult stage. adult form, cannot multiply in humans

3 main groups of helminths are parasite

1. nematodes
2. trematodes
3. cestodes

Question 6

medically important helminths

Answer 6

soil transmitted = ascaris/trichruis/hookworm

filarial parasites = wuchereria

Question 7

medically important helminths = trematodes and cestodes

Answer 7

trematodes = schistosoma 
cestodes = taenia saginata

Question 8

what are ectoparasites

Answer 8

blood sucking arthopods e.g. ticks/fleas/lice and mites that attach or burrow into skin and remain there for long time

Question 9

medically important ectoparasites

Answer 9

mites
ticks
lice
flies

Question 10

determinants of parasite infections

Answer 10

depends on mode of transmission and opportunities for transmission

1. faecal-oral route = household sanitation/ access to clean water/ personal hygiene behaviours
2. food = animal husbandry/ surveillance/ regulations and government
3. complex life cycles = distributions of vectors and intermediate/definitive hosts
4. others:
   gov resources, education, country level and regional control programmes and price availability

Question 11

acute chagas

Answer 11

occurs within 3 weeks
mild or asymptomatic
local swelling
nodule or chagoma

Question 12

chronic chagas

Answer 12

heart and intestinal tract affected
bugs like ANS, purkinje fibres = damage to conduction system causing inflammation and arrhythmias
heart muscle becomes thinner

Question 13

chagas pathogenesis

Answer 13

acute = tissue damage caused by inflammatory response to parasite in nest of amastigotes in cardiac, skeletal and smooth muscle

parasite killing by antibodies = activates innate immune response and th1 pro-inflammatory cytokines

Question 14

indeterminate

Answer 14

regulatory immune response characterised by IL-10 and IL-17

Question 15

chronic

Answer 15

response to persistent parasites in muscle and nerve cell
autoimmune mechanism

may vary by parasite strain and tissue tropism
predominance of th1 cytokines and cd8 t cells

Question 16

what are visceral leishmaniasis

Answer 16

asia/middle east/latin america

1. sandfly bites you
2. enters immune cells, form promastigotes
3. infect other cells

Question 17

clinical forms of viseral leishmaniasis

Answer 17

ulcers develop
scars
reactivation of lesions around old scars, inadeuqate immune response
can lead to mucocutaeuous disease

Question 18

pathogenesis of cutaneous leishamaniasis

Answer 18

acute lesions = tissue damage caused by inflammatory response to presence of parasites in macrophages
parasite killing by Th1 pro-inflammatory response and macrophage killing

latency = parasite remain present long term. regulatir immune response characterised by balance of th1 and anti-inflammatory response

relapse = rare