Ectoparasites

Question 1

what is the difference between endo and eco parasites

Answer 1

endo= live inside the host
ect= live on the surface of the host

fish gill parasites an intermediate between ecto and endoparasites as the gill is both an internal and external organ

Question 2

which ectoparasites are vectors of various pathogens and parasites

Answer 2

fleas
ticks
mites
lice

Question 3

outline the morphologies of the ectoparasite the flea which make it easily identifiable

Answer 3

• laterally compressed bodies
• wingless
• 3 pairs of powerful jumping legs
• conspicuous black eyes

Question 4

outline some characteristics of the flea

Answer 4

few are pests or parasites to humans
94% of fleas bite mammals and 6% birds
worldwide distribution but species specific
can be zoonotic, generalist or specific

Question 5

outline the chigoe/jigger flea aka Tunga penetrans

Answer 5

a flea which secretes proteolytic enzymes resulting in the formation of a callus where they feed and lay eggs
the formation of callus makes it hard to notice presence as unable to feel it= only when cyst begins to press on nerves surrounding the callus is it noticable but by then the eggs are released from the skin

Question 6

outline the lifecycle of Tunga penetrans aka chigoe/jigger flea

Answer 6

1) females lay eggs once they leave the host in debris such as sand, or they may lay them whilst on host

2) eggs are coated with a sticky substance allowing accumulation of dirt and debris = camouflage, hatch after 5-6 days

3) larvae (made up of 13 segments and dark head capsule) spin a silk cocoon where it pupates, can live in this cocoon for 4-12 months

4) adults emerge following environmental cues such as heat/co2 looking for blood meal

Question 7

what are the two different types of ticks

Answer 7

class = Arachnida
soft ticks = family Aragasidae

hard ticks = family Ixodidae

= different ecologies, forms and functions

Question 8

how to hard and soft ticks differ

Answer 8

soft
- no scutum (sheild)
- mouthparts not visable
- eggs laid in small batches
- 4-5 nymphal larval stages
- rapid feeding of 20-30 mins
- tick borne releapsing fever

hard
- scutum present
- mouthparts visable
- eggs laid in one large batch
- 1 nymphal stage
- slow feeding 1-4 weeks
- attach to host for long time
- lyme disease, typhusus

Question 9

outline some characteristics of mites

Answer 9

infest the skin of a variety of animals including humans
Scarpotes scabei = highly infectious and causes mange

• caused by adult females burrowing into the skin by the release of proteolytic enzymes being spat forming a channel for it to use
• lays eggs in this channel
• causes itching releasing eggs

Question 10

outline some characteristics of the ectoparasite lice

Answer 10

common name for 3000 wingless insects
- obligate ectoparasites of every avian and mammalian order
- some feed on secretions and blood
- eggs= nits
most are highly species and site specific

Question 11

what species of lice infect humans

Answer 11

1) prediculus humanus humanus= hair
2) pediculus humanus capitis = body
3) pthuris pubis =pubic hair
= very site specific, wont be found anywhere else on the body but where it is adapted to

Question 12

outline the ectoparasite bedbugs

Answer 12

not vectors of disease but are ectoparasites of humans
causes rashes and allergic reactions

Question 13

outline the ectoparasite myiasis

Answer 13

invades organs and tissues of verterbrates by dipteran larave which feed on the living or dead tissue
different types depending on the affected body part

Question 14

what are the different types of myiasis

Answer 14

1 )cutaneous
- creeping/ eruption myasis = surface layers of skin
2) urogenital
3) ophthalimic/ ocular
4) nasaopharangeal
5) intestinal

Question 15

what are warble flies

Answer 15

genus = Hypoderma
parasitic on cattle and deer mainly but also in horses, cats dogs
eggs laid on the forelegs of large animals
larvae burrow into the skin through connective tissues or the oesphogus

after a few months the larvae migrate to the skin causing swelling (warbles)
= eradicated in uk in 1990s due to economic impact on livestock

Question 16

what are the three different dipteran families

Answer 16

1) calliphoridae = metallic and non metallic

2) Sarcophagidae

3) Oestridae

Question 17

outline the characteristics of non-metallic flies from the dipteran family calliphoridae

Answer 17

e.g. Mango fly
- found in Africa and Saudi Arabia
-adults are robust large flies dull yellow and brown in colour
- females lay 100-300 eggs in the soil in the presence of urine, soiled nappies/ washed clothes
- larvae hatch and use powerful hooks to burrow into host tissue
- spiracles used to breath protrude from host

Question 18

outline the characteristics of the newworld metallic flies from the family calliphoridae

Answer 18

new world screwworm
found in southern states of USA, Mexico and central America/south America
- limitied range due to successfull eradication programme (mass release of sterile males)
- adults 8-10mm long, metallic green/blue in colour
- lay 100-400 eggs on the edges of wounds, scabs, eyes and mucous membranes
- larvae burrow into healthy flesh for 4-12 days
- if distrubed they burrow deeper

Question 19

outline the characteristics of the old world metallic flies from the family calliphoridae

Answer 19

obligatory parasite of living tissues
found in tropical africa, indian subcontinent, most of SE asia
introduced to west coast of perisian gluf and iraq

adult flies and larvae simialr to new world flies expect larvae have 4-6 finger like protuberances on the arterial spiracles

• massive economic damage as affect cattle, goats and horses

Question 20

outline the medical importance of metallic blue bottle flies

Answer 20

• dirty habits - potential vectors for a number of pathognes
• faculative myiasis, infest wounds
• maggot therapy
  raise flies and maggots in sterile conditions which can be used to treat ulcers, pressure sores and infected surgical wounds as they feed on dead tissue not living

Question 21

outline some characteristic of the dipteran family sarcophagidae

Answer 21

aka flesh flies
- they lay no eggs just first instar larvae
two genus
1) sarcophaga = falculative myasis
2) wohlfahrita = furuncular myiasis

Question 22

outline some characteristics of the dipterian family oestridae

Answer 22

bot flies
when on flesh they secrete ammonia which damages skin and surrounding tissue = ammonia poisoning
economic impact = damages fleece of livestock such as sheep

Question 23

outline some characteristics of the subfamily cuterebrinae from the oestridae family (botflies)

Answer 23

found in north argentina and south mexico
- lowland forests espcially along paths and margins of forests
- females lay 6-30 eggs

eggs can either be glued to body of another arthropod or layed directly onto the hsot

larvae matures inside egg but doesnt hatch until in contact with the host

Question 24

outline some biological control of dipteran flies

Answer 24

• release of sterile insects which have been irradiated with gamma radiation to kill sperm before being released into the wild

successfull in
= mexican fruit fly
=Medfly
= melon fly

future targets = anopheles and aedes mosquitos, Tstes fly and painted apple moth

Question 25

what are the advantages of sterile male techniques

Answer 25

• highly specific
• no pesticide so no residue
• it works
• opens the door to genetic modification e.g. using GM mosquitos to stop breeding instead of radiation

Question 26

what are the disadvantages of using sterile male techniques to control pest populations

Answer 26

• no residue means repeated treatment needed
• sex seperation needed which can be hard
• radioactive elements used which may provide selective disadvantage to sterile males
• if irradiation doesn’t work just released a batch of healthy males
• high cost as requires dedicated facilities