Ectoparasites and vectors
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- What are the three stages of a gradual metamorphosis?
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1.Eggs
2.Nymphs
3.Adults - What are the four stages of a complete metamorphosis?
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1.Eggs
2.Larva
3.Pupa
4.Adult - What two diseases are houseflies thought to be a vector for?
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1.Bacterial dysentary
2.trachoma - About how many days are required for a housefly egg to mature into a reproductive adult?
- ~10 days
- Do lice show a gradual or complete metamorphosis?
- Complete
- Describe the appearance of lice.
- They are flat and resemble walking birthmarks.
- Head lice and body lice are similar in that they both suck blood. What feature separates them?
- They do not interbreed.
- Where does each species of lice lay its eggs?
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*Head lice: hair shafts
*Body lice: seams of clothing - How are lice treated? Are they able to survive off of the human body?
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*insecticide lotions and creams
*adults can survive 10 days off of the host, nits much longer - Name three diseases that lice serve as a vector for.
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1.epidemic typhus (rickettsia prowazecki)
2.trench fever (rickettsia quintana)
3.Relapsing fever (borrelia recurrentis) - Describe the metamorphosis of fleas.
- Complete with 3 larval instars and pupa stages.
- How many legs does a flea have? Describe their special adaptations.
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*6 legs
*hind pair have resilin which endow jumping ability
*also legs have hooks to grab onto hair or fur -
T/F:
An unfed flea can survive for only three months. - False: an unfed flea can survive three years in high humidity.
- Where does the sand flea or chigger commonly bite?
- Penetrates the skin at the nail base or between the toes; painful and irritating.
- Name two diseases fro which the flea is a vector.
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1.Yersinia pestsis
2.Endemic typhus (rickettsia typhii/mooseri) - One bacillus carried by the flea causes a special adaptation that faciltates its spread. What is the bacillus and what is this adaptation?
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*yersinia pestis
*proventricular blockage causes regurgitation of the bacillus - Describe the metamorphosis of the chelicerata.
- Gradual: larva (6 legs), nymph, adult (8 legs).
- Describe the appearance of argasids. What are their feeding habits?
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*soft ticks, head not visible
*nocturnal feeders, stay on host for only a few minutes - Describe the appearance of ixodidae.
- *hard ticks, head visible, dorsum scutum (shield)
- Describe the life cycle of ixodidae.
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*female drops off host and lays eggs
*larvae find host, feed for several days and drop off
*larvae molt on ground into nymphs, which find a host, feed 4-8 days, and drop off
*molts into adult, which finds a host, mates, feeds for several days and drops off - What special adaptations do ixodidae have to allow them to find a host?
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1.able to sense ground vibrations
2.Haller's organs on front legs respond to odors, temperature, and carbon dioxide - How do ticks find a place to bite on the host?
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*Haller's organs
*chelicerae sense ATP - What two organs does the tick use to attach to a host?
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*checlicerae: pierce skin
*hypostome: anchor - How much weight does a tick gain during engorgement?
- 200x
- How do male ticks attract a mate?
- Secretion of a blend of phenols.
- What are three methods of control of ticks and tick-borne illness?
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1.dipping
2.vaccine
3.repellant - How many ticks are necessary to cause tick paralysis? What is the latent period before symptoms appear?
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*a single female tick
*5-7 days - Ticks are known to be vectors for at least 8 diseases. Name 5 of them.
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1.RMSF
2.Ehrlichiosis
3.Lyme disease
4.Babesiosis
5.East coast fever
6.Endemic relapsing fever
7.Coxiella burnetti (Q fever)
8.Congo-Crimean hemorrhagic fever - what is the life cycle of the mite?
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1.Eggs
2.Larva
3.Nymph (2-3 stages)
4.Adult - How do larger mites breathe? How do smaller mites breathe?
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*larger: through stigmata
*smaller: cutaneously - How big is an adult sarcoptes scabei? With what two conditions is it associated?
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*250um
*Scabies in humans and mange in animals - Why do dust mites prefer a humid environment?
- They are able to extract water from the air.
- How are dust mites commonly raised in the lab?
- On beard clippings from an electric razor.
- What two diseases are mites vectors for?
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1.Scrub typhus
2.Rickettsial pox - What is the target of pyrethrins and DDT?
- Block voltage-gated sodium channel to slow nerve conduction.
- How do organophosphates and carbamates work?
- Target ACh-esterase; bind serine to prevent recyling of ACh in the synapse.
- Name two ways ectoparasites have developed resistance to insecticides.
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1.Point mutations in target
2.Detoxifying enzymes