Richard wall - Myiasis

Question 1

what is myiasis?

Answer 1

infestation of the organs or tissues of living host animals by the larval stages of dipterous flies.

can be obligate in fly lifecycle or facultative - majority, primary forms wound, secondary follow wound initiating species, tertiary after that.

Question 2

5 types of wounds caused by myiasis

Answer 2

Open wound - traumatic
superficial - cutaneous
boil like - furuncular
creeping - maggots under skin, burrow leaving a track.
blood sucking - sanguinivorous.

Question 3

which 2 families are important in myiasis?

Answer 3

Calliphoridae - blow flies:
- chrysoma
- cochliomyia
- lucilia
- calliphora
- cordylobia
- protophormia
Sarcophagidae- Flehflies:
- Wolfhartia
- Sarcophaga

Question 4

2 larvae adaptations to myiasis

Answer 4

posterior spiracle to breathe from

ability to close spiracle, so can enclose themselves in the wound.

Question 5

example of primary facultative agent of cutaneous myiasis

Answer 5

Lucilia sericata.
larvae secrete proteolytic enzymes, later stages abrade skin with mouth hooks. maggots extract ammonia which attracts secondary and tertiary flies.
83% of cases in SW england
managed with organophosphate dips, synthetic pyrethroid dip/pour on, or insect growth regulators.

Question 6

3 eg of obligate agents of traumatic myiasis of mammals.

Answer 6

Cochliomyia hominivorax- New World Screw worm Fly
Chrysomya bezziana- Old World Screw worm Fly
Wohlfahrtia magnifica

Question 7

Cochliomyia hominivorax- New World Screw worm Fly

how does it affect hosts?

Answer 7

1935 - texas, 230,000 cases, 51 in humans.
burrow into flesh, creating cavern behind small cut, oviposit in any body orifice.
seasonal pattern - N in summer, S in winter.

Question 8

what did sebrovski find out about Cochliomyia hominivorax?

then how was SIT developed?

Answer 8

could induce dominant lethal mutations using x rays in sperm of male flies., to make them sterile.
kipling and Bushland picked up this idea and developed SIT, sterile insect technique.
initial pop - 100F/100M flies.
release 900 sterile M
1000M/100F
each mating makes 9:1 sterile:fertile males.
100 x (100/1000) = 10fertile matings.
Release another 900 sterile males.
10 x( 10/910) < 0.1 fertile matings.

Question 9

what factors affect SIT?

Answer 9

Complete sterilization 
  Male competitiveness
  Immigration
  Basic rate of reproduction 
  Size of the target population
  Multiple mating
advantages: minimal impact on enviro as released males only interact with own species.  larvae only survive on living host, breeding in lab is v hard. took 10-15 years to imitate host conditions in lab.

Question 10

where did a trial successfully eradicate screwworm fly?

Answer 10

1953-55
curacao, small island, venezuela.
also eradicated in florida, 1957-59.

Question 11

Chronological summary of screwworm eradication in USA and mexico

Answer 11

1972 - sudden increase in screwworm cases, due to genetic differences between pops within a species.
made 3 biological barriers to screwworm flies, top of colombia and above and below mexico. preventing spread up from S america.
first reported cases of NWS in USA in Texas.

Question 12

OWS distributions in africa.

how was an outbreak controlled in 1991 and why successful??

Answer 12

appearance in Libya 1988. spread rapidly across N africa. worries of spread down Nile, would be dangerous as no previous exposure to screwworm.
1991. C. hominivivax reared in Mexico sterilised with gamma radiation and transported in boxes of 1600 pupae. flew at 500m along flight paths 4km apart. released at 3-10 boxes per minute. initially 3.5m flies per week released, increased to 40 million flies per week.
Eradication successful because there was a good understanding of fly ecology, complete geographic isolation, pre existing infrastructure and followup survaillance and treatment.

Question 13

why have other attempts of SIT not been successful?

Answer 13

too expensive

does not work on a small scale

Question 14

how can areas have an outbreak where the pest is not present before that?

Answer 14

florida NWS, blown over in air currents from cuba

introduced from PNG to australia.

Question 15

what is autosterilization?

Answer 15

Sterilize the wild population (m and f). Sterilized females do not reproduce – sterilized males will mate with remaining unsterilized females.
If enough can be sterilized the suppressive effect should be quicker than conventional SIT
requires powerful attractant, problem finding sterilants which are strong enough yet safe to use in the field.

Question 16

how were houseflies controlled in poultry houses in india?

Answer 16

Targets coated with triflumuron (IGR) and sugar
M sterilized with IGR and pass onto females.
pop decreased after 40 days but then increased again when targets removed. still lower overall.

Question 17

how can GM be used to control pest populations?

Answer 17

induce deleterious mutations, may be recessive.

eg GM mosquitoes to have 95% male offspring.

Question 18

what is RIDL

Answer 18

Release of Insects carrying Dominant Lethals
GM technique
eg in Aedes aegypti, mosquitoes have domint allel encoding protein tTA, controlling activity of other genes, blocking metabolic function. in lab reared in presence of tetracycline which prevents gene from working but in wild, offspring inherit lethal allele and die.