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Flies and arthropods > Flies and Myiasis > Flashcards

Flies and Myiasis Flashcards

1
Q

Flies background

A

Diptera - two winged

Synanthropic - live in close association with man and human settlements

Some species cause myiasis in man and domestic animals whilst others are biting nuisance

enormous reproductive potential

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2
Q

What diseases do flies transmit

A

bacteria and viruses

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3
Q

Important house flies

A

Musca domestica - common housefly - indoors and shade

Musca sorbens - bazaar fly or bush fly - outdoors and open

Fannia - lesser housefly - latrines and poultry excreta

Muscina - greater housefly - greater housefly - stables and farms

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4
Q

Musca domestica - common housefly - morphology

A

Four dark stripes on grey thorax

Wing vein 4 bends to meet vein 3

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5
Q

Musca domestica - housefly behaviour

A

Feeds on human food, garbage, excreta, decayed plant and animal matter

Feeding sites 100-500m from breeding sites

Breeds often in same decaying organic matter on which it feeds

Found by day near food sources and breeding sites

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6
Q

Musca domestica - housefly

A

Eggs 0.8-1.0mm, 75-100 at a time and up to 5 batches
Larvae - 3 instars
Puparium
Adults

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7
Q

Musca domestica - housefly breeding sites

A 
Animal manure 
Grass cuttings 
Latrines 
Household garbage 
Prawn meal 
Refugee camps 
Chicken farms - more usually Fannia - lesser housefly
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8
Q

Housefly development is dependent on what

A

Dependent on temperature

Pupal optimum around 29 C and larval optimum around 36 C

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9
Q

Medical importance of Musca domestica

A

Omnivorous - faeces and food

Enteric bacteria - Shigella, Salmonella, E.coli

Cholera

Enteroviruses - including polio

Helminth eggs

Major routes of transmission are defecation, regurgitation and transport on the body surface

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10
Q

What do houseflies feed on

A

Feeds on liquid and semi-liquid food

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11
Q

How do houseflies feed

A

Undigested food is stored in the crop and vomited where it is digested in the mid-gut

feeds with soft, fleshy and suctorial mouthparts

Defecates every 5 minutes

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12
Q

Features of Fannia larvae

A

Larva with prominent lateral processes

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13
Q

Fly control in pakistan

A

Fly control using ULV Deltamethrin resulted in elimination of fly population and reduction of diarrhoea

No reduction outside the fly season

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14
Q

Fly control in Israel

A

Fly control using traps placed around latrines, kitchens and mess areas in military camps with high compliance

After 11 weeks clinical visits for diarrhoeal disease reduced by 42% as well as shigella incidence down by 85%
Antibody conversion for shigella down by 76% and coli down by 57%

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15
Q

Musca sorbens - Bazaar fly

A

Breeds particularly in human faeces but less frequently
Attracted to discharge from the eyes and or nose
May be common in refugee camps

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16
Q

What does Musca sorbens - The Bazaar fly transmit

A

Transmit trachoma - Chlamydia trachomatis

17
Q

Trachoma control in The Gambia

A

Fly control using ULV Deltamethrin resulted in
Decrease in Musca population by 75%
75% decrees in incidence of trachoma
22% less diarrhoea in children
Incrimination of Musca sorbens as a vector

Mass oral azithromycin treatment resulted in a drastic reduction in fly carriage

18
Q

Issue with using insecticides on flies

A

Insecticide resistance develops incredibly quickly - failure to control

needs to be reliant on prevention of breeding and not on insecticide use

19
Q

How can breeding be prevented

A

good waste disposal practice - cover refuse with >25cm of soil, keep only the working edge of a tip exposed and make sure tip is tightly packed, increased temp kills larvae

disposal of human and animal excreta - ventilated pit latrine and manure piles

20
Q

Control of houseflies and blowflies

A

Screen premises - kitchens and hospitals
Traps and insecticidal control - stripes, baits, space sprays, tip dressings, animal medication

Biological control - sterile insects and Bacillus thurngiensis in chicken mash

21
Q

What is myiasis

A

The invasion of living tissues of humans and other animals by the larvae of dipterous insects

22
Q

Clinical classifications of myiasis

A

cutaneous -
furuncular - boil like swellings with one fly larvae per boil (tumbu)
other invasive traumatic (screw worms)
non-invasive (Lucilia, Calliphora etc.)

Nasopharyngeal, ocular - oestrus

urogenital - fannia

intestinal

23
Q

obligate myiasis

A

essential for larvae to live on the host for one part of the life cycle - cordylobia, cochliomyia, chrysomya, dermatobia

facultative - normally free living (dead tissues) but will grow on open wounds and sores - calliphora, lucilia, sarcophaga

accidental (pseudomyiasis) - enteric, urinary tract - Musca, Fannia and Sarcophaga

24
Q

Myiasis pathology

A

Irritation, discomfort, pruritus (itching), tissue damage, haemorrhaging, secondary bacterial infections, anaphylaxis and shock toxaemia

25
Q

Tumbu fly - Cordylobia anthropophaga

A

Obligate parasite from Africa

Eggs laid on urine soaked clothes or sandy soil
Normal host is the rat
Grub shaped larva which from boil like swellings
Common around the buttocks, genitalia and the back
Merge from the skin after 8 days
Pupate in the soil
Adult inconspicuous brown coloured fly

26
Q

How to remove tumbu fly

A

lubricate the wound e.g. with paraffin wax and gently prise out

27
Q

Tumbu fly control

A

iron clothes

28
Q

Dermatobia (human botfly

A

causes new world myiasis
Eggs attached to a biting insect e.g mosquito or stomoxys
Burrow into the skin to form a boil like swelling

29
Q

Dermatobia (human botfly) larvae

A

possess stout rose-thorn spines

30
Q

Screw-worms species

A

Chrysomya in the old world

Cochliomyia in the new world

Adults are a metallic blue-green colour

31
Q

Screw worms

A

obligate parasites of living tissues

very serious as they consume living tissue which causes severe tissue trauma and pain

can invade the natural orifices - nose, mouth, eyes and genitals

larvae with spines giving a screw-thread appearance

32
Q

Fleshflies - Sarcophagidae

A

Common in refuse, butchers shops etc
Larvae occasionally cause myiasis
Feed mostly on necrotic tissue

33
Q

Non invasive myiasis (blowflies)

A

Blue bottles (Calliphora)
Green bottles (Lucilia)
usually breed in similar habitats to houseflies
Will infest and consume necrotic tissue e.g. foul smelling wounds, ulcers etc. - sometimes found under bandages
Usually do not cause harm since they feed on dead and decaying tissue/ Baer’s maggot therapy
Larvae without screw thread of spines

34
Q

Maggot therapy for chronic wounds

A

Uses non invasive species
Larval movement stimulates serous exudate which flushes bacteria from the wound
Larvae consume the necrotic tissue and bacteria
Larvae lower pH
Larvae secrete therapeutic agents - urea ammonium bicarbonate, bactericidal proteins, allantoin
Useful where antibiotic resistance, limited drugs or surgery

Flies and arthropods (5 decks)

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