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| {{toplink
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| |backcolour =
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| |linkpage =Insecta
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| |linktext =INSECTA
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| |pagetype=Bugs
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| |sublink1=Parasites
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| |subtext1=PARASITES
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| }}
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| <br>
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| ==Introduction==
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| Myiasis is the parasitism of living animals by dipteran larvae. Myiasis can be oligatory or facultative (optional) and is described as cutaneous, nasal or somatic.
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| ==Oestridae==
| | #REDIRECT[[:Category:Myiasis Producing Flies]] |
| [[Image:Warble flies.jpg|thumb|right|150px|Warble Fly - Geo. H. Carpenter, Cambridge University Press 1913 - Wikimedia Commons]]
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| *The larvae of Oestridae spp. are '''obligatory''' parasites
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| *The three important species of veterinary interest are ''Hypoderma'', ''Oestrus'' and ''Gasterophilus''
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| ===''Hypoderma'' spp.===
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| *Also known as warble flies
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| *Important cattle parasites
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| **Also parasitise horses, small ruminants and sometimes humans
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| *The two main species in cattle are ''H. bovis'' and ''H. lineatum''
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| *''H. diana'' parasitises deer
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| *Infestation is largely confined to the Northern Hemisphere
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| '''Recognition'''
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| *Large 13-15mm long
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| *Similar to bumble bees in appearance
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| **Yellow abdomen
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| *Band of black hairs
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| *One pair of wings
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| '''Life Cycle'''
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| *Adult flies emerge on warm, sunny days between June and August
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| *White eggs are laid around the belly and legs of the animal
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| **Eggs are attached to hairs by cement and a small terminal clasp
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| **''H. lineatum'' lays a whole row of eggs as it approaches the animal stealthily
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| **''H. bovis'' only deposits a single egg before the animal runs away (''''gadding''') as it makes a loud buzzing noise
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| *The adult lives for 3 weeks
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| *Females can lay several hundred eggs in their life
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| *A few days after eggs are laid, larvae emerge and crawl down the hairs into the hair follicles
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| *Larvae penetrate the skin through wounds made by [[Biting Flies - WikiBlood|biting flies]]
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| *Larvae migrate through the subcutaneous tissue towards the diaphragm
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| **Enzymatic secretions and mouth hooks aids larval migration
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| *After 3 months larvae reach '''winter resting sites''' where they remain from November to Feburary/March whilst moulting to the L2 stage
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| **Epidural fat in the spinal canal for ''H. bovis''
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| **Wall of the oesophagus for ''H. lineatum''
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| *Larvae then migrate back to the subcutis along the midline of the back where they bore a breathing hole through the skin and moult to the L3 stage
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| **Larvae are palpable as distinct swellings called '''warbles'''
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| *L3 larvae emerge after 4-10 weeks where they fall to the ground and pupate under loose vegetation
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| *Adult flies emerge from the pupa after one month where they copulate, lay eggs and die within two weeks
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| *''H. lineatum'' are on the wing 6-8 weeks before ''H. bovis''
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| *There is only '''one''' generation of warble flies per year
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| '''Pathogenesis'''
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| *Causes[[Muscles Inflammatory - Pathology#Arthropods| myositis]]
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| *Production losses
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| **Condemnation and down-grading of hides
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| **Reduced milk yield and reduced weight gain
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| **Injury from stock panic
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| **Trimmed meat losses from ''H. lineatum''
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| ***'Butcher's Jelly' around warbles which is green due to mass [[Eosinophils - WikiBlood|eosinophil]] attraction
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| *Paraplegia resulting from:
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| **Toxin release
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| **Pressure on the spinal cord (''H. bovis'')
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| **Bloat from pressue on the oesophageal wall (''H. lineatum'')
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| '''Control'''
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| *Total eradication should be aimed for
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| *Old methods include popping out warbles
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| **But could lead to anaphylactic shock
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| *[[Ectoparasiticides]]
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| **Systemic organophosphorus [[Ectoparasiticides|insecticides]] in pour-on formula
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| **Avermectins and milbemycins in pour-on and injectible formulations
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| *Timing is crucial for treatment
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| **Larvae residing in winter resting sites, if killed, can lead to bloat and paraplegia
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| **It is safe to treat in the '''autumn''' before larvae reach their winter resting sites and in the '''spring''' when the warbles have migrated to the midline of the back
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| **Ivermectin can be given at any time without risking host infection as larval antigen is released much slower
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| '''Legislation in the UK'''
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| *'Warble Fly Order 1978' requires all clinically affected animals to be treated
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| *Notifiable disease
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| *'Warble Fly Infected Area Order 1983'
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| *For more information on the warble fly orders, see [http://www.defra.gov.uk/animalh/diseases/notifiable/brucellosis/surveillance.htm| here]
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| ===''Oestrus ovis''===
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| *Also known as the sheep nasal bot fly
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| *Larvae parasitise the nasal chambers of sheep and goats
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| *Found in most sheep rearing areas of the world
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| '''Recognition'''
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| *13-15mm long
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| *Grey colouring
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| *Black spots on abdomen
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| *Clear wings
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| *Larvae have distinct black bands on each body segment
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| '''Life Cycle'''
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| *Larvae are squirted into the nostils of sheep in a jet of liquid
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| *The larvae crawl caudally into the nasal cavity and feed on the nasal mucosa and mature before returning to the nostrils
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| *Larval development takes up to two months
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| **Larvae can overwinter in the nasal cavity if deposited late in the summer
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| *Once the larvae have developed they are sneezed out and pupate on the ground
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| *The adult fly emerges one months later
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| *Adult flies only live for 2-3 weeks
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| '''Pathogenesis'''
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| *Adult flies can annoyance
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| **Interrupts feeding
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| **Leads to a decreased weight gain
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| *Larvae cause nasal irritation, nasal discharge and sneezing
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| **Irritate the nasal mucosa with oral hooks and spines causing a viscous exudate to be produced from which they feed
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| **Heavy infestations lead to erosion of the bones in the sinuses (turbinate bones)
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| **Penetration of the brain leads to '''false gid''' (high stepping gait and incoordination)
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| *[[Respiratory Parasitic Infections - Pathology#Oestrus ovis|Apthology in the nasal cavity]]
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| '''Control'''
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| *Systemic [[Ectoparasiticides|insecticides]] can be used in heavy infestations
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| *In warmer countries, strategic prophylactic treatment can be used
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| ===''Gasterophilus'' spp.===
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| [[Image:Horse Bot Fly.jpg|thumb|right|150px|Horse Bot Fly - Dennis Ray - Wikimedia Commons]] | |
| *Also known as the horse bot fly
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| *Obligate parasites of equids
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| *Spend most of lifecycle in equine stomach
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| **Cause little pathogenesic significance
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| *Three important species (in the UK)
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| **''G. intestinalis'' which is the most common
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| **''G. nasalis''
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| **''G. haemorrhoidalis'' which is rare
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| *Two other important veterinary species
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| **''G. nigricornis''
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| **''G. inermis''
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| '''Recognition'''
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| *Medium to large flies at 10-20mm long
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| *Look similar to drone bumble bees
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| **Body covered with dense yellow hair
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| **Dark coloured hairs produce a banding pattern
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| *Clear wings with brown patches
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| '''Life Cycle'''
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| *Adults are most active in late summer
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| *Eggs hatch spontaneously or are stimulated to hatch through an increase in warmth and moisture from the animal self-grooming
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| **''G. intestinalis''
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| ***Creamy-white eggs
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| ***1-2mm in length
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| ***Eggs laid in the hair of the shoulders and fore legs
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| **''G. nasalis''
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| ***Eggs laid in the intermandibular area
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| *''G. haemorrhoidalis''
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| ***Eggs laid around the lips
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| *Larvae crawl into the mouth and penetrate the tissues of the buccal mucosa which takes a few weeks
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| *Larvae then emerge and are swallowed
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| *Larvae pass into the stomach and attach to the gastric mucosa
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| **Larvae are now known as '''bots'''
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| *Each species attaches to a specific part of the stomach
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| **''G. intestinalis'' attaches to the cardiac region
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| **''G. nasalis'' attaches to the pylorus
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| *After 10-12 months in the stomach, the larvae detach and are passed out in the faeces
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| **''G. haemorrhoidalis'' attaches to the rectal mucosa before being passed out
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| *Larvae pupate on the ground
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| *Adults hatch after 1-2 months and survive for a few days up to two weeks
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| **Adults have non-functional mouthparts so cannot feed
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| *There is only one generation per year in temperate regions of the world
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| '''Pathogenesis'''
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| *Adult cause annoyance when egg laying
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| **Disturbance and panic can ensue
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| *Larvae cause a marked inflammatory reaction when attached to the gastric mucosa
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| **Ring like thickening around the base of each attached larvae
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| *Large numbes of larvae may interfere with the passage of food and action of the sphincters
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| *''G. haemorrhoidalis'' can cause mild irritation to the rectal wall
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| **Host reaction to larvae in the mouth is minimal
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| '''Control'''
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| *Treatment of horses with [[Ectoparaciticides|insecticides]] over winter
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| **Breaks the life cycle as all the population are present as bots in the stomach
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| *If eggs are present in late summer, the horse's coat can be sponged with an [[ectoparasite|insecticide]]
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| **Stimulates hatching
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| **Kills larvae
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| ===''Dermatobia hominis''===
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| [[Image:Human Bot fly.jpg|thumb|right|150px|Human Bot Fly - Captain R. Goodman, United States Air Force]]
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| [[Image:Human Bot fly Larvae.jpg|thumb|right|150px|Human Bot Fly Larvae - Captain R. Goodman, United States Air Force]]
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| *Also called the human bot fly
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| *Larvae are important parasites of both humans and animals
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| *Specifically found in South America
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| '''Recongition'''
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| *Adult can grow up to 25mm in length
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| *Similar to [[Myiasis Flies - WikiBlood#Calliphoridae|''Calliphora'']] in appearance
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| **Blue/black
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| **Yellow/orange head and legs
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| *Larvae are dinstincive as they taper towards the posterior end
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| '''Life Cycle'''
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| *Eggs laid on blood sucking flies
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| **E.g. On mosquitos, which hatch when the mosquito next lands on a warm blooded animal
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| *Larvae penetrate skin causing painful swellings
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| *Larvae emerge after 35-42 days and fall to ground to pupate
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| *4 month life cycle
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| '''Pathogenesis'''
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| *In humans, the larvae are msot often found in swellings on the head and limbs
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| *Larvae cause painful swellings and distress to cattle
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| *Larvae cause production losses
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| *Larvae exit wounds can increase the prevalence of attack by other myiasis flies
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| ==Calliphoridae==
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| '''Recongition'''
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| '''Life Cycle'''
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| '''Pathogenesis'''
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| '''Control'''
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| ==Screw Worm Myiasis==
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| [[Image:Scree Worm.jpg|right|thumb|150px|Screw worm larvae - John Kucharski - Wikimedia Commons]]
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| *''C. bezziana'' cause myiasis in both animals and humans
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| *Located mainly in tropical regions
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| *Larvae are '''obligate''' parasites
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| '''Recongition'''
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| *Similar to ''Calliphora''
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| **Irridescent
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| **Clear wings
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| **Blue abdomen
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| *Longitudinal stripes on thorax
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| *Larvae have bands of spines
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| **Look like screws
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| '''Life Cycle'''
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| *Eggs laid in wounds or body cavities
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| *Larvae feed as colonies
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| *Larvae drop to the ground to pupate
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| '''Pathogenesis'''
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| *Spiracles are exposed as larvae feed which expands the wound
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| **Creates a foul smelling lesion
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| *Cause irritation and pyrexia
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| '''Control'''
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| *In the USA
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| **Mass eradication through the release of sterile males
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| **Currently only persists where flies have migrated across the Mexican border
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| *In Africa
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| **Introduced into Libya through the importation of infested livestock
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| **Sterile meales released
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| **Eradication occured in 1991
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| ===Maggot Debridement Therapy===
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| *Human medicine
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| **Sterile ''Lucilla sericata'' maggots used to treat infected and necrotic wounds
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| **Larvae secrete proteolytic enzymes and antimicrobial agents into the wound
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| ***Larvae do not burrow under the skin or attack healthy tissue
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| *Veterinary medicine
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| **Published reports rare
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| **Recently used successfully to treat a suppurative wound in a donkey that did not respond to conventional methods and surgery
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| ==''Wohlfahrtia'' sp.==
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| *'''Obligatory''' parasite
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| *Occurs in North America
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| *Parasite of mink and sometimes humans
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| '''Recongition'''
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| *Large 8-14mm long
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| *Pale grey
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| *Black stripes in thorax
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| *Black spots on abdomen
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| '''Life Cycle'''
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| *Larvae deposited directly onto host
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| **No egg stage
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| *Larvae moult twice on host then fall to ground to pupate
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| '''Pathogenesis'''
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| *Larvae penetrate intact skin
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| **Cause boil like swellings
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| ==Links==
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| *[[Viruses]]
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| *[[Ectoparasiticides]]
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