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− | {{review}}
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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 obligatory or facultative (optional) and is described as cutaneous, nasal or somatic.
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− | | + | #REDIRECT[[:Category:Myiasis Producing Flies]] |
− | ==Oestridae==
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− | [[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
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− | **''Hypoderma''
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− | **''Oestrus''
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− | **''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
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− | **''H. bovis''
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− | **''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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− | | |
− | *1 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 aid larval migration
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− | | |
− | *After 3 months larvae reach '''winter resting sites''' where they remain from November to February/March whilst moulting to the L2 stage. These sites are different between the 2 species
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− | **Epidural fat in the spinal canal for ''H. bovis''
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− | **Wall of the [[Oesophagus - Anatomy & Physiology|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 1 month where they copulate, lay eggs and die within 2 weeks
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− | | |
− | *''H. lineatum'' are on the wing 6-8 weeks before ''H. bovis''
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− | | |
− | *There is only '''1 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 pressure on the [[Oesophagus - Anatomy & Physiology|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 this 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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− | | |
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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 nostrils of sheep in a jet of liquid by the adult fly
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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 2 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 1 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 cause 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|Pathology 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]]
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− | *Also known as the horse bot fly
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− | | |
− | *Obligate parasites of equids
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− | | |
− | *Spend most of life cycle in the equine stomach
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− | **Of little pathogenic 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 are laid on the body and hatch spontaneously or are stimulated to hatch through an increase in warmth and moisture from the animal self-grooming. They are laid in different areas according to species
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− | **''G. intestinalis'' eggs are laid in the hair of the shoulders and fore legs
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− | **''G. nasalis'' eggs are laid in the intermandibular area
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− | **''G. haemorrhoidalis'' eggs are laid around the lips
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− | | |
− | *Creamy-white eggs
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− | | |
− | *1-2mm in length
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− | | |
− | *Larvae crawl into the mouth and penetrate the tissues of the tongue and buccal mucosa
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− | | |
− | *Larvae then emerge after a couple of weeks and are swallowed
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− | | |
− | *Larvae pass into the [[Forestomach - Anatomy & Physiology|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 from a few days to 2 weeks
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− | **Adults have non-functional mouthparts so cannot feed
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− | | |
− | *There is only '''1 generation per year''' in temperate regions of the world
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− | | |
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− | '''Pathogenesis'''
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− | *Adults 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 numbers of larvae may interfere with the passage of food and action of gastric 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 [[Ectoparasiticides|insecticides]] over winter
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− | **Breaks the life cycle as all the population are present as bots in the [[Forestomach - Anatomy & Physiology|stomach]]
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− | | |
− | *If eggs are present in late summer, the horse's coat can be sponged with an [[Ectoparasiticides|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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− | | |
− | | |
− | '''Recognition'''
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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 distinctive as they taper towards the posterior end
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− | | |
− | | |
− | '''Life cycle'''
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− | *Eggs laid on blood sucking flies such as mosquitoes
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− | **These 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 most 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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− | | |
− | *Wounds caused by exiting larvae can increase the prevalence of attack by other myiasis flies
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− | | |
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− | ==Calliphoridae==
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− | [[Image:Calliphoridae.jpg|thumb|right|150px|Pollenia rudis (Calliphoridae) - Richard Bartz, Munich - Wikimedia Commons]]
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− | [[Image:Lucilia cuprina.jpg|thumb|right|150px|''Lucilia cuprina'' - Wikimedia Commons]]
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− | [[Image:Blow fly head.jpg|thumb|right|150px|Blowfly Head Close Up - Martin Pot - Wikimedia Commons]]
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− | *The ''Calliphoridae'' family are '''facultative''' parasites
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− | *Cause '''blowfly strike'''
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− | *If the fly lays eggs on an animal, the animal is said to be '''blown'''
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− | *The damage the larvae cause to the animal is known as '''strike'''
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− | *Worldwide distribution
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− | *Affects sheep mostly
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− | **Rabbits can also be affected
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− | '''Species of veterinary importance in the Europe'''
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− | *''Lucilia sericata''; Greenbottle
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− | *''Phormia terra-novae''; Blackbottle
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− | *''Calliphora erythrocephala''; Bluebottle
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− | *''Callipohora vomitoria''; Bluebottle
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− | '''Species of veterinary importance in the Tropics'''
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− | *''Lucilia cuprina''; South Africa and Australia
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− | *''Chrysomya spp.''; Africa, Asia and Australia
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− | *''Wohlfahrtia''; Fleshfly
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− | '''Recognition of Adults'''
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− | *Medium sized flies under 10mm long
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− | | |
− | *Metallic sheen to abdomen
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− | **Colour depends on species
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− | | |
− | *Clear wings
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− | '''Recognition of Larvae'''
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− | *Smooth maggots
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− | *10-15mm long
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− | *Spiracles and stigmatic plates on the tail can be used for species differentiation
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− | | |
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− | '''Life cycle'''
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− | *Eggs laid in wounds, soiled fleece and on carrion
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− | **Females attracted by the odour emitted
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− | **Clusters of yellow-cream eggs laid
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− | | |
− | *Larvae hatch 24 hours later and crawl down onto the skin
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− | **Feed rapidly
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− | **Grow rapidly
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− | **Moult twice before becoming full maggots
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− | **Process takes 1-2 weeks
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− | | |
− | *Larvae fall to the ground to pupate
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− | *Adult emerges in under 1 week (during summer)
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− | | |
− | *The female reaches sexual maturity after a protein meal
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− | **Lays eggs in batches of 100-200
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− | | |
− | *Adult flies survive for 1 month
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− | | |
− | *'''Four generations can develop between May and September '''
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− | **In warmer climates, up to 9 or 10 generations can develop per year
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− | | |
− | *Flies can survive the winter as pupae and emerge the next spring
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− | | |
− | | |
− | '''Epidemiology'''
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− | <br>Blowflies are divided into categories depending on their ability to initiate strike
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− | *Primary flies are capable of initiating a strike on living sheep. Larvae can penetrate intact skin
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− | **''Lucilia''
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− | **''Phormia''
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− | **''Calliphora spp.''
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− | | |
− | *Secondary flies cannot initiate a strike. Larvae attack an area already struck or damaged, extending it
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− | **''Calliphora spp.''
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− | **''Chrysomya spp.'' (in warmer climates)
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− | | |
− | *Tertiary flies attack lesions on carcasses which have become dry
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− | **''Musca''
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− | **''Sarcophaga spp.''
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− | | |
− | Predisposing factors to flystrike
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− | *Temperature
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− | **Temperature in the spring will determine when the overwintering larvae hatch
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− | **High temperature and humidity will create a microclimate in the fleece, attracting adult flies to lay eggs
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− | | |
− | *Rainfall
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− | **Persistent rainfall will make the fleece microclimate attractive to adult flies. Females lay eggs after the rain ceases
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− | **Breeds with long, fine wool are the most susceptible
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− | | |
− | *Host susceptibility
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− | **This is increased when putrefactive odours develop on the fleece due to bacterial decomposition of organic matter following soiling with urine or faeces
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− | **Merino sheep have a narrow breech area with excessive wrinkling making them more susceptible to soiling
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− | **A narrow opening of the penile sheath in rams and wethers may result in accumulation of urine and increase blowfly strike in this area
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− | **Cuts during shearing, fighting and barbed wire will also increase the incidence of blowfly strike
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− | | |
− | Blowfly season
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− | *Temperate regions in '''June to September'''
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− | **Mostly in unshorn sheep in June
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− | **Lambs from July to September
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− | | |
− | *Warmer regions have a more prolonged season due to greater number of blowfly generations
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− | | |
− | | |
− | '''Pathogenesis'''
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− | *Severe skin damage
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− | **Larvae lacerate skin with oral hooks and liquefy host tissue by secreting proteolytic enzymes
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− | | |
− | *Skin lesions are extended and deepened
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− | **Secondary blowfly attack
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− | **Flies attracted to odour of decomposing tissue
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− | | |
− | *Secondary bacterial infection
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− | | |
− | *Production losses
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− | **Irritation and distress associated with skin lesions
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− | **Poor weight gain (often the first clinical sign)
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− | | |
− | *Risk of strike is highest in warm, moist weather
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− | | |
− | | |
− | '''Clinical signs'''
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− | *Anorexia
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− | *Listlessness
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− | *Animals standing apart from flock
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− | | |
− | *Fleece may appear darker, be damp and have a foul smell
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− | | |
− | | |
− | '''Control'''
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− | *Prophylactic [[Ectoparasiticides|insecticide]] treatment
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− | **Must kill larvae and remain in fleece to prevent flies from laying eggs
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− | **Applied by spraying, dipping, spray race or jetting
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− | | |
− | *Insect growth regulators
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− | **Pour-on
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− | **2-4 month protection depending upon the product used
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− | | |
− | *Effective worm control
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− | **To minimise diarrhoea and therefore soiled fleece
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− | | |
− | *Crutching to prevent soiling
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− | | |
− | *'Mule's operation'
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− | **Surgical removal of breech skin in Merino breeds
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− | | |
− | *Tail docking of lambs
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− | | |
− | *Proper carcass disposal
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− | **Eliminates fly breeding sites
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− | | |
− | *Vaccination
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− | **Experimental use against ''Luculia cuprina'' in Australia
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− | | |
− | | |
− | ===Screw Worm Myiasis===
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− | [[Image:Screw 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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− | | |
− | '''Recognition'''
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− | *Similar to ''Calliphora''
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− | **Iridescent
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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 males released
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− | **Eradication occurred in 1991
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− | | |
− | ====Maggot Debridement Therapy====
| |
− | [[Image:Maggot Therapy.jpg|thumb|right|150px|Maggot therapy on a wound - Wikimedia Commons]]
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− | *Human medicine
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− | **Sterile ''Lucilia 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
| |
− | | |
− | ===''Wohlfahrtia'' sp.===
| |
− | | |
− | *'''Obligatory''' parasite
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− | | |
− | *Occurs in North America
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− | | |
− | *Parasite of mink and sometimes humans
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− | | |
− | '''Recognition'''
| |
− | *Large 8-14mm long
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− | | |
− | *Pale grey
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− | | |
− | *Black stripes on thorax
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− | | |
− | *Black spots on abdomen
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− | | |
− | '''Life Cycle'''
| |
− | *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'''
| |
− | *Larvae penetrate intact skin
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− | **Cause boil like swellings
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− | ==[[Insecta Flashcards - WikiBugs#Myiasis Producing Flies|Myiasis Producing Flies Flashcards]]==
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− | ==Links==
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− | *[[Viruses]]
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− | *[[Ectoparasiticides]]
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− | *[http://www.strikewise.com/index.html| Blowfly strike]
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