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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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| | | | |
| − | ==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 February/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 - 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 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 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 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 nostrils of sheep in a jet of liquid
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| − | | |
| − | *The larvae crawl caudally into the [[Nasal cavity - Anatomy & Physiology|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 - Anatomy & Physiology|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 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 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 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 - Anatomy & Physiology|lips]]
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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 [[Forestomach - Anatomy & Physiology|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 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 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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| − | | |
| − | '''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 distinctive 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 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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| − | | |
| − | ==Calliphoridae==
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| − | [[Image:Calliphoridae.jpg|thumb|right|150px|Pollenia rudis (Calliphoridae) - Richard Bartz, Munich - Wikimedia Commons]] | |
| − | [[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
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| − | | |
| − | *Affects sheep mostly
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| − | **Rabbits can also be affected
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| − | | |
| − | '''Species of Veterinary importance'''
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| − | *''Lucilia serrata''
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| − | **Greenbottles
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| − | | |
| − | *''Phormia terra-novae''
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| − | **Blackbottle
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| − | | |
| − | *''Calliphora erythrocephala''
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| − | **Bluebottle
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| − | | |
| − | *''Callipohora vomitoria''
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| − | **Bluebottle
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| − | | |
| − | *''Lucilia cuprina''
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| − | **South Africa, Australia
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| − | | |
| − | *''Chrysomya'' spp.
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| − | **Africa, Asia, Australia
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| − | | |
| − | *''Wohlfahrtia''
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| − | **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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| − | | |
| − | '''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 falls to the ground to pupate
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| − | | |
| − | *Adult emerges in under a 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 one month
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| − | | |
| − | *Between May and September four generations can develop
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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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| − | *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 so larvae can penetrate intact skin
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| − | ***E.g. ''Lucilia'', ''Phormia'' and ''Calliphora''
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| − | **Secondary flies cannot initiate a strike, larvae attack an area already struck or damaged, extending it
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| − | ***E.g. ''Calliphora'' and ''Chrysoma'' (in warmer climates)
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| − | **Tertiary flies attack lesions on carcasses which have become dry
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| − | ***E.g. ''Musca'' and ''Sarcophaga'' spp.
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| − | | |
| − | *Temperature will affect the prevalence of strike
| |
| − | **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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| − | | |
| − | *Persistent rainfall will make the fleece microclimate attractive to adult flies
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| − | **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 is increased when putrefactive odours develop on the fleece due to bacterial decomposition of organic matter
| |
| − | **Merino sheep have a narrow breech area with excessive wrinkling making them more susceptible to soiling
| |
| − | **A narrow opening of the penile sheath in rams and wethers may result in accumulation of urine and increase blowfly strike in this area
| |
| − | **Cuts during shearing, fighting and barbed wire will also increase the incidence of blowfly strike
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| − | | |
| − | '''Pathogenesis'''
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| − | *Severe skin damage
| |
| − | **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, listlessness, animals standing apart from flock
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| − | | |
| − | *Fleece may appear darker, be damp and have a foul smell
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| − | | |
| − | *Strike is classified according to where the body is affected
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| − | | |
| − | '''Control'''
| |
| − | *Prophylactic [[Ectoparasiticides|insecticide]] treatment
| |
| − | **Must kill larvae and remain in fleece to prevent flies from laying eggs
| |
| − | **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
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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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| − | | |
| − | ===Screw Worm Myiasis===
| |
| − | [[Image:Screw Worm.jpg|right|thumb|150px|Screw worm larvae - John Kucharski - Wikimedia Commons]]
| |
| − | *''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''
| |
| − | **Iridescent
| |
| − | **Clear wings
| |
| − | **Blue abdomen
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| − | | |
| − | *Longitudinal stripes on thorax
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| − | | |
| − | *Larvae have bands of spines
| |
| − | **Look like screws
| |
| − | | |
| − | '''Life Cycle'''
| |
| − | *Eggs laid in wounds or body cavities
| |
| − | | |
| − | *Larvae feed as colonies
| |
| − | | |
| − | *Larvae drop to the ground to pupate
| |
| − | | |
| − | '''Pathogenesis'''
| |
| − | | |
| − | *Spiracles are exposed as larvae feed which expands the wound
| |
| − | **Creates a foul smelling lesion
| |
| − | | |
| − | *Cause irritation and pyrexia
| |
| − | | |
| − | '''Control'''
| |
| − | *In the USA
| |
| − | **Mass eradication through the release of sterile males
| |
| − | **Currently only persists where flies have migrated across the Mexican border
| |
| − | | |
| − | *In Africa
| |
| − | **Introduced into Libya through the importation of infested livestock
| |
| − | **Sterile males released
| |
| − | **Eradication occurred in 1991
| |
| − | | |
| − | ====Maggot Debridement Therapy====
| |
| − | [[Image:Maggot Therapy.jpg|thumb|right|150px|Maggot therapy on a wound - Wikimedia Commons]]
| |
| − | *Human medicine
| |
| − | **Sterile ''Lucilia sericata'' maggots used to treat infected and necrotic wounds
| |
| − | **Larvae secrete proteolytic enzymes and antimicrobial agents into the wound
| |
| − | ***Larvae do not burrow under the skin or attack healthy tissue
| |
| − | | |
| − | *Veterinary medicine
| |
| − | **Published reports rare
| |
| − | **Recently used successfully to treat a suppurative wound in a donkey that did not respond to conventional methods and surgery
| |
| − | | |
| − | ===''Wohlfahrtia'' sp.===
| |
| − | | |
| − | *'''Obligatory''' parasite
| |
| − | | |
| − | *Occurs in North America
| |
| − | | |
| − | *Parasite of mink and sometimes humans
| |
| − | | |
| − | '''Recognition'''
| |
| − | *Large 8-14mm long
| |
| − | | |
| − | *Pale grey
| |
| − | | |
| − | *Black stripes on 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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| − | | |
| − | ==[[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]
| |