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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==
  −
[[Image:Warble flies.jpg|thumb|right|150px|Warble Fly - Geo. H. Carpenter, Cambridge University Press 1913 - Wikimedia Commons]]
  −
*The larvae of ''Oestridae spp.'' are '''obligatory''' parasites
  −
 
  −
*The three important species of veterinary interest
  −
**''Hypoderma''
  −
**''Oestrus''
  −
**''Gasterophilus''
  −
 
  −
 
  −
===''Hypoderma spp.''===
  −
 
  −
*Also known as warble flies
  −
 
  −
*Important cattle parasites
  −
**Also parasitise horses, small ruminants and sometimes humans
  −
 
  −
*The two main species in cattle are
  −
**''H. bovis''
  −
**''H. lineatum''
  −
 
  −
*''H. diana'' parasitises deer
  −
 
  −
*Infestation is largely confined to the Northern Hemisphere
  −
 
  −
 
  −
'''Recognition'''
  −
*Large 13-15mm long
  −
 
  −
*Similar to bumble bees in appearance
  −
**Yellow abdomen
  −
**Band of black hairs
  −
 
  −
*1 pair of wings
  −
 
  −
 
  −
'''Life cycle'''
  −
*Adult flies emerge on warm, sunny days between '''June and August'''
  −
 
  −
*White eggs are laid around the belly and legs of the animal
  −
**Eggs are attached to hairs by cement and a small terminal clasp
  −
**''H. lineatum'' lays a whole row of eggs as it approaches the animal stealthily
  −
**''H. bovis'' only deposits a single egg before the animal runs away ('''gadding''') as it makes a loud buzzing noise
  −
 
  −
*The adult lives for 3 weeks
  −
 
  −
*Females can lay several hundred eggs in their life
  −
 
  −
*A few days after eggs are laid, larvae emerge and crawl down the hairs into the hair follicles
  −
 
  −
*Larvae penetrate the skin through wounds made by [[Biting Flies - WikiBlood|biting flies]]
  −
 
  −
*Larvae migrate through the subcutaneous tissue towards the diaphragm
  −
**Enzymatic secretions and mouth hooks aid larval migration
  −
 
  −
*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
  −
**Epidural fat in the spinal canal for ''H. bovis''
  −
**Wall of the [[Oesophagus - Anatomy & Physiology|oesophagus]] for ''H. lineatum''
  −
 
  −
*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
  −
**Larvae are palpable as distinct swellings called '''warbles'''
  −
 
  −
*L3 larvae emerge after 4-10 weeks where they fall to the ground and pupate under loose vegetation
  −
 
  −
*Adult flies emerge from the pupa after 1 month where they copulate, lay eggs and die within 2 weeks
  −
 
  −
*''H. lineatum'' are on the wing 6-8 weeks before ''H. bovis''
  −
 
  −
*There is only '''1 generation''' of warble flies per year
  −
 
  −
 
  −
'''Pathogenesis'''
  −
*Causes [[Muscles Inflammatory - Pathology#Arthropods|myositis]]
  −
 
  −
*Production losses
  −
**Condemnation and down-grading of hides
  −
**Reduced milk yield and reduced weight gain
  −
**Injury from stock panic
  −
**Trimmed meat losses from ''H. lineatum''
  −
***'Butcher's Jelly' around warbles which is green due to mass [[Eosinophils - WikiBlood|eosinophil]] attraction
  −
 
  −
*Paraplegia resulting from
  −
**Toxin release
  −
**Pressure on the spinal cord (''H. bovis'')
  −
**Bloat from pressure on the [[Oesophagus - Anatomy & Physiology|oesophageal wall]] (''H. lineatum'')
  −
 
  −
 
  −
'''Control'''
  −
*Total eradication should be aimed for
  −
 
  −
*Old methods include popping out warbles
  −
**But this could lead to anaphylactic shock
  −
 
  −
*[[Ectoparasiticides]]
  −
**Systemic organophosphorus [[Ectoparasiticides|insecticides]] in pour-on formula
  −
**Avermectins and milbemycins in pour-on and injectible formulations
  −
 
  −
*Timing is crucial for treatment
  −
**Larvae residing in winter resting sites, if killed, can lead to bloat and paraplegia
  −
**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
  −
**Ivermectin can be given at any time without risking host infection as larval antigen is released much slower
  −
 
  −
 
  −
'''Legislation in the UK'''
  −
*'Warble Fly Order 1978' requires all clinically affected animals to be treated
  −
 
  −
*Notifiable disease
  −
 
  −
*'Warble Fly Infected Area Order 1983'
  −
 
  −
*For more information on the warble fly orders, see [http://www.defra.gov.uk/animalh/diseases/notifiable/brucellosis/surveillance.htm| here]
  −
 
  −
===''Oestrus ovis''===
  −
 
  −
*Also known as the sheep nasal bot fly
  −
 
  −
*Larvae parasitise the nasal chambers of sheep and goats
  −
 
  −
*Found in most sheep rearing areas of the world
  −
 
  −
 
  −
'''Recognition'''
  −
*13-15mm long
  −
 
  −
*Grey colouring
  −
 
  −
*Black spots on abdomen
  −
 
  −
*Clear wings
  −
 
  −
*Larvae have distinct black bands on each body segment
  −
 
  −
 
  −
'''Life cycle'''
  −
*Larvae are squirted into the nostrils of sheep in a jet of liquid by the adult fly
  −
 
  −
*The larvae crawl caudally into the nasal cavity and feed on the nasal mucosa and mature before returning to the nostrils
  −
 
  −
*Larval development takes up to 2 months
  −
**Larvae can overwinter in the nasal cavity if deposited late in the summer
  −
 
  −
*Once the larvae have developed they are sneezed out and pupate on the ground
  −
 
  −
*The adult fly emerges 1 months later
  −
 
  −
*Adult flies only live for 2-3 weeks
  −
 
  −
 
  −
'''Pathogenesis'''
  −
*Adult flies cause annoyance
  −
**Interrupts feeding
  −
**Leads to a decreased weight gain
  −
 
  −
*Larvae cause nasal irritation, nasal discharge and sneezing
  −
**Irritate the nasal mucosa with oral hooks and spines causing a viscous exudate to be produced from which they feed
  −
**Heavy infestations lead to erosion of the bones in the sinuses (turbinate bones)
  −
**Penetration of the brain leads to '''false gid''' (high stepping gait and incoordination)
  −
 
  −
*[[Respiratory Parasitic Infections - Pathology#Oestrus ovis|Pathology in the nasal cavity]]
  −
 
  −
 
  −
'''Control'''
  −
*Systemic [[Ectoparasiticides|insecticides]] can be used in heavy infestations
  −
 
  −
*In warmer countries, strategic prophylactic treatment can be used
  −
 
  −
 
  −
===''Gasterophilus spp.''===
  −
[[Image:Horse Bot Fly.jpg|thumb|right|150px|Horse Bot Fly - Dennis Ray - Wikimedia Commons]]
  −
*Also known as the horse bot fly
  −
 
  −
*Obligate parasites of equids
  −
 
  −
*Spend most of life cycle in the equine stomach
  −
**Of little pathogenic significance
  −
 
  −
*Three important species (in the UK)
  −
**''G. intestinalis'' which is the most common
  −
**''G. nasalis''
  −
**''G. haemorrhoidalis'' which is rare
  −
 
  −
*Two other important veterinary species
  −
**''G. nigricornis''
  −
**''G. inermis''
  −
 
  −
 
  −
'''Recognition'''
  −
*Medium to large flies at 10-20mm long
  −
 
  −
*Look similar to drone bumble bees
  −
**Body covered with dense yellow hair
  −
**Dark coloured hairs produce a banding pattern
  −
 
  −
*Clear wings with brown patches
  −
 
  −
 
  −
'''Life cycle'''
  −
*Adults are most active in '''late summer'''
  −
 
  −
*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
  −
**''G. intestinalis'' eggs are laid in the hair of the shoulders and fore legs
  −
**''G. nasalis'' eggs are laid in the intermandibular area
  −
**''G. haemorrhoidalis'' eggs are laid around the lips
  −
 
  −
*Creamy-white eggs
  −
 
  −
*1-2mm in length
  −
 
  −
*Larvae crawl into the mouth and penetrate the tissues of the tongue and buccal mucosa
  −
 
  −
*Larvae then emerge after a couple of weeks and are swallowed
  −
 
  −
*Larvae pass into the [[Forestomach - Anatomy & Physiology|stomach]] and attach to the gastric mucosa
  −
**Larvae are now known as '''bots'''
  −
 
  −
*Each species attaches to a specific part of the stomach
  −
**''G. intestinalis'' attaches to the cardiac region
  −
**''G. nasalis'' attaches to the pylorus
  −
 
  −
*After 10-12 months in the stomach, the larvae detach and are passed out in the faeces
  −
**''G. haemorrhoidalis'' attaches to the rectal mucosa before being passed out
  −
 
  −
*Larvae pupate on the ground
  −
 
  −
*Adults hatch after 1-2 months and survive from a few days to 2 weeks
  −
**Adults have non-functional mouthparts so cannot feed
  −
 
  −
*There is only '''1 generation per year''' in temperate regions of the world
  −
 
  −
 
  −
'''Pathogenesis'''
  −
*Adults cause annoyance when egg laying
  −
**Disturbance and panic can ensue
  −
 
  −
*Larvae cause a marked inflammatory reaction when attached to the gastric mucosa
  −
**Ring like thickening around the base of each attached larvae
  −
 
  −
*Large numbers of larvae may interfere with the passage of food and action of gastric sphincters
  −
 
  −
*''G. haemorrhoidalis'' can cause mild irritation to the rectal wall
  −
 
  −
*Host reaction to larvae in the mouth is minimal
  −
 
  −
 
  −
'''Control'''
  −
*Treatment of horses with [[Ectoparasiticides|insecticides]] over winter
  −
**Breaks the life cycle as all the population are present as bots in the [[Forestomach - Anatomy & Physiology|stomach]]
  −
 
  −
*If eggs are present in late summer, the horse's coat can be sponged with an [[Ectoparasiticides|insecticide]]
  −
**Stimulates hatching
  −
**Kills larvae
  −
 
  −
 
  −
===''Dermatobia hominis''===
  −
[[Image:Human Bot fly.jpg|thumb|right|150px|Human Bot Fly - Captain R. Goodman, United States Air Force]]
  −
[[Image:Human Bot fly Larvae.jpg|thumb|right|150px|Human Bot Fly Larvae - Captain R. Goodman, United States Air Force]]
  −
*Also called the human bot fly
  −
 
  −
*Larvae are important parasites of both humans and animals
  −
 
  −
*Specifically found in South America
  −
 
  −
 
  −
'''Recognition'''
  −
*Adult can grow up to 25mm in length
  −
 
  −
*Similar to [[Myiasis Flies - WikiBlood#Calliphoridae|''Calliphora'']] in appearance
  −
**Blue-black
  −
**Yellow-orange head and legs
  −
 
  −
*Larvae are distinctive as they taper towards the posterior end
  −
 
  −
 
  −
'''Life cycle'''
  −
*Eggs laid on blood sucking flies such as mosquitoes
  −
**These hatch when the mosquito next lands on a warm blooded animal
  −
 
  −
*Larvae penetrate skin causing painful swellings
  −
 
  −
*Larvae emerge after 35-42 days and fall to ground to pupate
  −
 
  −
*'''4 month''' life cycle
  −
 
  −
 
  −
'''Pathogenesis'''
  −
*In humans, the larvae are most often found in swellings on the head and limbs
  −
 
  −
*Larvae cause painful swellings and distress to cattle
  −
 
  −
*Larvae cause production losses
  −
 
  −
*Wounds caused by exiting larvae can increase the prevalence of attack by other myiasis flies
  −
 
  −
 
  −
==Calliphoridae==
  −
[[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]]
  −
[[Image:Blow fly head.jpg|thumb|right|150px|Blowfly Head Close Up - Martin Pot - Wikimedia Commons]]
  −
*The ''Calliphoridae'' family are '''facultative''' parasites
  −
 
  −
*Cause '''blowfly strike'''
  −
 
  −
*If the fly lays eggs on an animal, the animal is said to be '''blown'''
  −
 
  −
*The damage the larvae cause to the animal is known as '''strike'''
  −
 
  −
*Worldwide distribution
  −
 
  −
*Affects sheep mostly
  −
**Rabbits can also be affected
  −
 
  −
 
  −
'''Species of veterinary importance in Europe'''
  −
*''Lucilia sericata''; Greenbottle
  −
 
  −
*''Phormia terra-novae''; Blackbottle
  −
 
  −
*''Calliphora erythrocephala''; Bluebottle
  −
 
  −
*''Callipohora vomitoria''; Bluebottle
  −
 
  −
 
  −
'''Species of veterinary importance in the Tropics'''
  −
*''Lucilia cuprina''; South Africa and Australia
  −
 
  −
*''Chrysomya spp.''; Africa, Asia and Australia
  −
 
  −
*''Wohlfahrtia''; Fleshfly
  −
 
  −
 
  −
'''Recognition of Adults'''
  −
*Medium sized flies under 10mm long
  −
 
  −
*Metallic sheen to abdomen
  −
**Colour depends on species
  −
 
  −
*Clear wings
  −
 
  −
 
  −
'''Recognition of Larvae'''
  −
*Smooth maggots
  −
 
  −
*10-15mm long
  −
 
  −
*Spiracles and stigmatic plates on the tail can be used for species differentiation
  −
 
  −
 
  −
'''Life cycle'''
  −
*Eggs laid in wounds, soiled fleece and on carrion
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**Females attracted by the odour emitted
  −
**Clusters of yellow-cream eggs laid
  −
 
  −
*Larvae hatch 24 hours later and crawl down onto the skin
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**Feed rapidly
  −
**Grow rapidly
  −
**Moult twice before becoming full maggots
  −
**Process takes 1-2 weeks
  −
 
  −
*Larvae fall to the ground to pupate
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  −
*Adult emerges in under 1 week (during summer)
  −
 
  −
*The female reaches sexual maturity after a protein meal
  −
**Lays eggs in batches of 100-200
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  −
*Adult flies survive for 1 month
  −
 
  −
*'''Four generations can develop between May and September '''
  −
**In warmer climates, up to 9 or 10 generations can develop per year
  −
 
  −
*Flies can survive the winter as pupae and emerge the next spring
  −
 
  −
 
  −
'''Epidemiology'''
  −
<br>Blowflies are divided into categories depending on their ability to initiate strike
  −
*Primary flies are capable of initiating a strike on living sheep. Larvae can penetrate intact skin
  −
**''Lucilia''
  −
**''Phormia''
  −
**''Calliphora spp.''
  −
 
  −
*Secondary flies cannot initiate a strike. Larvae attack an area already struck or damaged, extending it
  −
**''Calliphora spp.''
  −
**''Chrysomya spp.'' (in warmer climates)
  −
 
  −
*Tertiary flies attack lesions on carcasses which have become dry
  −
**''Musca''
  −
**''Sarcophaga spp.''
  −
 
  −
 
  −
Predisposing factors to flystrike
  −
*Temperature
  −
**Temperature in the spring will determine when the overwintering larvae hatch
  −
**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
  −
**This is increased when putrefactive odours develop on the fleece due to bacterial decomposition of organic matter following soiling with urine or faeces
  −
**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
  −
 
  −
 
  −
Blowfly season
  −
*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
  −
 
  −
*Warmer regions have a more prolonged season due to greater number of blowfly generations
  −
 
  −
 
  −
'''Pathogenesis'''
  −
*Severe skin damage
  −
**Larvae lacerate skin with oral hooks and liquefy host tissue by secreting proteolytic enzymes
  −
 
  −
*Skin lesions are extended and deepened
  −
**Secondary blowfly attack
  −
**Flies attracted to odour of decomposing tissue
  −
 
  −
*Secondary bacterial infection
  −
 
  −
*Production losses
  −
**Irritation and distress associated with skin lesions
  −
**Poor weight gain (often the first clinical sign)
  −
 
  −
*Risk of strike is highest in warm, moist weather
  −
 
  −
 
  −
'''Clinical signs'''
  −
*Anorexia
  −
*Listlessness
  −
*Animals standing apart from flock
  −
 
  −
*Fleece may appear darker, be damp and have a foul smell
  −
 
  −
 
  −
'''Control'''
  −
*Prophylactic [[Ectoparasiticides|insecticide]] treatment
  −
**Must kill larvae and remain in fleece to prevent flies from laying eggs
  −
**Applied by spraying, dipping, spray race or jetting
  −
 
  −
*Insect growth regulators
  −
**Pour-on
  −
**2-4 month protection depending upon the product used
  −
 
  −
*Effective worm control
  −
**To minimise diarrhoea and therefore soiled fleece
  −
 
  −
*Crutching to prevent soiling
  −
 
  −
*'Mule's operation'
  −
**Surgical removal of breech skin in Merino breeds
  −
 
  −
*Tail docking of lambs
  −
 
  −
*Proper carcass disposal
  −
**Eliminates fly breeding sites
  −
 
  −
*Vaccination
  −
**Experimental use against ''Luculia cuprina'' in Australia
  −
 
  −
 
  −
===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
  −
 
  −
*Located mainly in tropical regions
  −
 
  −
*Larvae are '''obligate''' parasites
  −
 
  −
 
  −
'''Recognition'''
  −
*Similar to ''Calliphora spp.''
  −
**Iridescent
  −
**Clear wings
  −
**Blue abdomen
  −
 
  −
*Longitudinal stripes on thorax
  −
 
  −
*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 medical methods and surgery
  −
 
  −
 
  −
===''Wohlfahrtia spp.''===
  −
 
  −
*'''Obligatory''' parasite
  −
 
  −
*Occurs in North America
  −
 
  −
*Parasite of mink and sometimes humans
  −
 
  −
 
  −
'''Recognition'''
  −
*Large 8-14mm long
  −
 
  −
*Pale grey
  −
 
  −
*Black stripes on thorax
  −
 
  −
*Black spots on abdomen
  −
 
  −
 
  −
'''Life cycle'''
  −
*Larvae deposited directly onto host
  −
 
  −
*No egg stage
  −
 
  −
*Larvae moult twice on host then fall to ground to pupate
  −
 
  −
 
  −
'''Pathogenesis'''
  −
*Larvae penetrate intact skin
  −
**Cause boil like swellings
  −
 
  −
==[[Insecta Flashcards - WikiBugs#Myiasis Producing Flies|Myiasis Producing Flies Flashcards]]==
  −
 
  −
==Links==
  −
 
  −
*[[Viruses]]
  −
 
  −
*[[Ectoparasiticides]]
  −
 
  −
*[http://www.strikewise.com/index.html| Blowfly strike]
 
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