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==Introduction==


Myiasis is the parasitism of living animals by dipteran larvae. Myiasis can be oligatory or facultative (optional) and is described as cutaneous, nasal or somatic.


#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 are ''Hypoderma'', ''Oestrus'' and ''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'' and ''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
 
*One 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 aids larval migration
 
*After 3 months larvae reach '''winter resting sites''' where they remain from November to Feburary/March whilst moulting to the L2 stage
**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 one month where they copulate, lay eggs and die within two weeks
 
*''H. lineatum'' are on the wing 6-8 weeks before ''H. bovis''
 
*There is only '''one''' 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 pressue on the [[Oesophagus - Anatomy & Physiology|oesophageal wall]] (''H. lineatum'')
 
'''Control'''
*Total eradication should be aimed for
 
*Old methods include popping out warbles
**But 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 nostils of sheep in a jet of liquid
 
*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
 
*Larval development takes up to two months
**Larvae can overwinter in the [[Nasal cavity - Anatomy & Physiology|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 one months later
 
*Adult flies only live for 2-3 weeks
 
'''Pathogenesis'''
*Adult flies can 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|Apthology 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 lifecycle in equine stomach
**Cause little pathogenesic 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 hatch spontaneously or are stimulated to hatch through an increase in warmth and moisture from the animal self-grooming
**''G. intestinalis''
***Creamy-white eggs
***1-2mm in length
***Eggs laid in the hair of the shoulders and fore legs
**''G. nasalis''
***Eggs laid in the intermandibular area
**''G. haemorrhoidalis''
***Eggs laid around the [[Lips - Anatomy & Physiology|lips]]
 
*Larvae crawl into the mouth and penetrate the tissues of the buccal mucosa which takes a few weeks
 
*Larvae then emerge 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 [[Forestomach - Anatomy & Physiology|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 for a few days up to two weeks
**Adults have non-functional mouthparts so cannot feed
 
*There is only one generation per year in temperate regions of the world
 
'''Pathogenesis'''
*Adult 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 numbes of larvae may interfere with the passage of food and action of the 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
 
'''Recongition'''
*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 dinstincive as they taper towards the posterior end
 
'''Life Cycle'''
*Eggs laid on blood sucking flies
**E.g. On mosquitos, which 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 msot often found in swellings on the head and limbs
 
*Larvae cause painful swellings and distress to cattle
 
*Larvae cause production losses
 
*Larvae exit wounds 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:Lucilla cuprina.jpg|thumb|right|150px|''Lucilla 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
 
*Affects sheep mostly
**Rabbits can also be affected
 
'''Species of Veterinary importance'''
*''Lucilla serrata''
**Greenbottles
 
*''Phormia terra-novae''
**Blackbottle
 
*''Calliphora erythrocephala''
**Bluebottle
 
*''Callipohora vomitoria''
**Bluebottle
 
*''Lucilla cuprina''
**South Africa, Australia
 
*''Chrysomya'' spp.
**Africa, Asia, Australia
 
*''Wohlfahrtia''
**Fleshfly
 
'''Recongition 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
**Females attracted by the odour emitted
**Clusters of yellow/cream eggs laid
 
*Larvae hatch 24 hours later and crawl down onto the skin
**Feed rapidly
**Grow rapidly
**Moult twice before becoming full maggots
**Process takes 1-2 weeks
 
*Larvae falls to the fround to pupate
 
*Adult emerges in under a week (during summer)
 
*The female reaches sexual maturity after a protein meal
**Lays eggs in batches of 100-200
 
*Adult flies survive for one month
 
*Between May and September four generations can develop
**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'''
*Divided into categories depending on their ability to initiate strike
**Primary flies are capable of initiating a strike on living sheep so larvae can penetrate intact skin
***E.g. ''Lucilla'', ''Phormia'' and ''Calliphora''
**Secondary flies cannot initiate a strike, larvae attack an area already struck or damaged, extending it
***E.g. ''Callipohora'' and ''Chrysoma'' (in warmer climates)
**Tertiary flies attack lesions on carcasses which have become dry
***E.g. ''Musca'' and ''Sarcophaga'' spp.
 
*Temperature will affect the prevalence of strike
**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
 
*Persistent rainfall will make the fleece microclimate attractive to adult flies
**Females lay eggs after the rain ceases
**Breeds with long, fine wool are the most susceptible
 
*Host susceptibility is increased when putrefactive odours develop on the fleece due to bacterial decomposition of organic matter
**Merino sheep have a narrow breach area with excessive wrinkling making them more suceptible 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
 
'''Pathogenesis'''
*Severe skin damage
**Larvae lacerate skin with oral hooks and liquefy host tissue by secreting proteloytic 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, dry weather
 
'''Clinical Signs'''
*Anorexia, listness, animals standing apart from flock
 
*Fleece may appear darker, be damp and have a foul smell
 
*Strike is classified according to where the body is affected
 
'''Control'''
*Prophylactic [[Ectoparasiticides|insecticide]] treatment
**Must kill larvae and remain in fleece to prevent flies from laying eggs
**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
 
*'Mule's operation'
**Surgical removal of breech skin in Merino breeds
 
*Tail docking of lambs
 
*Proper carcass disposal
**Eliminates fly breeding sites
 
*Vaccination
 
===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
 
'''Recongition'''
*Similar to ''Calliphora''
**Irridescent
**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 meales released
**Eradication occured in 1991
 
====Maggot Debridement Therapy====
[[Image:Maggot Therapy.jpg|thumb|right|150px|Maggot therapy on a wound - Wikimedia Commons]]
*Human medicine
**Sterile ''Lucilla 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
 
'''Recongition'''
*Large 8-14mm long
 
*Pale grey
 
*Black stripes in 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
 
==Links==
 
*[[Viruses]]
 
*[[Ectoparasiticides]]
 
*[http://www.strikewise.com/index.html| Blowfly strike]
Retrieved from "https://en.wikivet.net/Myiasis_Producing_Flies"