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==Introduction==
 
  
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
 
**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 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
 
 
 
*Affects sheep mostly
 
**Rabbits can also be affected
 
 
 
'''Species of Veterinary importance'''
 
*''Lucilia serrata''
 
**Greenbottles
 
 
 
*''Phormia terra-novae''
 
**Blackbottle
 
 
 
*''Calliphora erythrocephala''
 
**Bluebottle
 
 
 
*''Callipohora vomitoria''
 
**Bluebottle
 
 
 
*''Lucilia cuprina''
 
**South Africa, Australia
 
 
 
*''Chrysomya'' spp.
 
**Africa, Asia, 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
 
**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 ground 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. ''Lucilia'', ''Phormia'' and ''Calliphora''
 
**Secondary flies cannot initiate a strike, larvae attack an area already struck or damaged, extending it
 
***E.g. ''Calliphora'' 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 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
 
 
 
'''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
 
 
 
*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
 
 
 
'''Recognition'''
 
*Similar to ''Calliphora''
 
**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 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
 
 
 
*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]
 

Latest revision as of 13:14, 5 April 2010