Difference between revisions of "Myiasis Producing Flies"

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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.
 
  
==Oestridae==
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#REDIRECT[[:Category:Myiasis Producing Flies]]
[[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 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 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 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 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
 
 
 
*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 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 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 [[Ectoparaciticides|insecticides]] over winter
 
**Breaks the life cycle as all the population are present as bots in the stomach
 
 
 
*If eggs are present in late summer, the horse's coat can be sponged with an [[ectoparasite|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==
 
 
 
*The ''Calliphoridae'' family are '''facultative''' parasites
 
 
 
*Cause '''blowfly strike'''
 
 
 
*If the fly lays eggs on an animals, the animals 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'''
 
 
 
'''Life Cycle'''
 
 
 
'''Pathogenesis'''
 
 
 
'''Control'''
 
 
 
===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]]
 

Latest revision as of 13:14, 5 April 2010