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Myiasis Producing Flies (view source)
Revision as of 12:37, 13 January 2009
, 12:37, 13 January 2009no edit summary
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.
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.
==Oestridae==
==Oestridae==
*The larvae of ''Oestridae spp.'' are '''obligatory''' parasites
*The larvae of ''Oestridae spp.'' are '''obligatory''' parasites
*The three important species of veterinary interest are ''Hypoderma'', ''Oestrus'' and ''Gasterophilus''
*The three important species of veterinary interest
**''Hypoderma''
**''Oestrus''
**''Gasterophilus''
===''Hypoderma'' spp.===
===''Hypoderma spp.''===
*Also known as warble flies
*Also known as warble flies
**Also parasitise horses, small ruminants and sometimes humans
**Also parasitise horses, small ruminants and sometimes humans
*The two main species in cattle are ''H. bovis'' and ''H. lineatum''
*The two main species in cattle are
**''H. bovis''
**''H. lineatum''
*''H. diana'' parasitises deer
*''H. diana'' parasitises deer
*Infestation is largely confined to the Northern Hemisphere
*Infestation is largely confined to the Northern Hemisphere
'''Recognition'''
'''Recognition'''
*Similar to bumble bees in appearance
*Similar to bumble bees in appearance
**Yellow abdomen
**Yellow abdomen
*Band of black hairs
**Band of black hairs
*1 pair of wings
'''Life Cycle'''
'''Life cycle'''
*Adult flies emerge on warm, sunny days between June and August
*Adult flies emerge on warm, sunny days between '''June and August'''
*White eggs are laid around the belly and legs of the animal
*White eggs are laid around the belly and legs of the animal
*Larvae migrate through the subcutaneous tissue towards the diaphragm
*Larvae migrate through the subcutaneous tissue towards the diaphragm
**Enzymatic secretions and mouth hooks aids larval migration
**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
*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''
**Epidural fat in the spinal canal for ''H. bovis''
**Wall of the [[Oesophagus - Anatomy & Physiology|oesophagus]] for ''H. lineatum''
**Wall of the [[Oesophagus - Anatomy & Physiology|oesophagus]] for ''H. lineatum''
*L3 larvae emerge after 4-10 weeks where they fall to the ground and pupate under loose vegetation
*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
*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''
*''H. lineatum'' are on the wing 6-8 weeks before ''H. bovis''
*There is only '''one''' generation of warble flies per year
*There is only '''1 generation''' of warble flies per year
'''Pathogenesis'''
'''Pathogenesis'''
*Causes[[Muscles Inflammatory - Pathology#Arthropods| myositis]]
*Causes[[Muscles Inflammatory - Pathology#Arthropods|myositis]]
*Production losses
*Production losses
***'Butcher's Jelly' around warbles which is green due to mass [[Eosinophils - WikiBlood|eosinophil]] attraction
***'Butcher's Jelly' around warbles which is green due to mass [[Eosinophils - WikiBlood|eosinophil]] attraction
*Paraplegia resulting from:
*Paraplegia resulting from
**Toxin release
**Toxin release
**Pressure on the spinal cord (''H. bovis'')
**Pressure on the spinal cord (''H. bovis'')
**Bloat from pressure on the [[Oesophagus - Anatomy & Physiology|oesophageal wall]] (''H. lineatum'')
**Bloat from pressure on the [[Oesophagus - Anatomy & Physiology|oesophageal wall]] (''H. lineatum'')
'''Control'''
'''Control'''
*Old methods include popping out warbles
*Old methods include popping out warbles
**But could lead to anaphylactic shock
**But this could lead to anaphylactic shock
*[[Ectoparasiticides]]
*[[Ectoparasiticides]]
**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
**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
**Ivermectin can be given at any time without risking host infection as larval antigen is released much slower
'''Legislation in the UK'''
'''Legislation in the UK'''
*For more information on the warble fly orders, see [http://www.defra.gov.uk/animalh/diseases/notifiable/brucellosis/surveillance.htm| here]
*For more information on the warble fly orders, see [http://www.defra.gov.uk/animalh/diseases/notifiable/brucellosis/surveillance.htm| here]
===''Oestrus ovis''===
===''Oestrus ovis''===
*Found in most sheep rearing areas of the world
*Found in most sheep rearing areas of the world
'''Recognition'''
'''Recognition'''
*Larvae have distinct black bands on each body segment
*Larvae have distinct black bands on each body segment
*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
'''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 two months
*Larval development takes up to 2 months
**Larvae can overwinter in the [[Nasal cavity - Anatomy & Physiology|nasal cavity]] if deposited late in the summer
**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
*Once the larvae have developed they are sneezed out and pupate on the ground
*The adult fly emerges one months later
*The adult fly emerges 1 months later
*Adult flies only live for 2-3 weeks
*Adult flies only live for 2-3 weeks
'''Pathogenesis'''
'''Pathogenesis'''
*[[Respiratory Parasitic Infections - Pathology#Oestrus ovis|Pathology in the nasal cavity]]
*[[Respiratory Parasitic Infections - Pathology#Oestrus ovis|Pathology in the nasal cavity]]
'''Control'''
'''Control'''
*In warmer countries, strategic prophylactic treatment can be used
*In warmer countries, strategic prophylactic treatment can be used
===''Gasterophilus'' spp.===
===''Gasterophilus spp.''===
[[Image:Horse Bot Fly.jpg|thumb|right|150px|Horse Bot Fly - Dennis Ray - Wikimedia Commons]]
[[Image:Horse Bot Fly.jpg|thumb|right|150px|Horse Bot Fly - Dennis Ray - Wikimedia Commons]]
*Also known as the horse bot fly
*Also known as the horse bot fly
*Obligate parasites of equids
*Obligate parasites of equids
*Spend most of life cycle in equine stomach
*Spend most of life cycle in the equine stomach
**Of little pathogenic significance
**Of little pathogenic significance
**''G. haemorrhoidalis'' which is rare
**''G. haemorrhoidalis'' which is rare
*Two other important veterinary species
*Two other important veterinary species
**''G. nigricornis''
**''G. nigricornis''
**''G. inermis''
**''G. inermis''
'''Recognition'''
'''Recognition'''
*Clear wings with brown patches
*Clear wings with brown patches
*Eggs hatch spontaneously or are stimulated to hatch through an increase in warmth and moisture from the animal self-grooming
'''Life cycle'''
**''G. intestinalis''
*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''
**''G. nasalis'' eggs are laid in the intermandibular area
**''G. haemorrhoidalis'' eggs are laid around the lips
**''G. haemorrhoidalis''
***Eggs laid around the [[Lips - Anatomy & Physiology|lips]]
*Creamy-white eggs
*1-2mm in length
*Larvae crawl into the mouth and penetrate the tissues of the tongue and buccal mucosa
*Larvae crawl into the mouth and penetrate the tissues of the tongue and buccal mucosa
**''G. nasalis'' attaches to the pylorus
**''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
*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
**''G. haemorrhoidalis'' attaches to the rectal mucosa before being passed out
*Larvae pupate on the ground
*Larvae pupate on the ground
*Adults hatch after 1-2 months and survive from a few days to two weeks
*Adults hatch after 1-2 months and survive from a few days to 2 weeks
**Adults have non-functional mouthparts so cannot feed
**Adults have non-functional mouthparts so cannot feed
*There is only one generation per year in temperate regions of the world
*There is only '''1 generation per year''' in temperate regions of the world
'''Pathogenesis'''
'''Pathogenesis'''
*Adult cause annoyance when egg laying
*Adults cause annoyance when egg laying
**Disturbance and panic can ensue
**Disturbance and panic can ensue
*''G. haemorrhoidalis'' can cause mild irritation to the rectal wall
*''G. haemorrhoidalis'' can cause mild irritation to the rectal wall
*Host reaction to larvae in the mouth is minimal
'''Control'''
'''Control'''
**Stimulates hatching
**Stimulates hatching
**Kills larvae
**Kills larvae
===''Dermatobia hominis''===
===''Dermatobia hominis''===
*Specifically found in South America
*Specifically found in South America
'''Recongition'''
'''Recognition'''
*Adult can grow up to 25mm in length
*Adult can grow up to 25mm in length