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Created page with 'thumb|right|150px|Warble Fly - Geo. H. Carpenter, Cambridge University Press 1913 - Wikimedia Commons *The larvae of ''Oestridae spp.'' are '''obligato…'
[[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|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
[[Category:Parasites]][[Category:Flies]][[Category:Myiasis Producing Flies]]
*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|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
[[Category:Parasites]][[Category:Flies]][[Category:Myiasis Producing Flies]]