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Created page with '*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…'
*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]
[[Category:Parasites]][[Category:Flies]][[Category:Myiasis_Producing_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]
[[Category:Parasites]][[Category:Flies]][[Category:Myiasis_Producing_Flies]]