Difference between revisions of "Hypoderma spp."
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− | + | [[Image:Warble flies.jpg|thumb|right|150px|Warble Fly - Geo. H. Carpenter, Cambridge University Press 1913 - Wikimedia Commons]] | |
− | Also known as | + | *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: | + | [[Category:Parasites]][[Category:Flies]][[Category:Myiasis_Producing_Flies]] |
Revision as of 16:13, 29 March 2010
- 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
- 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 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 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 eosinophil attraction
- Paraplegia resulting from
- Toxin release
- Pressure on the spinal cord (H. bovis)
- Bloat from pressure on the 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 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 here