Difference between revisions of "Hypoderma spp."

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==Scientific Classification==
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Also known as: '''''Warble Flies'''''
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{| cellpadding="10" cellspacing="0" border="1" 
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| Kingdom
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| Animalia
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|-
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| Phylum
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| Arthropoda
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|-
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| Class
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| Insecta
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|-
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| Order
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| Diptera
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|-
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| Family
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| Oestridae
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|-
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| Genus
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| Hypoderma
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|}
  
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== Introduction ==
 
 
[[Image:Warble flies.jpg|thumb|right|150px|Warble Fly - Geo. H. Carpenter, Cambridge University Press 1913 - Wikimedia Commons]]
 
[[Image:Warble flies.jpg|thumb|right|150px|Warble Fly - Geo. H. Carpenter, Cambridge University Press 1913 - Wikimedia Commons]]
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This is a fly of the family [[:Category:Oestridae|Oestridae]], which parasitises animals. There are two important ''Hypoderma spp.'' found in cattle, namely; ''H. bovis'' and ''H. lineatum''. ''H. diana'' is also a parasite of clinical significance, affecting the deer population. ''Hypoderma'' species are also known as 'warble flies'. The parasite is found in the northern hemisphere in Europe, America and some of Africa. Both cattle species have been eradicated from the UK, but ''H. diana'' still exists. The disease is notifiable.
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*Also known as warble flies
 +
 
 +
*Important cattle parasites
 +
**Also parasitise horses, small ruminants and sometimes humans
 +
 
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*The two main species in cattle are
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**''H. bovis''  
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**''H. lineatum''
 +
 
 +
*''H. diana'' parasitises deer
 +
 
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*Infestation is largely confined to the Northern Hemisphere
 +
 
 +
 
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'''Recognition'''
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*Large 13-15mm long
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*Similar to bumble bees in appearance
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**Yellow abdomen
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**Band of black hairs
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*1 pair of wings
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'''Life cycle'''
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*Adult flies emerge on warm, sunny days between '''June and August'''
  
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''H. bovis'' is around 15mm in length and has a bumble-bee appearance. The abdomen is yellow and there is a band of black hairs located around the middle. ''H. bovis'' lays single eggs on hairs around the lower legs of the host. The larvae develop and enter the body through the skin, where they migrate to the epidural fat found along the thoracic and lumbar vertebrae of the spine. The larvae stay here for the duration of the winter. The larvae are palpable as distinct swellings, known as warbles.
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*White eggs are laid around the belly and legs of the animal
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**Eggs are attached to hairs by cement and a small terminal clasp
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**''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
  
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''H. lineatum'' are around 13mm in length, and like ''H. bovis'' have a bee-like appearance. The eggs are laid in rows of around 6 on single hairs. The eggs then penetrate the skin and move along the connective tissue toward the diaphragm. They will continue to migrate, until they reach the oesophagus where the larvae will spend the duration of the winter. After 3 months larvae reach '''winter resting sites''' where they remain from November to February/March whilst moulting to the L2 stage.
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*The adult lives for 3 weeks
  
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Adult flies emerge on warm, sunny days between '''June and August'''. The adult lives for around 3 weeks.
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*Females can lay several hundred eggs in their life
  
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''H. diana'' is around 15mm in length. The adults have a short life-span, and do not feed. Eggs are laid on the legs and lower body of the host. Larvae crawl down the hairs, and begin migration through the skin. The larvae burrow along the spinal cord, and spend the winter in the epidural fat of the spine around the thoracic and lumbar region. The migration is then initiated in the spring and warbles then begin to form along the back of the host.
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*A few days after eggs are laid, larvae emerge and crawl down the hairs into the hair follicles
  
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*Larvae penetrate the skin through wounds made by [[Biting Flies|biting flies]]
  
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== Clinical Signs ==
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*Larvae migrate through the subcutaneous tissue towards the diaphragm
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**Enzymatic secretions and mouth hooks aid larval migration
  
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There may be no clinical signs until after slaughter when the hide will have holes in and will be condemned and down-graded. There will usually be seen a reduced milk yield and reduced weight gain. There may also be injury from stock panic when the cattle can hear the characteristic noise of the warble fly. There may also be trimmed meat losses from ''H. lineatum'' as 'Butcher's Jelly' around warbles is green due to mass eosinophil attraction.
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*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
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**Epidural fat in the spinal canal for ''H. bovis''
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**Wall of the [[Oesophagus - Anatomy & Physiology|oesophagus]] for ''H. lineatum''
  
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In severe cases, paraplegia resulting from toxin release and pressure on the spinal cord (''H. bovis'') can occur. This is most common when the larvae are killed in their winter resting sites. In a ''H. lineatum'' infection bloat may ensue, due to pressure on the oesophageal wall.
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*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
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**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
  
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== Diagnosis ==
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*Adult flies emerge from the pupa after 1 month where they copulate, lay eggs and die within 2 weeks
  
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Usually not discovered until post mortem examination. If they are known to exist in the area, close examination of the back of cattle may reveal signs of them in their breathing holes.  
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*''H. lineatum'' are on the wing 6-8 weeks before ''H. bovis''
  
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*There is only '''1 generation''' of warble flies per year
  
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== Control ==
 
  
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Total eradication should be aimed for and timing is crucial for treatment. Larvae residing in winter resting sites can lead to bloat and paraplegia if killed. 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. Systemic organophosphorus insecticides in pour-on formula and avermectins and milbemycins in pour-on and injectable formulations can be used for this.
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'''Pathogenesis'''
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*Causes [[Muscles Inflammatory - Pathology#Arthropods|myositis]]
  
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Old methods include popping out warbles, but this can lead to anaphylactic shock.
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*Production losses
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**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|eosinophil]] attraction
  
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*Paraplegia resulting from
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**Toxin release
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**Pressure on the spinal cord (''H. bovis'')
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**Bloat from pressure on the [[Oesophagus - Anatomy & Physiology|oesophageal wall]] (''H. lineatum'')
  
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== Other Information ==
 
  
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Legislation in the UK:
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'''Control'''
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:'Warble Fly Order 1978' requires all clinically affected animals to be treated
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*Total eradication should be aimed for
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:'Warble Fly Infected Area Order 1983'- Notifiable disease
 
  
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*Old methods include popping out warbles
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**But this could lead to anaphylactic shock
  
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{{Learning
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*[[Ectoparasiticides]]
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|flashcards = [[Myiasis Producing Flies Flashcards|Myiasis Producing Flies Flashcards]]  
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**Systemic organophosphorus [[Ectoparasiticides|insecticides]] in pour-on formula
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|literature search = [http://www.cabdirect.org/search.html?rowId=1&options1=AND&q1=Hypoderma&occuring1=title&rowId=2&options2=AND&q2=&occuring2=freetext&rowId=3&options3=AND&q3=&occuring3=freetext&x=48&y=17&publishedstart=yyyy&publishedend=yyyy&calendarInput=yyyy-mm-dd&la=any&it=any&show=all ''Hypoderma'' spp. publications]  
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**Avermectins and milbemycins in pour-on and injectible formulations
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|Vetstream = [https://www.vetstream.com/canis/Content/Disease/dis60301.asp Myiasis]
 
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}}
 
  
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== References==
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*Timing is crucial for treatment
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**Larvae residing in winter resting sites, if killed, can lead to bloat and paraplegia
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**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
  
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Andrews, A.H, Blowey, R.W, Boyd, H and Eddy, R.G. (2004) '''Bovine Medicine''' (Second edition),'' Blackwell Publishing''
 
  
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Blood, D.C. and Studdert, V. P. (1999) '''Saunders Comprehensive Veterinary Dictionary''' (2nd Edition)'' Elsevier Science''
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'''Legislation in the UK'''
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*'Warble Fly Order 1978' requires all clinically affected animals to be treated
  
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Divers, T.J. and Peek, S.F. (2008) '''Rebhun's diseases of dairy cattle''''' Elsevier Health Scieneces''
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*Notifiable disease
  
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Fox, M and Jacobs, D. (2007) '''Parasitology Study Guide Part 1: Ectoparasites''''' Royal Veterinary College''
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*'Warble Fly Infected Area Order 1983'
  
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Merck & Co (2008)''' The Merck Veterinary Manual''' (Eighth Edition)'' Merial''
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*For more information on the warble fly orders, see [http://www.defra.gov.uk/animalh/diseases/notifiable/brucellosis/surveillance.htm| here]
  
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Radostits, O.M, Arundel, J.H, and Gay, C.C. (2000) '''Veterinary Medicine: a textbook of the diseases of cattle, sheep, pigs, goats and horses''''' Elsevier Health
 
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Sciences''
 
  
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in cattle
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**May occasionally burrow into muscle
  
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{{review}}
 
  
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{{OpenPages}}
 
  
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[[Category:Oestridae]] [[Category:Expert_Review - Farm Animal]]
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[[Category:Oestridae]]
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[[Category:To_Do_-_Max]]

Revision as of 13:25, 16 July 2010

Scientific Classification

Kingdom Animalia
Phylum Arthropoda
Class Insecta
Order Diptera
Family Oestridae
Genus Hypoderma
Warble Fly - Geo. H. Carpenter, Cambridge University Press 1913 - Wikimedia Commons
  • 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

  • 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
  • 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


in cattle

    • May occasionally burrow into muscle
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