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Myiasis Producing Flies (view source)
Revision as of 19:49, 5 November 2008
, 19:49, 5 November 2008no edit summary
==Introduction==
==Introduction==
Myiasis is the parasitism of living animals by dipteran larvae. Myiasis can be oligatory or facultative (optional) and is described as cutaneous, nasal or somatic.
==Oestridae==
==Oestridae==
*The larvae of Oestridae spp. are '''obligatory''' parasites
*The three important species of veterinary interest are ''Hypoderma'', ''Oestrus'' and ''Gasterophilus''
===''Hypoderma'' spp.===
===''Hypoderma'' spp.===
*Also known as warble flies
*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'' and ''H. lineatum''
*''H. diana'' parasitises deer
*Infestation is largely confined to the Northern Hemisphere
'''Recognition'''
'''Recognition'''
*Large 13-15mm long
*Similar to bumble bees in appearance
**Yellow abdomen
*Band of black hairs
*One pair of wings
'''Life Cycle'''
'''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 - WikiBlood|biting flies]]
*Larvae migrate through the subcutaneous tissue towards the diaphragm
**Enzymatic secretions and mouth hooks aids larval migration
*After 3 months larvae reach '''winter resting sites''' where they remain from November to Feburary/March whilst moulting to the L2 stage
**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 one month where they copulate, lay eggs and die within two weeks
*''H. lineatum'' are on the wing 6-8 weeks before ''H. bovis''
*There is only '''one''' generation of warble flies per year
'''Pathogenesis'''
'''Pathogenesis'''