Ectoparasites: Flies of Veterinary Importance Flashcards
what is the general morphology of dipteran flies
- single pair of antennae
- one pair of functional wings
- 3 pairs of legs
- body divided into 3 parts
- modified hind wings (halteres)
what is musca & phortica spp
non-biting flies
how are pathogens spread by non-biting flies
- pathogens when feeding on feces
- contaminate foodstuff
- open sores
- contaminate host when feeding
- sectetions from eyes, mouth, nose
how do non-biting flies cause damage
sponge feeding
rasping device on mouthparts –> increases size of existing wounds and prevents wound healing
what are the examples of non-biting flies
mucosa domestica (house fly)
mucosa autumnalis (face fly)
hydrotaea irritans (head fly)
what is the morphology of non-biting flies
pair of veined wings
sticky hairs or pads at end of legs
how are non-biting flies biologically transmitted
- horse expels eggs/L1 in feces
- fly lays eggs in feces
- fly larvae ingest eggs/L1 nematodes
- fly larvae and parasites develop together
- adult flies emerge from pupae
- L3 nematodes migrate to fly mouthparts
- flies deposit L3 whilst feeding near nose/mouth
- L3 travel to stomach where they mature to adults
what are culicoides spp
biting midges
what are the morphology of biting midges
thorax humped over small head
mottled wings, folded over back
prominent antennae
small, vertically hanging mouthparts
most species are crepuscular/noctunral
what is Schmallenberg virus (SBV)
transmitted by biting midges
adult –> transitory infection lasting a few days (inappetence, diarrhea, loss of body condition, reduced milk yield)
transplacental infection –> lead to severe congenital malformation
what is blue tongue
notifiable disease in UK
what are the pathological significance
culicoides are the cause of sweet itch
horses and donkeys
pruritic dermatitis –> allergy to midge saliva, scratching leads to bald patches, skin damage (secondary infection, myiasis)
seasonal –> UK; April-Sept
how are culicoides controlled
difficult due to extensive breeding habitat
animals should be housed/protected during flies most active periods (early evening/morning)
repellents/screens –> fine mesh
what are melophagus ovis (sheep ked)
established in most temperate sheep rearing areas
hairy and wingless
dorsoventrally flattened
blood feeding
what is melophagus ovinus life cycle
live entire life cycle on host
adults live for several months
- viviparous –> produce a signle larva every ~10-12 days
- newly produced larvae adhere to the wool
- adult emerges 19-30 days
- infestation builds slowly
what is the pathology and significance of melophagus ovinus
pierce skin and suck blood (neck, breast, shoulders, flanks and rump)
bites cause intense pruritus
heavy infestations lead to loss of condition and anemia (esp in lambs)
damage to hides
how can melophagus ovinus be controlled
shearing removes pupae and adults
combined shearing before lambing followed by insecticide helps reduce
use of insecticides
specific control rarely necessary due to routine treatment
what is myiasis
the invasion of living vertebrate animal by fly larvae
what is obligate myiasis
parasitic development of the larvae on a living host is a necessary stage within the life cycle
what is faculative myiasis
opportunistic
have ability to exploit living tissue but not a required stage in life cylce
what is accidental myiasis
fly eggs or larvae contaminate food
what does myiasis result in
serious tissue damage
often accompanied by putrid discharge
ulceration
loss of tissue function
secondary infection
death
what are hypoderma spp
warble flies
obligate myiasis
what do warble flies affecg
cattle, rarely man, horses, deer or sheep
distributed in northern hemisphere
when are hypoderma seen
in summer months –> calm weather
bright sunshine
cement eggs to hair
what occurs after eggs of hypoderma spp are cemented to hair
L1 larvae penetrate skin via hair follicles
migrate through flesh (2-4m) –> secreting digestive enzymes & macerating tissue with their oral hooks
create tracks of gelatinous material –> reduces value of meat
where do hypoderma larvae remain
in esophageal wall
spinal canal
grow to ~12 mm (2-4m)
migrate through the flesh under skin back (1-2 months)
develop from L1 through L2-L3 instars (1-2 months)
larvae penetrate hide to breath (furuncles)
mature L3 forces throgh hole and drops to grond to pupate (1-3 months)
what is the significance of warbles
animals panic on sound of fly
hide damage
butches jelly
what is the blow fly
facultative myiasis
imporant in UK
large
what is primary myiasis
primary myiasis
flies can initiate a strike on living animals without the need for existing tissue damage
what is secondary myiasis
flies cannot initiate strike
they attack areas of existing strike or damage
what are the types of blow fly strike
- body
- breech/tail
- poll
- penile sheath
what is the epidemiology of blowfly strike
temperature
climate & rainfall
breed
soiling (due to diarrhea)
wounds
how does temperature affect blowfly development off host
soil temp >90C are required for pupal development
how does temperature affect blowfly development on host
temperature in fleece must remain constant around 31C
how does climate and rainfall affect blowfly
rain wets wool –> warm wet conditions result in wool rot –> odour attracts female flies which then deposit eggs
how does breed affect blowfly strike
- fine wool breeds (merino, rambouillet) more susceptible
- wriknled/folded skin
- wrinkled breech, narrow breech (merino)
- horned sheep
how does diarrhea affect blowfly strike
infections lead to soiling of fleece around breech and tail attracting flies –> breech & tail strike
how does wounds or lesions affect blowfly strike
fighting (horned breeds)
injuries due to barbed wire/bushes
badly managed post-surgery wounds
foot lesions (foot rot)
how is blowfly strike controlled
- prevention of diarrhea
- clip wool from around breech
- tail docking
- shearing
- polled breeds
- removing any carcasses
