Insect Ectoparasites Flashcards
Ectoparasites can play triple role of:
- Parasite
- Intermediate Host
- Vector
ARTHROPODA phylum consists of:
- Insects: Flies, lice, fleas
2. Arachnida: mites, ticks
Vector
Animal (often arthropod) that transmits an infective organism from one host to another
Mechanical vector
Transmits organisms directly to recipient host without development or multiplication of organism occurring.
- Not essential for life cycle of infective organism
Biological vector
Intermediate (final) host
- infective organisms undergo development or multiply or both before being transmitted to recipient host.
- Essential for LC of infective organism
Diptera
True flies
Life cycle of Buffalo fly
Haematobia irritans exigua
2-3 weeks (like most flies)
- Females lay egg on fresh dung
- eggs hatch in <24 hrs
- Larvae (maggots) in dung for 4-5 days
- Puparia in dung or soil 5-7 days
- Young adult fly
- Fly stays on host to feed
Screwworm fly (Cocliomyia hominivorax)
- Female flye lays 4 batches of 400 eggs on edge of wound
- After 12h, larvae hatches and enters wound for feeding
- After 5 days, larvae drops to ground and develops into pupae for 8 days
- After 2 days, fly is sexually mature
- highly aggressive
Fly strike on sheep is mostly cause by
Lucilia cuprina
Signs of external fly infestation
- Fly “worry”
- Restlessness, tail swish, kicking
- swollen ears, bloody legs - Fly infection and strike:
- biting at wool or infested area
- rubbing, itching
- anaemia from blood loss
- loss of condition/ death
- away from other sheep
Control methods for fly infestation
- Physical barriers
- Fly traps
- Insecticides
- Mulesing
Mosquitoes are vectors for:
- Protozoa e.g. Malaria
- Viruses e.g. Dengue virus
- Worms e.g. Heartworm
Phthiraptera Order
Lice
Lice
Spends entire life cycle on host
- have claws & 6 legs
- all stages are parasite
- host specific & region specific
Sub-order: Mallophaga
Biting and chewing lice (rounded front, chomps scurf)
- feed by chewing hairs, skin –> ITCHY
Sub-order: Anoplura
Sucking lice (sharp front end for piercing skin) --> TRAUMA/ANAEMIA
Transmission of lice occurs through:
Direct contact but can also occur via fomites
Epidemiology of Lice
- obligate parasite
- Peak infestations in winter
- Infestations heavier in sheep with poor conditions and already affected by disease (lower immunity)
- spread by direct contact, but can survive for short periods on combs, fences
- host specific
3 Control of Lice
- Killed by light (shearing) or water
- Chemical control: pour-ons after shearing
- Dipping shears between animals
Lice diagnosis
- Sheep rubbing against fences, fleece tags
- Fleece partins to look for lice
- Biting lice present on woolly areas
- sucking lice on hairy skin
- Use lice detection test
Are sucking lice more or less active than biting lice?
Sucking lice are less active than biting lice
Why is winter the peak production for lice?
In summer, skin temps and humidity is unsuitable for lice reproduction
Flea features
- Exoskeleton
- 6 legs
- Head, abdomen, thorax
- Genal & pronatal combs
- Lateral compression
- no wings
- Body has scales and hairs
Why are fleas so hard to catch?
They can jump high due to protein resilin in their leg hinge (97% elasticity)
Flea cycle
3 weeks cycle
-egg to larvae to pupa to adult flea
Flea bites
are painful. When hypersensitivity developes–> itchy
Skin trauma occurs and skin thickens
Diagnosis of fleas
lesions including flea and flea dirt
Flea epidemiology
- development increases with warmth and humidity
- eggs fall to ground and larvae and pupae survive in carpet and soil
- pupae respond to vibrate so hatch only when host is near
- most are in animal’s environment
Control of fleas
Vacuum, wash blankets, treat and remove all flea reservoirs (other pets)
Treat fleas
Using flea treatment that kills fleas rapidly after feeding and before and can develop will deplete the environment of larvae and pupae
