What are 4 key features of ectoparasites?
Exoskeleton
Segmented
Jointed limbs
Ability to moult
Compare insects and arachnids
Insects has 6 legs and distinct body regions (flies, fleas and lice)
Adults have 8 legs and fused body regions (ticks and mites)
What are some Veterinary considerations surrounding ectoparasites?
- ‘Fly worry’ - decline in milk, weight gain, livestock flies
- Fly strike of sheep
- Anaemia
- Toxic and allergic responses (FAD, sweet itch)
- Inflammation
- Self-wounding/secondary infections
- Pathogen transmission
- Zoonoses
What is an exoskeleton made of and what is its function?
- Cuticle of exoskeleton made of alpha-chitin
- provides support and protection
- muscles attached to inside of exoskeleton
How do ectoparasites grow?
By moulting
How does respiration occur in ectoparasites?
- Gas exchange via openings in the protective cuticle
- spiracles in insects
- stigmata in ticks/mites
What are the 3 distinct body regions of an insect?
Head
Thorax
Abdomen
Give the names of the different parts of the insects mouthpart
Palp Mandible, maxilla - cutting Labrum - upper lip Hypopharynx - tongue Labium, labellum- lower lip
What are the body regions of acarines?
- Cephalothorax (head is fused with thorax)
- Abdomen
How many pairs of legs are present in adult and larvae acarines?
Adult - 4
Larvae - 3
Do either insects or acarines have wings or antennae?
Insects have 2 antennae and some species have wings
Acarines don’t have wings on antennae
What part of the mouthpart is specific to ticks and what is its function?
Hypostome - anchors into the skin of host
What is the only reason flies pester cattle?
Females must obtain protein to mature eggs
How do mites and ticks reproduce?
Spermatophore (sperm packet) released into female through hypostome
What are the terms given for complete and incomplete metamorphesis?
Holometabolous = complete - flies Hemimetabolous = incomplete metamorphosis - lice and ticks
What are control methods in dogs and cats?
- Stay kill
- Spot ons
- Chewable tablets
- Collars
What is the mode of action of SPs?
- Repellency, knock down and rapid kill
- Excites cell membranes, depolarisation/Na ions,
- Hence paralysis
What forms do SPs come in for use in controlling ectoparasites?
Pour-ons, Spot-ons, dips, sprays, ear tags against nuisance flies,
Lice and ticks. Collars for dogs. Absorbed onto skin and diffuses through coat
Not systemic
What is the mode of action of MLs?
- Stimulate the release of GABA from parasitic nerve endings, enhancing the binding to its receptor on the post-synaptic motor neurone membrane
- Results in an increased flow of chloride ions causing hyperpolisation
What forms do MLs come in for use in controlling ectoparasites?
Injectables, orally, pour-ons, spot-ons
Which drug is used in companion animals in controlling fleas and ticks?
Fipronil
Which drugs is used in companion animals, it is effective against fleas but doesn’t work against ticks?
Imidacloprid
Name the latest products that are now available as readily absorbed, chewable tablets?
Isoxazolines:
- Fluralaner
- Afoxolaner
- Lotilaner
What are the 2 main types of Insect Growth Regulators?
- Chitin inhibitors
- Juvenile hormone analogues
