Arthropods 3 Flashcards
3 main groups of insects of Veterinary and Medical Significance
- Lice
- Fleas
- Flies
Lice
- Permanent ectoparasites
- Small, wingless dorso-ventrally flattened body
- Host specific
The 2 types of lice
- Chewing lice (Mallophaga- M) mammals, birds, feed on skin
- Sucking lice (Anoplura- A) mammals only, feed on blood
How do lice attach to their host?
With hooked tarsi (terminal segments of legs) that grip hair
How do lice cause harm to host?
- Irritation, skin damage (M & A)
- Anaemia from blood loss (A & M)
- Vectors of disease organisms e.g. typhus, trench fever (A),
- Intermediate hosts of parasites:
tapeworms (M)
What type of development do lice have?
Hemimetabolous development
Life cycle of lice
- Egg laid on hair
- 1st nymph
- 2nd nymph
- 3rd nymph
- Male and female adults
What are some common lice of animals, and what do they cause?
- Sheep body louse, feeds on skin and wool but causes intense irritation
- Hematopinus - Blood sucking louse of pigs and ruminants
- The head/body louse Pediculus humanus P. capitis
Fleas
- Non-permanent ectoparasites
- Small, laterally compressed adults.
- Muscular hind legs.
- Have multiple hosts
Adult stage of fleas
- Blood feeder - have sucking mouthparts adapted to piercing skin and feeding on blood
Egg stage of fleas
Laid on host or in nest of host (kennels, pet blankets, cracks in floor, couches)
Larvae stage of fleas
- Detritus feeder, not on hosts.
- Chewing mouthparts.
- In cat and dog flea, larvae feed on adult flea faeces and gain essential nutrition from blood in faeces
How do fleas cause harm to host?
- Direct harm: flea-bite allergy (hypersensitivity); blood loss, anaemia in kittens, pups and aged animals
- Vector: bacteria (plague, cat scratch disease - Bartonella), virus (myxomatosis)
- Intermediate host: fleas host to “cucumber” tapeworm of dogs and cats (Dipylidium caninum)
Life Cycle of cat flea Ctenocephalides felis
On host:
- Adult: Drinks host blood
Off host:
- Egg: Nutritive source derived from parent during egg formation
- Larvae in bedding/carpets/soils/nests feeds on detritus (faeces of adults)
- Pupa: Lives off energy it stored when it was a larva
Important Flies and Mosquitoes in relation to animal and human disease
- Filth flies (house and blow flies) with blood sucking adults
- Flesh fly maggots
- Strike flies (myiasis)
- Bot flies (maggots grow in internal
organs)
How do filth flies cause harm?
- Blood sucking adults cause blood loss
- Vectors of disease – mosquitoes and
malaria, heartworm; tsetse fly and
trypanosomiasis - Decomposition of bodies- blow fly,
flesh fly maggots
How do Strike flies cause harm?
Myiasis: where maggots feed on
living tissue of animals
What is another important group of mandibulates other than hexapods?
Crustaceans
Crustaceans
- Dominant aquatic arthropods
- Some moist terrestrial (isopods e.g.
wood lice, pill bugs) - Extensively specialised appendages
Examples of crustaceans
- Some plankton (copepods, krill)
- Barnacles on whales
Copepods
- Important food source in aquatic systems
- Some copepods are predatory
- Can be parasites on fish
Cephalothorax
Fused structure consisting of the head and thorax regions
Typical structure of crustaceans
- Head, thorax and abdomen or
- Cephalothorax and abdomen
