Ectoparasites

• Ectoparasites


  An organism that sends part of or all of its life on the outside of the host
• Ectoparasites


  • Damage host directly
  • Act as carriers of other pathogens
• Main types of ectoparasites

  • Arachnids - mites, ticks
  • Insects - flies, lice, fleas
• Arachnids - mites and ticks

  • Two body parts
  • 4 pairs of legs
  • No antennae
• Mites

  • Small (<0.5mm)
  • Prolonged period of time in contact with host skin - many entire lifecycle
• Transmission of mites

  Mainly direct contact
• Forms of mange


  • Under the top skin layer
  • Burns on skin surface
  • Inside hair follicles
• Sarcoptes scabiei (Sarcoptic mange)


  • Burrowing mite
  • Affects all mammals
• Sarcoptes scabiei


  • Mouthparts - Chelicere (paired cutter) and palps (pawed legs)
  • Small but enlarge after feeding, can enlarge abdomen to start food for a year
• Basic lifecycle of mites

  1. Egg

  2. Larvae

  3. Nymph

  4. Adult
• Types of ticks


  • Ixodidae - hard ticks
  • Argasidae - soft ticks
• Ticks


  Vectors for protozoa, bacteria, viruses
• Ticks are common in the UK, e.g. Ixodes ricinus - sheep tick
• Sarcoptic mange of dogs


  • Most severe type of mange
  • Found in neck, face, back
  • Infected animals will scratch until bleeding
• Lifecycle of Sarcoptic mange

  1. Fertilised female burrows into upper layer of epidermis, feeds on resultant diseased tissue

  2. Eggs hatch in 3-5 days into larvae which burrow into mounting pockets

  3. Adult male emerges and seeks out female, mating takes place and female seeks out new burrow to lay eggs

  4. Lifecycle takes 17-21 days
• Sarcoptic mange


  Host - mammal or bird but particularly ruminant
• Predilection sites for Sarcoptic mange


  • All over body but particularly neck, shoulders and elbows
• Psoroptic mange (sheep scab)


  • Psoroptes mite - intense irritation and loss of condition
  • Non-burrowing
  • Cannot replicate away from sheep
  • Lives on surface
  • Gloves 2-3 weeks max not on sheep
  • Long legs to facilitate movement
• Otodectes cynotis (ear mite)

  • Poropticia mite
  • Non-burrowing
  • Common mange in dogs and cats
  • Lives in inner ear, feeds on ear debris
• Demodectic mange


  • Caused by Demodex canis
  • Lives in hair follicles
  • Two forms - mild (localised to head) and severe (generalised widespread hair loss)
• Mosquitoes (Culicidae)


  • 3500 species worldwide
  • Tiny - 1-6mm
  • Eggs laid in standing water
  • Larvae live in water
  • Female adults suck blood, make swarms
• Mosquitoes


  • Control - insecticide, repellent, barriers, fans
• Biting flies (Brachycera)


  • Large flies 2.5cm
  • Interruptions to animal feeding
  • Deep painful bites - females suck blood
  • Vectors for other diseases
  • Fly silently and do not feel them land
• Biting flies (Brachycera)


  • Associated around wood, active peak summer July-August
  • Attracted to pale skin, white clothes
• Non-biting flies (Cyclorrhapha)


  • Small-medium size
  • Feed on secretions, wounds
  • Irritation to animals and humans
  • Transmit bacterial, viral and protozoal diseases
• Lifecycle of non-biting flies

  1. Eggs hatch within 24 hrs to produce larvae (maggots)

  2. 3 larval stages feed on decomposing matter

  3. Final larval stage moves to drier area to pupate

  4. Adult fly emerges after 3-26 days depending on temp, humidity, food
• Control of non-biting flies

  • Remove breeding sites or avoid them
  • Remove manure from grazing area
  • Use insecticide, pour-on, spray prep
  • Use screens, electrocution grids
• Blowflies (Calliphoridae)


  • Myiasis - infestation of a living animal with dipteran larvae
  • Commonly affects sheep, can cause running around or scampeding
• Blowfly lifecycle


  1. Female lays eggs on host

  2. Larvae hatch and feed on host

  3. Maggots drop to ground and pupate

  4. Pupate for 3-7 days

  5. Adult emerges and mates
• Blowfly strike


  • Primary - lays eggs on wool, larvae hatch and crawl out wool, lacerate skin
  • Secondary - attracted by odour, lay eggs on or around rotting flesh
• Blowfly strike


  • Affected areas - breech, tail, body, poll
  • Symptoms - dull, depressed, off food, isolation, damp foul smell
  • Can result in death
• Treatment of blowfly strike

  1. Isolate affected animals

  2. Clip wool around lesions

  3. Remove maggots

  4. Dress lesions with appropriate insecticide
• Prevention of blowfly strike

  • Insecticide - dip, spray, pour-on
  • Worming, tailing, dagging
• Gasterophilus (bot flies)


  • Adult causes irritation, larval stage causes damage if in high numbers
  • Found on limbs, ingested by horse and live in stomach
• Lice


  • 2 types - biting, sucking
  • Host specific
  • Live on skin, transmitted by direct contact
• Cat flea - Ctenocephalides felis


  • Suck blood - anaemia
  • Transmit diseases
  • Cause allergic dermatitis from flea saliva
• Anthelmintic resistance


  • No chemical is 100% effective
  • Underdosing or excessive frequent dosing can lead to resistance
• Avoiding anthelmintic resistance


  • Accurately assess weight
  • Ensure full dose administered
  • Rotate chemical groups annually
  • Treat at right time of year
  • Conduct faecal egg counts
• Reducing parasites


  • Breed for resistance
  • Manage stocking rates
  • Implement rotational grazing
  • Remove manure
  • Prevent scavenging
• Parasite control programmes


  • Eradication is unrealistic - parasites adapt
  • Treatment and control - predominantly chemotherapy
  • Resistance, environmental concerns, residues
  • Sustainable alternatives