Lecture 10

Question 1

List the farm animal actoparasites

Answer 1

• Ticks (and tick-borne diseases)
• Mites
• Lice
• Flies
• Fleas: not important in large animals!

Question 2

Arachnids

Answer 2

• 4 pairs of legs
• No wings/antennae
• Ticks and mites

Question 3

Ticks

Answer 3

• Obligate, blood-feeding actoparasites
• Hard and soft ticks

Question 4

Ixodes ricinus (‘sheep tick’)

Answer 4

• Temporary parasite
• Spends 98% of life off host
• Distribution
  -> Humidity
  -> Temperature
  -> Vegetation cover
• Chiefly affect livestock (sheep, cattle) on rough pasture
• Most common on west coast/ Donegal

Question 5

Clinical significance of Sheep Ticks

Answer 5

• Irritation, inflammation, allergy
• Secondary infections:
  -> Tick pyaemia (Staphylococcus aureaus)
  -> Anaemia
• Transmission of disease (‘vectors’)

Question 6

Tick-borne diseases

Answer 6

• ‘Tick-borne fever’: cattle, sheep, goats
• ‘Redwater fever’: cattle
• Louping ill: sheep
• Lime disease: humans

Question 7

Mites

Answer 7

• ‘Mange’, ‘Scab’
• In intimate contact with host for entire life
• Transmission by direct contact, contaminated pens, vehicles, pieces of wool, fences
• Very short generation times = rapid build up
• Inhabit skin and feed on blood, lymph, skin debris, sebaceous secretions
• Livestock affected: cattle, sheep, poultry, pigs
• Cause of direct damage to skin, allergic reactions, secondary infections

Question 8

Psoroptes Ovis

Answer 8

• Most important ectoparasitic disease of sheep: Psoroptic mange or sheep scab
• Presumed eradicated in UK/ Ireland 1950’s
• Reappearance in 1970’s
• Notifiable to DAFM

Question 9

Psoroptic Mange

Answer 9

• Mites feed on skin cells, bacteria and lymph
• Hypersensitivity = inflammation, crusts, wool loss, skin thickening
• Shoulders and sides, all over
• Nibble reflex
• Secondary infections

Question 10

When and how does Psoroptic mange effect sheep?

Answer 10

• Distribution of mites varies by season:

Winter= Thickening fleece- Increases spread over body
Mites numbers drop off after shearing
Summer= Reservoir sites: Hidden from sunlight (axilla, groin, ear)
- Lambs and sheep in poor condition most susceptible
- Mites can survive off host for up to 2.5 weeks

Question 11

Psoroptes: transmission

Answer 11

• Highly contagious
• Spread by direct contact (and contaminated environment) eg marts, transport, shearing equipment
• Introduction of new sheep with latent (asymptomatic infections
• Poor fencing

Question 12

Dermanyssus

Answer 12

• Red poultry mite
• Main ectoparasite of laying birds
• Do not live permanently on birds
  -> Nocturnal feeders
  -> Rest (in cracks and crevices) during the day
• Survive long time without feeding
• All production types
• Aniaml welfare issue: Skin irritation/ restlessness
• Agression
• Lower egg production and weight gain
• Anameia
• Mortality in newly hatched chickens
• Disease vector
• Infectious to small animals, horses and humans

Question 13

Insects

Answer 13

• 3 pairs of legs
• Lice and flies

Question 14

Lice

Answer 14

• ‘Pediculosis’- important in poultry, pigs, cattle and horses
• Walk, don’t jump
• Permanet, obligate parasites
• Transmission: Direct contact from host, contact with shared materials eg bedding, brushes and combs
• Strictly host specific
• Two types:
  Chewing lice that feed on skin scales and scabs
  Suckling lice that feed on blood

Question 15

Clinical Significance of lice

Answer 15

• Depends on numbers
• Low numbers = no problems
• High numbers = Alopecia, pruritus, excoriation and self trauma
• Loss of hair and damage to hide matting of wool
• Anaemia (suckling lice)
• Weight loss
• Infestations peak in late winter/ early spring

Question 16

Blowflies

Answer 16

• Green/bluebottles
• Myiasis (‘flystrike’)
• Females attracted to odour of decaying organic matter
• Lay clusters of eggs on wounds/soiled hair
• Larval stages (maggots) feed on dead and living tissue and lymph (oral hooks and proteolytic enzymes)
• Pupate on the ground

Question 17

Epidemiology of Blowflies

Answer 17

• Important in sheep, medical emergency in domestic rabbits
• At risk animals: soiled (diarrhoea), sick and debilitated (wool/foot rot), wounded
• Strong seasonality
• Climate:
  Temperature determines number of generations
  Rainfall increases survival of eggs and larvae

Question 18

Clinical Significance of Blowflies

Answer 18

• Irritation, distress, anorexia, depression
• Foul odour: attract further blowflies
• +/- secondary bacterial infections (septicaemia)
• May be fatal

Question 19

Ectoparasites: Treatment and control

Answer 19

• Dipping, spraying, pour on, spot on, injectable, oral medication
• Repellents, insecticides, acaricides
• =/- antibiotics
• Repeat treatment if necessary (emerging lice)
• Treatment of the environment and keep premises vacant for several weeks (eg psoroptes, dermanyssus)

Question 20

Psoroptic mange

Answer 20

• Treat under supervision of Local Authority Vet