Infectious challenges

• Infectious challenges: sheep blowfly

  Main type: Lucilia cuprina
• Sheep blowfly (Lucilia cuprina)

  1. Eggs laid on sheep

  2. Develop into maggots

  3. Maggots feed on infested sheep skin

  4. Create serious welfare & economic problems

  5. Cause considerable distress to sheep

  6. Left untreated - death in few days
• Sheep blowfly (Lucilia cuprina)

  • Mainly breed + multiply where: Carcass
  • Native to: Africa - spread to Asia and Australia
• Sheep blowfly - preventive measures

  • Soaking with organphosphates - help treat strike + prevent secondary infection
  • Dipping
  • Grazing in open pastures
  • Efficient disposal of dead animals
• Sheep ticks

  Transmit bacteria Borrelia burgdorferi can lead to Lyme disease + paralysis of body
• Tick needs to live

  • Needs moisture
  • Loves woodland
• Life cycle of tick, the four stages

  1. Egg

  2. Larva

  3. Nymph

  4. Adult
• How does a tick transmit infection

  1. An infected tick feeds on host and passes pathogen into hosts body

  2. Another tick picks up pathogen when feeding on infected animal

  3. Passes it onto other animals
• Liver fluke in sheep: symptoms

  • Abdominal pain & diarrhoea
  • Long-standing infections
  • Ulcers
  • Haemorrhage
  • Abcesses of intestinal wall
  • Liver damage
• Life cycle of Liver fluke

  1. Adult fluke produces egg, passed out in faeces

  2. Miracidia hatched from eggs

  3. Miracidia invades Lymnaeid snail - acts as intermediate host, develops into sprocyst

  4. Cercariae exit snail and swim to vegetation, form metacercariae

  5. Metacercariae ingested by sheep - in the infective stage

  6. Adult fluke ends up in bile duct of sheep when mature
• Diagnosis of liver fluke

  • Post mortem = presence of liver fluke in body
  • Fluke egg count (FEC) identified in faeces
  • Liver enzymes: raised liver enzyme level
• Control of liver fluke

  • Reduce pop of infected snails
  • Eliminate flukes from animals via: drainage of snail habitats
• Treatment of liver fluke

  • Different anthelmintic / flukicides = effective against adult fluke not immature stages
  • Tailored fluke control systems for individual farms
• Virus

  • Small infectious agent - replicates inside living cell of another organism
  • Live in all ecosystems = infect plants, animals, humans, bacteria
• Avian Influenza (AI) AKA

  Bird flu - infectious viral disease of birds
• Cause of Avian Influenza (bird blu)

  Caused by 15 subtypes of the Influenza A virus
• Flu Virus structure

  • Neuraminidase (outside)
  • Hemaggluttin (outside)
  • Lipid envelope
  • Capsid
  • Nucleoprotein - RNA
• Transmission of Avian Influenza: wild birds Introduce AI virus to poultry


  1. Direct contact with domestic poultry

  2. Faeces & other secretions

  3. Contaminated drinking water & feed
• Transmission of Avian influenza: within & between farms

  1. Direct contact: contaminated equipment or vehicles

  2. Infected species

  3. Air transmission over short distances

  4. Live bird markets or abbattoirs
• Symptoms of AI in birds

  • Swollen head
  • Dullness
  • Low egg production
  • Loss of appetite
  • Sudden death
• Symptoms of AI in humans, severe

  • High fever, chest infection, respiratory failure, death
• Symptoms of AI in humans, mild

  • Fever, sore throat, cough, headache, muscle aches and pains
• How the Avian Influenza (AI) virus attacks

  1. Virus enters and replicates

  2. Travels to lungs & triggers immune system

  3. Cytokines sent to attack virus

  4. Cytokines cause deadly inflammation - blood + fluid leaks into air sacs

  5. Host drowns in own blood

  6. Virus tricks immune system
• AI, vaccination Advantages

  • Stop unethical measures
  • Protection against infectious diseases
  • Economic benefits
• AI vaccination disadvantages

  • Difficult to distinguish between vaccinated + unvaccinated animals
  • Vaccinated animals are still carriers
  • Vaccinated animals cannot be exported
• Foot and mouth disease (FMD)

  • Acute infectious disease caused by a virus
  • Picornavirus - aphthovirus genus = RNA
• Signs of FMD

  • Fever
  • Dullness
  • Shivering
  • Loss of appetite
  • Reduced milk yield
• Spread of FMD - indirectly via contamination

  • Lorries
  • Clothing
  • Feed
  • Water
  • Containers
• FMD spread in UK
• FMD control procedure

  Infected slaughtered within 24 hrs of detection - contiguous cull
• FMD emergency vaccination

  • Suppressive: Vaccinated animals subsequently killed
  • Protective: Allow animals to live normal life
• life cycle of tick?

  1. egg hatches into larva
  2. larva attaches to passing bird or mammal and feeds on blood for 3-4 days
  3. drops onto soil, stays for 3-4 months
  4. emerges as a nymph
  5. nymph attaches to a host, feeds and drops off to mature into adult