Ectoparasites in sheep

• Important common parasites in sheep

  Psoroptes Ovis (sheep scab mite) - severe and contagious.

  Myiasis (blowfly) strike - massive welfare concern.

  Lice - less severe than sheep scab but associated with daily weight loss.

  Ticks - vector for Louping III, S.aureus and TBF
• Different types of lice infestation

  Sucking lice:

  • Haematopinus spp
  • Linognathus spp

  Biting lice:

  • Damalinia (Bovicola) spp.

  Life cycle of both is direct and simple:

  Eggs - nymphs - adults
• Signs of lice infestation (pediculosis)

  Asymptomatic.

  Pruritis

  Excoriation

  Fleece damage and loss

  Sever infestations can result in aneamia

  Can look similar to sheep scab.
• Diagnosis of life infestation

  Visual inspection (Can be seen with the naked eye).

  Direct microscopy of hair samples.
• Treatment of lice infestation in sheep

  Options:

  1. Pour on synthetic preparation such as deltamethrin or cypermethrin. Kills biting lice.
  2. Organo-phospahte dips (not sprays or jet systems as can be harmful to people). Kills everything so be very careful that correct PPE and protocols are used.
  3. Shearing can be useful by itself bit if severe infection needs to be treated as well.

  All sheep in direct contact must be treated. Treat at the start of winter.
• Tick lifecycle

  As in cattle, don‘t cause many problems directly, mainly act as a vector. Ticks spend most of the time off the host which has implications for control. Ixodes Ricinus is the most common sheep tick.

  
• What are the 3 main ticks in sheep?

  1. Lousing III
  2. Tickborne fever
  3. Tick pyaemia
• Louping III

  Viral infection (RNA flavivirus) causing encephalomyelitis resulting in death, seizures, paralysis and death.

  Most common in weaned lams and yearlings (lambs get passive immunity protection in colostrum).

  Mainly affects sheep and grouse, but can cause disease in Other animals and is zoonotic.

  Control is mainly through tick control, although vaccination can play a role (but not currently available).
• Tickborne fever

  Immunosuppressive disease caused by bacteria Anaplasma phagocytophilum. Bacteria infects and destroys WBC causing leukopenia.

  Affected animals are Pyrexic, anorexic and depressed. Pregnant ewes may abort and naive rams may become infertile.

  Lambs born in endemic areas are infected within the first 2 weeks of life and have mild symptoms. Naive animals introduced to endemic areas show more severe signs.
• Tick pyaemia

  Staphylococcal infection of lambs, often following immunosuppression die to tickborne fever.

  Lambs are mainly affected at 2-12 weeks old with abscesses developing throughout the body, often in joints, tendons (making them lame), muscle and brain.

  Lambs may display severe lameness, paralysis of the backend and death in severe cases. Up to 30% of lambs in a group may be affected.
• Tick control

  Host control

  • Avoid buying in naive animals.
  • Synthetic pyrethroids (deltamethrin and cypermethrin) - Better operator safety than organophosphate dips, but no immediate kill).
  • Organophosphate dips - requires care with application, but also proects agains blowfly strike, scab, lice and keds. Also provides an immediate kill.

  Environment control:

  • Active and start to feed in early spring - expose lambs while they have some passive protection.
  • Avoid tick prone pasture if possible
  • Attempts to decrease tick population = astute improvement.
  • Drainage and scrub clearance.
• Types of mites that affect sheep

  Surface feeders:

  • Chorioptes spp - can cause mange around lower limbs and scrotum (tends to be less pruritic than Psoroptes)
  • Psoroptes spp

  Burrowing mites:

  • Sarcoptes spp - uncommon in farm animal
  • Demodex spp - uncommon in farm animal.
• What is Sheep scab?

  Psoroptes Ovis.

  Notifiable in scotland but not england. Legal requirement to treat or slaughter in all parts of the UK. Estimated to cost the UK sheep industry £78-202 million per year.

  Is a mote - highly contagious, is viable of the most for 17 days and has lifecyle of 14 days (from adult to egg).
• Sheep scab diagnosis

  Epidemiology - winter, lots of contact.

  Diagnosis:

  • Skin scrape (just about visible to the eye) - oval shape mites identified by their three visible segmented pedicels and funnel shaped suckers.
  • Blood antibody ELISA
• Sheep scab treatment

  1. Organophosphate plunge dipping:
  2. Diazinon
  3. Difficult to Peform.
  4. 2. Macrolytic lactone injections:
  5. One injection of Moxidectin gives at least 28 days residual protection (1% is 28 days, 2% is 60 days). You can get moxidectin resistance.
  6. Doramectin gives 14 days residual protection. But you can get persistence of mites in the environment of up to17 days so only use if you have a completely clean new pasture you can move them too once treated.
  7. Ivermectin - gives no residual protection. Two ivermectin injections required 7 days apart to treat scab.
• Challenges of sheep scab control

  Safety - safety of chemical control measures (humans, animals and environment)>

  Resistance - Of mites to macrolytic lactones, and concern over increase exposure of endoparasites to them.

  Sub-clinical scab infestations.

  Biosecurity - risk increases with scab-infested neighbours and common grazing.

  Farmer motivation - social stigma leading to under reporting of scab.
• Solutions to scab control

  Quarantine - treatment key to avoid bringing in scab.

  ML resistance - dipping is the only consistently reliable way to protect against scab.

  Serology - blood test with high sensitivity and specificity provides ability to detect scab within 2 weeks of infestation.