Mites, lice and keds

1. Realise the global significance of mange caused by Psoroptes ovis (sheep scab mite) and history of this highly contagious, pathogenic disease in the UK, and the present day epidemiology; disease pathogenesis and clinical signs; 2. Understand legal issues for sheep scab and sheep welfare and accurate specific diagnosis: mite identification and features which enable distinction from other mites; 3. Understand approaches to control and how these can be integrated for other ectoparasites; 4. Recognise sheep lice and keds, biology and control 5. Macrocyclic Lactones

What ectoparasite causes sheep scab?

psoroptes ovis (mite)

What are the symptoms of sheep scab (ovine psoroptic mange)

Mainly : intene itching, lesions, wool loss.

can also include: hyperkeratosis, aural haematomas, weight loss, decreased weigth gain, decreased birth weight, restlessness, epileptiforn seizures, death and secondary bacterial infections.

Describe the lifecycle of psoroptes ovis

16 day life cycle (10d minimum)

Obligate, perminent parasite

non-burrowing

egg→larvae→protonymph→tritonymph→adult

describe the pathogenesis of psoroptes ovis (sheep scab)

feed on skin surface, cause a type 1 hypersensitivity response = serous exudate, servere pruritis.

chronic exudative superficial dermatitis

centre of lesion forms a crust, mites feed on edge, exanding the lesion. can cover 75% of body in 6-8 weeks.

What two methodsca be used to diagnose psoroptes ovis

1. blood elisa

2. skin scrape + clinical signs

how does elisa test for psoroptes ovis work?

detects IgG in sheep serum up to 2 week after infestation, before appearance of clinical signs.

how do you diagnose sheep scab using a skin scraping

part wool to examine for lesions

use scaple to do a superficial skin scrape on the edge of a lesion, for several lesions.

macerate in KOH for 5-10 mins

view under microscope, look for mites, eggs, cuticle.

Describe the morphology of psoroptes ovis (sheep scab)

• all mange mites have the thumbprint pattern

• pointed mouthpart

• jointed tarsi with long pedicel

• legs extend past margins of body

What are some common co-infections with psoroptes ovis

1. forage mites

• lack of thumbprint pattern

2. chewing lice

• bovicula ovis

How is psoropte ovis transmited between sheep?

direct contact

• common grazing

• neighbour sheep (single fences)

indirect contact via fomites

• plants, rocks, ect

• can survive 16days off host

What are some risk factors (other than other sheep transmitting) for psoroptes ovis?

time of year - late autumn / winter

longer fleece

shearig helps to reduce, although resurvoirs in axilla, ears and skin folds.

What ares have higher rates of sheep scab?

uplands

is sheep scab notifiable?

yes

Name some legislations that apply to sheep scab

sheep scab order 1997 (eng + wales)

sheep scab order 2010 (scotland)

List ways to prevent scab infestation

avoid introduction

• quarrantine

• treat (elisa will show before sympt)

• disinfect equipment

prevent contact

• double fencing

prophylactic treatment

• dipping with diazinon (organophosphate)

• moxidectin 1% injection lasts 28 days

• moxidectin injection LA lasts 60 days

  • moxidectin is a macrocytic lactone

How can you treat a scab infestation?

LEGAL REQUIREMENT - treat all individuals in flock!!!

• sheep scab order

1. dip in diazinon (organophospate)

2. moxidectin (1% lasts 28d, LA lasts 60d)

3. doramectin

4. ivermectin (2, 7 days apart)

What ectoparasite causes choripotic mange?

choripotes bovis (mite)

what are the symptoms of chorioptic mange?

affects hairy (not wooly) areas like head, legs, belly, scrotum

less severe, but more common than sheep scab

How can you diagnose chorioptic mange? (chorioptes bovis)

ID of mites

• round mouthparts

• no pedicels

• cup shaped suckers

• thumb print patterns

What is pediculosis?

infestation of lice (louse)

List some lice of sheep

Chewing

• bovicula ovis

sucking

• linognathus pedalis (foot)

What are the symptoms of pediculosis in sheep, and what louse is most likely to cause this?

Bovicula Ovis

• wool loss, restlessness, itching, reduced appetite, rubbing lesions (attract blowflys)

How would you diagnose a bovicula ovis infestation?

presence of adult lice + eggs on skin / wool

What areas are more likely to have bovicula ovis infestations (pediculosis)

upland farms with common grazing

How can you treat pediculosis from bovicula ovis

synthetic pyrethroids

diazinon (organophosphate) dip

What are keds?

flies - diptera.

no wings!

What ked most commonly effects sheep?

melophagus ovinus

Describe pathogenesis and symptoms of melophagus ovinus (sheep keds)

direct transmission only

mainly in winter

suck blood, cause pruritis, loss of condition

What can sheep keds (melophagus ovinus) transmit?

trypanosoma melaphagium

• non-pathogenic