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Flashcards in Ectoparasites - Sheep Deck (46):


Infestation of organs or tissues of living animals by fly larvae.


This obligate myiasis species of fly is also known as the sheep nasal bot fly.

Oestrus ovis


Is calliphoridae an obligate myiasis species? Where is it found on the animal?

No, its facultative. It is found cutaneously


Name the five relevant species of blow fly in sheep.

Lucilia sericata, Lucilia cuprina (greenbottles),Phormia terranovae (blackbottles), Calliphora vicina (bluebottles), C. vomitoria


Describe the morphological features of the blowfly adult and larvae.

Adult - 1cm, dorsal bristles, metallic sheen
Larvae - Smooth, segmented, 10-14mm, anterior oral hooks


Outline the lifecycle of Lucilia sericata.

Temperature-dependent. Adult flies lay eggs on the wool, close to the skin. First stage larvae (1mm) at 8 - 24hrs. Second and third stage feed. The third stage larvae (10mm) wandering phase & falls to the ground and pupate. Adult flies hatch, 7 -10 days later unless they diapause the 3rd stage larvae enter diapauses and over-winter


How do the second and third stage larvae of L. sericata cause skin lesions on sheep?

They penetrate the skin with hooked mouth parts and secretion of proteolytic enzymes, creating a red, raw lesion.


What is the egg to adult interval of L. sericata?

2 weeks with optimal conditions.
Up to four generations a year in April/May and Sept/Oct


Which areas of the sheep are most commonly affected by blowfly strike?

Breech, Tail, Body, Poll, Penile sheath, foot


Which species of blowfly are common UK primary and secondary blowflies?

Primary blowflies – nitiate strike - Lucilia sericata, Phormia sp.
Secondary blowflies – cannot initiate strike. Calliphora sp


Outline the pathology of blowfly strike.

Larvae emerge and digest tissue. Odour, bacterial infection Loss of condition, anorexic, dull, isolated. Wool not lost, but at skin level larvae can be seen in wound. Death from toxaemia.


How can infestations with blowfly be controlled?

Separate sheep, Clip lesion, Insecticides, Docking tails, Dagging and crutching, Prevention of scours, Carcase disposal, Treatment of wounds, foot rot etc, Mules operation


Name ectoparasiticides which can be used to treat blowfly strike.

Diazinon, cypermethrin (+alpha), deltamethrin.


What is problematic about control of blowfly control?

Short time on host, Repeated infestations, Rapid tissue damage, Extensive breeding sites


Describe the characteristic features of Oestrus ovis.

Short-lived obligate parasite of sheep worldwide, Common in some parts of Southern UK but sig. local variations. Adult flies are larviparous, L1 squirted into the nose. Active in July mainly, grey body, vestigial mouth


Outline the lifecycle of Oestrus ovis.

L1 deposited by adults in sheeps nose, feeds in nasal passages and sinuses, moult to L2, moult to L3 in frontal sinus, L3 moves to nostrils, sneezed out and pupariates, fly emerges 3-8 weeks later.


Which larval stages of Oestrus ovis overwinter and where?

L1/2 overwinter in the nasal passages of the sheep and move to the frontal sinus in Spring.


Which ectoparasiticides can be used to control Oestrus ovis infection in sheep? Which lifecycle stages are they effective against?

IVM, MOX has efficacy against the 3 larval stages


Which tick borne diseases are transmitted to sheep by Ixodes ricinus? (x3)

Anaplasma phagocytophilum (fever), louping ill virus (zoonotic, vaccine available, red grouse), tick pyaemia (joint infection by S.aureus, paralysis/lameness)


Which ectoparasiticides are recommended for control of ticks in sheep?

Diazinon, cypermethrin, deltamethrin


This species of fly has losts is wings and so is often known as a louse fly.

Melophagus ovinus
Sheep ked


Describe the characteristic features of sheep keds and their disease process.

Flattened in the same way as lice, they have short legs with stout claws. Females develop larvae within (cf tsetse flies)
Larvae pupariate in the wool, and the flies emerge 2-5 weeks later.
Transmission is sheep to sheep. Winter problem.
Suck blood, causes pruritis, loss of condition.
Transmits non-pathogenic Trypanosoma melophagium.


Sheep scab is caused by which species of mite?

Psoroptes ovis


Describe the morphology of psoroptes ovis.

pointed mouthparts, legs extend beyond margin of body, jointed pedicels, trumpet shaped suckers (c.f. Chorioptes), thumb print pattern on dorsum


What are the feeding habits of Psoroptes ovis?

Non-burrowing and feed at surface of skin, feeding on lipids, superficial fluids, cells, bacteria, lymph


Outline the lifecycle of Psoroptes ovis.

Adults lay eggs which go through three larval stages before moulting to an adult which lives 40-60 days. The lifecycle lasts a min of 10d (mostly 11-19d)


What are the pathogenic features of sheep scab?

Chronic exudative superficial dermatitis, type I hypersensitivity due to ES antigens particularly in mite faeces, hyperkeratosis, Aural haematomas, Intense irritation, decreased weight gain, epileptiform seizures, death


Where would you find psoroptes mites on sheep scab lesions?

On the moist edge of the lesions.


How can Psoroptes ovis mites be isolated from lesions?

Scrape edge of lesions, macerate scab in 1-5%KOH for 5-10 mins (releases mites), view under microscope (lifecycle stages, eggs, cuticles)


Name three clinical signs of sheep scab on a flock level.

Signs of severe pruritis and irritation: sheep scratch against posts, walls, wire etc, standing or found lying alone
depressed, clean areas of fleece where biting, dirty areas of fleece where rubbing, tags of wool in mouths or on flanks


Name five clinical signs of sheep scab on an individual sheep level.

Part wool and examine, ’nibble’ reflex, possible seizure on contact, restlessness, pruritis
wool loss, lesions on neck, back, shoulders, flanks, weight loss, secondary bacterial infections


How is sheep scab transmitted?
How long can mites survive off the host?

Direct contact, contaminated environment, fomites
Mites can survive off the host ~14-16 days


Sheep scab is often known as a winter disease, why?

Fleece length, Climate, Mixing and stocking density increase, Off host survival increases


Which areas of the sheep can be reservoirs of Psoroptes ovis?

Axilla, ears and folds of skin


Outline the history of legislation pertaining to sheep scab.

1953; eradicated from UK, 1973; reintroduced into Lancs, 1983; compulsory double dipping, 1989; single dipping, 1992; deregulated as a notifiable disease.


In which area of the UK is sheep scab still a notifiable disease?



Notifiable disease

any disease that is required by law to be reported to government authorities. The collation of information allows the authorities to monitor the disease, and provides early warning of possible outbreaks. In the case of livestock diseases, there may also be the legal requirement to destroy the infected livestock upon notification


Outline the control measures used against sheep scab.

Dipping (an organophosphate, Diazinon), Injectable (Ivermectin, Doramectin, Moxidectin),Biosecurity measures; Common land grazing, Fencing, Markets, Shearing equipment, vehicles, Regular Flock inspection, Quarantine


This species of Psoroptes primarily affects rabbits. Which part of the rabbits anatomy does this regularly affected?

Psoroptes cuniculi, localises to the ears and causes amange in the auditory canal.


How does Chorioptes bovis cause disease in sheep? Is this mite more or less severe than psoroptes?

Chorioptic mange results from chewing (rather than skin piercing) activity; considerably less severe than psoroptic mange but is far more common.


Which areas of the body are affected by chorioptes?

All haired areas; especially lower hind limb and abdomen with hair loss and thickened skin.


This mite species feeds on scabs/ fungus of sheep.

Forage mites


Name one biting/ chewing louse and two species of sucking lice of sheep.
Which species is more pathogenic and why?

B/C: Damalinia ovis. S: Linognathus pedalis, L. ovillus
Damalinia since it is more active.


How can lice be controlled in sheep?

Consider quarantine for incoming stock for at least 3 weeks and Remove all debris (wool etc) from contaminated housing


What are the epidemiological features of lice infection in sheep?

Breed, fleece length, overall health of the host, temperature. Lice populations thrive during winter. Shearing reduces populations by 30-50%.


What injectable and dip ectoparasiticides can be used in the control of lice in sheep?

Injectable; moxidectin, doramectin, ivermectin (ML). Dip; organophosphate