16. Sheep Parasites

Question 1

What are the GI nematode sof sheep

Answer 1

Same broad principles apply as w/ cattle (affect yg anims, pasture transmission)
clinical dz is more common and widespread
anthelmintic resistance a huge global problem
PGE - mixed infection of multiple species that cause chronic diarrhea, poor growth, anorexia, 2 fly strike
Main solo player is haemonchus contortus - cause severe, even fatal anemia; resistant

Question 2

What is the basic trichostrongyle development in ruminants

Answer 2

teladorsagia, trichostrongylus, haemonchus, cooperia, nematodirus
Eggs hatch > L3 ensheathed and ingested > L4 in mucosa > L5 in muscosa or tissue? > adults > eggs repeat

Question 3

How do we dx the barber pole worm?

Answer 3

clinical signs (esp. lambs <6mo)
hyperacute: suddend either due to haemorrhagic anemia
Acute: anemia, bottle-jae, ascites, dark feces, anorexia
Chronic: weight loss, weakness, anorexia
Don’t usually see diarrhea
FEC can be low (PPP) or very high (1,000-20,000 EPG)
Definitive Dx: L3 coproculture, PCR or adults at necropsy

Question 4

How do we control trichostrongyles and other GI nematodes in sheep

Answer 4

Maximize overall health, pasture mgmt, breed resistant hosts, strategic txs - spring/fall, tx yg anims 6-8wks into first grazing season
Targeted selective tx - only tx when famacha or FEC score is high

Question 5

What is the large lungworm of sheep?

Answer 5

dictyocaulus filaria, essentially D. viviparus in cattle but less pathogenic in sheep
Anterior cone on L1 larvae in feces (baermann)

Question 6

What is the lifecycle of dictyocaulus filaria?

Answer 6

PPP: 3-4wks
L1 in feces > L2-3 in enviro > L3 ingestion > tracheal migration to lungs > adults in lungs??

Question 7

What are the two cestodes in sheep?

Answer 7

Moniezia spp and thysanosoma spp
indirect life cycle, involving mite IH w/ cysticercoid
more pathogenic in lambs than cattle (diarrhea) tx praziquantel

Question 8

What is taenia ovis - cystercercus ovis?

Answer 8

Dogs eat sheep tissue w/ cycsticerci in muscle > adults in dog > immediately infective eggs in enviro > sheep eats eggs

Question 9

How do we dx and control taenia ovis?

Answer 9

Dx: no clin signs associated w/ adult stages in dogs or cysticerci in sheep
At post mortem, cysticerci in skeletal muscle and heart leads to carcass condemnation (not a zoonosis).
Control: no tx for sheep but dogs get praziquantel 2x/yr at least
prevent dogs from eating sheep carcasses and prevent dogs from eating sheep feed

Question 10

What is the life cycle of fasciola hepatic and magna

Answer 10

PPP f. hepatica is 10-12 wks, F. magna 7mo

Adults in liver > eggs in feces > miracidium > Snail IH > cercariae > metacercaria on vegetation > ingested by sheep

Question 11

How do we dx F. hepatica in sheep?

Answer 11

Normal DH
Acute fasciolosis - migration of juvenile flukes ingested in short time span
liver damage and hemorrhage
Sudden death, anemia, ascites, dyspnea, abdominal pain 2-6wk after infection

Question 12

How do we dx F. magna in sheep

Answer 12

Aberrant DH
non-patent infections
Flukes continue to migrate around liver and cause damage
aberrant hosts usually die within a few months of infection

Question 13

How do we control flukes in sheep?

Answer 13

in problem herds: avoid known contamination pastures, prevent livestock access to wetlands, cervid access to pastures
Control involves: tx of all exposed ruminants on farm
Closantel or triclabendazole in fall season (resistance) to kill juvenile flukes, albendazole early winter to kill adults

Question 14

What are the keds of sheep?

Answer 14

diptera - melophagus ovinus
Sheep tick, wingless flies
NOT ACTUALLY A TICK

Question 15

What is the life cycle of the sheep tick?

Answer 15

Adults on host - larviparous - larvae on host - pupae on host - repeat
life cycle takes 4-5wks

Question 16

How do we dx and control melophagus ovinus?

Answer 16

Dx: clinical signs - non to general pruritis and almost every flock will have this. Direct inspection of fleece for adults and pupae
Control: pour on pyrethroids (pupae resistant), dips, shearing, keds are not zoonotic

Question 17

What is the nasal bot of sheep? What is the life cycle of them?

Answer 17

oestrus ovis
L3 sneezed out in spring > pupae > Adult flies in late summer/fall > larvae L1 laid in nose > larvae migrate in nasal chambers then sinuses

Question 18

What is myiasis in sheep?

Answer 18

Fly strike - the invasion of animal tissues by larvae of dipterans (flies)
They are obligate - hosts for lorval development must be LIVE
Or could be facultative - hosts for larval development can be LIVE or DEAD and larvae can develop in organic matter

Question 19

How do we prevent myasis - fly strike?

Answer 19

worst season is summer
frequent examination - in sheep, fly strike most often affect region below anus and btw hind legs
Shearing, tail docking, wound care, manage diarrhea from PGE, breed selection

Question 20

What is eimeria in sheep

Answer 20

includes both pathogenic and non-pathogenic species - diarrhea, dehydration, in lambs as apposed to ewes and rams
dx. on oocysts found in feces

Question 21

What is toxoplasma gondii in sheep?

Answer 21

important pathogen in sheep and goats, causing abortion, stillbirth, and/or neonatal dz in ewes infected for the first time
outcomes depend on when exposed in gestation
infection by eating cat feces

Question 22

What is the lifecycle of toxoplasma gondii in sheep?

Answer 22

unsporulated oocysts in cat feces, becomes sporulated oocysts w/ 8 sporozoites in 2 sporocytes > ingested by IH (sheep) > ingest that meat w/ tissues w/ bradyzoites

Question 23

How do we control toxoplasma gondii?

Answer 23

regional variation in seroprevalence in sheep (20-100%)
in sheep: prevent access of cats to feed
to prevent zoonotic transmission: after handling aborted or stillborn fetuses, thorough hand washing
Cook lamb and mutton to 70C or free -20 for at least 3 days