sheep worming

Life cycle

·    Fasciola hepatica

·    Fluke ingested as metacercaria ® migrate to intestine (cause peritonitis) ® migrate to liver (2d) ® settle in bile ducts (4-6w) ® mature to adult and lay eggs (>8w)

History

·    Worming protocol?

·    What clinical signs seen? – weight loss, poor fleece quality, oedema

·    Any deaths?

·    What aged sheep affected? How many?

Investigations

Clinical signs:

·    Weight loss – rapid, can be emaciated

·    Poor fleece quality

·    Mortality

·    Oedema – bottle jaw, brisket oedema

Further investigations:

·    Differentiate from Johne’s – low albumin + globulin = fluke (low alb, normal glob = Johne’s)

·    FEC – but needs to be >8w from infection as eggs not shedded yet

·    Fluke ELISA – ab present if immune response developed

·    PM exam

o  Acute fluke – pale/anaemic liver, necrosis

o  Chronic fluke – adults present, calcified bile ducts, severe inflammation/necrosis

o  Evidence of peritonitis and haemorrhage – where fluke tracked through abdomen

Treatment

·    Triclabendazole – effective against all stages

·    Albendazole – kills adults

·    Closantel – larvae >6w

Prevention/ control

·    Immunity not developed

·    Reduce egg shedding – tx

·    Prevent sheep from ingesting metacercaria

o  Improve pasture management

o  Reduce access to snails habitat (e.g. fence off wet areas)

Worms

·    Nematodirus battus

·    Haemonchus contortus

·    Teladorsagia

·    Trichostrongylus

Sources

·    N. battus – animals on pasture year before (eggs resistant, survive 2y on pasture)

o  Hatching stimulated by cold period followed by warmer period

When to test

·    N. battus

o  If no lambs on pasture previous year = low risk pasture, ewes not likely to be source of contamination

o  If lambs on pasture previous year = high risk pasture – regularly test

Clinical signs

·    N. battus

o  Clinical disease = dehydration, death, eggs on FWEC

o  PP disease = due to larvae, no eggs on FEWC

 Main worms

·    PGE

o  Nematodirus battus – ewes around lambing time

o  Haemonchus contortus

o  Teladorsagia – lambs

o  Trichostrongylus – lambs

·    Fluke

o  Fasciola hepatic (liver fluke)

o  Rumen fluke

·    Lungworm

o  Dictyocaulus filaria

Which animals and when?

·    Lambs

o  If DLWG <300g/day

o  If FWEC results indicate

·    At risk ewes

o  Increased risk of PGE around lambing

§ Under nutritional stress ® periparturient relax in immunity ® hypobiosed L4 larvae ® adults ® contaminates pasture ® lambs more likely to be affected

§ Reduce PP relax in immunity

·        Multiple doses of anthelmintic (but risk of developing resistance)

·        Only treat those at risk – low BCS, immature/young lambs, ewes with multiple lambs, those with concurrent disease

o  Target treatment – treat older/sick animals, and those carrying multiple lambs

§ Monitor FWEC and treat if >300epg

·    New arrivals

o  Use group 4/5 + moxidectin injection

o  Keep in yard48h then move to contaminated pasture, keep isolated for 3w

·    Nematodirus battus – spring

·    Fluke – if >1 egg seen

Immunity?

·    Develop immunity to PGE after first grazing season

o  Periparturient relax in immunity

·    Not to fluke or Haemonchus contortus

·    Short-lived immunity to lungworm, but vaccine available

Products

·    Group 1 – benzomidazoles/white – resistance common

o  Albendazole – adult fluke (late winter/spring), adult PGE, lungworm

o  Fenbendazole – adult PGE, lungworm

o  Triclabendazole – all stages of fluke

·    Group 2 – levamisole/yellow – lungworm, adult PGE

·    Group 3 – macrocylic lactones/clear – worry about withdrawal times, also kill invertebrates

o  Ivermectin – adult PGE, lungworm

o  Moxidectin – adult PGE, lungworm, sheep scab

·    Group 4 and 5 – orange and purple

o  Newer, less resistance – don’t really use unless multidrug resistance, mid/end of grazing season or quarantine protocols

Grazing management

·    Weaning – move lambs to low-risk pasture

·    Co-grazing – reduces stocking density of host

·    Nutrition – minimise effect of parasites

·    Grazing by mature animals – hoover up larvae

Anthelmintic resistance

·    Monitoring resistance

o  Drench testing – 7-14d post-dosing FWEC (14d if used BZ or ML, 7d if LV)

o  FEC reduction test – individual samples pre and post-drenching (7-14d)

§ If <95% reduction = resistance

·    Contributors to anthelmintic resistance

o  Injectables last for 6w (concentration wanes before dosing worms) – avoid long acting MLs

o  Not maintaining in refugia population – in refugia = not treating the entire population to leave some parasites unexposed to a dewormer, in order to prevent resistance

o  Dosing animals which don’t need treatment

o  Not dosing for heaviest weight in the group

o  Not timing correctly

·    Prevention

o  Pasture rotation

o  Administer the correct product, to correct animals, at correct time

o  Quarantine new stock

o  Dose-delay-move (if wait a bit after dosing to move flock, will prevent carrying most resistant worms to fresh pasture)

o  Rotate wormer

o  Post treatment FWEC