Parasites Of Sheep Flashcards
What parasite typically causes scour in lambs in August to September following ingestion of larvae on the pasture in July?
Telodorsagia circumsincta
- type 1 disease seen in August to September
- type 2 disease seen in late winter / early spring the year after exposure
What is the source of telodorsagia circumsincta?
Ewes - periparturient egg rise
What parasite typically causes high morbidity, high mortality acute diarrhoea in 4-12 week old lambs in May-June time?
Nematodirus battus
What parasite causes acute weakness, anaemia and sudden death in Autumn?
Fasciola hepatica
Ddx haemonchus
What parasite causes weight loss, bottle jaw and anaemia in January to May?
Fasciola hepatica (chronic)
What is the epidemiology of nematodirus battus?
Source - eggs from lambs on pasture in the previous year
Hatching occurs after a period of chill and mean day / night temperature of greater than 10c
Overwinter and ingested by lambs in spring
Cause disease in May - July
What parasite causes black scour in lambs or replacements in late autumn / winter?
Trichostrongylus vitrines
Trichostrongylus colubriformis
Trichostrongylus axei
What parasite causes disease in both adults and lambs?
Haemonchus contortus
At what age do lambs start developing immunity to parasites?
5-6 months
When does peri-parturient immunosuppression occur in the ewe?
2-4 weeks before lambing, until 6-8 weeks after the end of lactation
What population of ewes should you leave in refugia?
10%
Leave the single bearing ewes - less immunosuppression
How can you avoid under dosing sheep?
Weight and dose to the heaviest animal Ensure that the gun is calibrated Use a good dosing technique Put on yard for 24h post treatment Dose into the oesophagus
When should you dose sheep?
Autumn
Winter
Early spring
- can coincide with lambing time and scab treatment
What is the SCOPs guidelines to reducing resistance on farms?
Work out targeted control strategy Use quarantine Test for anthelmintic resistance Administer correctly Use anthelmintics only when necessary Select appropriate anthelmintic for task Adopt strategies to preserve susceptible populations Reduce dependence
How should you control parasites in lambs that are born in January and finished outside in May / June?
Nematodirus risk
Assess pasture risk
- if turned out onto pasture not grazed by lambs in the previous 2 years then no treatment is required
If turned out on dirty pasture
- dose Benzamidazoles - every 15 days (PPP) April - June
- could suggest to combine this with weighing
(not moxidectin - resistance)
Perform FEC every 3-4 weeks - check for coccidia
Also consider coccidiostats - diclazuril / toltrazuril
Devise a worming strategy for lambs born in February / March which are finished outside in March - July?
Nematodirus risk
Telodorsagia, Trichostrongylus and Haemonchus - peak in later Summer so not a concern
Turn out on to pasture not grazed in past 2y if possible
Benzamidazoles q 15 days from turnout until June
Perform FEC every 3-4 weeks and check for coccidia - diclazuril / toltrazuril if required
What parasite prophylaxis should you provide for lambing in March and turnout March - May, finished in July?
Nematodirus risk
Telodorsagia, trichstrongylus and haemonchus cause disease after July so not a concern
Turn out onto pasture not grazed in the past 2 years if possible
If not possible treat with Benzamidazoles q 15 days until finishing
Perform FEC every 3-4 weeks
- diclazuril and toltrazuril if necessary
Devise a worming strategy for store lambs on pasture summer to later Autumn and finished inside.
Risk:
Telodorsagia, haemonchus, fasciola, Trichostrongylus
Nematodirus can occasionally cause disease in Autumn too
Turn out onto clean pasture where possible
Try to use home bred stores
Quarantine any bought in stores
- treat with monapantel / derquantel for roundworms
- triclabendazole for fluke
Perform FEC every 3-4w
If nematode risk…
Treat with ivermectin q 5w (PPP 3w + 2w RA)
Treat with moxidectin q 6w (PPP 3w + 2w)
Treat with Benzamidazoles q3w
If fluke risk…
Treat with triclabendazole at housing
Treat with closantel in January
Treat with Albendazole in spring
How should you treat nematodes in hill flocks?
Treat when they are handled
Moxidectin? Good and long acting
Ivermectin - RA and no resistance in N.battus
Triclabendazole Autumn, closantel January, Albendazole March
What is a good quarantine worming strategy for sheep?
Monapantel or derquantel and abamectin - nematodes
Triclabendazole - fluke
Closantel in 7w and again in another 7w - fluke
Moxidectin/ doramectin - sheep scab
Hold off pasture for 24-48h
Then return to the contaminated pasture
When should you dose the ewe?
48h before turn out - moxidectin / ivermectin
- reduces pasture contamination for lambs
Only treat - thin sheep, triplet bearing ewes, shearlings
How does acute fasciolosis present?
Sudden death, anaemia, dysponea, pale
Disease in September - December
2-6 weeks after ingestion
How does subacute fasciolosis present?
Late autumn onwards
Haemorrhagic anaemia Hypoalbuminaemia Weight loss Enlarged liver Oedema Blacks disease - Clostridium novyi
How does chronic fasciolosis present?
January to March - 4-5 months post infection due to adults in the bile ducts
Hepatic fibrosis Hypoalbuminaemia Anaemia Weight loss Sub mandibular oedema
How can you diagnose fasciola hepatica?
History and CS
FEC - only positive 12w post-infection
Abattoir returns - migration tracts or adults in bile duct
PME
Haematology
Elevated liver enzymes - 13 day post infection
ELISA - 3w post infection
Coproantigen for fluke - 8-10w post-infection
What dosing strategy for fluke should be used for an aver all rainfall in a known fluke area?
October (bought in for housing) - triclabendazole (acute)
January - closantel (subacute and chronic)
April - Albendazole (chronic)
What additional dosing should be used on high risk farms during high risk years?
November - triclabendazole
June - triclabendazole (winter infection of snails)
