Worm egg counts for sheep, an essential part of your flock management

Sheep

Protect your sheep

All sheep are prone to parasitism. Once on the pasture, infective larvae can survive for over a year. Although the numbers of larvae on ungrazed pastures are likely to decline over the winter, they will not be eliminated. Therefore, a single treatment of an infected animal will not prevent reinfection.

It is also possible for sheep to be infected by different worms at the same time. A common disease resulting from mixed infections is parasitic gastroenteritis (PGE). Severe infections can lead to diarrhoea and significant loss of condition.

Regular WECs will help confirm a PGE diagnosis.

Effective worm control

Therefore, WECs should be an essential part of your flock management. They will help you:

  • Only treat your sheep when necessary
  • Use a targeted treatment
  • Predict future heavy worm burdens
  • Monitor the effectiveness of your worm control programme
  • Slow the rate of AR

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The aim of effective worm control is to stop worms completing their lifecycle and prevent future contamination.

A WEC tells you about your sheep’s parasite burden at a single point in time. However, the lifecycle of a worm includes several larval stages that do not show in WECs. So even if the test results show no evidence of active adult worms, your sheep may still carry a worm burden.

Therefore, to build an accurate picture of your animal’s internal health, you should repeat the test regularly.

Worms commonly found in sheep

Teladorsagia circumcincta

Notes Teladorsagia circumcincta is known as the brown stomach worm. Infected sheep may not initially show any obvious signs of disease (www.wormboss.com.au).

Due their pathogenicity in infected sheep we keep Teladorsagia (Ostertagia) circumcincta in our Parasite Catalogue.

Most commonly affect Lambs at grass.
Signs and symptoms Profuse watery diarrhoea; loss of appetite; weight loss; failure to thrive; drop in wool growth and milk production (www.nadis.org.uk).
Can lead to PGE.
Control See SCOPS advice.

Haemonchus contortus

Notes Haemonchus contortus feeds on the sheep’s blood. Large numbers of larvae ingested over a short period of time cause acute disease.

Due their pathogenicity in infected sheep we keep Haemonchus contortus in our Parasite Catalogue.

Most commonly affect Growing lambs.
Signs and symptoms Anaemia; lethargy; submandibular oedema; increased heart and respiratory rates; loss of condition; emaciation (www.nadis.org.uk).
Can lead to May be fatal.
Control See SCOPS advice.

Dictyocaulus filarial (Lungworm)

Notes The parasite infects the lower respiratory tract. The development of the disease is similar to that for lungworms in cattle, but interstitial emphysema is not a common complication.
Most commonly affect Grazing sheep
Signs and symptoms Loss of appetite; drop in milk production.
Can lead to Breathing compromise.
Control

Cooperia spp.

Notes This is called the small intestinal worm. Symptoms associated with Cooperia oncophora are often less obvious than with Ostertagia infections. There is no presence of anaemia as the parasite does not feed on the sheep’s blood.
Most commonly affect Young grazing lambs.
Signs and symptoms Weight loss; failure to thrive; diarrhoea
Can lead to PGE.
Control Alternate grazing with cattle. Early season treatment to prevent buildup of larvae on pasture.

Nematodirus spp.

Notes Nematodirus spp. has characteristically large eggs.
Most commonly affect Lambs in spring.
Signs and symptoms Weight loss; failure to thrive; rapid dehydration; emaciation; diarrhoea.
Can lead to PGE. May be fatal.
Control Graze lambs on fresh pasture.

Oesophagostomum spp.

Notes Adult worms are found in the large intestine.
Most commonly affect Lambs and young sheep at grass.
Signs and symptoms Fetid diarrhea; anaemia; oedema.
Can lead to PGE. May be fatal.
Control Alternate grazing with cattle. Early season treatment to prevent buildup of larvae on pasture.

Trichostrongylus spp.

Notes The parasite feeds on blood from the gastrointestinal tract.
Most commonly affect Young grazing sheep.
Signs and symptoms Persistent watery diarrhea; weight loss; failure to thrive.
Can lead to PGE. May be fatal.
Control Alternate grazing with cattle. Early season treatment to prevent buildup of larvae on pasture.

Muellerius capillaris (Lungworm)

Notes The infection represents the lower end of the pathogenic spectrum for lungworms.
Most commonly affect Grazing sheep.
Signs and symptoms Occasional breathlessness and coughing.
Can lead to Diffuse interstitial pneumonitis; chronic, eosinophilic, granulomatous pneumonia; raised ‘greenish’ lesions in the lung.
Control Anthelmintic treatment where necessary.

Fasciola hepatica (liver fluke)

Notes Liver fluke cause considerable economic loss to farmers in the UK and worldwide. They are trematode parasites responsible for the disease fasciolosis. Disease is caused by immature fluke migrating through the liver, by adult worms present in the bile duct, or both.

Liver fluke use snails as an intermediate host, so are usually more prevalent on land that doesn’t drain well and during wet summers. Infective larvae can survive on pasture for several months.

However, prevalence of the disease is increasing, possibly due to changes in climate and farming practises, an increase in animal movement around the UK and the increase of AR in fluke.

Most commonly affect Sheep grazing on poorly drained pasture with snail habitats.
Signs and symptoms Weight loss; anaemia; drop in milk production.
Can lead to May be fatal.
Control Drain pasture where possible. Remove snail habitats. Anthelmintic treatment.