Roundworms are estimated to cost UK sheep producers £84 million pounds per annum in treatment and lost productivity.
Sheep become infected by ingesting the larval stage with pasture resulting in roundworms living in the stomach or small intestine where they can cause an infection of the gut known as parasitic gastroenteritis (PGE). The severity of disease caused by these worms (also known as gastrointestinal nematodes) depends on the size of the challenges faced by the sheep and their susceptibility to infection.
Although roundworm infection can lead to overt clinical disease, in many cases these parasites result in sub-clinical infections in which sheep perform below their full potential. Production losses are associated with reduction in live weight gain, as well as a reduction in both the quality and quantity of meat and wool.
The major roundworm species involved in disease in UK sheep flocks:
|Scientific Name||Common Name||Season|
|Nematodirus battus||Thread-necked worm||Spring|
|Teladorsagia (Ostertagia) circumcincta||Brown stomach worm||Early summer|
|Haemonchus contortus||Barber's pole worm||Early summer|
|Trichostronglus vitrinus||Scour worm||Late summer/autumn|
|Trichostrongylus colubriformis||Black scour worm||Late summer/autumn|
Ill thrift in sheep may not be just as a result of roundworm infections and it is therefore important to identify the root cause of any problem. Faecal worm egg counts (FWEC) can be a useful tool in not only confirming that roundworms are indeed the cause of the problem but can also provide information regarding the species of worm present, and can also be used to help monitor the effectiveness of any treatment.
Current control is largely achieved through the therapeutic and prophylactic use of drugs known as anthelmintics. However the development of resistance by gastrointestinal nematodes to the anthelmintics used to control them has become a major threat to the sustainability of sheep farming.
Watch our short animated film, War of the Worms, which highlights the important elements involved in the development and spread of anthelmintic resistance as well as the crucial messages on sustainable methods of worm control.
Current interests and future aims:
For further Information about Parasitic Roundworms in Sheep please see Moredun Newssheets 6.12 - Sustainable Roundworm Control in Sheep and 6.13 - Nematodirus: a changing parasite