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Gut worms have a significant detrimental effect on the health and welfare of lambs and are one of the most significant production-limiting and costly diseases in the UK sheep flock - estimated to be costing the UK sheep flock £84 million pounds per year.1 The financial losses seen with gut worms are due to loss of production through reduced weight gain of lambs and treatment/prevention costs. Worms should be on every shepherd’s mind throughout the year and should be a focus for all flock sizes and types.
The clinical presentation can vary from sudden death with no sign of illness to mild disease which may not be easy to see with the naked eye but could be causing significant loss of production.
Gut worms in lambs
There are around 20 species of gut worm which can affect sheep in the UK2.The clinical disease caused by these worms can vary depending on the species present and the time of year/weather.
There are three main diseases we tend to see in sheep in the UK:
- Parasitic gastroenteritis (PGE)
- Nematodirosis (Nematodirus battus)
- Haemonchosis (Haemonchus contortus)
Parasitic gastroenteritis (PGE) in lambs
PGE is a general term used to describe gut worms in lambs. It is mainly caused by two species of worm; Teleadorsagia, which affects lambs in their first grazing season from summer to early autumn, and Trichostrongylus, which affects older lambs in their first season from autumn to winter. There can also be mixed infections of these two species of worm, Nematodirus, Haemonchus and other, less pathogenic worms.
Life cycle
The main source of infection is from ewes around lambing contaminating the pasture with eggs. Lambs will then pick up eggs as they graze and shed eggs themselves, which will further contaminate the pasture over the summer. The life cycle of these worms can take from 2 weeks to 3 months, depending on weather conditions. Wet and warm weather tend to be higher risk for PGE.
The larval stage of the worm can stop developing inside the ewes (hypobiosis) over winter, which is a survival tactic of the two main species of worm causing PGE, as well as Haemonchus. These larvae will resume their development in spring, which can cause disease in yearlings but can also contribute to the periparturient rise discussed below.
What are the signs of PGE?
PGE is usually seen as a few dirty lambs in a group, which have stopped growing as they should and lambs ‘not doing’. PGE can also present as severe disease, causing lamb losses if the weather conditions are right and pasture contamination is high. Yearlings that are affected by the mass development of hypobiotic larvae will occasionally present with scour and poor condition in late winter/spring. Whilst ewes can contaminate pasture with eggs for lambs to become infected, it is rare that the ewes themselves are affected by PGE if they are healthy, in good condition and on a suitable diet.
What is the impact of PGE in lambs
Although lamb losses can occur with very heavy infections, the main impact of PGE is in the loss of production. Time, effort, and money spent getting lambs to the summer may be wasted if they then do not grow and fatten as they should, despite good grass provision. Dirty back ends will also increase the risk of fly strike, as flies are attracted to dirty, wet wool.
Prevention of PGE in lambs
Prevention of PGE in lambs is based on reducing pasture contamination:
- FECs can be useful here to determine which of your pastures are heavily contaminated. Some pastures will have a far higher contamination than others, and ‘mapping’ your farm through recording FECs throughout a season can tell you which pastures to avoid grazing lambs on.
- Some of the main worms involved in PGE in lambs do not survive very well on pasture in hot weather, so breaking the life cycle of the worms by not grazing high-risk pasture in the summer can help. This can be achieved by taking a crop from these fields or rotating stock classes. Grazing dry adult ewes or cattle on these very highly contaminated pastures can reduce the burden as they will pick up the worm eggs as they graze but be unaffected by them. Improving the pasture by reseeding can also reduce the parasite burden.
- Selectively worming ewes/groups of ewes with high FECs around lambing could be necessary to reduce pasture contamination for the lambs. In general, healthy fit ewes do not need worming. However, ewes may shed more eggs at this time as their immunity drops (sometimes referred to as the periparturient rise). We will discuss this in more detail in the next blog.
Diagnosis and treatment of PGE in lambs
Diagnosis of PGE in lambs is based on FECs (faecal worm egg counts) and monitoring weight gain, condition, and lamb cleanliness.
It is important to have a plan in place for managing PGE in your flock – your vet/SQP/RAMA can help you devise the best strategy. Best practice should always be followed, including pasture management, monitoring and using targeted treatments of wormers that you know work on your farm in rotation to help reduce the development of resistance when treating your flock for worms. The SCOPS manual provides a useful guide for this. See ‘Gut worms in lambs – Diagnosis and treatment of parasitic gastroenteritis (PGE)’ for more detail.
The Chanelle anthelmintic range includes wormers for sheep across the three main wormer classes to help support responsible worming:
- Group 1 BZ – Albex
- Group 2 LV –Chanaverm
- Group 3 ML – Animec
- 3a. Group 3 ML (Moxidectin) – Moxodex, long-lasting residual activity for 8 weeks, with a meat withdrawal of just 14 days
Nematodirus – the early worm
This worm can also form a part of PGE as discussed above and will normally be reported as part of a total FEC count, but separately to the strongyles (Teladorsagia and Trichostrongulus) as the eggs are very distinctive under a microscope. Look out for the blog in April next year, where we focus on Nematodirus.
Haemonchus – the blood-sucking worm/barber pole worm
This worm presents completely differently to all the diseases above as there is usually no scour present in animals affected by Haemonchus alone. It also differs from the other worms in that sheep do not develop good immunity to Haemonchus, which means that the whole flock needs to be monitored.
Haemonchus is becoming more of a problem in the UK, especially as our weather becomes more suited to the worm’s life cycle3. Disease due to Haemonchus will usually be seen in late summer/autumn when the weather conditions are suitable (hot and dry weather followed by rainfall).
References:
- Nieuwhof, GJ., & Bishop,SC. (2005). Costs of the major endemic diseases of sheep in Great Britain andthe potential benefits of reduction in disease impact. Animal science, 81,23-29.
- Species-table.pdf(scops.org.uk)
- Carson, A., Reichel, R., Bell,S., Collins, R., Smith, J. and Bartley, D. (2023), Haemonchus contortus:an overview. Veterinary Record, 192: 26-28. https://doi.org/10.1002/vetr.2613
Gut worms have a significant detrimental effect on the health and welfare of lambs and are one of the most significant production-limiting and costly diseases in the UK sheep flock - estimated to be costing the UK sheep flock £84 million pounds per year.1 The financial losses seen with gut worms are due to loss of production through reduced weight gain of lambs and treatment/prevention costs. Worms should be on every shepherd’s mind throughout the year and should be a focus for all flock sizes and types.
The clinical presentation can vary from sudden death with no sign of illness to mild disease which may not be easy to see with the naked eye but could be causing significant loss of production.
Gut worms in lambs
There are around 20 species of gut worm which can affect sheep in the UK2.The clinical disease caused by these worms can vary depending on the species present and the time of year/weather.
There are three main diseases we tend to see in sheep in the UK:
- Parasitic gastroenteritis (PGE)
- Nematodirosis (Nematodirus battus)
- Haemonchosis (Haemonchus contortus)
Parasitic gastroenteritis (PGE) in lambs
PGE is a general term used to describe gut worms in lambs. It is mainly caused by two species of worm; Teleadorsagia, which affects lambs in their first grazing season from summer to early autumn, and Trichostrongylus, which affects older lambs in their first season from autumn to winter. There can also be mixed infections of these two species of worm, Nematodirus, Haemonchus and other, less pathogenic worms.
Life cycle
The main source of infection is from ewes around lambing contaminating the pasture with eggs. Lambs will then pick up eggs as they graze and shed eggs themselves, which will further contaminate the pasture over the summer. The life cycle of these worms can take from 2 weeks to 3 months, depending on weather conditions. Wet and warm weather tend to be higher risk for PGE.
The larval stage of the worm can stop developing inside the ewes (hypobiosis) over winter, which is a survival tactic of the two main species of worm causing PGE, as well as Haemonchus. These larvae will resume their development in spring, which can cause disease in yearlings but can also contribute to the periparturient rise discussed below.
What are the signs of PGE?
PGE is usually seen as a few dirty lambs in a group, which have stopped growing as they should and lambs ‘not doing’. PGE can also present as severe disease, causing lamb losses if the weather conditions are right and pasture contamination is high. Yearlings that are affected by the mass development of hypobiotic larvae will occasionally present with scour and poor condition in late winter/spring. Whilst ewes can contaminate pasture with eggs for lambs to become infected, it is rare that the ewes themselves are affected by PGE if they are healthy, in good condition and on a suitable diet.
What is the impact of PGE in lambs
Although lamb losses can occur with very heavy infections, the main impact of PGE is in the loss of production. Time, effort, and money spent getting lambs to the summer may be wasted if they then do not grow and fatten as they should, despite good grass provision. Dirty back ends will also increase the risk of fly strike, as flies are attracted to dirty, wet wool.
Prevention of PGE in lambs
Prevention of PGE in lambs is based on reducing pasture contamination:
- FECs can be useful here to determine which of your pastures are heavily contaminated. Some pastures will have a far higher contamination than others, and ‘mapping’ your farm through recording FECs throughout a season can tell you which pastures to avoid grazing lambs on.
- Some of the main worms involved in PGE in lambs do not survive very well on pasture in hot weather, so breaking the life cycle of the worms by not grazing high-risk pasture in the summer can help. This can be achieved by taking a crop from these fields or rotating stock classes. Grazing dry adult ewes or cattle on these very highly contaminated pastures can reduce the burden as they will pick up the worm eggs as they graze but be unaffected by them. Improving the pasture by reseeding can also reduce the parasite burden.
- Selectively worming ewes/groups of ewes with high FECs around lambing could be necessary to reduce pasture contamination for the lambs. In general, healthy fit ewes do not need worming. However, ewes may shed more eggs at this time as their immunity drops (sometimes referred to as the periparturient rise). We will discuss this in more detail in the next blog.
Diagnosis and treatment of PGE in lambs
Diagnosis of PGE in lambs is based on FECs (faecal worm egg counts) and monitoring weight gain, condition, and lamb cleanliness.
It is important to have a plan in place for managing PGE in your flock – your vet/SQP/RAMA can help you devise the best strategy. Best practice should always be followed, including pasture management, monitoring and using targeted treatments of wormers that you know work on your farm in rotation to help reduce the development of resistance when treating your flock for worms. The SCOPS manual provides a useful guide for this. See ‘Gut worms in lambs – Diagnosis and treatment of parasitic gastroenteritis (PGE)’ for more detail.
The Chanelle anthelmintic range includes wormers for sheep across the three main wormer classes to help support responsible worming:
- Group 1 BZ – Albex
- Group 2 LV –Chanaverm
- Group 3 ML – Animec
- 3a. Group 3 ML (Moxidectin) – Moxodex, long-lasting residual activity for 8 weeks, with a meat withdrawal of just 14 days
Nematodirus – the early worm
This worm can also form a part of PGE as discussed above and will normally be reported as part of a total FEC count, but separately to the strongyles (Teladorsagia and Trichostrongulus) as the eggs are very distinctive under a microscope. Look out for the blog in April next year, where we focus on Nematodirus.
Haemonchus – the blood-sucking worm/barber pole worm
This worm presents completely differently to all the diseases above as there is usually no scour present in animals affected by Haemonchus alone. It also differs from the other worms in that sheep do not develop good immunity to Haemonchus, which means that the whole flock needs to be monitored.
Haemonchus is becoming more of a problem in the UK, especially as our weather becomes more suited to the worm’s life cycle3. Disease due to Haemonchus will usually be seen in late summer/autumn when the weather conditions are suitable (hot and dry weather followed by rainfall).
References:
- Nieuwhof, GJ., & Bishop,SC. (2005). Costs of the major endemic diseases of sheep in Great Britain andthe potential benefits of reduction in disease impact. Animal science, 81,23-29.
- Species-table.pdf(scops.org.uk)
- Carson, A., Reichel, R., Bell,S., Collins, R., Smith, J. and Bartley, D. (2023), Haemonchus contortus:an overview. Veterinary Record, 192: 26-28. https://doi.org/10.1002/vetr.2613