The range of summer health concerns in sheep production is varied from blowfly protection to lameness control and mineral deficiencies. However, the greatest challenge on many farms is from gastrointestinal worms – parasitic gastroenteritis, or PGE.
Worm resistance to the three commonly used anthelmintics has been identified on some farms with a high percentage of flocks who have tested having some form of resistance to at least one anthelmintic class. While a relatively new challenge, haemonchus contortus, or what is commonly known as barber’s pole worm, has caused significant problems on some farms in recent years.
Barber’s pole worm
This worm is not new in a global context and has been a significant challenge in countries with a hot climate for decades. It’s prevalence has been growing in the south of the UK over the last decade, but it was thought that it wouldn’t be a major challenge in Ireland due to cooler climatic conditions.
However, this theory has now been dispelled, with cases on the rise. It’s prevalence was discussed by Seamus Fagan from the Athlone Regional Veterinary Laboratory (RVL) at this year’s Teagasc sheep conferences.
Seamus presented the data detailed in Figure 1, which shows a spike in cases in the last two years. In excess of 50% of cases were identified in the Kilkenny RVL, but there was also in the region of a third of cases identified in the Athlone RVL, along with a few in Sligo.
This shows that while the greatest threat is in the southeast and the midlands areas, all farmers need to be conscious of the threat posed by haemonchus contortus. The UK’s Animal and Plant Health Agency (APHA) recently released a warning to farmers there which also highlighted that while overall disease levels are likely to be low, individual farms can be hit hard, with the risk heightened by recent higher temperatures.
Warning signals
The worm species has a remarkably efficient reproductive system with the potential to multiply rapidly. Standard faecal egg count (FEC) tests do not differentiate the worm species, but a tell-tale sign is an explosion in egg counts spiralling to upwards of 5,000 eggs per gramme (epg) in a relatively short period of time. Previous post-mortems on sheep which succumbed to the disease show FECs possible of up to 50,000 epg of faeces.
Seamus explains the presence of such a high number of parasites can have devastating consequences in a short period of time, with adult worms capable of sucking 0.5ml of blood per day from blood vessels in the abomasum.
Combine this with numbers present and it is easy to see how rapid the disease can take hold. A sheep or goat with 5,000 haemonchus contortus worms would lose upwards of 250ml of blood a day, with a much lower concentration also capable of causing significant problems.
Clinical signs are sheep quickly losing body condition and demonstrating similar classical symptoms to liver fluke. Typical signs include paleness of gums and conjunctivae, the characteristic swelling under the jaw or bottle-jaw appearance and an increased rate and depth of breating / increased heart rate. Sudden deaths or ill-thrift despite sheep being offered a good plane of condition should be explored. Diarrhoea, which can be typical in other PGE infections, is not a classical symptom of haemonchus contortus.
Anthelmintic resistance and faecal egg count reduction tests
A FEC reduction test can be successfully used to help establish if anthelmintic resistance is an issue. The practice is similar to a standard FEC count except the lambs from which samples are collected from must be identified. The samples are submitted as normal and lambs are treated following a sample being taken.
A repeat FEC is collected from the same lambs seven days later in the case of products with a Group 2 – LV (levamisole) active ingredient and 14 days later for lambs treated with a Group 1 – BZ (benzimidazoles) or Group 3 – ML (macrocyclic lactone) product. The initial egg count needs to be in excess of 200epg to draw conclusions and as such the test should be completed where a worm burden is expected or known. A reduction of greater than 95% of worms shows the product is working effectively, while a reduction of less than 95% shows there are resistance issues.
Control
As already outlined, the disease is not widespread in Ireland. Normal climatic conditions tend not to be suitable for worms to survive over the winter in large numbers. Plus, treatment for liver fluke is also likely to have controlled numbers in some areas. However, where it does hit flocks it can lead to big problems, with some vets pointing to the prospect of greater problems if milder winters become the norm. As such, farmers are being encouraged to be mindful of the possible threat, to be aware of the symptoms and in possible cases of mortality to keep the threat of haemonchus in mind.
Optimum practices
There are a number of practices that will help to reduce the rate of anthelmintic resistance developing and these should be adopted at farm level.
The volume of product administered should follow manufacturers’ guidelines and be determined by the heaviest lamb in the group. Alter dose volumes where there is a significant difference in weight. Calibrate dosing equipment before beginning and during the process where treating a high number of animals. Ensure lambs are dosed correctly with product delivered to the back of the tongue. Return animals to the field they were grazing in and not fresh pasture to help maintain a population of susceptible worms.Avoid dosing ewes for stomach worms where there is no demonstrated need, including avoiding inadvertent treatment for worms (eg products that treat a number of ailments). Quarantine any animals moving on to the farm and implement a robust biosecurity plan.
The range of summer health concerns in sheep production is varied from blowfly protection to lameness control and mineral deficiencies. However, the greatest challenge on many farms is from gastrointestinal worms – parasitic gastroenteritis, or PGE.
Worm resistance to the three commonly used anthelmintics has been identified on some farms with a high percentage of flocks who have tested having some form of resistance to at least one anthelmintic class. While a relatively new challenge, haemonchus contortus, or what is commonly known as barber’s pole worm, has caused significant problems on some farms in recent years.
Barber’s pole worm
This worm is not new in a global context and has been a significant challenge in countries with a hot climate for decades. It’s prevalence has been growing in the south of the UK over the last decade, but it was thought that it wouldn’t be a major challenge in Ireland due to cooler climatic conditions.
However, this theory has now been dispelled, with cases on the rise. It’s prevalence was discussed by Seamus Fagan from the Athlone Regional Veterinary Laboratory (RVL) at this year’s Teagasc sheep conferences.
Seamus presented the data detailed in Figure 1, which shows a spike in cases in the last two years. In excess of 50% of cases were identified in the Kilkenny RVL, but there was also in the region of a third of cases identified in the Athlone RVL, along with a few in Sligo.
This shows that while the greatest threat is in the southeast and the midlands areas, all farmers need to be conscious of the threat posed by haemonchus contortus. The UK’s Animal and Plant Health Agency (APHA) recently released a warning to farmers there which also highlighted that while overall disease levels are likely to be low, individual farms can be hit hard, with the risk heightened by recent higher temperatures.
Warning signals
The worm species has a remarkably efficient reproductive system with the potential to multiply rapidly. Standard faecal egg count (FEC) tests do not differentiate the worm species, but a tell-tale sign is an explosion in egg counts spiralling to upwards of 5,000 eggs per gramme (epg) in a relatively short period of time. Previous post-mortems on sheep which succumbed to the disease show FECs possible of up to 50,000 epg of faeces.
Seamus explains the presence of such a high number of parasites can have devastating consequences in a short period of time, with adult worms capable of sucking 0.5ml of blood per day from blood vessels in the abomasum.
Combine this with numbers present and it is easy to see how rapid the disease can take hold. A sheep or goat with 5,000 haemonchus contortus worms would lose upwards of 250ml of blood a day, with a much lower concentration also capable of causing significant problems.
Clinical signs are sheep quickly losing body condition and demonstrating similar classical symptoms to liver fluke. Typical signs include paleness of gums and conjunctivae, the characteristic swelling under the jaw or bottle-jaw appearance and an increased rate and depth of breating / increased heart rate. Sudden deaths or ill-thrift despite sheep being offered a good plane of condition should be explored. Diarrhoea, which can be typical in other PGE infections, is not a classical symptom of haemonchus contortus.
Anthelmintic resistance and faecal egg count reduction tests
A FEC reduction test can be successfully used to help establish if anthelmintic resistance is an issue. The practice is similar to a standard FEC count except the lambs from which samples are collected from must be identified. The samples are submitted as normal and lambs are treated following a sample being taken.
A repeat FEC is collected from the same lambs seven days later in the case of products with a Group 2 – LV (levamisole) active ingredient and 14 days later for lambs treated with a Group 1 – BZ (benzimidazoles) or Group 3 – ML (macrocyclic lactone) product. The initial egg count needs to be in excess of 200epg to draw conclusions and as such the test should be completed where a worm burden is expected or known. A reduction of greater than 95% of worms shows the product is working effectively, while a reduction of less than 95% shows there are resistance issues.
Control
As already outlined, the disease is not widespread in Ireland. Normal climatic conditions tend not to be suitable for worms to survive over the winter in large numbers. Plus, treatment for liver fluke is also likely to have controlled numbers in some areas. However, where it does hit flocks it can lead to big problems, with some vets pointing to the prospect of greater problems if milder winters become the norm. As such, farmers are being encouraged to be mindful of the possible threat, to be aware of the symptoms and in possible cases of mortality to keep the threat of haemonchus in mind.
Optimum practices
There are a number of practices that will help to reduce the rate of anthelmintic resistance developing and these should be adopted at farm level.
The volume of product administered should follow manufacturers’ guidelines and be determined by the heaviest lamb in the group. Alter dose volumes where there is a significant difference in weight. Calibrate dosing equipment before beginning and during the process where treating a high number of animals. Ensure lambs are dosed correctly with product delivered to the back of the tongue. Return animals to the field they were grazing in and not fresh pasture to help maintain a population of susceptible worms.Avoid dosing ewes for stomach worms where there is no demonstrated need, including avoiding inadvertent treatment for worms (eg products that treat a number of ailments). Quarantine any animals moving on to the farm and implement a robust biosecurity plan. 
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