Anthelmintic

Question 1

• Impact of Parasite Burden:

Answer 1

• Greatest impact on pasture-based systems, affecting sheep health and performance.
• Parasites like roundworms cause ill-thrift, reduced performance, and occasional death.
• Control relies on optimal grazing management and chemical anthelmintics, but resistance is developing.

Question 2

• Anthelmintic Resistance

Answer 2

• Parasites are developing resistance to anthelmintics, surviving exposure and producing offspring.
• Increased anthelmintic use leads to more prevalent resistant worms in sheep flocks.
• Clinical evidence for failed treatment becomes apparent over time.

Question 3

• Effects of Worm Burdens on Lambs:

Answer 3

• Decreased appetite, leading to reduced feed intake and growth rates.
• Impaired mineral retention, affecting skeleton size and exacerbating mineral deficiencies.
• Reduced protein metabolism, impacting carcass quality and muscle growth.
• Permanent damage to gut lining, hindering nutrient absorption and causing diarrhea.

Question 4

• Worm Groups in Ireland:

Answer 4

• Main groups include Haemonchus contortus, Ostertagia, Nematodirus, Trichostrongylus, and Cooperia.
• These groups have medium-high pathogenicity in the abomasum and small intestine.

Question 5

• Pasture Management:

Answer 5

• Distribution of infective larvae is low to the ground, necessitating effective grazing management.
• Key period for management is May to December.
• Eggs from ewes become important from January to April, contributing to initial infection in lambs.

Question 6

• Parasite Threats Throughout the Year:

Answer 6

• Coccidiosis and Nematodirus from February to May.
• Ostertagia from May to September.
• Haemonchus from May to November.
• Fluke and Trichostrongylus from July to January.

Understanding these patterns and implementing appropriate management strategies are crucial for effective parasite control and sheep health.

Question 7

• Common Approach in NZ, UK, and Ireland:

Answer 7

• Focus on drenches and chemicals for worm management.
• Successful plan includes monitoring, good nutrition, having a plan, reducing worm challenge, genetics, and then drenches.
• Correct approach is to conduct faecal egg count (FEC) and then dose in response.
• In Ireland and the UK, dosing occurs only if threshold levels of 400-500 eggs/g are present.
• In NZ, dosing happens every 4-5 weeks regardless, leading to increased resistance.

Question 8

• Broad Spectrum Anthelmintic Drenches:

Answer 8

1. BZ (Benzimidazoles)
2. LV (Levamisole)
3. ML (Macrocyclic lactones)
4. AD (Monepantel)
5. SI (Spiroindoles)

Question 9

• Issue of Increased Natural Resistance:

Answer 9

• Continued use of drenches has increased resistance within parasite populations.
• Drenching entire groups can lead to survival of resistant worms, increasing resistance.
• Strategies to minimize resistance include leaving 10-20% of sheep undrenched or shedding both susceptible and resistant parasites.

Question 10

• Detection of Resistance:

Answer 10

• Faecal egg counting (FEC) is used to detect resistance.
• Larval development tests and egg hatch assays are expensive but available for LV and BZ groups.

Question 11

• Efficacy Measurement:

Answer 11

• After treatment, take another dung sample to measure efficacy.
• Timing is crucial depending on the drench group used.

Question 12

• Research and Concerns: Resistance

Answer 12

• Study by Cara Hamilton in 2019 across 15 farms showed worrying results.
• 100% resistance to Benzimidazoles, 40% susceptibility to clear drenches, and 20% resistance to Levamisole.
• Sheep Technology Adoption Programme (STAP) aimed at increasing profitability through best management practices.
• Faecal egg count reduction tests were modified and conducted, revealing issues like ineffective treatments and unnecessary treatment due to low levels of gut parasitism.

Question 13

• Anthelmintic Resistance:

Answer 13

• Defined as the heritable ability of worms to survive anthelmintic doses.
• Resistance indicated if more than 5% of worms are “drug tolerant”.

Question 14

• Parameters Accelerating Resistance:

Answer 14

1. No rotation of anthelmintic drugs: Overuse of specific drug groups, like Benzimidazole drugs, without rotation.
2. Underdosing of animals: Guessing weights and using low dosage rates.
   * Always dose to the heaviest lamb to avoid selection for resistance.
3. Not dosing based on FEC (Fecal Egg Count): Dosing when not required, leading to unnecessary exposure.
4. Lack of dose gun or scale calibration: Inaccurate dosing can contribute to resistance.
5. Insufficient susceptible parasites in refugia: Failure to maintain a population of unexposed worms.
   * Ensuring a high population in refugia dilutes resistant worms after treatment.

Question 15

• Management Strategies:

Answer 15

• Closed flock operation is ideal.
• Quarantine and dose bought-in animals with monopantel and moxidectin.
• Keep away from pasture for up to 48 hours.
• Expose to dirty pasture upon turning out to reduce resistance.
• Future control relies on better detection methods and adopting best practices.
• Nutritional and management strategies can minimize resistance.

Question 16

• Multispecies Swards:

Answer 16

• Show promise in reducing resistance.
• Herbs like chicory and plantain contain condensed tannins, improving protein utilization and mineral status.
• Studies show reduced FECs and improved animal performance with multispecies swards.
• E.g., feeding ribwort plantain to ewes saw a 42% reduction in FEC and 49% reduction in helminth parasitic intensity.

Question 17

• Grazing Strategies:

Answer 17

• Efficient grazing crucial for herb persistency.
• Overgrazing damages root structures.
• Grazing principles include not grazing below 5cm and maintaining 3-6-week rotation lengths.
• Management principles to avoid tap root damage are vital.
• A study demonstrated that overgrazing in rotation of herb species damages root structure.
• Proper management blueprints to optimize botanical composition and utilization need to be identified and experimented.
  These strategies aim to combat anthelmintic resistance while maximizing animal health and performance.