Anthelmintic Flashcards
1
Q
- Impact of Parasite Burden:
A
- 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.
2
Q
- Anthelmintic Resistance
A
- 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.
3
Q
- Effects of Worm Burdens on Lambs:
A
- 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.
4
Q
- Worm Groups in Ireland:
A
- Main groups include Haemonchus contortus, Ostertagia, Nematodirus, Trichostrongylus, and Cooperia.
- These groups have medium-high pathogenicity in the abomasum and small intestine.
5
Q
- Pasture Management:
A
- 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.
6
Q
- Parasite Threats Throughout the Year:
A
- 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.
7
Q
- Common Approach in NZ, UK, and Ireland:
A
- 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.
8
Q
- Broad Spectrum Anthelmintic Drenches:
A
- BZ (Benzimidazoles)
- LV (Levamisole)
- ML (Macrocyclic lactones)
- AD (Monepantel)
- SI (Spiroindoles)
9
Q
- Issue of Increased Natural Resistance:
A
- 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.
10
Q
- Detection of Resistance:
A
- 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.
11
Q
- Efficacy Measurement:
A
- After treatment, take another dung sample to measure efficacy.
- Timing is crucial depending on the drench group used.
12
Q
- Research and Concerns: Resistance
A
- 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.
13
Q
- Anthelmintic Resistance:
A
- Defined as the heritable ability of worms to survive anthelmintic doses.
- Resistance indicated if more than 5% of worms are “drug tolerant”.
14
Q
- Parameters Accelerating Resistance:
A
- No rotation of anthelmintic drugs: Overuse of specific drug groups, like Benzimidazole drugs, without rotation.
- Underdosing of animals: Guessing weights and using low dosage rates.
* Always dose to the heaviest lamb to avoid selection for resistance. - Not dosing based on FEC (Fecal Egg Count): Dosing when not required, leading to unnecessary exposure.
- Lack of dose gun or scale calibration: Inaccurate dosing can contribute to resistance.
- Insufficient susceptible parasites in refugia: Failure to maintain a population of unexposed worms.
* Ensuring a high population in refugia dilutes resistant worms after treatment.
15
Q
- Management Strategies:
A
- 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.
