Nematode and cestode infections in sheep Flashcards
What are the roles of vets when there are nematode/cestode infections in sheep?
- Devising worm control strategies (Flock Health Plans)
- Advising on outbreak parasitic disease occurs
- Advising on poor growth in lambs/ thin ewes
- Advising when anthelmintic resistance problems occur
What are the 3 main current problems with parasite control in sheep?
- Drug resistance
- Climate change
- Parasites
Describe how drug resistance is becoming a major problem with parasite control in sheep
- Maintaining high levels of production relies on heavily stocked pasture and intensive anthelmintic use
- Inappropriate use of anthelmintics
Describe how climate change is becoming a major problem with parasite control in sheep
Mild winters warmer spring summer increased new species and increased parasite numbers on pasture
How is anthelmintic resistance defined?
Defined as drug <95% efficacy
What can be done about anthelmintic resistance?
- Devise sustainable parasite control plans
- Reduce selection pressure to slow progression of resistance
- Improve biosecurity to prevent introduction of resistant strains
How do nematode infections cause clinical disease in sheep?
- Damage lining of guts (reducing absorption)
- Remove nutrients
- Remove blood (Haemonchus)
- Host immune response (host resources and damage)
What are the overall clinical signs of nematode infections in sheep?
Reduced appetite. Poor weight gain/ weight loss
Submandibular oedema
Diarrhoea
Anaemia
Death
Outbreaks of acute severe diarrhoea and death lambs 6-12 weeks old are caused by which nematode infection?
Nematodirus battus
Describe type I and II Teladorsagia infections
Type 1: Lambs first grazing season, mid summer onwards
Type 2: yearlings winter months, emergence of hypobiotic larvae
Lambs with black scour occurring the the late summer/autumn months is caused by which nematode?
Trichostrongylus
What are the signs of Haemonchus contortus infections?
Adults and lambs
Acute regenerative anaemia
Chronic hypoproteinaemia, anaemia bottle jaw
Sudden death
How long does is take for the egg to develop into L3 in:
1. early spring
2. early summer
1 = 10-12 weeks
2 = 1-2 weeks
Development L3 to eggs in sheep takes how long?
16-21 days
Which nematode spp numbers peak in early summer?
Teladorsagia
Which nematode spp numbers peak in late summer/autumn?
Trichostrongylus
Describe hypobiosis
L3 late autumn early winter over winter period interrupted development L4 stage inside sheep
What is the consequence of hypobiosis?
Pasture contamination in spring and early summer
Describe the epidemiology of N.battus
- Eggs shed by lambs one year, remain on pasture and infect next year lambs
- Mass hatching of L3
- Severe outbreaks of diarrhoea in 6-12 week old lambs
When does hatching/release of N.battus eggs occur?
Prolonged period of chill followed temperature range of 10C-18C leads to large numbers of L3 hatching simultaneously
Describe sheep immunity to nematodes
Providing they have been exposed to nematodes LAMBS should be developing resistance to nematodes around 5-6 mo
Immunity to nematodes is influenced by which factors?
Nutrition (protein)
Genetics (opportunity breeding)
Stage of production
What does SCOPS stand for?
Sustainable control of parasites in sheep
Which anthelmintics are described as ‘white drench’?
Benzimidazoles
What is the function of benzimidazoles?
Tubulin binding, prevents uptake of glucose, ovicidal (kills eggs)
Describe use/resistance to benzimidazoles
- Broad spectrum
- N.battus resistance reported
- More resistance so may not work
Which anthelmintics are described as ‘yellow drench’?
Levamisole - imidazothiazines
What is the function of levimisole?
Ganglion blocking drugs, paralysis not ovicidal
Which anthelmintics are described as ‘clear drench’?
Macrocytic lactones
What is the action of macrocytic lactones?
Block Cl- and GABA channels -> paralysis
All injectable forms of which anthelmintic are active against mange mites (sheep scab)
Moxidectin (MLs)
Which group of anthelmintics are known as ‘orange drenches’?
Amino-acetonitrile
Which group of anthelmintics are known as ‘purple drenches’?
Spiroindoles
How should group 4 and 5 (new generation) antibiotics be used?
Do not keep for best, should be used regularly as part of drug rotation in worm control plan, especially useful at quarantine dose
Key factors influencing the development of Anthelmintic Resistance in a population are?
- Treatment frequency
- Under dosing
- Biosecurity: new strains introduced
- Proportion of population exposed to treatment “in refugia”
How can you detect that resistance is present?
Clinical signs:
- Lamb growth rates reduced - EID regular weighing DLWG really useful
- Diarrhoea
- Death
Which test can be used to know if resistance is present?
Faecal Egg Count Reduction Test - should be reduced to zero after administration of drug. If reduction is 95% or less, resistance has been detected.
Describe how to carry out the faecal egg count reduction test
- 10 lambs per group - Weigh and mark
- Pre-treatment FEC
- Accurate dose drug
- 7-14 days post treatment (depending on drug used) FEC
Describe the drench test
(cheaper quicker less accurate) post treatment FEC check
* FEC 7-14 days post treatment (depending on drug)
* Pooled worm egg count
What are the 4 SCOPS principles?
- Always make sure treatment is fully effective
- Reduce dependence on anthelmintics using management and monitoring
- Avoid bringing in resistant worms and/or other parasites by following a robust quarantine routine. Test for anthelmintic resistance
- Minimise the selection for worms that are resistant to anthelmintics when you treat sheep.
How can you avoid under-dosing?
- Pick the heaviest sheep in group, weigh it - If big range in sizes then sub group
- Check dosing gun
- Test for resistance
- Make sure you are using the correct product for the task
Adult sheep should have immunity to all but which nematode?
Haemonchus contortus
Why are adult sheep treated?
To reduce pasture contamination for lambs
Which adult sheep should be treated?
only treat thin sheep, triplet bearing ewes, shearlings ewe lambs, ie not fit singles, twin bearing ewes - not routine to dose everything
When are adult sheep treated for nematode infections?
At tupping time
Barbervax is used for?
Haemonchus
How can management of growing lambs be used to reduce anthelmintic use?
- Rotational grazing
- Leave ewes on high risk pastures
- Good nutrition
- Manage concurrent disease
- Genetic selection
- Vaccination program
Why cant faecal egg counts be used to target treatment for N.battus?
Larval stages causing disease can cause false negatives
How is forecasting used for N.battus
Temperature conditions across the country indicate when the risk is
Preventative dosing with BZ wormer (white drench)
How are brought in sheep managed to avoid bringing in resistant worms?
Dose with monopantel
Hold off pasture 24-48 hours allow treatment to work
Return to contaminated pasture
When will lambs not need to be wormed?
If they are growing at their required growth rates
What is the FAMANCHA test for Haemochus?
Use pallor of eye mucous membranes. Pale = dose!
What are the other clinical signs of Haemonchus infections?
Weakness, Collapse, Hyperpneoa, Tachycardia, Sudden death
Describe ‘in refugia’
If we dose the sheep with anthelmintic when the majority of worm population is in the sheep, ie when free living population is lowest rapidly select for resistance.
When are the ‘in refugia’ times of the year?
Autumn
Winter
Early spring
What are the effects of cestode infections in sheep?
Carcass condemnation
Echinococcus granulosus is zoonotic
Gid cysts in the brain
The sheep is the final host of which tapeworm infection?
Monezia expansa
