Lecture 9 and 10 Flashcards
Explain the lifecycle of GI nematodes
L3 = infective stage
What is the requirements for GI nematodes
Low temperature
Moisture
What is the prepotent period for GI nematodes
3 weeks
What are some species that undergo hypobiosis
Telodorsagia circumcinctia - larvae ingested in late winter and early spring -> resume development in autumn
Haemonchus contorts -> larvae ingested in winter and autumn -> resume development in spring
What occurs in winter rainfall sones
Telodorsagia circumcincta and Trichostrongylus
Nematodirus
Harmonchus contortus
What occurs in summer rainfall zones
Haemonchus contorts
Telodorsagia circumcincta and Trichostrongylus
Effects of GI nematodes on sheep
Reduce appetite, skeletal growth, haemopiesis, protein and mineral metabolism
Subclinical
- Reduced body growth
- Reduced wool production
What are the clinical signs of GI nematodes
Sudden death, Anaemia, Bottle Jaw, Loss of appetite, weight loss, diarrhoea, death
Explain immunity to GI parasites in lambs
Timing of development of natural immunity depends on rate larval intake -> exposure to larvae is needed to build up natural immunity
Most immunity is acquired by 18 months
Explain GI immunity in mature sheep
Once developed, immunity remains strong against against most scour worms -> low worm burden
Exception: H.contortus developed immunity is less strong and reliable
Natural immunity may break down if extreme larval pressure and/or poor nutrition
How to diagnose GI nematodes
History, Clinical signs, Worn egg count, haemonchus dip stick, WEC with larval differentiation, Total worm count, ELISA, Blood pepsinogen
What are the potential problems with a worm eggs count
Unreliable indicators of the size of an adult worm burden and the severity of pasture infection
What is the diagnostic purposes of the Worm Egg Count
- Estimate size of burden -> immediate treatment, not treatment, re-sampling in short term
- Degree of pasture contamination occurring at time of testing
- Assessment of anthelmintic efficacy
What is seen with a PM of GI nematodes
Acute and chronic liver fluke lesions
200 adult flukes -> chronic disease symptoms
Explain the Barbervax vaccine program
New tool to protect sheep against barber pole
- SC injections at not more than 6 weekly intervals
- Monitor WEC 4-5 weeks after vaccination to assess if drench is needed at next muster
- Breeding worm resistant sheep + grazing management will enhance effectiveness of vaccination
What is anthelmintic resistance
Ability of parasites to survive doses of drugs that would normally kill parasites of the same species and age
How does anthelmintic resistance develop
- Under dosing
- Frequent drenching
- Use of single active drenches
- Persistent anthelmintics
- Ecological interactions with drenching
How to detect anthelmintic resistance
Drench check: WormTest with larval differentiation before and after drench
DrenchTest/WECRT: WEC and larval differentiations of each treatment group are compared with those underenched control group
Total worm count
What are the consequences of drench resistance
Reduces effectiveness of long-term control programs
Reduces ability to treat clinical disease
How to manage drench resistance
- Regular drench resistance testing
- Use combination products
- Do not under dose
- Use short acting products
- Quarantine drench to any introduced sheep
- Develop an effective worm control program
- Maintain a proportion of the worm population in refugia
Explain a quarantine drench
- Avoids bringing drench-resistance strains onto a farm
- Use a combination of minimum 4 unrelated drench active with at least of these being the newest drench activity: monepantel or derquantel +/- liver fluke treatment
- Hold sheep in secure quarantine paddocks
- Perform WormTest 14 days after drenching
What is integrated parasite management
- The right drench at the right time
- Paddock/grazing management
- Use Barbervax vaccine for Barberpole worm
- Maintain good nutrition
- Flock and weaner management
- Worm resistant sheep
- Biological control
- Fine-tuning based on sound information
How to prepare a low worm risk paddock
Allow time for most of the existing work eggs and larvae to die
Prevent more worms contaminating pastures
What are the tactical and strategical treatments
- Curative drench
- If severe clinical signs
- Highly effective drench needed + more sheep to safer pasture if possible - Tactical drench
- Short term response to overt or imminent outbreaks of pasasitism, based on WEC - Strategic drench
- Effect levels of pasture contamination later in the season for the benefit of the whole mob +/- immediate production benefit
What is strategic drenching
Summer drenching program: - 1st summer drench: Nov/Dec - Monitor WEC in Jan/Feb - 2nd summer drench: feb Weaning drench - Drench and wean at 14 weeks after lambing + move to weaning paddock
What are the acute signs of fasciola hepatica
- Severe liver damage
- Found dead in the paddock
- Most common in young sheep in summer and early autumn
What are the subacute signs of fasciola hepatica
- Jaundice, ill-thrift, anaemia and possible death after certain weeks
What are the chronic signs of fasciola hepatica
- Mature flukes in bile ducts +/- immature flukes in the liver
- Illthrift, anorexia, anaemia, bottle jaw
- Most common in adult sheep in winter
What are the subclinical signs of fasciola hepatica
Reduced wool production and body growth
What is Black disease
- Clostridium novae type B
- Most common in summer and early autumn
- Rapid course of disease
How to treat fasciola hepatica
Grazing management
Flukicides: triclabendazole, closantel, abendazole
How are sheep infected with tape worm
Faecal-oral route - needs and intermediate host -> free living pasture mites
