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Internal parasite control in sheep. Fewer worms More dollars. Course aim. Monitor and manage sheep worm populations to improve production, by: Using worm egg counts to detect infestations early. Becoming competent at the faecal egg count test. Regular drench resistance tests.

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internal parasite control in sheep

Internal parasite control in sheep

Fewer worms

More dollars

course aim
Course aim

Monitor and manage sheep worm populations to improve production, by:

  • Using worm egg counts to detect infestations early.
  • Becoming competent at the faecal egg count test.
  • Regular drench resistance tests.
  • Use of WormBoss in decision making.
  • Setting the scene
  • Types of internal parasites
  • Parasite damage to sheep
  • Introduction to WormBoss
  • Worm egg counting
  • Drench resistance
setting the scene
Setting the scene
  • Worms cost the Australian sheep industry $369M/yr
  • This could increase to $700M by 2010
    • drench resistance
    • more production losses
figure 1 national cost million of major sheep health issues in australia source holmes et al 2006
Figure 1. National cost ($million) of major sheep health issues in Australia. (Source: Holmes et al. 2006)
types of internal parasites
Types of internal parasites
  • Strongyles or Round worms
  • Cestodes or Tapeworms
  • Trematodes or Liver flukes
round worms strongyles
Round worms (Strongyles)
  • Major cause of production losses in sheep
  • Summer dominant rainfall
    • Barbers Pole
    • Black Scour
  • Winter dominant rainfall
    • Brown Stomach
    • Black Scour
    • Lung worms
life cycle of round worms
Life cycle of round worms

(Source: Cole1980)

  • Temperature and moisture are critical for the survival of worm eggs and larvae
  • Round worms require avg. daily temp. of 10oC and 50% humidity (50 – 75mm) to hatch
  • Except Barbers Pole – temp. above 15oC
tape worms cestodes
Tape worms (Cestodes)
  • Most common/important species
    • Moniezia
      • live in intestines
      • no known ill effects
    • Echinococcus
    • Taenia
liver flukes trematodes
Liver flukes (Trematodes)
  • Only species in sheep is Fasciola hepatica
  • Complex life cycle and has a fresh water snail as an intermediate host
  • Live in bile ducts of liver
parasite damage to sheep
Parasite damage to sheep
  • Tissue damage
  • Competition for protein
  • Appetite reduction
  • Scouring
  • Anaemia (Barbers Pole)

( )

overall production effects
Overall production effects

Parasites will cause a reduction in:

  • fertility
  • milking ability
  • meat production
  • wool production
  • wool soundness
  • immunity
introduction to wormboss
Introduction to WormBoss
  • Developed by Sheep CRC and AWI
  • Recommendations:
    • monitor worm populations
    • regular drench resistance tests
    • use non-chemical management strategies
    • if unsure, seek professional advice
exercise 1 using wormboss
Exercise 1 – Using WormBoss
  • Select “know your worms”
  • List major summer and winter rainfall worms
  • Select one worm from each rainfall group and list its scientific and common name, distribution, location in sheep and affects on sheep
worm egg counting
Worm egg counting
  • Number of worm eggs in a sample of sheep dung - “eggs per gram” (epg)
  • Can’t distinguish between different round worm species “strongyle eggs”
  • More accurate than visual assessment
worm egg counting1
Worm egg counting
  • Useful to decide:
    • if treatment is necessary
    • if previous treatments were effective
    • assess level of worm contamination being put into paddocks
    • which sheep are worm resistant
view of worm eggs
View of worm eggs

(Source: WormBoss website, Dr R Woodgate)

worm egg typing
Worm egg typing
  • Larval culture and differentiation is required to differentiate between different worm species

(Source: WormBoss website, Dr R Woodgate)

exercise 2 worm egg count test
Exercise 2 – Worm Egg Count Test
  • Aim of procedure
  • Materials
    • including use and care of microscopes
  • Method
  • Counting
  • Calculations
  • Interpreting results
use and care of microscopes
Use and care of microscopes
  • Start at lowest magnification
  • Rotate the focus wheel so you know which direction lowers/raises microscope
  • Focus using coarse focus first, then fine tune
  • Don’t allow microscope head to come in contact with slide
  • Rest eyes regularly
  • Always clean immediately after use
wec test method
WEC test method
  • Weigh 2g faeces from each sample into mixing bowl
  • Add 60ml of saturated salt solution and mix
  • Pour through strainer to remove course material
  • Stir in a N-S E-W motion before allowing material to flow into pipette
  • Moisten counting chambers of slide
  • Fill the slide chambers from right to left and with the slide verandah facing away from operator
  • Allow about 1 min. between preparation and counting for eggs to float to top of slide
counting the faecal eggs
Counting the faecal eggs
  • See Egg Identification Sheet to identify different worm egg species
  • Place slide on microscope with verandah facing away from operator, use fine focus knob to focus slide
  • Begin counting using lines as a guide
  • For each sample, count and record number of eggs seen for each species

The images on this page were sourced from:





2. Haemonchus (Barbers Pole worm)

1. Trichostrongylus (Black scour worm)

4. Moniezia (Tapeworm)

3. Coccidia

Egg identification (page 1)


5. Trichuris (Whipworm)

6. Nematodirus (Thin necked Intestinal worm)

9. Dictyocaulus (Lungworm)

7. Fasciola (Liver Fluke)

The images on this page were sourced from:





Egg identification (page 2)

calculation for fec test
Calculation for FEC test

Number of eggs/gram of faeces =

number of eggs counted x total volume of mix (ml)

volume of counting chamber (ml) x wt of faeces in mix

interpretation of fec test results
Interpretation of FEC test results

  • Click on “Ask the Boss” and read
  • Click on “Consult the Boss” and follow the prompts
  • A report will be generated based on the information you enter
drench resistance
Drench resistance
  • Essential to know to be able to effectively manage worms
  • Occurs once worms can survive a dose of a drench that would have previously killed them
  • Measured by a Faecal Egg Count Reduction Test (FECRT)
  • Accepted industry definition = a reduction in worm egg count of less than 95%
factors influencing development of drench resistance
Factors influencing development of drench resistance
  • Chemical group and persistency of the product involved
  • Frequency of treatments
  • Worm species involved
  • Environmental factors
how common is drench resistance
How common is drench resistance?
  • Widespread, probably 90% or more of farms have a problem
  • Sheep worms have evolved resistance fairly quickly to each new drench group
drench resistance testing
Drench resistance testing
  • Essential to know the efficacy of drenches on your property
  • Assessed through a Faecal Egg Count Reduction Test (FECRT)
  • Should be conducted every 2 years
exercise 3 setting up a fecrt
Exercise 3 – Setting up a FECRT
  • Select appropriate sheep
    • young, wormy and undrenched
    • at least 12 weeks old
  • Do a worm egg count
    • collect dung samples from min. 10 sheep
    • samples tested for enough worm species (min. 300 epg)
setting up a fecrt
Setting up a FECRT
  • Decide drenches to test
    • seek professional advice
    • depends on previous test results and property drench history
  • Set up test groups
    • at least 15 sheep in each group plus one control (undrenched) group
    • ID each group
setting up a fecrt1
Setting up a FECRT
  • Drench each group
    • drench each group with correct drench
    • make sure:
      • no cross contamination of drenches
      • control group not drenched
      • correct drenching technique used
  • Return sheep to paddock together
setting up a fecrt2
Setting up a FECRT
  • Collect faecal samples for worm egg counting
    • 10-14 days after initial treatment collect 10 fresh faecal samples from each group including the control group
    • obtain a larval culture and differentiation on samples from each group
setting up a fecrt3
Setting up a FECRT
  • Interpreting results
    • compare average no. of faecal eggs in each sheep group with that of the control
    • Fully effective drench = 95% worm egg reduction in relation to undrenched control group

% efficacy = (control – treatment) / control x 100