Internal parasite control in sheep

1
Internal parasite control in sheep

• Fewer worms
• More dollars

2
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.

3
Outline

• Setting the scene
• Types of internal parasites
• Parasite damage to sheep
• Introduction to WormBoss
• Worm egg counting
• Drench resistance

4
Setting the scene

• Worms cost the Australian sheep industry 369M/yr
• This could increase to 700M by 2010
• drench resistance
• more production losses

5
Figure 1. National cost (million) of major sheep
health issues in Australia. (Source Holmes et
al. 2006)
6
Types of internal parasites

1. Strongyles or Round worms
2. Cestodes or Tapeworms
3. Trematodes or Liver flukes

7
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

8
Round worms and site of infection
Site Round worm scientific name Round worm common name
Abomasum Haemonchus contortus Teladorsagia circumcincta Trichostrongylus axei Barbers Pole Brown Stomach Stomach Hair
Small intestine Trichostrongylus colubriformis Trichostrongylus vitrinus Nematodirus spathiger Cooperia curticei Bunostomum trigonocephalum Strongyloides papillosus Black Scour Black Scour Thin Necked Intestinal Small Intestinal Hook Worm Strongyloides
Large intestine Trichuris ovis Oesophagostomum columbianum Oesophagostomum venulosum Chabertia ovina Whip Worm Nodule Worm Large Bowel Large Mouthed Bowel
Lungs Dictyocaulus filaria Muellerius capillaries Large Lung Small Lung
(Source Cole 1980)
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Life cycle of round worms
(Source Cole 1980)
10
Epidemiology

• 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

11
Tape worms (Cestodes)

• Most common/important species
• Moniezia
• live in intestines
• no known ill effects
• Echinococcus
• Taenia

12
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

13
Parasite damage to sheep

• Tissue damage
• Competition for protein
• Appetite reduction
• Scouring
• Anaemia (Barbers Pole)

(Sourcewww.dpiw.tas.gov.au )
14
Overall production effects

• Parasites will cause a reduction in
• fertility
• milking ability
• meat production
• wool production
• wool soundness
• immunity

15
Introduction to WormBoss

• Developed by Sheep CRC and AWI
• www.wormboss.com.au
• Recommendations
• monitor worm populations
• regular drench resistance tests
• use non-chemical management strategies
• if unsure, seek professional advice

16
Exercise 1 Using WormBoss

• www.wormboss.com.au
• 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

17
Worm egg counting

• Number of worm eggs in a sample of sheep dung -
  eggs per gram (epg)
• Cant distinguish between different round worm
  species strongyle eggs
• More accurate than visual assessment

18
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

19
View of worm eggs
(Source WormBoss website, Dr R Woodgate)
20
Worm egg typing

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

(Source WormBoss website, Dr R Woodgate)
21
Exercise 2 Worm Egg Count Test

• Aim of procedure
• Materials
• including use and care of microscopes
• Method
• Counting
• Calculations
• Interpreting results

22
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
• Dont allow microscope head to come in contact
  with slide
• Rest eyes regularly
• Always clean immediately after use

23
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

24
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

25
Egg identification (page 1)
26
Egg identification (page 2)
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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

28
Interpretation of FEC test results

• www.wormboss.com.au
• 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

29
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

30
Factors influencing development of drench
resistance

• Chemical group and persistency of the product
  involved
• Frequency of treatments
• Worm species involved
• Environmental factors

31
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

32
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

33
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)

34
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

35
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

36
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

37
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
38

• www.wormboss.com.au