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

• Strongyles or Round worms
• Cestodes or Tapeworms
• 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
(Source Cole 1980)
9
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)
27
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