Internal parasite control in sheep

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Internal parasite control in sheep

Fewer worms

More dollars

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Course aim

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

1. Using worm egg counts to detect infestations early.

2. Becoming competent at the faecal egg count test.

3. Regular drench resistance tests.

4. Use of WormBoss in decision making.

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Outline

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

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Setting the scene

Worms cost the Australian sheep industry $369M/yr

This could increase to $700M by 2010

drench resistance

more production losses

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Figure 1. National cost ($million) of major sheep health issues in Australia. (Source: Holmes et al. 2006)

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Types of internal parasites

1. Strongyles or Round worms

2. Cestodes or Tapeworms

3. Trematodes or Liver flukes

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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

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Round worms and site of infectionSite Round worm scientific name Round worm common name

Abomasum

Haemonchus contortusTeladorsagia circumcinctaTrichostrongylus axei

Barbers PoleBrown StomachStomach Hair

Small intestine

Trichostrongylus colubriformisTrichostrongylus vitrinusNematodirus spathiger Cooperia curticeiBunostomum trigonocephalumStrongyloides papillosus

Black ScourBlack ScourThin Necked IntestinalSmall IntestinalHook WormStrongyloides

Large intestine

Trichuris ovisOesophagostomum columbianumOesophagostomum venulosumChabertia ovina

Whip WormNodule WormLarge BowelLarge Mouthed Bowel

LungsDictyocaulus filariaMuellerius capillaries

Large LungSmall Lung

(Source: Cole 1980)

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Life cycle of round worms

ADULT

3rd larval stage

2nd larval stage

1st larval stage

EGG

4th larval stage 21 days

Sheep phase

Pasture phase

1-21 days

(Source: Cole 1980)

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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

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Tape worms (Cestodes)

Most common/important species Moniezia

live in intestinesno known ill effects

Echinococcus Taenia

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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

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Parasite damage to sheep

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

(Source:www.dpiw.tas.gov.au )

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Overall production effects

Parasites will cause a reduction in: fertility

milking ability

meat production

wool production

wool soundness

immunity

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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

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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

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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

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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

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View of worm eggs

(Source: WormBoss website, Dr R Woodgate)

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Worm egg typing

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

(Source: WormBoss website, Dr R Woodgate)

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Exercise 2 – Worm Egg Count Test

Aim of procedure Materials

– including use and care of microscopes

Method Counting Calculations Interpreting results

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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

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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

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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

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Egg identification (page 1)

3. Coccidia

1. Trichostrongylus (Black scour worm)

4. Moniezia (Tapeworm)

2. Haemonchus (Barbers Pole worm)

The images on this page were sourced from:1. www.stanford.edu/class/humbio103/ParaSites2005/Trichostrongyliasis/agent.htm2. www.sheepandgoat.com/HairSheepWorkshop/parasitism.html3. commons.wikimedia.org/wiki/Image:Coccidia.JPG4. www.medata-systems.co.uk

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7. Fasciola (Liver Fluke)

5. Trichuris (Whipworm) 6. Nematodirus (Thin necked Intestinal worm)

9. Dictyocaulus (Lungworm)

The images on this page were sourced from:5. w3.ufsm.br/parasitologia/arquivospagina/ovosdebovinos.htm6. www.stanford.edu/class/humbio103/ParaSites2005/Trichostrongyliasis/agent.htm7. cal.vet.upenn.edu/projects/parasit06/website/lab6.htm8. www.medicalvetonline.com.br/atlas.php

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

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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

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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%

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Factors influencing development of drench resistance

Chemical group and persistency of the product involved

Frequency of treatments

Worm species involved

Environmental factors

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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

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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

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Exercise 3 – Setting up a FECRT

1. Select appropriate sheep − young, wormy and undrenched− at least 12 weeks old

2. Do a worm egg count− collect dung samples from min. 10 sheep− samples tested for enough worm species

(min. 300 epg)

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3. Decide drenches to test − seek professional advice− depends on previous test results and

property drench history

4. Set up test groups− at least 15 sheep in each group plus one

control (undrenched) group− ID each group

Setting up a FECRT

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Setting up a FECRT

5. Drench each group − drench each group with correct drench− make sure:

• no cross contamination of drenches• control group not drenched • correct drenching technique used

6. Return sheep to paddock together

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Setting up a FECRT

7. 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

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Setting up a FECRT

8. 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

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www.wormboss.com.au