S118-119 Internal parasites

8/14/2019 S118-119 Internal parasites

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COMMONWEALTH OF AUSTRALIA

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Control of parasites of sheep

Important parasites

Winter rainfall areas Summer rainfall areas

1. [Haemonchus contortus ] Haemonchus contortus

2. Trichostrongylus spp. Trich. colubriformis

[ Trich. axei ]

3. Ostertagia circumcincta

4. Nematodirus spp ( in lambs )

Other parasites:

Oesophagostomum venulosum

Chabertia ovina

Trichuris ovis

ictyocaulus filaria

PARASITES OF SHEEP

Nasal cavity

Oestrus ovisLungsDictyocaulus filariaProtostrongylus rufescensMuellerius capillarisEchinococcus granulosus

OesophagusGongylonema pulchrum

Rumen

Calicophoron calicophorumParamphistomum ichakawaiCeylonocotyle streptocoeliumGongylonema verrucosum

AbomasumHaemonchus contortusOstertagia circumcinctaTrichostrongylus axei

Small intestineImmature paramphistomes***Moniezia expansa, benedeniTrichostrongylus colubriformis, rugatus, vitrinusNematodirus spathiger, filicollis, abnormalis(Cooperia spp.)Strongyloides papillosusBunostomum trigonocephalum

Eimeria spp.

Large intestineTrichuris ovis, skrjabiniOesophagostomum venulosum, columbianumChabertia ovina

LiverFasciola hepatica

Echinococcus granulosus

Copyright of the University of Melbourne - Faculty of Veterinary Science 2008


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EXTENT OF PROBLEM:

Detailed analysis in 1989 put costs at $5,000 per farm per year

Production losses at sites in South Australia :

Site Kybybolite Turretfield Minnipa

(SE near Vic border) (N of Adelaide) (West Coast)

Rainfall (mm) 700 500 350

_____________________________________________________

Deaths (%) 22-56* 0 0

Bodyweight loss (%) 9-58* 12 13

Wool cut (%) 28 18 4

_____________________________________________________

* annual variation



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Seasonal variationin parasite numbers



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Seasonal pattern of

mortality in weaner

sheep



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variation in worm burdens between years



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FACTORS AFFECTING NUMBERS OF LARVAE ONPASTURE :

(winter rainfall areas)

Summer too hot and dry for development

Autumn "break" provides moisture

Low winter temperatures only affect a few species(eg T. colubriformis,H. contortus)

Grass short during winter, closely grazed

In spring pasture growth "dilutes larvae"

In late spring, rising temperatures limit survival




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AUTUMN CONTAMINATION AND SUMMER SURVIVAL

Parasites used : Trichostrongylus spp.Turretfield, SA, 1 m2 plots, faeces with 100,000 eggs

No. of larvae/kg of pasture in plot______________________________________________Plot no. 1 2 3 4

Dec ContaminatedJan 0Feb 0March 0 ContaminatedApril 0 0May 0 0June 0 45,900 ContaminatedJuly 0 17,500 830Aug 0 1,400 1,500Sept 0 750 400 ContaminatedOct 0 0 100 2,600Nov 0 0 0 640Dec 0 0 0 420

Jan 0 0 0 100Feb 0 0 0 0_______________________________________________

Survival over summer varies with type of experiment andlocationAutumn break critical

Surviving larvae called a "refugium"Patterns are basis for timing of chemical treatments


C l f i f h


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OPTIONS FOR CHEMICAL CONTROL

1. No treatment

2. Monthly treatment ( PPP= 21 days )

Produce more wool - may be economicallyjustifiable if commodity prices are high

Some treatments will have marginal effect( eg. mid-summer, mid-winter)

Risks with resistance

3. Strategic treatments

at optimum times of year to give maximum control

less pressure on development of resistance (???)

see benefit in gross margins



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Control of parasites of sheepGROSS MARGINS ANALYSIS

Kybybolite, SA 1978/79

Low stocking rate (7.5 / ha)______________________________________________

No treatment Strategic Regular(4 / year) (12 / year)

G M/sheep $ -3.45 3.14 1.60

G M/hectare -25.88 23.55 12.00___________________________________________________

High stocking rate (16 / ha)______________________________________________

No treatment Strategic Regular(4 / year) (12 / year)

G M/sheep $ -10.82 1.12 0.34

G M/hectare -173.12 17.92 5.44___________________________________________________



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CHEMICAL GROUPS AVAILABLE

Broad spectrum anthelmintics

Benzimidazoles

safety margin 20 timeseffective against inhibited larvae

ovicidalresistance widespreadside- resistance occurs

Levamisole/Morantel

peak plasma concn in 30 mins, eliminated in 6 hnot effective against inhibited larvae

not ovicidalsafety margin 5 timesavailable in oral, injectable and pour-on preparationresistance widespread

Macrocyclic lactones

ivermectin, doramectin, eprinomectin, moxidectineffective against inhibited larvaehighly potent, non toxicalso kills many arthropodsmoxidectin has longer persistence intervalside resistance occurs

resistance spreading




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Organophosphates

not in widespread usenot extremely effective alone; useful in combinations

main compound used : naphthalophos

Narrow spectrum anthelmintics

Salicylanilidesmain compound used : closantelbinds to plasma proteins; persists for 6 weeksonly kills blood-feeding nematodes (Haemonchus)resistance present in New England area



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Control of parasites of sheep DRENCHES IN WINTER RAINFALL AREAS

Most efficient treatment will be when numbers of larvae onpasture are at a minimum ie summer

"First summer drench"

aim is to minimise contamination of pasture from late springgiven when intake of larvae ceasestiming variable depending upon regiondrying off of pastures a good guide

some larvae persist on dry pasturein areas with late or no drying off, give in Dec

"Second summer drench"

aim is to remove any larvae picked up after first drench

and thereby to have minimum contamination during autumn

optimum time is about 6 weeks before breaktherefore beginning of Feb is besthowever autumn break is unpredictable

"Summer drenching" strategy well known, but farmers may havery broad interpretation of "summer"

in lower rainfall areas, single summer drench may be sufficienttest with FEC before drenching in Feb"bulk" count adequate

highly effective summer drenches may facilitate developmentof resistance




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"Wet years"

if summers are wet, summer drenching strategiesmay fail

at Hamilton, over 25 years, number of drenchesneeded varied from 0 to 5

can determine number of drenches by monitoringwith FECs following autumn break

FEC indicates rate at which pasture is beingcontaminated - future levels of larval intake

give additional drench if FEC > 150 epg

different to "diagnostic" procedures in which FECsof >500 epg indicate pathogenic burdens

spontaneous reductions in FEC during winterbecause of host immunity may complicatemonitoring procedures

above problem can be identified by removing to

clean paddock (or use capsules)




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seasonal changes in worm

burdens & egg counts




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Control of parasites of sheepLAMBING DRENCHES

Periparturient rise in faecal egg countsdue to:maturation of inhibited larvae

more fecund female nematodesingested larvae develop to adults

in spring lambing systems, no additional treatments needed

in autumn lambing systems, prelambing treatment of ewes is

beneficial

make sure lambs are weaned as early as possible

no justification (usually) for treatment at marking

WEANER DRENCHES

drenching at weaning is a standard practice

weaners must be moved to a clean paddock

careful preparation of weaner paddock essential

ADULT DRY SHEEP

should need only 2 summer drenches



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p p

CAPSULES

devices which lodge in rumen and releaseanthelmintic for 90 days

usually contain albendazole or ivermectin

sustained release of albendazole will removesignificant proportion of BZ resistant nematodes

Possible uses :

1. at first summer drench - eliminates needfor 2nd drench

2. at second summer drench - eliminates needfor FEC monitoring after break

3. "salvage" situations4. scouring with negative egg counts

Principal limitation : cost


C t l f it f h


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Control ofHaemonchus

no published data for southeastern Australia

main periods of larval availability : autumn & spring

tends to affect lambing ewes in autumn and lambs inspring

use closantel with first summer drench

mixtures of closantel and BZ (Closal) are available

otherwise have to use closantel and broad spectrumseparately

usually, if broad spectrum drench is effective, this issufficient

in severe cases may also need closantel at second summerdrench




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"SMART DRENCHING"

techniques to improve efficacy of existing

drugs

1. making sure drug is delivered into rumen, not intoabomasum - technique of administration

2. restricting food intake for 12 hours alters peak plasmaconcentrations and persistence in body -increases killing period for drug




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Smart Drenching

abomasum/ rumen

solid line -abomasal admin

dotted line - rumen

reducing food intake


C l f i f h


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Control of parasites of sheep NON-CHEMICAL CONTROL

Pasture spelling - best over summerof little use after autumn breakless effective aga instNematodirus

Cropping/ stubbles

Other species

cattle - good except for T. axeihorseskangaroos

Dry sheep have lowest egg outputscan be used to "clean" up paddockscan monitor FEC

Vaccines developed forHaemonchus

Nematode trapping fungi Duddingtonia

Selection of resistant sheep "Nemesis"selected on the basis of FEC

FEC is heritablecross resistance between all generaindependent of wool and body traitscannot select on dag score -

independent of FECestimated to be able to drop one

drench after 9-13 yea rs of selection


C t l f it f h


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Selection of resistant sheep - Nemesis

Selection for resistance

toHaemonchus

upper line - controls

lower line - selected sheep

no of generationsCopyright of the University of Melbourne - Faculty of Veterinary Science 2008



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Nematophagous fungi

Duddingtonia flavescens nematode

trapping hyphae

spore


Control of parasites of sheep Smart Grazing experiment


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SD1 SD2

mart

razing

37 wethers/ha

Nov Dec Jan Feb Mar

SD1 SD2

tandard15 wethers/ha

Nov Dec Jan Feb Mar

Smart Grazing experimentpreparation oflow-risk

pastures


Control of parasites of sheep Smart Grazing


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0

100

200

300

400

500

16-

Mar

30-

Mar

13-Apr

27-Apr

11-May

25-May

8-Jun

22-Jun

6

-Jul

20

-Jul

3-Aug

17-

Aug

31-

Aug

14-

Sep

28-

Sep

12-Oct

26-Oct

199

A

p p g

blue line - conventional grazing

red line - Smart Grazing




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UNIFORM AND SUMMER RAINFALL AREAS

Uniform rainfalluse two summer drench system plus FECmonitoring

Irrigated pasturesno data availableuse same system as above

Summer rainfall

different nematode generaHaemonchus of overwhelming importancelarval availability reverse of southern areaHaemonchus hypobiotic over wintertreatments are closantel in September,December and if need be, Februarycombine with broad spectrum for other geresistance a looming problem


Control of parasites of sheepMANAGEMENT OF RESISTANCE


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"Generic" programs assume no resistance

Determine resistance status on individual properties using:

faecal egg count reduction testcommercial Drenchrite test

Estimates of levels of resistance in Victoria:BZ 93%

LEV 76%BZ+LEV 47%OP ?0%ML ? low

Annual rotations

various combinations of BZ/LEV/OP - ML

Mixtures

BZ+OP LEV+OP ML+?

Incoming sheepBZ + LEV + ML

Grazing management/ flock structure

Partial treatment of flock - refugiumCopyright of the University of Melbourne - Faculty of Veterinary Science 2008


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Computer models : effects of type

of resistance and droughtsComputer models : effects of (a) number

of treatments, (b) efficacy and (c) rotation

versus combinationCopyright of the University of Melbourne - Faculty of Veterinary Science 2008



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p pCASE HISTORY

Farm profile : 1500 ha; winter rainfall, 600 mm.4000 ewes, 3000 weaners

Hay-making enterprise from November-December;has no time for sheep

Lambs in April, weans in JulyDrenches ewes and lambs at marking, then lambs only at

Drenches weaners in September and November;busy during November-December with hay;drenches all sheep in January and April;uses LEV in January and April and BZ for rest of year

Results of drench resistance test:

Controls: 360, 120, 200, 360, 320, 280, 40, 200, 200, 240(mean = 232)

BZ: 240, 40, 0, 200, 360, 320, 240, 160, 0, 240 (180)LEV: 40, 200, 320, 0, 40, 160, 80, 0, 120, 80 (104)2xLEV: 0,0,0,0,40,0,0,240,80,40 (40)

BZ+LEV: 0,0,0,0,0,0,80, 0,40,0 (12)ML: 0,0,0,0,0,40,0,0,0,0 (4)

reductions:BZ 22%LEV 55%2 x LEV 83%BZ+LEV 95%ML 98%


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S118-119 Internal parasites