s118-119 internal parasites
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COMMONWEALTH OF AUSTRALIA
Copyright Regulations 1969
WARNING
This material has been reproduced and communicated to you by or
on behalf of the University of Melbourne pursuant to Part VB of the
Copyright Act 1968 (the Act).
The material in this communication may be subject to copyright under
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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
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Control of parasites of sheep
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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Control of parasites of sheep
Seasonal variationin parasite numbers
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Control of parasites of sheep
Seasonal pattern of
mortality in weaner
sheep
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Control of parasites of sheep
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
Control of parasites of sheep
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Control of parasites of sheep
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
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Control of parasites of sheep
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
Control of parasites of sheep
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Control of parasites of sheep
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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Control of parasites of sheep
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Control of parasites of sheep
"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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Control of parasites of sheep
seasonal changes in worm
burdens & egg counts
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Control of parasites of sheep
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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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Control of parasites of sheep
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Control of parasites of sheep
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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
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Control of parasites of sheep
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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Control of parasites of sheep
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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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Control of parasites of sheep
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Control of parasites of sheep
Smart Drenching
abomasum/ rumen
solid line -abomasal admin
dotted line - rumen
reducing food intake
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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
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Control of parasites of sheep
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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Control of parasites of sheep
Nematophagous fungi
Duddingtonia flavescens nematode
trapping hyphae
spore
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Control of parasites of sheep Smart Grazing experiment
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Control of parasites of sheep
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
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Control of parasites of sheep Smart Grazing
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blue line - conventional grazing
red line - Smart Grazing
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Control of parasites of sheep
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
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Control of parasites of sheepMANAGEMENT OF RESISTANCE
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Control of parasites of sheep
"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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