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 the Act. Any further copying or communication of this material by you may be the subject of copyright protection under the Act. Do not remove this notice.
Control of parasites of sheep PARASITES OF SHEEP
Important parasites
Winter rainfall areas
Summer rainfall areas
1.
[ Haemonchus contortus ]
Haemonchus contortus
2.
Trichostrongylus spp.
Trich. colubriformis
[ Trich. axei ] 3. 4.
Ostertagia circumcincta Nematodirus spp ( in lambs )
Other parasites: Oesophagostomum venulosum Chabertia ovina
Nasal cavity Oestrus ovis Lungs Dictyocaulus filaria Protostrongylus rufescens Muellerius capillaris Echinococcus granulosus Oesophagus Gongylonema pulchrum Rumen Calicophoron calicophorum Paramphistomum ichakawai Ceylonocotyle streptocoelium Gongylonema verrucosum Abomasum Haemonchus contortus Ostertagia circumcincta Trichostrongylus axei Small intestine Immature paramphistomes*** Moniezia expansa, benedeni Trichostrongylus colubriformis, rugatus, vitrinus Nematodirus spathiger, filicollis, abnormalis (Cooperia spp.) Strongyloides papillosus Bunostomum trigonocephalum Eimeria spp. Large intestine Trichuris ovis, skrjabini Oesophagostomum venulosum, columbianum Chabertia ovina Liver
Trichuris ovis Dictyocaulus filaria Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Fasciola hepatica Echinococcus granulosus
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 (%)
18
4
28
_____________________________________________________ * annual variation
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
Seasonal variation in parasite numbers
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
Seasonal pattern of mortality in weaner sheep
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
variation in worm burdens between years
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
FACTORS AFFECTING NUMBERS OF LARVAE ON PASTURE :
(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
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
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 Contaminated Jan 0 Feb 0 Contaminated March 0 April 0 0 May 0 0 June 0 45,900 Contaminated July 0 17,500 830 Aug 0 1,400 1,500 Contaminated Sept 0 750 400 Oct 0 0 100 2,600 Nov 0 0 0 640 Dec 0 0 0 420 Jan 0 0 0 100 Feb 0 0 0 0 _______________________________________________ Survival over summer varies with type of experiment and location Autumn break critical Surviving larvae called a "refugium" Patterns are basis for timing of chemical treatments Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep OPTIONS FOR CHEMICAL CONTROL
1. No treatment
2. Monthly treatment ( PPP= 21 days ) Produce more wool - may be economically justifiable 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
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
GROSS 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 ____________________________________________________ Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep CHEMICAL GROUPS AVAILABLE Broad spectrum anthelmintics Benzimidazoles safety margin 20 times effective against inhibited larvae ovicidal resistance widespread side- resistance occurs Levamisole/Morantel peak plasma concn in 30 mins, eliminated in 6 h not effective against inhibited larvae not ovicidal safety margin 5 times available in oral, injectable and pour-on preparations resistance widespread Macrocyclic lactones ivermectin, doramectin, eprinomectin, moxidectin effective against inhibited larvae highly potent, non toxic also kills many arthropods moxidectin has longer persistence interval side resistance occurs resistance spreading
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
Organophosphates not in widespread use not extremely effective alone; useful in combinations main compound used : naphthalophos
Narrow spectrum anthelmintics Salicylanilides main compound used : closantel binds to plasma proteins; persists for 6 weeks only kills blood-feeding nematodes (Haemonchus) resistance present in New England area
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
DRENCHES IN WINTER RAINFALL AREAS Most efficient treatment will be when numbers of larvae on pasture are at a minimum ie summer "First summer drench" aim is to minimise contamination of pasture from late spring given when intake of larvae ceases timing variable depending upon region drying off of pastures a good guide some larvae persist on dry pasture in 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 break therefore beginning of Feb is best however autumn break is unpredictable
"Summer drenching" strategy well known, but farmers may hav very broad interpretation of "summer" in lower rainfall areas, single summer drench may be sufficient test with FEC before drenching in Feb "bulk" count adequate highly effective summer drenches may facilitate development of resistance Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep "Wet years" if summers are wet, summer drenching strategies may fail at Hamilton, over 25 years, number of drenches needed varied from 0 to 5 can determine number of drenches by monitoring with FECs following autumn break FEC indicates rate at which pasture is being contaminated - future levels of larval intake give additional drench if FEC > 150 epg different to "diagnostic" procedures in which FECs of >500 epg indicate pathogenic burdens spontaneous reductions in FEC during winter because of host immunity may complicate monitoring procedures above problem can be identified by removing to clean paddock (or use capsules) Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
seasonal changes in worm burdens & egg counts
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
LAMBING DRENCHES Periparturient rise in faecal egg counts due to: maturation of inhibited larvae more fecund female nematodes ingested 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 Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
CAPSULES
devices which lodge in rumen and release anthelmintic for 90 days usually contain albendazole or ivermectin sustained release of albendazole will remove significant proportion of BZ resistant nematodes Possible uses : 1. at first summer drench - eliminates need for 2nd drench 2. at second summer drench - eliminates need for FEC monitoring after break 3. "salvage" situations 4. scouring with negative egg counts Principal limitation : cost
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep Control of Haemonchus
no published data for southeastern Australia main periods of larval availability : autumn & spring tends to affect lambing ewes in autumn and lambs in spring use closantel with first summer drench mixtures of closantel and BZ (Closal) are available otherwise have to use closantel and broad spectrum separately usually, if broad spectrum drench is effective, this is sufficient in severe cases may also need closantel at second summer drench
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
"SMART DRENCHING" techniques to improve efficacy of existing drugs
1. making sure drug is delivered into rumen, not into abomasum - technique of administration
2. restricting food intake for 12 hours alters peak plasma concentrations and persistence in body increases killing period for drug
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
Smart Drenching abomasum/ rumen
solid line -abomasal admin dotted line - rumen
reducing food intake
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
NON-CHEMICAL CONTROL
Pasture spelling -
best over summer of little use after autumn break less effective aga inst Nematodirus
Cropping/ stubbles Other species cattle - good except for T. axei horses kangaroos Dry sheep
have lowest egg outputs can be used to "clean" up paddocks can monitor FEC
Vaccines
developed for Haemonchus
Nematode trapping fungi
Duddingtonia
Selection of resistant sheep "Nemesis" selected on the basis of FEC FEC is heritable cross resistance between all genera independent of wool and body traits cannot select on dag score independent of FEC estimated to be able to drop one drench after 9-13 yea rs of selection
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
Selection of resistant sheep - Nemesis
Selection for resistance to Haemonchus upper line - controls lower line - selected sheep
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
no of generations
Control of parasites of sheep
Nematophagous fungi
Duddingtonia flavescens
nematode trapping hyphae
spore
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Smart Grazing experiment Š preparation of Ōlow-riskÕ pastures
Control of parasites of sheep
SD1
SD2
Smart
37 wethers/ha
Grazing Nov Dec Jan Feb Mar
SD1
SD2
StandardÕ
15 wethers/ha Nov Dec Jan Feb Mar
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Smart Grazing
Control of parasites of sheep
500 400 300 200 100
A
1999
blue line - conventional grazing red line - Smart Grazing
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
26-Oct
12-Oct
28-Sep
14-Sep
31-Aug
17-Aug
3-Aug
20-Jul
6-Jul
22-Jun
8-Jun
25-May
11-May
27-Apr
13-Apr
30-Mar
16-Mar
0
Control of parasites of sheep UNIFORM AND SUMMER RAINFALL AREAS
Uniform rainfall use two summer drench system plus FEC monitoring Irrigated pastures no data available use same system as above Summer rainfall different nematode genera Haemonchus of overwhelming importance larval availability reverse of southern areas Haemonchus hypobiotic over winter treatments are closantel in September, December and if need be, February combine with broad spectrum for other gen resistance a looming problem
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
MANAGEMENT OF RESISTANCE
Control of parasites of sheep "Generic" programs assume no resistance Determine resistance status on individual properties using: faecal egg count reduction test commercial 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 -
Mixtures BZ+OP LEV+OP
ML+?
Incoming sheep BZ + LEV + ML Grazing management/ flock structure Partial treatment of flock - refugium
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
ML
Computer models : effects of type of resistance and droughts
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Computer models : effects of (a) number of treatments, (b) efficacy and (c) rotation versus combination
Control of parasites of sheep
CASE 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 July Drenches 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 LEV 2 x LEV BZ+LEV ML
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
22% 55% 83% 95% 98%
Control of parasites of sheep PARASITES OF SHEEP
Important parasites
Winter rainfall areas
Summer rainfall areas
1.
[ Haemonchus contortus ]
Haemonchus contortus
2.
Trichostrongylus spp.
Trich. colubriformis
[ Trich. axei ] 3. 4.
Ostertagia circumcincta Nematodirus spp ( in lambs )
Other parasites: Oesophagostomum venulosum Chabertia ovina
Nasal cavity Oestrus ovis Lungs Dictyocaulus filaria Protostrongylus rufescens Muellerius capillaris Echinococcus granulosus Oesophagus Gongylonema pulchrum Rumen Calicophoron calicophorum Paramphistomum ichakawai Ceylonocotyle streptocoelium Gongylonema verrucosum Abomasum Haemonchus contortus Ostertagia circumcincta Trichostrongylus axei Small intestine Immature paramphistomes*** Moniezia expansa, benedeni Trichostrongylus colubriformis, rugatus, vitrinus Nematodirus spathiger, filicollis, abnormalis (Cooperia spp.) Strongyloides papillosus Bunostomum trigonocephalum Eimeria spp. Large intestine Trichuris ovis, skrjabini Oesophagostomum venulosum, columbianum Chabertia ovina Liver
Trichuris ovis Dictyocaulus filaria Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Fasciola hepatica Echinococcus granulosus
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 (%)
18
4
28
_____________________________________________________ * annual variation
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
Seasonal variation in parasite numbers
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
Seasonal pattern of mortality in weaner sheep
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
variation in worm burdens between years
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
FACTORS AFFECTING NUMBERS OF LARVAE ON PASTURE :
(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
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
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 Contaminated Jan 0 Feb 0 Contaminated March 0 April 0 0 May 0 0 June 0 45,900 Contaminated July 0 17,500 830 Aug 0 1,400 1,500 Contaminated Sept 0 750 400 Oct 0 0 100 2,600 Nov 0 0 0 640 Dec 0 0 0 420 Jan 0 0 0 100 Feb 0 0 0 0 _______________________________________________ Survival over summer varies with type of experiment and location Autumn break critical Surviving larvae called a "refugium" Patterns are basis for timing of chemical treatments Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep OPTIONS FOR CHEMICAL CONTROL
1. No treatment
2. Monthly treatment ( PPP= 21 days ) Produce more wool - may be economically justifiable 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
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
GROSS 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 ____________________________________________________ Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep CHEMICAL GROUPS AVAILABLE Broad spectrum anthelmintics Benzimidazoles safety margin 20 times effective against inhibited larvae ovicidal resistance widespread side- resistance occurs Levamisole/Morantel peak plasma concn in 30 mins, eliminated in 6 h not effective against inhibited larvae not ovicidal safety margin 5 times available in oral, injectable and pour-on preparations resistance widespread Macrocyclic lactones ivermectin, doramectin, eprinomectin, moxidectin effective against inhibited larvae highly potent, non toxic also kills many arthropods moxidectin has longer persistence interval side resistance occurs resistance spreading
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
Organophosphates not in widespread use not extremely effective alone; useful in combinations main compound used : naphthalophos
Narrow spectrum anthelmintics Salicylanilides main compound used : closantel binds to plasma proteins; persists for 6 weeks only kills blood-feeding nematodes (Haemonchus) resistance present in New England area
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
DRENCHES IN WINTER RAINFALL AREAS Most efficient treatment will be when numbers of larvae on pasture are at a minimum ie summer "First summer drench" aim is to minimise contamination of pasture from late spring given when intake of larvae ceases timing variable depending upon region drying off of pastures a good guide some larvae persist on dry pasture in 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 break therefore beginning of Feb is best however autumn break is unpredictable
"Summer drenching" strategy well known, but farmers may hav very broad interpretation of "summer" in lower rainfall areas, single summer drench may be sufficient test with FEC before drenching in Feb "bulk" count adequate highly effective summer drenches may facilitate development of resistance Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep "Wet years" if summers are wet, summer drenching strategies may fail at Hamilton, over 25 years, number of drenches needed varied from 0 to 5 can determine number of drenches by monitoring with FECs following autumn break FEC indicates rate at which pasture is being contaminated - future levels of larval intake give additional drench if FEC > 150 epg different to "diagnostic" procedures in which FECs of >500 epg indicate pathogenic burdens spontaneous reductions in FEC during winter because of host immunity may complicate monitoring procedures above problem can be identified by removing to clean paddock (or use capsules) Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
seasonal changes in worm burdens & egg counts
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
LAMBING DRENCHES Periparturient rise in faecal egg counts due to: maturation of inhibited larvae more fecund female nematodes ingested 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 Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
CAPSULES
devices which lodge in rumen and release anthelmintic for 90 days usually contain albendazole or ivermectin sustained release of albendazole will remove significant proportion of BZ resistant nematodes Possible uses : 1. at first summer drench - eliminates need for 2nd drench 2. at second summer drench - eliminates need for FEC monitoring after break 3. "salvage" situations 4. scouring with negative egg counts Principal limitation : cost
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep Control of Haemonchus
no published data for southeastern Australia main periods of larval availability : autumn & spring tends to affect lambing ewes in autumn and lambs in spring use closantel with first summer drench mixtures of closantel and BZ (Closal) are available otherwise have to use closantel and broad spectrum separately usually, if broad spectrum drench is effective, this is sufficient in severe cases may also need closantel at second summer drench
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
"SMART DRENCHING" techniques to improve efficacy of existing drugs
1. making sure drug is delivered into rumen, not into abomasum - technique of administration
2. restricting food intake for 12 hours alters peak plasma concentrations and persistence in body increases killing period for drug
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
Smart Drenching abomasum/ rumen
solid line -abomasal admin dotted line - rumen
reducing food intake
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
NON-CHEMICAL CONTROL
Pasture spelling -
best over summer of little use after autumn break less effective aga inst Nematodirus
Cropping/ stubbles Other species cattle - good except for T. axei horses kangaroos Dry sheep
have lowest egg outputs can be used to "clean" up paddocks can monitor FEC
Vaccines
developed for Haemonchus
Nematode trapping fungi
Duddingtonia
Selection of resistant sheep "Nemesis" selected on the basis of FEC FEC is heritable cross resistance between all genera independent of wool and body traits cannot select on dag score independent of FEC estimated to be able to drop one drench after 9-13 yea rs of selection
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Control of parasites of sheep
Selection of resistant sheep - Nemesis
Selection for resistance to Haemonchus upper line - controls lower line - selected sheep
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
no of generations
Control of parasites of sheep
Nematophagous fungi
Duddingtonia flavescens
nematode trapping hyphae
spore
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Smart Grazing experiment Š preparation of Ōlow-riskÕ pastures
Control of parasites of sheep
SD1
SD2
Smart
37 wethers/ha
Grazing Nov Dec Jan Feb Mar
SD1
SD2
StandardÕ
15 wethers/ha Nov Dec Jan Feb Mar
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Smart Grazing
Control of parasites of sheep
500 400 300 200 100
A
1999
blue line - conventional grazing red line - Smart Grazing
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
26-Oct
12-Oct
28-Sep
14-Sep
31-Aug
17-Aug
3-Aug
20-Jul
6-Jul
22-Jun
8-Jun
25-May
11-May
27-Apr
13-Apr
30-Mar
16-Mar
0
Control of parasites of sheep UNIFORM AND SUMMER RAINFALL AREAS
Uniform rainfall use two summer drench system plus FEC monitoring Irrigated pastures no data available use same system as above Summer rainfall different nematode genera Haemonchus of overwhelming importance larval availability reverse of southern areas Haemonchus hypobiotic over winter treatments are closantel in September, December and if need be, February combine with broad spectrum for other gen resistance a looming problem
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
MANAGEMENT OF RESISTANCE
Control of parasites of sheep "Generic" programs assume no resistance Determine resistance status on individual properties using: faecal egg count reduction test commercial 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 -
Mixtures BZ+OP LEV+OP
ML+?
Incoming sheep BZ + LEV + ML Grazing management/ flock structure Partial treatment of flock - refugium
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
ML
Computer models : effects of type of resistance and droughts
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
Computer models : effects of (a) number of treatments, (b) efficacy and (c) rotation versus combination
Control of parasites of sheep
CASE 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 July Drenches 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 LEV 2 x LEV BZ+LEV ML
Copyright of the © University of Melbourne - Faculty of Veterinary Science 2008
22% 55% 83% 95% 98%
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