Sheep drench resistance in Australia – how common?

Stephen LoveVeterinarian/State coordinator-internal parasites

NSW Department of Primary Industries

Australian Sheep Veterinarians Conference, South Australia, 2011

Drench resistance – who cares?

Important because worms are important Even with good IPM, drenches are important

Worms are important because– Economic cost– Animal welfare– Farmer satisfaction (when sheep are healthy)

Stephen Love, 2011

Cost of sheep worms in Australia

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National Cost ($m)

National Cost ($m)

Sackett and others, 2006.Stephen Love, 2011

About 80% of worm cost is production losses…. i.e. ~ invisible

Cost of worms – northern NSW (Kelly)

Gareth Kelly. Studies over 2 years on sheep on farms in northern tablelands, NSW. Cited in Australian Farm Journal, Sept. 2011. (See also Kelly, Kahn, Walkden-Brown. 2010. An Prod Sci 50 1043-1052)

Stephen Love, 2011

Saucy details Sources: Colleagues around Australia Their sources

Older large surveys in AU (1970s-1990s)On-going WECRTs on farmObservations

What we are saying:– Just best-guess estimates of prevalence– ‘Resistance’ generally means <95 WECR%

More details in paper than presented here

Stephen Love, 2011

Collaborators in crime M Lyndal-Murphy, R Nielsen, J Bailey, A Biddle, S Eastwood

S Slattery, L Reid, D Lunau,

T IrwinRB Besier, J

Lyon, R Woodgate

D Lehmann

Many thanks!

P Nilon

D Gardiner, M Rogers, B Edmonstone, J McDonald, W Johnson,

R Templeton, B Watt.

D StarD Salmon, H

Suddes

D HuckerC Haylock

C Trengove, S Ellis

Stephen Love, 2011

Resistance – how fast?Sheep drenches (AUSTRALIA) Released 1st report

resistanceYears

Thibenzole ®

[BZ]

1961 1966 5

Rametin ®

[OP]

1960s 1981 ~20?

Levamisole

[LEV]

1968 1979 11

Closantel 1982 1988 6

Ivomec®

[ML]

1988 1993 5

Cydectin®

[ML]

1995 2001 6

Combinations

- triples and 4-way

[Resistance? Yes!]

Modified from Love, 2011-Primefact-Drench Resistance. BZ=benzimidazoles, OP=organophosphates, LEV=levamisole, ML=macrocyclic lactone; combinations include ML+BZ+LEV+/-Closantel (CLOS)

Stephen Love, 2011

Broad overview of prevalence (AU)% sheep farms with resistance

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BZ LEV BZ-LEV MLs -lowest MLs-highest AADs

•Above graph. Australia-wide thumbnail sketch. (Excl pastoral/arid zones)

•Exceptions e.g. lower prevalence of LEV resistance in Haem.

•All products on market affected except ‘Zolvix’ (and ‘Startect’ –not here yet)

•Even 3- and 4-way combinations in some areas

Modified from Love, 2011-Primefact-Drench Resistance. Zolvix®=monepantel, Startect®=derquantel+abamectin

Stephen Love, 2011

summer rainfall zone (~700mm + pa)

Stephen Love, 2011

New England region of NE NSW + SE Qld

Queensland

New South Wales

Western Australia

South Australia

Summer rainfall zone (Haemonchus-endemic)…

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BZ LEV BZ/LEV ML CLOS

Est prevalence resistance

Haem

Trich

Tel

* Date on graph: indicative only *Prevalence ML resist. Haem: Mox >30% farms (+50%? emerging), IVM: ~ 80+%. * Resist to combos * NAP – reports of resist : Haem (Green , Trich (Le Jambre) + cases with reduced efficacy *CLOS and TCBZ-fluke

* ML (mox) resist Trich (sheep) confirmed Qld (Knox et al).

BZ:benzimidazole, LEV:levamisole, ML:macrocyclic lactone, CLOS:closantel, Haem: Haemonchus contort., Trich:Trichostrongylus sp; Tel: Teladorsagia circum. NAP:naphthalophos; MOX:moxidectin; IVM:ivermectin

Stephen Love 2011

NSW North West Slopes (450-650 mm rain pa)

• similar resistance patterns to higher rainfall summer rain fall zone (New England to the east, but lower prevalence (about half)

•ML resistance not yet detected

Pastoral zones of NSW/Qld (western plains) (<400 mm)

Resistance status unknown, but consider status of the NSW Riverina (also low rainfall)

Stephen Love, 2011

NSW Central and Southern Tablelands/Slopes

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BZ LEV BZ/LEV ML

Est prevalence resistance

Haem

Trich

Tel

*some cases suspect ML-resist. Trich. * BZ resist. Nematodirus common * cases with reduced MOX protective period seen with Tel. * some cases MOX resist Haem *NAP+BZ or LEV commonly 92-95 % WECR

WECR: worm egg count reduction. Date in graph indicative only; see paper for details

Stephen Love, 2011

Mostly uniform rainfall: ~700-850 mm pa

NSW South West slopes(Cootamundra-Gundagai area)

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BZ LEV NAP IVM ABA MOX A+B+L

% of WECRTs (n=5) with 'Resistance' or 'Suspect Resistance'

Trich

Tel

* D Star, Novartis. * OK, histogram slightly ridiculous as n=5 (n is from 1-5 for the different results. See paper) * A+B+L=ABA+BZ+LEV * ‘Resistance’ <95% WECR (may not be resistance with NAP); Suspect R: <95% WECR but control WEC for genus was <150. * Suspect ML resist Trich

Stephen Love, 2011

Western Victoria (1)

Stephen Love, 2011

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BZ LEV B+L N+B N+L N+B+L P+B

% of WECRTs (n up to 99) with <95% WECR

Strong.

* D Hucker (Para Tech Services). * WECRTs 2008, 2010, 2011 (n ranges from 8 to 99). * Strong =strongyle, usually Tel+.Trich * B=BZ, L=LEV, N=naphthalophos, P=pyraclofos

Western Victoria (2)

Stephen Love, 2011

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IVM I+B+L MOX ABA A+B+L

% of WECRTs (n up to 99) with <95% WECR

Strong.

* D Hucker (Para Tech Services). * See notes previous slide, and paper. * I=IVM=ivermectin. A=ABA=abamectin. MOX=moxidectin. B=BZ. L=LEV. * Most IVM resist in past in Tel. Some of MOX resist may be in Trich.

Tasmania (P. Nilon, 2010)

Tas. About 10 years behind mainland (wrt resistance)

Tel still the genus with most resistance Most farms: WECR 99% for MLs. Trich often resist to BZ, rarely BZs Combinations work on most. OP use still uncommon Cases of suspect ML-resistant Trich

Stephen Love, 2011

South Australia

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BZ LEV IVM ABA MOX ML+B+L

Approx.% of farms with <95% WECR

Strong.

C Trengove (s-east); S Ellis (mid north). Strong=strongyle, mostly Tel + Trich. Haem rarely an issue; Fasciola rare. B=BZ, L=LEV. IVM usually 97-98% WECR (Trich), 85-95% (Tel). One case (WECR for IVM): Trich 80%, Tel 60%

Stephen Love, 2011

South Australia – Kangaroo Island (1)% WECRTS with <95% WECR (mostly Trich/Tel)

1988-1999 (n=44)

2001-2005 (n=19)

2006-2010

(n=21)

BZ 98

LEV 89

BZ+LEV 37 76

(BZ+LEV)x2 5 38

IVM 75 93

ABA 38

MOX 38

IVM+BZ+LEV 25 50

ABA+BZ+LEV 20

PYR+BZ 25

NAP+BZ+LEV 11 46

Stephen Love, 2011Source: D Lehmann

South Australia – Kangaroo Island (2)

•Debra Lehmann. (Not in conf. proceedings, but in amended paper )•Haemonchus is rare and liver fluke is absent.•PYR=pyraclofos. NAP=naphthalophos•Resistance emerging to MOX(idectin) LA injection.•BZ, LEV, BZ+LEV resistance: prevalence is similar in both Trich and Tel. •ML resistance seen in Tel; no evidence of resistance in Trich. •Evidence of reduced efficacy of OPs against Tel and Trich.

Concluding comments MLs

– Rapid increase prevalence last 10 years, notably Haem (summer), Tel (uniform/winter)

– All MLs (avermectins, milbemycins) now affected

– ML-resist Trich emerging

How long will long acting products provide a safey net?

OPs – evidence of declining efficacy, many regions

Thank you for your attention