Treatment Strategies to control Parasitic Roundworms In Cattle

Transcription

1 Treatment Strategies to control Parasitic Roundworms In Cattle Dave Bartley

2 Which roundworms are most likely to cause problems? Scientific name Common name Disease Ostertagia ostertagi Brown stomach worm Type I & II Cooperia oncophora No common name - Dictyocaulus viviparus Lung worm Husk, hoose Haemonchus contortus Barber s pole worm Haemonchosis

3 The need for control Health and welfare Effects on food quality

4 Effects of gastro-intestinal parasitism Impaired gut function Protein diverted from productive tissues to repair damage Reduced feed intake and conversion Decreased production of: Muscle Skeleton Milk Fertility Tissue damage Loss of gut integrity leading to loss of proteins and minerals Decreased nutrient absorption Increased turnover and replacement of damaged cells/tissue

5 The need for control Health and welfare Effects on food quality Reduced profitability

6 Production losses associated with PGE? Age group First Season grazing (FSG) calves Second season grazing (SSG) Dairy cows Beef cows Production effect Reduced growth rate Reduced growth rate Delay in puberty & reduced conception rates in replacement heifers Reduced in-calf rate in heifers Loss of carcass yield and quality Decreased milk yield Longer calving to conception interval Decreased in-calf rates Decreased milk yield Longer calving to conception interval Lower weaning weight of their calves Decreased in-calf rates Adapted from Forbes PhD Thesis 2008

7 How to tell if worms are causing the problem? Clinical signs, season Grazing history FEC (not Type 2 Ostertagiosis) Plasma pepsinogen (Ostertagiosis) animals < 2 yr Pasture larval (L 3 ) counts L3 Eggs Mar Apr May Jun Jul Aug Sep Oct

8 Worm control strategies IMMUNOLOGICAL Vaccines Genetic selection Optimised nutrition MANAGEMENTAL Grazing management Biological control Organic farming CHEMICAL Anthelmintics Bioactive forages

9 Strategies - considerations Factors Enterprise type Beef Dairy Age Adult Calf Exposure FSG SSG Birth date Spring born Autumn born Exposure times Parasite species Parasite exposure levels Management strategies

10 Anthelmintics Anthelmintic class BZ (I) LEV (II) ML (III) Pour on - - Injectable - Drench - Bolus - - In feed mix - -

11 Anthelmintic usage pattern ML only ML + BZ BZ only LEV only III only I + III I only II only Anthelmintic class used in preceding 12 months Pour-on (n=69) Pour-on Bolus Injectable Oral drench Bolus (n=28) Injectable (n=22) Drench (n=21) Anthelmintic application methods

12 Do treatments always work, if not why not? Some questions to consider Was the correct dosage given? Was the drench administered correctly? Had the anthelmintic been stored correctly? Was the correct formulation used for your host species? Is the treatment effective against the target species?. Is anthelmintic resistance a problem?

13 Anthelmintic resistance When worm populations survive a correctlyapplied, standard dose of anthelmintic GENETIC - resistant worms produce resistant offspring A PRE-ADAPTIVE phenomenon genes that confer resistant already present in population IRREVERSIBLE no effective return to susceptibility even after removal of selecting anthelmintic

14 Anthelmintic resistance in cattle Country BZ LEV ML Country BZ LEV ML Australia Germany Argentina Mexico Bangladesh New Zealand Belgium Sweden Brazil UK Chile USA AR to MLs reported worldwide, little known in UK but previous reports of inefficacy of ML vs Cooperia spp.

15 Faecal egg count reduction test 50% IVM sensitive 39% IVM efficacy 50-95% 11% <50% ML inefficacy in UK Two isolates further investigated both IVM and MOX resistant Farm Suppression in egg development and oviposition ML resistant Cooperia species SO WHAT?! McArthur unpublished data

16 Recent studies NZ study - IVM and ABZ resistance on 74% farms where Cooperia spp present Resistance of Ostertagia spp to IVM evident (9% of farms), ABZ (35% of farms), LEV (9% of farms) Possibility resistant Cooperia are more pathogenic than susceptible ones Can cause production loss up to 12kg weight loss over grazing season Wikipedia

17 Sustainable control

18 Pasture management - Risk factors Factor Risk Low Medium High Age/exposure >2 years/adult 1-2 years/ssg <1 year/fsg Herbage mass kg DM/ha > <1000 Sward height >8 cm 4-8 cm <4 cm Pasture type Previous grazing history (< 12 months) Newly sown, clean grazing Grazed by adult cows, sheep** or other species Silage/hay aftermath Grazed by cattle 1-2 years old Permanent pasture Grazed by cattle <1 year old Adapted from AHI parasite control leaflet 2012

19 Rotation grazing In short term rotational grazing has been shown to reduce need for treatment frequency BUT may lead to Changes in species composition on pasture, such as increase in Cooperia species, Trichostrongylus axei Parasites developing ability to infect non traditional hosts e.g. Ostertagia ostertagi in sheep Changes in life history traits delayed/increased development times from eggs to L 3

20 Targeted treatments

21 TT What information is needed Targeted treatments (TT) are those where the entire group (whole flock or mob) of animals is treated Over time monitoring can provide the necessary information e.g. What parasites are present during the season The extent of challenge and risk of disease Which anthelmintics are working on the farm This information should guide the development of farm specific worming programmes

22 Treatment/Monitoring timings Enterprise Calving Areas to think about Beef Spring Adults relatively refractory to worms BUT generate huge quantities of faeces add to pasture contamination Pre-wean consume mostly milk lower L3 intake Monitoring in autumn advised May delay development of immunity and be prone to type II ostertagiasis Autumn Mostly housed early Turned out after winter, see pasture/l3 following year Grass intake early L3 intake early Early monitoring advised Dairy Spring May go to pasture early following milk substitute & concentrates exposed to L3 early Early monitoring advised Autumn See pasture following year Grass intake early L3 intake early Early monitoring advised No one size fits all /blue print advice available

23 TT Examples O. ostertagia ELISA applied on bulk tank milk at end of grazing season Measure of exposure of the herd to GI nematodes, high values (> 0.8 ODR). 53 % of UK herds 0.8 ODR (UK study; Forbes et al., 2008 ) Serum pepsinogen concentration indicator of abomasal damage caused by O. ostertagi - correlated with weight gains Charlier et al., 2010 Live weight gain trial in Sweden Prelim results promising

24 What can be done to better target treatments? Speak to your vet or health advisor Are treatments necessary? Reduce treatment frequency if possible Adult cattle, calves at turn out.. Non-chemical as well as chemical control Use correct dose + optimum drenching technique (avoiding under-dosing) Monitor wormer effectiveness Quarantine treat to avoid bringing in resistant worms Monitor in order to target treatments effectively

25 Where now?

26 Dispensing anthelmintics Seller must give up-to-date knowledge in an understandable format Epidemiology/farming practices Anthelmintic sensitivity/resistance Sustainable control = better knowledge exchange

27 Acknowledgements Claire McArthur, Fiona Kenyon and Jacqui Matthews at Moredun for supplying information Norbrook Laboratories Ltd and AHDA for invitation to present