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Dealing with anthelmintic resistance in small ruminants

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  • 1. Dealing with anthelmintic resistance in small ruminants SUSAN SCHOENIAN SHEEP & GOAT SPECIALIST UNIVERSITY OF MARYLAND EXTENSION (UME) WESTERN MARYLAND RESEARCH & EDUCATION CENTER (WMREC) SSCHOEN@UMD.EDU - WWW.WORMX.INFO - WWW.SHEEPANDGOAT.COM
  • 2. Gastro-intestinal parasites (worms) are the primary health problem affecting small ruminants.
  • 3. The barber pole worm (Haemonchus contortus) is the primary parasite affecting small ruminants in warm, moist climates. Bottle jaw Anemia
  • 4. The barber pole worm has developed resistance to all anthelmintics and all anthelmintic classes. Anthelmintic resistance When an anthelmintic treatment fails to reduce fecal egg counts by 95% or more.
  • 5. Anthelmintic resistance was (is) inevitable. No treatment will kill 100% of worms.
  • 6. Numerous on-farm practices have accelerated the development of resistant worms in small ruminants.  Frequent deworming, especially without regard to clinical need.  Underdosing drugs (failure to dose based on accurate weights).  Injecting an anthelmintic instead of using a drench.  Pouring an anthelmintic on the back instead of using a drench.  Improper administration of drenches, e.g. depositing drug in mouth  Use of persistent-activity dewormers (e.g. moxidectin).  Treating all animals in flock/herd, leaving no refugia.  Putting treated animals onto a clean pasture: no refugia.  Treating animals when pasture contamination is low.  Giving more than one dewormer at a time.  Introduction of resistant worms to a farm via new animals; failure to quarantine drench.
  • 7. Anthelmintic resistance  Is not fully appreciated by some producers and veterinarians.  Varies by geographic region and farm.  Is result of past deworming practices.  On most farms, resistance is probably still at a level where there is still time to slow it down and enable the continued use of (some) anthelmintics.  Most small ruminant producers do not know which dewormers work on their farm. ? ? ??
  • 8. Dealing with anthelmintic resistance on the farm.  The first thing you need to do is determine which dewormer(s) still work on your farm.  All producers need to devise production/ management systems that minimize the need for deworming.
  • 9. There are two methods to determine anthelmintic (dewormer) resistance. Fecal egg count reduction test (FECRT)  Comparison of pre- and post- treatment fecal egg counts.  Must compare egg counts for each individual anthelmintic. DrenchRite® larval development assay (LDA)  In vitro test for anthelmintic resistance (for all drugs).
  • 10. Fecal egg count reduction test (FECRT)  Collect samples at the time of treatment (deworming).  Collect post-treatment samples  8-10 days, benzimidazoles  14-17 days, macrocylic lactones  5-7 days, levamisole  10-14 days, all dewormers  Need FECs > 250 epg  Favor animals with higher FAMACHA© scores and positive dag scores.  Should include a control group for comparison. DrenchRite® larval development assay (LDA)  Collect pooled fecal sample from at least 10 animals.  Need FECs > 350-500 epg  Favor animals with higher FAMACHA© scores and positive dag scores.
  • 11. Fecal egg count reduction test (FECRT)  Takes 7-14 days (or more) to get results, longer if done by someone else.  Cost of testing varies (15 samples x 4 anthelmintics + control group) 75 x free labor = no cost 75 x $5/sample = $350 75 x $10/sample = $750  Requires a lot more animals (ideally, 12-15 per treatment group); many producers don’t have enough animals for accurate testing.  Results % reduction (whole flock/herd) Results from individual animals can be quite variable. DrenchRite® larval development assay (LDA)  Takes 3-4 weeks to get results  Only one lab in US that does test: Dr. Ray Kaplan’s lab at the University of Georgia College of Veterinary Medicine.  $450 per sample  Results Resistant (R) Susceptible (S) Suspected resistance (SR)
  • 12. There are many things a producer can do to potentially reduce the number of animals that require deworming and/or the frequency of deworming.  Pasture and grazing management  General management  Animal management  Nutritional management  Genetic selection  Targeted selective treatment (TST)  “Natural” things
  • 13. The foundation of parasite control is good pasture and grazing management.  Evasive grazing: pasture rest and rotation  Maintaining minimum grazing heights (> 3 in.)  Browsing  Mixed swards  Clean pastures  Annual pastures  Tannin-rich forages  Mowing, haying, cropping  Mixed species grazing w/alpacas, llamas  Low/reduced stocking rates ****
  • 14. Certain management practices may reduce the need for deworming. Management  Winter or fall lambing/kidding  Early marketing  “Early” weaning  Night penning  Zero grazing  Delay grazing until after dew lifts  Put treated animals in dry lot for 48 hours after deworming  Good sanitation/hygiene Nutrition  Manage pastures so that plants are in a vegetative stage for grazing.  Plant annuals, legumes, and warm season plants to improve nutrition of pasture.  Provide supplemental nutrition when pasture quantity or quality is low/poor and/or to susceptible animals.  Soy hulls  Distiller’s grains (DDSG)  By-pass protein (?)  Increase protein in late gestation ration to counter periparturient egg rise.  Maintain animals in good body condition (BCS > 2.5)
  • 15. Genetic selection can reduce the number of animals that require deworming. Between species/breed  Goats are usually more susceptible to parasites than sheep.  Some sheep breeds are more resistant to parasites.  Hair sheep of tropical origin: St. Croix, Barbado, Katahdin  Native breeds of the Southeast: Natives, Crackers  Other breeds: Texel (?)  Some goat breeds seem to be more resistant to parasites than others: Kiko, Spanish, Myotonic. Within breed  80:20 (or 70:30) rule 20-30 percent of flock/herd is responsible for 70-80% of pasture contamination (egg shedding).  Can select any breed for improved resistance to parasites  Select individuals with lower FECs.  Use EBVs (estimated breeding values) to choose resistant males for breeding.  Parasite resistance (fecal egg counts) is a moderately heritable trait (20-40%): heritability of prolificacy is only 10%.  Resilience is less heritable.
  • 16. Targeted Selective Treatment (TST) Only treating animals that require treatment or would benefit from treatment; increases refugia. FAMACHA© SYSTEM  Uses color eye chart to estimate level of anemia (packed cell volume/PCV); thus, need for deworming.  Only useful for blood-feeding parasites, such as barber pole worm. Category Color PCV Tx? 1 Red > 28 No 2 Red-Pink 23-27 No 3 Pink 18-22 ? 4 Pink-White 13-17 Yes 5 White < 12 Yes Refugia – worms not exposed to anthelmintic(s).
  • 17. Targeted Selective Treatment (TST) Only treating animals that require treatment or would benefit from treatment; increases refugia. FIVE POINT CHECK© - 5.  Extension of FAMACHA© system: decision- making tool for all parasites that commonly affect small ruminants.  Involves 5 check points on animal’s body 1. Eye FAMACHA© score (anemia) (1-5) 2. Jaw Submandibular edema (bottle jaw) 3. Back Body condition score (1-5) 4. Tail Dag score, fecal soiling (scouring) (0-5) 5. Nose Sheep: nasal discharge (bot flies) Goats: coat condition
  • 18. The FAMACHA© system is a perfect example of the land grant mission: to get producers to apply research-based knowledge to solve a problem.  Producers must take an approved training in order to receive a FAMACHA© card.  Since 2003, over 29,000 FAMACHA© cards have been sold to over 40 states and various Caribbean and Latin American countries.  Two formal evaluations of FAMACHA© workshops have been conducted. 91% 78% 76% 95% 74% 75% 0 10 20 30 40 50 60 70 80 90 100 Using FAMACHA Deworming less Saving money 2004 2009
  • 19. What are limitations to producers adopting the FAMACHA© system/Five Point Check©?  Conflicting information Many veterinarians give out-dated advice.  Tradition Many producers still think of deworming as a preventative and best management practice.  Availability of training Workshops are not always available at convenient locations or times.  New anthelmintic There is a new anthelmintic in the pipeline (Zolvix®); the urgency of anthelmintic resistance may be abandoned (?).  The FAMACHA© system was developed for “small” farms; FAMACHA© scoring is labor- intensive.  It is easier to deworm all members of the flock/herd than to check their FAMACHA© and other scores.  Sub-clinical parasitism is not treated; it is a cost of Targeted Selective Treatment.
  • 20. “Natural” dewormers SOME: (GENERALLY) EFFECTIVE  Kill parasites  Copper oxide wire particles (COWP)  Copper sulfate ()  Tobacco and nicotine sulfate ()  Reduce treatment #’s  Condensed tannins Sericea lespedeza  Duddingtonia flagrans nematode-trapping fungus ***not commercially available yet** MOST: INEFFECTIVE AND/OR UNPROVEN  Diatomaceous earth (DE)  Garlic  Papaya  Paprika  Pine bark  Pumpkin seeds  Commercial herbal dewormers (e.g. Hoegger’s herbal dewormer)  Many, many more…
  • 21. Copper oxide wire particles (COWP)  Copper oxide wire particles have been shown to reduce parasite burdens (H. contortus) in lambs and kids.  Less effective in mature animals.  Copper oxide wire particles are a slow-release form of copper  Less potential for toxicity in sheep; sheep are sensitive to excess copper in the diet.  Copasure® is a copper supplement (12.5 and 20 g) for cattle that can be repackaged into smaller doses for sheep and goats (0.5 to 4 g).  Copasure® capsules are now available in 2 g and 4 g dosages for sheep and goats (as Cu supplement).  Selective treatment with COWP advised.  FAMACHA© scores of 3, 4, 5 only.
  • 22. Effect of copper oxide wire particles on the parasite status of bucks in the 2014 Western Maryland Pasture-Based Meat Goat Performance Test (0.5 g COWP administered on d-42) 0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 d (-6) d-0 d-14 d-28 d-42 d-56 d-70 d-84 Test - COWP Study - no COWP
  • 23. Condensed tannins  Tannins are plant compounds that bind to proteins and other molecules.  Effects of tannins vary depending upon type, concentration, and the animal consuming the tannin.  Tannins can have both negative or positive effects.  Sericea lespedeza (AU Grazer™) is a high-tannin forage (warm season legume) that has been scientifically-proven to reduce parasite burdens in sheep and goats.  Fresh forage  Hay  Leaf meal (pellets) [simsbrothers.com] Sericea cuneata
  • 24. “Natural” dewormers (IMO)  Most likely effect of “natural” dewormers will be to reduce the number of animals that require deworming by . . .  Disrupting the free-living stage of the parasite (e.g. egg hatching, larval development)  Improving the immune function of the host.
  • 25. THANK YOU. QUESTIONS? COMMENTS. American Consortium for Small Ruminant Parasite Control - www.wormx.info