Dealing with anthelmintic resistance in small ruminants


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Dealing with anthelmintic resistance in small ruminants

  2. 2. Gastro-intestinal parasites (worms) are the primary health problem affecting small ruminants.
  3. 3. The barber pole worm (Haemonchus contortus) is the primary parasite affecting small ruminants in warm, moist climates. Bottle jaw Anemia
  4. 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. 5. Anthelmintic resistance was (is) inevitable. No treatment will kill 100% of worms.
  6. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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) [] Sericea cuneata
  24. 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. 25. THANK YOU. QUESTIONS? COMMENTS. American Consortium for Small Ruminant Parasite Control -