ParasiteResistance

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ParasiteResistance

  1. 1. 2013 PASA Conference 2/7/2013 STRATEGIES, TECHNIQUES AND EXPERIENCE TO FOSTER PARASITE RESISTANCE & RESILIENCE SUSAN SCHOENIAN & JEFF SEMLER UNIVERSITY OF MARYLAND EXTENSION GASTRO-INTESTINAL PARASITES Gastro-intestinal parasites are the primary health problem affecting sheep and goats in warm, moist climates and areas with summer rainfall. Sheep and especially goats are more susceptible to the effects of internal parasites than other farm livestock. Goats are not natural grazers, nor well-adapted to moist climates.Susan Schoenian and Jeff Semler 1
  2. 2. 2013 PASA Conference 2/7/2013 GASTRO-INTESTINAL PARASITES • Sheep and goats share the same internal parasites (except for coccidia). • Not all parasites are pathogenic or equally pathogenic. • Close grazing facilitates the ingestion of infective worm larvae (L3). • Grazing near fecal pellets also facilitates ingestion of infective worm larvae (L3). GASTRO-INTESTINAL PARASITES • Sheep and especially goats are slow to develop immunity to internal parasites and experience a relaxation of immunity around the time of parturition (known as the “periparturient egg rise”). • Worms have developed varying degrees of resistance to ALL of the dewormers (anthelmintics). • Drug resistance is inevitable! Worms will eventually develop resistance to any new dewormer, quicker if we over-use it or use it improperly (like we’ve done in the past!).Susan Schoenian and Jeff Semler 2
  3. 3. 2013 PASA Conference 2/7/2013 SHEEP AND GOATS CAN BE AFFECTED BY A VARIETY OF INTERNAL (AND EXTERNAL) PARASITES AND IT IS NORMAL FOR THEM TO HAVE SOME WORMS IN THEIR GUTS AND EGGS IN THEIR FECES. 1. Helminths (worms) 1) Roundworms I have worms! (gut, lung, meningeal) 2) Trematodes (tapeworms) 3) Cestodes (flukes) Me, too! 2. Protozoa (single cell) 1) Coccidia PRIMARY PARASITES AFFECTING SHEEP AND GOATS • Roundworms, especially Haemonchus contortus • Coccidia (Eimeria spp.) (barber pole worm). • Other parasites (e.g. meningeal worm) can be • Also, Trichostrongylus a problem on individual spp. and Teladorsagia farms or in some years. (Ostertagia). Barber pole worm Coccidia “nodules” in small intestines Image from Novartis Image from ScienceDirectSusan Schoenian and Jeff Semler 3
  4. 4. 2013 PASA Conference 2/7/2013 MOST ECONOMICALLY-DEVASTATING PARASITE IS USUALLY HAEMONCHUS CONTORTUS. 2012 2010 100 100 80 80 60 60 40 40 20 20 0 0 6/2 6/28 7/26 8/22 6/7 7/1 7/29 8/25 Haemonchus Trichostrongylus Other Haemonchus Trichostrongylus Other 2011 2009 100 100 80 80 60 60 40 40 20 20 0 0 6/3 7/7 8/4 9/1 6/6 7/1 7/16 7/30 8/13 8/26 9/10 9/26 Haemonchus Trichostrongylus Other Haemonchus Trichostrongylus LARVAE ID (PERCENT HAEMONCHUS IN RED) FROM WESTERN MARYLAND PASTURE-BASED MEAT GOAT PERFORMANCE TEST. THE BARBER POLE WORM IS AN INCREDIBLE PARASITE! • Very pathogenic: kills a lot of sheep and goats, especially weanlings. • Difficult to control • Simple, direct life cycle • Prolific egg layer • Undergoes hypobiosis (inhibited developmental stage) • Adaptable: from the Tropics to the Artic.Susan Schoenian and Jeff Semler 4
  5. 5. 2013 PASA Conference 2/7/2013 SYMPTOMS IN THE ANIMAL HAEMONCHOSIS 1. Hyperacute (< 1 week) • “Sudden death” • No obvious signs 2. Acute (> 1 week) • Anemia • Edema (bottle jaw) • Weight loss Voracious blood-sucker! • Loss of body condition • Anorexia • Loss of stamina • Diarrhea 3. Chronic (sub-clinical) • Loss of performance GENETICS OF PARASITES: TWO TRAITS RESISTANCE RESILIENCE • Prevent parasitic disease • Tolerate (perform, remain from establishing. healthy) despite parasite burden (could still have • Quantified by fecal egg high egg count). counts (FECs), which are an estimate of the • For barber pole worm, number of worms in the quantified by packed cell animal’s gut. volume (PCV) and estimated by FAMACHA© EPG: eggs per gram (of feces) eye anemia scores. PCV - percent; FAMACHA© - 1-5Susan Schoenian and Jeff Semler 5
  6. 6. 2013 PASA Conference 2/7/2013 ABOUT FECAL EGG COUNTS (EPG) • They are “relative”: a “snapshot” in time. McMaster slide • A single egg count is not necessarily a good measure of the parasite burden in an individual animal; however, it is a measure of pasture contamination. • Fecal egg counts include all strongyle-type eggs: Haemonchus, Trichostrongylus, and Teladorsagia: you must hatch eggs to identify strongyle species by worm larvae. • Worms vary in their egg-laying ability. You can learn to do your own FECs. ABOUT PACKED CELL VOLUME (PCV) • Is proportion (%) of blood represented by red blood cells. McMaster slide • Also known as blood hematocrit. • 25 to 35 percent is normal in sheep/goats. • Is usually lower for goats. • Is estimated by FAMACHA© scores. Score 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 YesSusan Schoenian and Jeff Semler 6
  7. 7. 2013 PASA Conference 2/7/2013 OTHER IMPORTANT MEASUREMENTS OF PARASITE RESILIENCE • Body condition (1-5) • Dag score (fecal soiling, 0-5) • Coat condition • Weight gain Dagginess Weight loss Poor body condition HERITABILITY (H2) OF RESISTANCE AND RESILIENCE RESISTANCE RESILIENCE • Moderately heritable • Low heritability ~0.25 ~ 0.10 (higher for Katahdins) • Less variability: • Extremely variable: coefficient of variation coefficient of variation usually between 20 is often over 100 and 40 percent. percent. Fecal egg counts are the standard for improving parasite resistance in sheep. Heritability (h2) is the proportion of phenotypic variation due to genetics.Susan Schoenian and Jeff Semler 7
  8. 8. 2013 PASA Conference 2/7/2013 GENETIC RELATIONSHIP BETWEEN RESISTANCE AND RESILIENCE • Resistance and resilience are usually positively correlated, Year Correlation though measurement numbers 2007 0.29 may be negatively related. 2008 0.42 2009 0.18 e.g. FEC PCV and 2010 0.27 FEC FAMACHA© Score. 2011 0.14 • In the Western Maryland Genetic correlations range from -1 to +1 and are an indication of the amount of Pasture-Based Meat Goat variation that two traits share. Performance Test, FEC and FAMACHA© scores have had In New Zealand, they found no correlation between parasite positive correlations, but they resistance and parasite resilience. have not been very strong. IN OUR BUCK TEST, WE USE FECAL EGG COUNTS (FEC) TO EVALUATE GENETIC RESISTANCE TO PARASITES. NOT TO MAKE DEWORMING DECISIONS.Susan Schoenian and Jeff Semler 8
  9. 9. 2013 PASA Conference 2/7/2013 WE USE FAMACHA© SCORES TO ESTIMATE PACKED CELL VOLUME …AND MAKE DEWORMING DECISIONS. TWO WAYS TO SELECT FOR PARASITE RESISTANCE AND RESILIENCE BETWEEN BREED WITHIN BREED • Some breeds are naturally • There is as much variation more resistant and resilient to within a breed as between internal parasites (round- breeds. worms) than others. • The 80-20 rule: it is estimated • This is well-documented in that 20-30 percent of the flock sheep; not very well- or herd is responsible for documented in goats causing 70 to 80 percent of the (mostly anecdotal). pasture contamination • Resistant breeds tend to be (fecal egg outlay). those with tropical origins or • Parasite resistance (FECs) is a landrace breeds that have moderately heritable trait. naturally adapted to their environment (“survival of the fittest”).Susan Schoenian and Jeff Semler 9
  10. 10. 2013 PASA Conference 2/7/2013 (MORE) RESISTANT BREEDS SHEEP GOATS • Landrace hair sheep Not • Kiko 1) St. Croix • Boer 2) Barbados Blackbelly • Spanish • Nubian 3) American Blackbelly • Swiss dairy • Myotonic • Composite hair x wool 1) Katahdin • Medium wool 1) Gulf Coast Native Florida Native St. Croix: the most • Dorper - not resistant, but resistant maybe more resilient. breed in US. • Others (?) WITHIN BREED SELECTION ANY BREED (OR POPULATION) CAN BE SELECTED FOR IMPROVED PARASITE RESISTANCE. 2012 Western Maryland Pasture-Based Meat Goat Performance Test Avg. FEC 2358 epg 80:20 rule: Fecal egg counts are not evenly dispersed in a herd or flock.Susan Schoenian and Jeff Semler 10
  11. 11. 2013 PASA Conference 2/7/2013 Selection for parasite resistance in Australia Selection for parasite resistance in AustraliaSusan Schoenian and Jeff Semler 11
  12. 12. 2013 PASA Conference 2/7/2013 Selection for parasite resistance in Australia HOW TO SELECT FOR PARASITE RESISTANCE • The immune system needs to be stimulated by a worm challenge before genetic differences can be expressed. • Measure fecal egg counts when animals are between 6 and 12 months of age. • No sooner than 6 weeks after weaning. • A high worm load is needed to do the best job of separating resistant vs. susceptible animals; • Avg. FEC of 500-1000 epg for barber pole worm • Less than 10% of animals should have zero egg counts.Susan Schoenian and Jeff Semler 12
  13. 13. 2013 PASA Conference 2/7/2013 PROTOCOL FOR MEASURING RESISTANCE IN KATAHDINS Source: NSIP, David Notter, Virginia Tech, 2004 HOW TO SELECT FOR PARASITE RESISTANCE • Take all samples on same day. • Store samples in a cool place to prevent eggs from hatching. • Compare animals in same contemporary group. • Compare individual FECs to group average. • Heritability will be higher if more than one FEC is used for comparison.Susan Schoenian and Jeff Semler 13
  14. 14. 2013 PASA Conference 2/7/2013 2012 Western Maryland Pasture-Based Meat Goat Performance Test 1 2 3 4 5 Top 10 6 7 8 9 10 10 9 8 7 6 Bottom 10 5 4 3 2 1 All goats were triple-dewormed (moxidectin + levamisole + albendazole) on 6/2. Twelve days later, the average fecal egg count was near zero. HOW TO SELECT FOR PARASITE RESILIENCE • Many criteria can be used a) Packed cell volume b) FAMACHA© score c) Time from fixed point that deworming is required d) Number of times dewormed during specific time period. e) Body condition score f) Dag scores (scour worms) g) Growth rates • Cull animals that require frequently deworming. • Select animals that do not require deworming and whose parents don’t require deworming.Susan Schoenian and Jeff Semler 14
  15. 15. 2013 PASA Conference 2/7/2013 2012 Western Maryland Pasture-Based Meat Goat Performance Test 1 2 3 4 5 Top 10 6 7 8 9 10 10 9 8 7 6 Bottom 10 5 4 3 2 1 All goats were triple-dewormed (moxidectin + levamisole + albendazole) on 6/2. For the next 8 weeks, the average FAMACHA© score improved and no goat required deworming. WE WANT BOTH RESISTANCE AND RESILIENCE! • You don’t want have to Let me out! deworm your stock, but you also don’t want to have animals that deposit a lot of eggs onto the pasture. • Heavily-contaminated pastures lead to clinical parasitism, as there are almost always susceptible animals in Fecal egg counts are a measure the herd or flock. of pasture contamination.Susan Schoenian and Jeff Semler 15
  16. 16. 2013 PASA Conference 2/7/2013 IT IS MOST IMPORTANT THAT THE MALE BE RESISTANCE TO PARASITES There are large differences between sires for resistance. WHAT WILL HAPPEN IF YOU DON’T PAY ATTENTION TO PARASITES? • Eventually all the dewormers will stop working on your farm. Kiko x Boer • You will need to feed more so that your animals can tolerate parasitic burdens. • You’ll want to raise your sheep and goats in complete confinement so that they are not exposed to much infective worm larvae. • You’ll have to stop raising sheep and especially goats. • Your compost pile will get full. Top-performing buck from 2011 Test Avg. FEC: 232 epg; Avg. FAM: 1.7; ADG ratio: 181%Susan Schoenian and Jeff Semler 16

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