This presentation is the third in a four part webinar series on internal parasites in sheep and goats. This presentation focuses on the diagnostic tools available to producers to help them control parasites in the flocks and herds. The presentation is by Susan Schoenian, University of Maryland Extension Sheep & Goat Specialist.
2. How do I tell if my sheep or goats are infected with parasites?
3. They all are. Almost all sheep and goats have parasites, probably of different kinds. “Positive” egg or oocyst counts are “normal.” Negative tests are rare (during the periods of risk). Some level of parasite infection is required for immunity.
4. They all are. Accept it! Clinical disease occurs at a certain level of infection that can vary by animal. Not all parasites are pathogenic or highly pathogenic. Not all straingsof parasites are pathogenic.
5. The more important question to ask is:How do I tell if my sheep or goat is clinically parasitized (suffering negative effects) and requires anthelmintic treatment?
18. Bottle jawSub-mandibular edema Source: G.F. Bath and J.A. van Wyk, Faculty of Veterinary Science, University of Pretoria, South Africa
19. Body condition score (BCS) Source: G.F. Bath and J.A. van Wyk, Faculty of Veterinary Science, University of Pretoria, South Africa
20. Dag Scoresbritch soiling, evidence of scouring (diarrhea) Source: G.F. Bath and J.A. van Wyk, Faculty of Veterinary Science, University of Pretoria, South Africa
21. Nasal discharge Source: G.F. Bath and J.A. van Wyk, Faculty of Veterinary Science, University of Pretoria, South Africa
22. Packed cell volume (PCV) Portion of whole blood occupied by red blood cells. A measure of anemia Primary symptom of Haemonchosis(or barber pole worms). A measure of resilience.
23. Uses of fecal testing Identify worm eggs and determine existence and levelof infection Simple fecal flotation Fecal egg counting Determine parasite species Larvae culture Lectin staining test Determine effectiveness of anthelmintic treatment Fecal egg count reduction test (FECRT) Larval development assay (LDA) or DrenchRite® test
24. Fecal testing QuantitativeFecal egg count (FEC) QualitativeSimple fecal flotation Use McMaster egg counting slide Weigh feces and measure flotation solution Determine general egg typesStrongyle vs. coccidia vs. tape Determine level of infection Eggs per gram of feces Use simple slide and cover slip Determine general egg typesStrongyle vs. coccidia vs. tape Determine existence and general level of infection Eggs per field of viewe.g. Eggs Plus system
25. What you need to do your own fecal egg counts Microscope40x objective x 10x eye piece = 400Only need 100xMechanical stage recommended Flotation solutionSaturated salt or sugar solutionSpecific gravity of 1.2Can also purchase McMaster egg counting slide www.vetslides.com Miscellaneous suppliesscale, beaker, pipettes, vials, craft sticks, cheese cloth or strainer
26. Fecal egg countseggs per gram of feces Indicate “potential” parasite burden in animal. Indicate potential parasite burden on pasture.. Use to determine level of drug efficacy. Use to determine genetic differences in parasite resistance.
27. Fecal egg counts are not definitive. Fecal egg counts are not always well-correlated with clinical disease. Presence of eggs or does not mean that the animal is clinically parasitized and needs treatment. Absence of eggs or oocytes (coccidia) or a low count does not mean that the animal is parasite-free and not needing treatment.
28. Limitations to fecal egg counts Some parasite eggs look the same and cannot be identified at the egg stage). There is a fairly regular fluctuation in fecal egg output. Egg output varies by season of the year. Eggs are not always evenly distributed in the feces. Parasite species vary in their egg producing capacity. Some parasites are prolific egg producers (e.g. Haemonchus) Some parasites do not produce very many eggs. (e.g. Nematodirus) Some parasites produce eggs intermittently Some parasites can produce asexually Immature worms (L4’s) do not lay eggs Inhibited larvae do not lay eggs Not all parasites are pathogenic (disease-causing) Total egg counts may include a mixture of species with different levels of fecundity and pathogenicity. Diarrhea increases fecal moisture and may dilute the number of eggs. Human error.
30. Fecal egg count reduction test (FECRT) First and most widely used method to access efficacy of anthelmintics. Before and after fecal egg counts. d 0 and d 7-14 post treatment With or without untreated controls Minimum of 10 animals.
32. Larvae culture and differentiation It is difficult to differentiate the eggs of many common species of worms during a worm egg count. Culture of the feces for the purpose of hatching parasite eggs and obtaining larvae for morphological identification. Image source: Dr. Woodgate, Western Australia Department of Agriculture
34. Lectin staining test Fast, easy, less-expensive way to test for the presence and quantity of barber pole worms. Lectin-staining test based on peanut agglutin that binds to egg of barber pole worm. Only requires a small amount of feces. Results available in as little as two days. Available through Oregon State University and University of Georgia. Image source: University of Georgia College of Veterinary Medicine.
35. New tests (not available in U.S.) CARLA® SALIVA TEST HAEMONCHUS DIPSTICK TEST Measures antibodies against worm larvae. Use to select animals which suffer less from parasites and pass fewer eggs onto pasture. Detects blood in feces to determine presence of barber pole worm and level of infection.
36. Small Ruminant Program Thank you for your attention. Any questions? SUSAN SCHOENIANsschoen@umd.eduwww.sheepandgoat.com Next webinar (last) : Using anthelmintics effectively - May 26