SUSAN SCHOENIAN (Shāy-ne-ŭn)EXTENSION SHEEP & GOAT SPECIALISTWESTERN MARYLAND RESEARCH & EDUCATION CENTERsschoen@umd.edu - www.sheepandgoat.com
Primary health problem affecting sheep and lambs, especially east of the Rockies. Severity varies by • Geographic region • Production system Control is limited by effectiveness of anti- parasitic drugs (called anthelmintics).
Eliminate parasites1. Prevent clinical disease, production losses, and mortality, and …2. Slow down drug resistance.
LACTATING EWESPERI-PARTURIENT EGG RISE EARLY WEANED LAMBS
Short, direct life cycles that are weather-dependent. L4, adult Can overwinter on pasture. Ability to go into hypobiotic (arrested) state (in host) when environmental conditions are not L3 conducive to their development. Vary in their egg laying ability. L1 L2 Eggs look same under microscope.
Primary parasite affecting sheep and lambs in warm, moist climates and/or with summer-dominated rainfall. Most pathogenic species Blood-sucker Image from University of Georgia Prolific egg layer
SYMPTOMS(due to blood and protein loss) Anemia (paleness) Edema - “bottle jaw” (accumulation of fluid) Not usually diarrhea Weight loss Loss of body condition Poor stamina Sudden death
SYMPTOMS(usually additive w/barber pole worm) Production loss Weight loss Dagginess Scours (diarrhea) Only occasional death Image source: NADIS UK
Usually not significant Usually additive in effect Possible respiratory symptoms Coughing Irritated airways Pneumonia Difficult to diagnose Usually no clinical signs Larvae (not eggs) in feces Post-mortem diagnosis
Normal parasite of white tail deer. Sheep are an abnormal host. Ingest intermediate host (snail or slug) Larvae migrates into central nervous system where it causes neurological disease (various symptoms). Treat with repeated doses of fenbendazole and anti- inflammatory drugs. Monthly treatments with ivermectin have been used as a preventative (camelids). Paralaphostrongylus tenius
Indirect life cycle; require pasture mite as an intermediate host. Tend to be non- pathogenic Usually no benefit to treatment. Treat with albendazole (Valbazen®), fenben- dazole (Safeguard®, or praziquantel (Quest Plus®). Moniezia expansa
Regional problem Fasciola hepatica (Gulf States, Pacific Northwest) Require an intermediate host (snail or slug) Infect bile ducts - liver damage Diagnosis based on finding eggs in feces and post-mortem Similar symptoms as barber pole worm (anemia and bottle jaw) Treat with albendazole (Valbazen®) or clorsulon (Ivomec® Plus).
Species-specific 10 species known to infect sheep, but not all are pathogenic. More complicated life cycle than most roundworms. Cause damage to cells lining small intestines. Most prevalent Indoor pens Feed lots Eimeria spp. Intensive grazing areas
FECAL EXAM CLINICAL SIGNS Of limited value – Adults are largely shouldn’t use as sole immune, but serve as a diagnostic tool reservoir of infection. Lambs (1-6 mos., esp. 4-8 Can have clinical coccidiosis with low oocyte count and wks.) are very susceptible. vice versa. Scours (diarrhea) Not all species of coccidia Open fleece are pathogenic. Weight loss Is normal to find coccidia Anorexia oocytes in fecal samples. Dehydration Weakness
A system developed in South Africa to assess barber pole worm infection and determine the need for deworming. Scores estimate packed cell volume (PVC) by measuring anemia using Eye lid color PCV Treatment recommendation a color eye chart. 1 Red > 28 Optimal No 2 Red-Pink 23-27 Acceptable No Each score has a 3 Pink 18-22 Borderline ? treatment 4 Pink-White 13-17 Dangerous Yes recommendation. 5 White < 12 Fatal Yes
Determining the number of worm eggs per gram of feces (EPG) in order to estimate the worm burden in an animal. Egg count includes all strongyle eggs; cannot differentiate at egg stage. Requires a measured amount of feces and flotation solution. A McMaster slide is used to count eggs. Most veterinarians and many diagnostic labs do not perform quantitative egg counts (only simple fecal flotations).
SHEEP AND LAMBS LACTATING DAIRY EWES Ivermectin Withdrawal periods have (Ivomec® drench) not been established for lactating dairy ewes. Albendazole Requires extra-label drug (Valbazen® liquid) use, as prescribed by a First 30-d gestation licensed veterinarian. Moxidectin Work with veterinarian to (Cydectin® drench) establish safe withdrawal periods for milk. Levamisole (Prohibit® drench)
ORAL DRENCHES INJECTABLES POUR-ONS FDA-approved Not FDA- Not-FDA for sheep. approved. approved. Easier to Sub- Not developed administer. therapeutic for sheep skin. Clear system levels select for Less effective. faster. resistant Sub- Shorter worms. therapeutic withdrawal Longer levels select for periods. withdrawal resistant More effective periods. worms.
1) When an anthelmintic treatment fails to reduce fecal egg counts by 95% or more; severe when less than 60%.2) There is varying degrees of resistance to all anthelmintic classes. Benzimidazoles - widespread Avermectins - widespread Moxidectin - emerging Levamisole - variable3) Resistance varies by geographic location and farm and is influenced by past anthelmintic use.
Each anthelmintic family has a different way to kill worms. Worms develop resistance to the mechanism of worm control not individual drugs. There is cross resistance among drugs in the same family. If a different drug in the same family appears to work, its efficacy will be short-lived.
1) Treatment response2) Fecal egg count reduction test (FECRT) ▪ Before (d-0) and after fecal egg counts (d 10-14)3) DrenchRite® test Larval development assay (LDA)
Decrease frequency of treatments. Do not treat everyone; leave some animals untreated. Do not move treated animals to a clean pasture. Do not deworm when there is a low level of pasture contamination. Re-introduce suceptable worms.
By exposing worms to sub-therapeutic levels of drugs. 1) Underdosing 2) Using injectable dewormers 3) Using pour-on dewormers 4) Depositing drug into mouth instead of esophagus. 5) Persistent activity dewormers (?)
For sale To prevent the Ram - $1,000 Resistant worms - free introduction of resistant worms to your farm, deworm all newly acquired animals with anthelmintics from all three chemical classes.
American Consortium for Small Ruminant Parasite Control wormx.org acsrpc.org wormcontrol.org controlworms.org Maryland Small Ruminant Page www.sheepandgoat.com Sheep 201: A Beginner’s Guide to Raising Sheep www.sheep101.info/201/parasite.html Today’s PowerPoint presentation www.slideshare.com/schoenian
Thank ewe for your attention. Lambs are 69% Katahdin x 31% Lacaune.
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