PARASITES AND DEWORMING YOUR HORSES Control vs. Eradication Karen Kalck, DVM, DACVIM Equine Medicine University of Tennessee Veterinary Medical Center Control, not eradication

PLAN Introduction Signs of parasitism Types of parasites Dewormers Diagnostics Designing a deworming program

QUESTIONS Raise your hand if you deworm your horse(s) every 2-3 months? Every 4-6 months? Once per year? Whenever you remember to?

COMMONLY ASKED QUESTIONS What type of wormer should I use? When should I worm my horse? Should I rotate my wormers each time? Should I use the same wormer all year long? How often should I worm and when? What are fecal egg counts and do I need to have these done? How effective are feed through wormers? My horse is rubbing it's tail, is this because of worms?

COMMON PRACTICES Deworm 4 times per year Deworm 2 times per year, once after the first frost and once after the first hay cutting Deworm all year with the same dewormer Rotate your dewormer each time Only deworm if your horse is thin and not putting on weight

PARASITES vs. BACTERIA No replication of numbers within the host Life cycle No immunity to parasites

SIGNS OF PARASITISM None Lethargy Loss of appetite Dull, rough haircoat Tail rubbing and hair loss Loss of condition/weight Slow growth in young horses Pot belly Coughing, nasal discharge Diarrhea Colic Death

TYPES OF PARASITES Large strongyles Small strongyles Roundworms Tapeworms Pinworms Lungworms Bots Strongyloides

Roundworms (Ascarids) Large Strongyles Pinworms Roundworms (Ascarids) Small Strongyles Tapeworm

Grazing  eggs/larvae swallowed LIFECYCLE Eggs Manure of infected horse Ground Grazing  eggs/larvae swallowed Larvae Immature worms Stomach/intestines Larvae migrate out of intestines, into other tissues, and then return to intestine Adults Mature worms passed in feces

STRONGYLES Also known as bloodworms, red worms Can cause anemia Damage colon Mesenteric arteritis (large only)

LARGE STRONGYLES

SMALL STRONGYLES

ROUNDWORMS Ascarids Young horses (<2 years) Large  up to 15 inches in length! Do not suck blood Small intestinal obstruction Can migrate through the lung, causing damage and pneumonia

TAPEWORMS Affect the last part of the small intestine and cecum Can cause ileal impactions Eggs often not found in the feces

PINWORMS Females deposit eggs around anus in a “cement- like” mixture This dries and cracks, causing irritation “Rat-tail” appearance

BOTS Not worms, but fly larvae Female flies lay eggs on horse legs Horse ingests eggs Larvae hatch and migrate to the stomach

DIAGNOSTICS - Collection Collect fresh feces in ziplock bag Label with horse name and date Send/take to veterinary laboratory Herd  Collect individual samples on same day

DIAGNOSTICS Fecal float Fecal egg count (FEC) Good screening test for all parasites Does not quantify Fecal egg count (FEC) Not to be used for screening Will quantify numbers of eggs per gram of feces Only for strongyles and roundworms

CONTROL VS. ERADICATION Must encourage anthelmintic-sensitive worms in population Do not want to become outnumbered by resistant worms

GOAL = CONTROL  NO!!! Keep FEC low Reduce transmission Reduce the development of drug resistance Have happy, healthy horses Kill adult parasites  NO!!!

DEWORMERS Pyrantel pamoate Ivermectin Praziquantel Moxidectin Strongid T Rotation 2 DEWORMERS Ivermectin Zimectrin Equimax Eqvalan Ivercare Rotation 1 Praziquantel Quest plus Zimectrin gold Equimax Moxidectin Quest Fenbendazole Panacur Safe-guard Oxibendazole Anthelcide

DEWORMERS Tape - Round - Pin - Strongyles Bots worms worms worms Ivermectin / X X X Moxidectin Pyrantel X X X pamoate Oxibendazole X X X Praziquantel X Fenbendazole X X X

DAILY DEWORMER Pyrantel tartrate (Strongid C) Does not resolve existing infections Not effective against tapeworms or bots Resistance! Only appropriate in very specific situations

DESIGNING A DEWORMING PROGRAM Do not deworm all horses every 8 weeks! High levels of drug resistance Biology of parasites has changed Different worm demographics from horse to horse

DESIGNING A DEWORMING PROGRAM New recommendations – strategic deworming Treat some horses more and others less Involves FEC Advantages Fewer deworming treatments Less drug resistance Better worm control

POSSIBLE DEWORMING PLAN First treatment in September Last treatment in March No further deworming until fall unless there is a very cool, wet summer

POSSIBLE DEWORMING PLAN Determine which anthelmintics are working in the herd September  Egg counts on all horses Categorize horses’ contaminative potential <200 epg = low contaminators 200- 500 epg = moderate contaminators > 500 = high contaminators

HYPOTHETICAL DISTRIBUTION OF STRONGYLE EGG COUNTS IN A HORSE HERD LOW (50%) MODERATE (30%) HIGH (20%) NUMBER OF HORSES FECAL EGG COUNT (per gram of feces)

LOW CONTAMINATORS (< 200 epg) September  Treat with Ivermectin-Praziquantel March  Treat with Moxidectin-Praziquantel OR

MODERATE CONTAMINATORS (200-500 epg) September  Treat with Ivermectin-Praziquantel November  Treat with oxibendazole and/or pyrantel (together) March  Treat with Moxidectin-Praziquantel OR +

HIGH CONTAMINATORS (> 500 epg) September  Treat with Ivermectin-Praziquantel November  Treat with oxibendazole and/or pyrantel (together) December  Treat with Moxidectin March  Treat with Moxidectin-Praziquantel OR +

DEWORMING: Strategic vs. Every 2 months Number of Classification # of horses Subtotal Grand total doses/year Low 10 2 20 Moderate 6 3 18 54 High 4 4 16 Every 2 mos. 20 6 120 120

DEWORMING IN FOALS/WEANLINGS Start at 2 months of age Deworm monthly Alternate pyrantel and ivermectin At 8 and 12 months give a product with praziquantel as well OR

ENVIRONMENTAL CONTROL Moisture Strongyle transmission occurs almost exclusively on pasture Stall and dry-lots are negligible Season (in TN) Summer  lowest pasture infectivity Winter  cool enough to promote larval persistence

ENVIRONMENTAL CONTROL Manure management Pasture rotation and management Avoid over-stocking Group horses by age Feeders

EQUINE WELLNESS PROGRAM UT Equine Hospital and Field Services Comprehensive health care program for horses Pleasure horse Performance horse Yearly health care needs in one package Packages are a 20% discount from individual pricing Eligible for additional discounts and benefits Sign-up beginning March 12th, 2011!

HORSE OWNERS CONFERENCE March 12th, 2011 @ 8 am At UT – Hollingsworth auditorium Topics Wellness program Small pasture management Fescue toxicosis Foot care and diseases Use of common medications in horses Lameness examinations $28/person ($15 for additional family members) www.vet.utk.edu/continuing _ed

UTVMC OPEN HOUSE Saturday April 16, 2011 from 9 am – 4 pm Educational day for families Teddy Bear Clinic Canine Parade of Breeds Equine Parade of Breeds – including Amigo! Farm Animals Wildlife and Exotic Animals Physical Therapy for Animals www.vet.utk.edu/openhouse

QUESTIONS?? Thank you to Dr. Sharon Patton for providing information and pictures