PARASITES AND DEWORMING YOUR HORSES

Control vs. Eradication

Karen Kalck, DVM, DACVIM Equine Medicine University of Tennessee Veterinary Medical Center

PLAN

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

QUESTIONS

1.

Raise your hand if you deworm your horse(s) every 2-3 months?

2.

Every 4-6 months?

3.

Once per year?

4.

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 Small Strongyles Tapeworm

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

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 ▫ 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

• • • • • Keep FEC low Reduce transmission Reduce the development of drug resistance Have happy, healthy horses Kill adult parasites 

NO!!!

DEWORMERS

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

DEWORMERS

Strongyles Tape worms Round worms Pin worms Bots

Ivermectin / Moxidectin Pyrantel pamoate X X X X X X 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%) FECAL EGG COUNT (per gram of feces)

LOW CONTAMINATORS

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

MODERATE CONTAMINATORS

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

HIGH CONTAMINATORS

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

DEWORMING: Strategic vs. Every 2 months

Classification # of horses

Low 10

Number of doses/year

2

Subtotal Grand total

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 12 th , 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