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

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

3. 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?

4. 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?

5. 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

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

7. 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

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

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

10. 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

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

12. LARGE STRONGYLES

13. SMALL STRONGYLES

14. 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

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

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

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

18. 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

19. 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

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

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

22. 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

23. 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

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

25. 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

26. 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

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

28. 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
epg = moderate contaminators
> 500 = high contaminators

29. 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)

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

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

32. 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 +

33. 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

34. 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

35. 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

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

37. 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!

38. HORSE OWNERS CONFERENCE
March 12th, 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)
_ed

39. 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

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