1. Equine Parasites
Timothy McDermott DVM

2. Parasite Types
Internal
External
Bots(kind of both)

3. Common Signs of Internal Parasites
Contrary to popular belief, horses can have large numbers of internal parasites while still appearing to be relatively healthy. But in some individuals, especially young horses, parasites can take a visible toll.
Common signs of parasitism include the following:
• Dull, rough haircoat
• Lethargy (decreased energy) or depression
• Decreased stamina
• Unthriftiness or loss of condition
• Slowed growth in young horses
• Pot belly (especially in young horses)
• Colic
• Diarrhea

4. Internal Parasite Types
Large Strongyles*
Roundworms*
Tapeworms*
Small Strongyles*
Pinworms
Bots

5. Fecal Testing Basic Float Fecal Egg Counts Specific Gravity
Distilled water = 1.00
Parasite Egg = 1.02
Fecal solution = to 1.03
Fecal Egg Counts
Special type of slide to measure parasite burden

6. Fecal Testing Need fresh sample, < 24 hrs old
Mix with small volume of fecal solution
Strain into tube
Place coverslip on tube for 5-10 minutes
Centrifuge
Check slide with microscope at 40X
Not negative, is NOS

7. Strongyles
The “worst’ of the worms. Largest and most significant of the Equine worms.
Large – Strongylus
Small - Cyathostomes
Either can be problem depending on region
Very prolific, direct life cycle(no intermediate host)
Almost all transmission in pastures
Need worming program, work with your Vet
Lots of resistance to wormers

8. -hard to ID, can look similar
Strongyle Eggs
-hard to ID, can look similar

9. Roundworms Parascaris equorum Foals/Yearlings/Elderly – immune system
Fairly common
Easy to find and treat generally

10. Roundworm Egg
Picture credit: proprofs.com

11. Tapeworms
Studies show 60-95% of pleasure horses(east of Mississippi) are tapeworm positive on blood testing, but only see eggs in feces % of time. (Midwest = highest)
Easier to see with eye instead of scope
Shed segments, not eggs
Intermediate host = forage mite
Can be subclinical, do not see any problems
Highest in October, highest in younger/older horses
Immune response?

12. Tapeworm Egg
Picture credit: vetagro-sup.fr

13. Picture credit: vetagro-sup.fr

14. Other Types Bots(Gastrophilus) Pinworms(Oxyuris) Any age affected
Anal itching
Yellow discharge

15. Dewormers Important part of equine health care
Many colic cases associated with parasites
Not all wormers treat all parasites
Use the right type and strategy, do not overuse as may cause resistance.
Develop worming plan with your Vet.
Pick up manure, drag fields to decrease burden

16. External Parasite Types
Flies
Mosquitos
Lice
Mites
Ticks

17. External Parasite symptoms
Restlessness
Irritable
Coat changes
Wounds/infection
Rubbing, twitching
Can transmit many diseases

18. Flies Horse Bot Fly Biting Flies Non-biting Flies Horse/Deer/Stable
Black/House

19. Bot Fly
Honeybee sized, lay eggs on coat, ingested by horse when they lick them off, develop as eggs in stomach, passed in manure
Colic signs
Examine coat
Frost kills eggs

20. Biting Flies Horse/Deer/Stable Daytime Fliers Vicious Biters(females)
Can transmit disease
Moist areas/near water
Control
Area control
repellants

21. Other Fly types Black/Horn Flies Non-biting flies Smaller types
Associated with cattle, other species
Blood feeders
Non-biting flies
House fly
Annoy, spread disease,
Manage manure

22. Lice –biting and sucking Ticks Mosquitos Mites
Species specific
Ticks
Similar to people
Mosquitos
Virus spread!!!
Mites
Itch
Demodex
Chiggers

23. External Parasite Control
Manure management
Eliminate standing water
Control brush/weed areas
Stable during peak times(bright sun)
Biological control
Repellants/traps
Examine your horse thoroughly

24. ?’s
Pic credits for External Parasite, University of Florida