Equine Parasites Timothy McDermott DVM

Parasite Types Internal External Bots(kind of both)

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

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

Fecal Testing Basic Float Fecal Egg Counts Specific Gravity Distilled water = 1.00 Parasite Egg = 1.02 Fecal solution = 1.025 to 1.03 Fecal Egg Counts Special type of slide to measure parasite burden

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

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

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

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

Roundworm Egg Picture credit: proprofs.com

Tapeworms Studies show 60-95% of pleasure horses(east of Mississippi) are tapeworm positive on blood testing, but only see eggs in feces 5 - 20% 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?

Tapeworm Egg Picture credit: vetagro-sup.fr

Picture credit: vetagro-sup.fr

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

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

External Parasite Types Flies Mosquitos Lice Mites Ticks

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

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

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

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

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

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

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

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