Internal Parasites

Internal ParasitesAn internal parasite lives at least part of its

life cycle inside the host.There are more than 150 types of internal

parasites that can infect equine.

SymptomsWeight lossListlessnessand poor performanceDry, rough hairPoor appetiteBowel problems and colicPeriodic lamenessBreathing problems and coughingAnemiaFoals that do not grow well and develop

pot bellies

Diagnosis Only sure way is veterinary examination of

both the horse and the fecesWorm eggs revel what type of parasite is

affecting the horse

The extent of injury from internal parasites depends on:The kind of parasite.The number of parasites involved, and The length of time the parasite lives in the

host.

The general life cycle of internal parasites includes five stages:

Stage 1- Eggs from the internal parasite pass out of the equine in the feces and is deposited on the pasture.

Stage 2- Eggs hatch on the pasture and become infective larvae.

Stage 3- The equine ingest the larvae on the grass stem

Stage 4- The immature parasites migrate through the equine’s tissues.

Stage 5- The mature parasites live in the digestive tract and lay eggs.

The MOST abundant and harmful internal parasites affecting equine are:

Large Stronglyes (blood worms)Small StrongylesAscarids (large round worms)Pin WormsBots* (external and internal)

Large StrongylesBloodwormsMost serious threat to horses’ healthMigrate to the arteries, liver, gut wallAdults are bloodsuckersBlood clots may form in the arteries,

resulting in blockage and deathMay cause damage to arteries leading to

internal bleeding and death

Small StrongyleSpends entire life-cycle in the intestinal

wallCause ulcers that can cause digestive

problemsNot as serious as the large strongyleNot blood suckers

Ascarids, large roundwormsLargest parasite to infect horses

May grow to 15” long and size of a pencilMigrate to the liver and lungsLater they are coughed up, reswallowed

and go to the small intestineNot bloodsuckersMay rupture the wall of small intestine and

cause deathYoung horses

Ascarids

Pinworms

Travel to the large intestineDo not migrate through other tissues of the

bodyCause irritation in the anal region Horse may rub the rear quarters to relieve

itching, resulting in hair loss from the tail

Tapeworms

Difficult to diagnose, it is estimated that 40% of the horses in the U.S. are affected. Tapeworms are contracted during grazing, when the horse ingests the intermediate host, a mite found on plants. Once infected, tapeworms contribute to digestive problems, colic and malnourishment. Tapeworms are often undetected using normal fecal flotation methods

Bots are flies that lay eggs on various parts of the equine.Eggs hatch into larvae and are ingested by the

equine when the equine licks the area where eggs are laid.

Other eggs hatch and larvae crawl into the mouth, from the nostrils and lips where they mature in the gums and membranes of the inner lips.

When horsemen refer to bots, they usually mean the mature larvae that attach to the lining of the stomach.

Bots cause stomach problems and can block the entrance to the small intestine causing the stomach to rupture.

Factors Affecting Horse’s worm loadAge- foals and young horses are more

susceptibleLocation- geographical and climatic Season- some are active only during

specific seasonsTravelPasture load- more horses=more parasitesPasture Pals- other species can carry

parasites to infect horses

TreatmentDrugs- Anthelmintic (Dewormers)

No one drug is effective against all the different parasites

Worm medications can be purchased in several forms and administered in different waysMost common is a paste or gel dewormerPellets feed daily

Classes of DewormerFenbendazoleOxibendazoleIvermectinPraziquantelPyrantel PamoateMoxidectin

Similar products, have different active chemical to fight infestation of different worms

Most are effective against more than 1 type of parasite

DewormingMost horses are on

a deworming scheduleFrequency depends

on:HistoryTravelNew horses coming

in?Number of horses in

pasture

Our horses are on a 3 month rotation

Every 3 months they are wormed with a different wormer to cover all types of worms

Dewormers

PreventionSanitation and good management practices are

the basis of preventionManure should not be spread on horse pasturesDrag pastures to break up manure and expose it

to sunlightDo not overstock pasturesAlternate horses with cattle or sheepFeed hay and grain in bunks and feeders rather

on the groundKeep the water supply cleanKeep stalls clean

SummaryEffects of disease and parasites are

costly to horse ownersProper feeding and management help

reduce lossCleanliness and sanitation are the basis

of preventionProper exercise and grooming also help

keep horses in good health

SummaryCommon external parasites are flies, lice,

mites, ringworm and ticksSerious internal parasites are strongyles,

ascarids, pinworms and botsInsecticides are used to control external

parasitesGood management practices are used to break

the life cycle of the internal parasiteA regular worming schedule should be followed

to treat internal parasites