Types of Internal Equine Parasites
There are four main types of internal parasites that pass through the horse's body during their life span. The most harmful of these are the large and small strongyles (Redworms and Bloodworms). These parasites are approximately 1/2 inch long and are reddish in color. The larval forms of these parasites can damage the blood vessels and other organs. Young horses are more susceptible to large infestations than older horses. Equine worming programs are primarily aimed towards the control of large and small strongyles.
Symptoms:
Loss of condition
Anaemia
Dry, staring coat
Diarrhea
Worms may be visible in droppings
Treatment:
Oxibendazole, Dichlorvos, Pyrantel Pamoate and Ivermection are effective against large and small strongyles.
Phenothiazone and Thiabendazole are not as strong against small strongyles as they were because of resistance build-up.
Thebenzimidazole anthelmintics are effective against large strongyles.
Ascarids, or Round Worms, are stiff, white and up to a foot long (30cm) in the adult stage.
Symptoms:
In large numbers, they may cause a loss of condition, irregularity of the bowels or colic.
In small numbers, they rarely cause any symptoms.
Young foals from 12 weeks to one year are most vulnerable.
Treatment:
Piperazines are effective against ascarids. These are best administered by a veterinarian by means of a stomach tube (known as "tube-worming")
Foals should be de-wormed at eight weeks. It is not necessary to tube worm foals, Telmin paste works well.
Ivemectin paste is also effective against ascarids but should not be given to young foals.
All horses over two months old should be de-wormed every 4 to 8 weeks.
Bots (gasterophilus) are the larvae of botflies. The yellow eggs are laid on the hairs on the front part of the horse, within reach of his tongue. The eggs hatch in 10 to 14 days and the horse will lick them off his coat and transfer them to his mouth, where the larvae burrow into the mucous membranes of the lips and gums. There they remain for a short growing period and then they pass on to the intestine where they attach to the stomach wall. They remain there for almost a year before passing out with the faeces to pupate in the soil. Adult botflies then emerge from the pupal cases in 3 to 9 weeks, depending on the temperature.
Symptoms:
Large quantities in the gut will cause a loss of condition along with a dy, staring coat.
Temperature and pulse rate may rise.
The horse may shows signs of colic - restlessness and kicking at belly.
Intermittent diarrhea or constipation may be apparent.
Prevention:
Keep horses off pasture when botflies are laying their eggs. Turn horses out after dark and bring in early in the morning.
Pick or clip the eggs of the coat as soon as they are seen.
Frequent grooming removes some eggs.
Put darkened shelter for pasture horses during the botfly season.
Treatment:
Dichlorvos, trichlorfon and carbon disulphide, administered by stomach tube, are effective in controlling bots. This should be done in early spring when the larvae are in the stomach and before they pass out of the horse in the faeces.
Ivermectin paste and mebendazole-trichlorfon (Telmin B) paste are also effective against both the stomach bots and the earlier migrating stages in the mouth tissues.
Pinworms are about 1 3/4 inches long (4.5 cm) and are long and thin and occur in the rectum.
Symptoms:
Pinworms cause irritation - the horse will rub his tail.
A discharge will be present and pinworms may be visible around the anus.
Treatment:
Piperazine, Fenbendazole, Mebendazole (Telmin) and Ivermectin are all effective against pinworms.
Use paper towels or disposable wipes for cleaning the dock area, do not use sponges as it will spread the eggs and infection.
Rotating wormers
It is a fact that large and small strongyles get a resistance to wormers and therefore it is generally recommended that wormers be rotated by chemical class, not just brand name, in an effort to prevent the occurrence of resistance.
Pasture Management
It is very important to regularly pick up horse manure at least every other day. Flies lay their eggs in the manure, so to help keep parasites and the flies under control it is important to regularly clean the horse’s environment.
Grazing other animals on the pasture such as cattle can help as they ingest the eggs and interrupt the life cycle, thereby reducing contamination. Only horses are affected by redworms. Ploughing and cropping for a year or two with a straw crop can also help.
A sample of feces may be sent to your veterinarian to perform a fecal egg count on a regular basis to monitor the levels of eggs. An untreated horse will become extremely debilitated.
