Red worms are dangerous for horses

Deworming horses

The most important endoparasites in horses can be divided into three different categories: roundworms, tapeworms and gastric dassels

A) Roundworms (nematodes):


Bloodworm or large stockade worm (Strongylus vulgaris)

The bloodworm is one of the most dangerous parasites for the horse. The greatest harmful effect is caused by the migration of the worm larvae. These are absorbed through the feed. When piercing the mucous membrane of the appendix and large intestine, they cause mucosal bleeding. The larvae migrate into small arteries and finally reach the anterior mesenteric artery. The vessels that have migrated through react to the larvae with inflammation of the vessel lining. This can lead to the formation of blood clots (thrombi), mainly in the area of ​​the anterior mesenteric artery. If the blood vessels are blocked by the thrombus, colic can result. However, other areas where the large arteries branch off from the main artery are also affected (blood supply to the hind limbs). This can cause lameness. The larvae migrating in the vessel can also cause widening of the blood vessels (aneurysms) to different degrees, which can burst. Horses infected with bloodworms usually have a fever, decreased appetite and a shaggy coat.

Small strongyles (Cyathostominae)
Small strongyles are both the most common as well as the most important parasites of theHorse at all. After ingestion, the worm larvae penetrate the colon wall with the grass and mature within nodules in the mucous membrane. After this development is complete, the larvae return to the inside of the intestine to develop into adult worms. These attach themselves to the mucous membrane and feed on the cells of the intestinal wall. The main harmful effect is caused by the larvae located in the intestinal mucosa. In winter this development cycle in the mucous membrane is interrupted: the ingested larvae remain encapsulated in the mucous membrane without further development (hypobiosis). In response to a special external stimulus, the hundreds of thousands of larvae encapsulated in the mucous membrane can develop further at the same time and emerge from the mucous membrane. This phenomenon, known as “mass migration”, leads to extreme damage to the intestinal mucosa. Young animals in particular are affected, as they can show shaggy hair, insatiable diarrhea, emaciation and water retention in the legs and lower abdomen. Deaths have been reported. The adult worms of some species of small strongyles feed directly by sucking blood. Depending on the degree of infestation, diarrhea, colic, poor appetite, shaggy hair, emaciation and reduced performance can be observed.

Roundworm (Parascaris equorum)
The larvae-containing roundworm eggs are ingested with the food. The larvae hatching from the eggs in the small intestine migrate to the lungs via the blood and lymph channels via the liver. Bleeding along the drill holes is the result. The larvae enter the pharynx via the bronchi, are swallowed and settle in the small intestine, where they mature into adult worms. The entire development in the horse takes at least 10 weeks. In the event of a massive infection, foals and yearlings in particular can experience coughs, fever, poor appetite and growth retardation. The damaged lungs become susceptible to infection by bacteria and viruses. Occasionally, roundworm larvae "get lost" via the bloodstream to other organs, where they usually die off with the formation of nodules. If the larvae get into the brain, central nervous disorders can occur. The adult roundworms, which feed on superficial layers of the mucous membrane in the small intestine, can cause chronic intestinal inflammation, which manifests itself in diarrhea, changing appetite, emaciation and shaggy hair. If the infestation is very severe, adult roundworms can also lead to an obstruction of the intestines with severe symptoms of colic. In the worst case, this leads to the rupture of the small intestinal wall. Slight roundworm infestation manifests itself in reduced performance, which can be of importance in rearing foals in particular.

Dwarf threadworm (Strongyloides westeri)
Dwarf threadworms occupy a special position among worms in several respects. Unlike all other horse worms, this type of worm can either become a parasite in the horse's intestine or multiply non-parasitically in soil or litter. An infestation with dwarf threadworms occurs particularly in suckling foals. The parasites cause catarrhal inflammation of the mucous membranes, which can manifest clinically as diarrhea, primarily in the second week of life. The larvae that penetrate through the skin can “drag along” germs and secondary local inflammations.
This parasite has zoonotic potential and is therefore a health hazard for humans! Infectious larvae can cause skin inflammation as so-called "Larva migrans cutanea"!

Awltail (Oxyuris equi)
Awl tails parasitize in the large intestine. The females migrate from the horse's intestines to the anal region, especially at night, in order to deposit their eggs in a sticky liquid in the form of so-called "egg cords" on the anus. The itching associated with laying eggs causes the horses to rub against all accessible objects. Hairless spots in the area of ​​the tail, also called "rat tail", and eczema in this region are the result. These skin lesions are particularly susceptible to secondary bacterial infections. The infestation with awl tails can lead to restlessness and loss of appetite, which have a negative effect, especially in high-performance animals.

Lungworm (Dictyocaulus arnifieldi)
Lungworm infestation usually only occurs in horses when they are kept together with donkeys, which are considered to be pathogen reservoirs. However, lungworm disease is often more severe in horses than in donkeys. The horse reacts to the infestation with increased mucus production and thickened bronchial mucous membranes. The visible symptoms are persistent dry cough, shortness of breath, reduced appetite and often bilateral nasal discharge. Since the lungs damaged by lungworms are particularly susceptible to bacterial and viral infections, pneumonia can also develop. The lungworm has a life expectancy of around one year in the horse and several years in the donkey. Donkeys infested with lungworms are constant excretors and are a permanent source of infection for horses.

B) tapeworms (cestodes)


Anoplocephala perfoliata
According to conventional wisdom, tapeworms are rare in horses. However, the number of unreported cases is probably very high and in some areas it is likely to reach 60% of the population. The development is tied to intermediate hosts (moss mites). The risk of infection is particularly high in late summer / early autumn, as the number of moss mites increases towards autumn. Since there is usually only a weak tapeworm infestation, clinical symptoms such as colic or diarrhea are rare. However, there is inflammation of the mucous membrane at the attachment point in the appendix or the ileo-caecal valve (transition from the hip to the appendix). The tapeworms absorb food components from the horse's intestine through their body surface and are therefore veritable blackheads. In the worst case, ulcers can form at the point where the tapeworms attach to the intestinal mucosa and even break through into the abdominal cavity, resulting in the death of the horse.

C) gastric dasseln (Gasterophilus intestinalis)


The main harmful effect is caused by the Dassella larvae parasitizing in the stomach. The larvae hatch from the eggs, which are set off by the bot fly, mainly on the forelegs, shoulders and flanks. By licking these places, the larvae I get into the oral cavity. They dig into the tongue, gums and roof of the mouth and stay here for 3 to 4 weeks. There may be swelling of the soft palate and inflammation of the tongue, followed by difficulty chewing and swallowing. In its further development, the larva II reaches its actual place of settlement, the stomach. With the help of their mouth hooks, they dig themselves deep into the gastric mucosa as larva II and later as larva III, which results in chronic gastric mucosal inflammation with ulceration. Occasionally there is even a gastric perforation with subsequent peritonitis. Colic, changing appetite, diarrhea, emaciation and anemia can appear as clinical symptoms. Developmental disorders, reduced performance, reduced resistance and (rarely) also deaths can be observed in foals in particular.