What are Parasacaris?
Parascaris equorum is a parasite in the Ascarididae family of roundworms which affects equines like horses, zebras, and donkeys. Horses seem to develop some resistance to this family of roundworms as they mature, but it can be a health concern for horses under the age of two or horses with extremely compromised immune systems. These worms can be as thick as a pen and may reach lengths of over a foot long. As these large parasites migrate through the host during their lifecycle, they can cause inflammation and scarring to the organs which they migrate through.
Parascaris equorum is a common parasitic disease in young horses. Mature animals have usually developed a natural resistance to these roundworms, but they can cause dangerous blockages in young horses.
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Symptoms of Parasacaris in Horses
Serious infestations of the parascaris nematode are exceedingly rare in adult horses as they have usually built up a resistance to the parasite. Horses without a resistance may begin showing respiratory signs when the larvae first migrate to the lungs and then the gastrointestinal distress as they migrate back into the intestinal system. Symptoms that you might see with an Ascarids in horses can include:
- Abdominal pain
- Colic symptoms
- Difficulty breathing
- Loss of appetite
- Nasal discharge
- Poor growth
- Rough coat quality
- Slowed development
- Weight loss
Other notable members of the Ascarididae family include:
- Ascaris - Parascaris nematodes are often referred to as Ascarid, but it does not belong in the similarly named Ascaris genus; this roundworm is known to infect humans and pigs, and in humans, it is responsible for the malady Ascariasis
- Baylisascaris - This is a prolific parasite that can infect over 50 different types of mammals, including humans and horses; they can spread throughout the body and cause dangerous inflammation in any organ that they travel through
- Toxascaris leonina - This relative of the parascaris roundworm infests mainly dogs, cats, and rodents and can interfere with their digestion and damage the intestinal lining
- Toxocaridae - This parasite uses mostly dogs and cats as hosts, although one of the species infests buffalo and cattle
Causes of Parasacaris in Horses
Parascaris equorum eggs are generally acquired from contaminated grass. The eggs of this parasite are created with a sturdy shell, and the larvae can sometimes develop fully in as little as ten days. Once developed, they can remain in their egg for several years, safe from the elements, until a passing horse inadvertently eats them while grazing or they stick to the udders of a mare and get swallowed by her foal.
Once ingested, they hatch in the intestines and burrow through the wall of the gut and migrate through the bloodstream to the liver. They spend about a week growing in the liver before moving on to the lungs, where they travel through the airways, triggering coughing that propels them to the upper airway, where they are swallowed back down into the intestines to finish maturing. After maturing in the intestines, they begin laying eggs, sometimes as many as 60,000,000 per year, which are expelled with the feces to start the cycle over again.
Diagnosis of Parasacaris in Horses
When your equine veterinarian examines your horse, they will perform a complete physical evaluation of the animal, as well as a complete blood count and equine blood chemistry panel. Quite often the blood tests will come back with levels in the normal ranges, particularly in the early stages of infection, although the liver enzymes and eosinophil levels may be slightly elevated. Palpation in the abdominal area may reveal if the liver is swollen and if there are any obstructions due to the concentration of parasites in the digestive system, gas or fluid sounds may be heard.
In advanced cases of infestation, the dead parasites may be evident in feces, but a definitive diagnosis is almost always made by using a fecal float test to identify to offending parasite. In advanced cases, clusters of worms can cause perforation to the intestines, and ultrasound imaging may provide valuable information about the functionality of the intestines.
Treatment of Parasacaris in Horses
If your horse is in distress when your veterinarian examines him, supportive treatments will likely start right away. Supportive measures may include IV fluid treatment, both to prevent dehydration and in cases where the intestine has perforated, to administer antibiotics directly into the bloodstream. Deworming treatments will generally be started right away when adult worms are found in your horse, but it is important to go over the deworming schedule with your veterinarian.
Fast acting dewormers have been known to lead to intestinal blockages due to the sheer numbers of the dead worms, so horses with moderate to large infestations of the worms will generally be started on slower acting treatments to prevent blockages of the digestive system from forming. Blockages caused by dead worms can be extremely dangerous as perforation and rupture can lead to fatal cases of sepsis.
Recovery of Parasacaris in Horses
In farms where parascaris infections have been recurrent, foals may be started on deworming routines around eight weeks of age, before the worms have had a chance to fully mature, and will generally need to be repeated every six to eight weeks until they have matured enough to fight the parasite off on their own. Decontamination of stalls and pastures is a difficult task and requires diligence. The eggs of this worm are sticky and tend to adhere to whatever surface that they come into contact with, survive for several years and are well protected from the elements, particularly resilient to dehydration and freezing.