Ascarids (Roundworms)
Ascarids are a group of large parasitic roundworms that affect many animal species, including horses, livestock, and poultry. They are especially common in young animals and can cause serious health problems when present in high numbers.
Unlike some other worms, ascarids are typically thick, long, and highly productive, meaning they release enormous numbers of eggs into the environment. These eggs are extremely hardy and can survive for years under the right conditions, making ascarids particularly difficult to control.
Why Ascarids Matter
Ascarids live in the digestive system, but their larvae often migrate through other organs before settling in the intestines. This migration causes internal irritation, inflammation, and tissue damage long before adult worms are even present.
Heavy burdens can lead to:
Poor growth and weight gain
A pot-bellied appearance (especially in young animals)
Dull coat or feathers
Diarrhoea or constipation
Reduced appetite
Lethargy
Respiratory signs (due to larval lung migration)
Intestinal blockages in severe cases
Young animals are most at risk because they have not yet developed strong immunity to these parasites.
Ascarids in Different Animals
Equines (Horses & Donkeys)
In horses, the most well-known ascarid is Parascaris. It mainly affects foals and young horses. Larvae migrate through the liver and lungs before reaching the intestines, which can cause coughing, nasal discharge, and poor growth.
In heavy infestations, adult worms can form large tangles in the intestine, sometimes leading to blockages or colic. This makes ascarids a serious health concern in young equines.
Livestock (Cattle, Sheep & Goats)
Ascarid-type worms in livestock are less common than strongyles but can still cause significant problems, particularly in young or intensively managed animals. Migration through the liver and lungs can reduce growth and increase susceptibility to other infections.
Poor condition, coughing, and general ill-thrift are often early warning signs.
Poultry (Chickens and other birds)
In poultry, Ascaridia species are among the most common intestinal worms. They can interfere with nutrient absorption, reduce weight gain, and cause a noticeable drop in egg production.
In young birds, heavy infestations may cause intestinal blockages, weakness, and even death if left untreated.
How Ascarids Spread
Ascarids have a direct life cycle and do not require an intermediate host.
Eggs are passed in manure or droppings and contaminate the environment. After a short development period, these eggs become infective. Animals then ingest them while grazing, pecking, or feeding.
Once inside the host, larvae hatch and migrate through organs such as the liver and lungs before returning to the intestines to mature into adult worms. This migration is responsible for many of the early clinical signs.
Ascarid eggs are extremely tough and resistant to drying, cold, and many disinfectants, allowing them to persist in soil, bedding, and enclosures for years.
Signs of an Ascarid Burden
Ascarid infections often build up gradually. Many animals show few signs at first, especially adults. When symptoms appear, they may include:
Poor growth or weight loss
Pot-bellied appearance
Dull coat or feathers
Coughing or nasal discharge
Reduced appetite
Diarrhoea or constipation
Lethargy
Reduced productivity
Detection
Ascarids are commonly detected using faecal egg counts (FECs). Because adult ascarids produce huge numbers of eggs, they are usually easy to detect once mature worms are present.
Testing allows for:
Early detection of burdens
Targeted treatment
Monitoring of reinfection
More responsible drug use
Treatment & Long-Term Control
While deworming can remove adult ascarids, long-term control requires environmental management. Because their eggs are so resilient, reinfection can happen very quickly.
A sustainable control plan includes:
Strategic, test-based treatment
Regular cleaning of enclosures and bedding
Avoiding overcrowding
Good hygiene around feeding areas
Age-specific parasite management for young animals
Resistance to some dewormers has already been reported in certain ascarid species, making targeted treatment and regular monitoring increasingly important.