Impala gastrointestinal parasitism (roundworms)

What is it?

Gastrointestinal parasitism by roundworms is a very widespread parasitic disease in impala, both in the wild and in captivity (zoological parks, reserves). It is caused by several species of nematodes that live in the animal's stomach and intestines. These worms feed on blood or nutrients and cause irritation to the digestive lining. The disease particularly affects young animals, weakened or stressed individuals, and becomes more problematic when impalas live in high density, such as in enclosures or restricted grazing areas.

Commonly observed signs

These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.

Causes and risk factors

The disease is caused by nematodes (roundworms) which parasitize the impala's stomach and intestine. Several genera are involved, including Haemonchus, Trichostrongylus, Cooperia and Ostertagia, parasites also well known in domestic ruminants. Impalas become infested by grazing on grass contaminated by infective larvae from the feces of carrier animals.

Young impalas, stressed or immunocompromised animals, and those living in high density (enclosures, fenced reserves) are more exposed. Wet periods favor the survival and development of worm larvae in the environment, increasing the risk of infestation. Insufficiently renewed pasture or soiled by accumulated excrement also constitutes a significant risk factor.

Transmission

Transmission occurs indirectly via the environment: infested impalas eliminate worm eggs in their feces, these eggs develop into infesting larvae on the ground or grass, then are ingested by other impalas during grazing. There is no direct contact necessary between animals for transmission.

Diagnosis and care

Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.

Treatment

Treatment is based on the administration of antiparasitics (wormers) belonging to families recognized in veterinary medicine, prescribed and adapted by a veterinarian according to the species and context. Nutritional support and sometimes supplementation may accompany treatment in weakened or anemic animals.

Prevention

Possible complications

A severe, untreated infestation can lead to profound anemia, extreme weight loss (cachexia), a weakening of the immune system favoring other diseases, and in severe cases the death of the animal, particularly in young or already weakened animals.

When to see a veterinarian

Prognosis

The prognosis is generally favorable if the infestation is detected early and treated, particularly in adult animals in good general condition. It becomes more reserved in young animals, already weakened subjects or in the event of a massive infestation associated with severe anemia and significant weight loss.

Frequently asked questions

References

WOAH — Organisation mondiale de la santé animale (ex-OIE)

ESCCAP — European Scientific Counsel Companion Animal Parasites

Content reviewed by the TunisieVet editorial team · Updated 16 September 2026