Otter gastrointestinal parasitism (roundworms)
Gastrointestinal parasitism by roundworms (nematodes) is a common condition in otters, whether wild or in captivity (animal parks, care centers).\n\nThese worms live in the intestine of the animal and feed at its expense. In small quantitie...
What is it?
Gastrointestinal parasitism by roundworms (nematodes) is a common condition in otters, whether wild or in captivity (animal parks, care centers).\n\nThese worms live in the intestine of the animal and feed at its expense. In small quantities, they often go unnoticed. But when the number of parasites increases, they can cause a real digestive disease, especially in young otters or weakened animals.\n\nThis parasitosis is well documented in European otters and is part of standard health monitoring in wildlife care centers.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
The signs are not always visible, especially if few worms are present.\n\nWhen the infestation becomes significant, we may observe diarrhea that is sometimes persistent, occasional vomiting, a coat that becomes dull and less waterproof, progressive weight loss despite a retained appetite at the beginning, then a more marked loss of appetite.\n\nIn young otters, growth retardation or a distended stomach may appear. In severe cases, entire worms may be visible in stools or vomit.\n\nA heavily parasitized animal may appear tired, down, with a dirty or damp coat because it grooms itself less.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
Several species of intestinal nematodes can be involved in otters, in particular worms belonging to families classically found in mustelids and semi-aquatic carnivores.\n\nContamination most often occurs by ingestion of eggs or larvae present in the environment, water, prey (fish, crustaceans, amphibians) or by transplacental route or via milk in young people.
Young otters and weakened, sick or stressed animals are more susceptible to a severe infestation.\n\nA polluted aquatic environment, a high density of parasitized prey, captivity with insufficient hygiene or a weakened immune system (other disease, injury, capture stress) increase the risk.\n\nOtters collected in care centers after trauma or orphan birth are often at greater risk due to their weakened general condition.
Transmission
Transmission occurs by ingestion of eggs or larvae present in water, soil or prey (fish, amphibians, crustaceans), and sometimes from the mother to the young via the placenta or milk.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The veterinarian relies on the clinical examination of the animal and especially on an analysis of the stools (coproscopy) which makes it possible to search for and identify the eggs of parasites under a microscope.\n\nIn certain cases, a blood test can help to assess the general impact (anemia, nutritional state).\n\nThe direct examination of the expelled worms, if there are any, can also guide the diagnosis.
Treatment
Treatment is based on the use of antiparasitics belonging to the family of broad-spectrum dewormers, chosen and adapted by the veterinarian according to the type of parasite identified and the condition of the animal.\n\nNutritional support and rehydration may be necessary in the event of a severe infestation with significant diarrhea.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
In captivity or in a care center, regular parasitic monitoring (stool examination) makes it possible to detect an infestation early.\n\nGood hygiene of ponds and living areas, proper management of feeding (controlled fish) and reasonable deworming on veterinary advice limit the risk.\n\nIn the wild, there is no direct prevention possible; health surveillance of wild populations via health centers remains the main tool.
Possible complications
A massive untreated infestation can lead to severe dehydration, significant weight loss, anemia and general weakening which makes the animal more vulnerable to other infections.\n\nIn young people, lasting growth retardation is possible. In extreme cases, intestinal obstruction by a mass of worms remains a rare but serious complication.
When to see a veterinarian
The animal has diarrhea which persists for several days.\nWorms are visible in the stools or vomit.\nThe animal loses weight or refuses to eat.\nThe coat becomes dull, dirty or loses its waterproofness.\nA young animal does not grow normally or has a swollen belly.\nThe animal seems dejected, tired or dehydrated.
Prognosis
The prognosis is generally good when the infestation is detected early and treated by a veterinarian.\n\nIn animals that are young, weakened or carrying a very heavy parasitic load, the prognosis becomes more guarded without rapid treatment.
Frequently asked questions
Is otter gastrointestinal parasitism transmissible to humans?
No, intestinal nematodes usually found in otters are not considered transmissible to humans under common conditions.
How do you know that an otter is parasitized if it lives in the wild?
It's hard to know without analysis. In a care center or in captivity, a stool examination by a veterinarian can confirm the presence of parasites.
Can an apparently healthy otter still have worms?
Yes, a small infestation may not cause any visible signs. This is why a stool analysis remains more reliable than a simple observation.
Can you deworm an otter yourself?
No, the identification of the parasite and the choice of treatment must be made by a veterinarian, particularly because otters are protected wild animals requiring specialized care.
References
ESCCAP — European Scientific Counsel Companion Animal Parasites
WOAH — Organisation mondiale de la santé animale (ex-OIE)
Content reviewed by the TunisieVet editorial team · Updated 19 September 2026
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