Gastrointestinal parasitism in bottlenose dolphins (roundworms)
Gastrointestinal parasitism caused by roundworms (nematodes) is a common condition in bottlenose dolphins, both in the wild and in dolphinariums. Worms belonging mainly to the family Anisakidae (such as Anisakis) and sometimes other nematod...
What is it?
Gastrointestinal parasitism caused by roundworms (nematodes) is a common condition in bottlenose dolphins, both in the wild and in dolphinariums. Worms belonging mainly to the family Anisakidae (such as Anisakis) and sometimes other nematodes settle in the stomach and intestines. In a healthy dolphin, a light parasite burden often goes unnoticed. Problems develop when worms become too numerous or when the animal is weakened by other factors—stress, another illness, or poor water quality.
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:
Signs are often subtle at first. Progressive weight loss may be seen despite maintained appetite, or conversely, poor appetite may develop. Vomiting of poorly digested fish or even live worms may be noticed by caregivers. Abnormally soft or discolored stools may sometimes be visible in the pool. The animal may appear less active, moving slowly during feeding sessions, and may show abdominal discomfort on examination by a veterinarian. In severe cases, dehydration and marked lethargy develop.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
The disease is caused by gastrointestinal nematodes, primarily Anisakidae (genera Anisakis, Pseudoterranova, Contracaecum, among others) and sometimes other roundworms such as ascarids. These parasites have a life cycle involving intermediate hosts—mainly fish and cephalopods (such as squid) that dolphins eat as part of their natural diet or the food provided in dolphinariums.
The main risk factor is consumption of raw fish or cephalopods carrying larvae of these worms, which is the dolphin's natural feeding method. Chronic stress, weakened immunity, concurrent illness, poor water or pool quality in captivity, and the source of the fish provided (unfrozen fish) increase the risk of heavy parasite burden or complications.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
Diagnosis relies on clinical observation by a veterinarian specialized in marine mammals, supplemented by fecal analysis to look for worm eggs or larvae, and sometimes by direct identification of parasites that have been vomited or expelled. Endoscopy or imaging studies may be considered in complex cases to assess the extent of digestive tract involvement.
Treatment
Treatment involves administering antiparasitic medications appropriate for nematodes, prescribed and dosed only by the veterinarian responsible for the animal. Nutritional support and rehydration may be provided if the animal shows signs of general weakness.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
In a delphinarium, freezing fish and cephalopods intended for feeding at a sufficient temperature and duration is the primary measure to kill parasite larvae before consumption. Regular veterinary checks with fecal examination allow detection of parasite burden before it becomes problematic. Maintaining good water quality and reducing stress also help minimize the risk of clinical disease.
Possible complications
Heavy parasite burden that goes untreated can cause lesions of the digestive wall, ulcers, or even perforations in severe cases. The resulting general weakness makes the animal more vulnerable to other infections and can compromise survival, particularly in young animals or those already in poor health.
When to see a veterinarian
The animal vomits repeatedly or expels visible worms.
Progressive weight loss despite apparently normal feeding.
Abnormally soft stools, discolored or unusual droppings observed in the pool.
Decreased activity, lethargy, or refusal to eat.
Signs of abdominal pain or discomfort during swimming or feeding.
Prognosis
The prognosis is generally good when parasite burden is detected and treated early. It becomes more guarded in case of severe digestive complications or when the animal is already weakened by another condition.
Frequently asked questions
Is gastrointestinal parasitism in dolphins transmissible to humans?
Anisakids that parasitize dolphins can also affect humans if they consume raw, untreated infested fish, but there is no direct transmission from dolphin to human. The human risk comes from eating improperly prepared fish.
Can a wild dolphin live normally with roundworms?
Yes, a low to moderate parasite load is common and often well tolerated by a healthy wild dolphin. Problems mainly arise in cases of high parasite load or when the animal is generally weakened.
How to prevent this disease in a dolphin in a dolphinarium?
Prior freezing of fish and cephalopods used as feed is the main preventive measure, combined with regular veterinary monitoring of faeces.
Can roundworms be seen with the naked eye?
Yes, some adult nematodes are large enough to be visible to the naked eye, particularly when they are vomited or present in stool.
References
WOAH — Organisation mondiale de la santé animale (ex-OIE)
Content reviewed by the TunisieVet editorial team · Updated 31 August 2026
Comments (0)
No comments yet.
AT A GLANCE
Need a veterinarian?
Find a practitioner near you on TunisieVet, with their specialities, hours and contact details.
Find a veterinarianCategories
Affected species
This information is provided for educational purposes only and is not a substitute for a veterinary consultation. If you have any concerns about your animal's health, consult a veterinarian.
Thinking of welcoming a pet? Dogs and cats are waiting for a family in Tunisia, and adoption is completely free.
Adoption listingsTo discover
Related diseases and linked Animalia content.
TunisieVet in your pocket 📱🐾 Access your veterinary services wherever you are. [ Download the app ]
Learn more