Gastrointestinal parasitism in goblin sharks (roundworms)
The goblin shark (Mitsukurina owstoni) is a deep-sea species that is rarely observed and almost never maintained in sustained captivity. Like most sharks, it can harbor roundworms (nematodes) in its digestive tract, particularly from the An...
What is it?
The goblin shark (Mitsukurina owstoni) is a deep-sea species that is rarely observed and almost never maintained in sustained captivity. Like most sharks, it can harbor roundworms (nematodes) in its digestive tract, particularly from the Anisakidae family, which are very common parasites in marine cartilaginous fish.
This parasitism is most often discovered during post-mortem examination or scientific observation of stranded or accidentally captured specimens, since the species lives at great depth and receives virtually no veterinary monitoring during life.
In sharks generally, a moderate parasite load is tolerated without visible signs. However, heavy infestation can weaken the animal, especially if it is already stressed by capture, injury, or sudden environmental change.
Key point
This species is very rarely observed alive; information on this condition is largely extrapolated from other sharks, due to the lack of data specific to the frilled shark.
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:
Knowledge of clinical signs in living goblin sharks is virtually nonexistent, as the species is practically never observed alive outside its natural environment.
Based on extrapolation from other shark species parasitized by digestive nematodes, one might expect decreased activity, refusal to eat, progressive weight loss, occasional vomiting, or abdominal distention in cases of heavy parasite load.
These signs remain hypothetical for this specific species and do not replace specialized veterinary advice.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
Infestation is caused by gastrointestinal nematodes, particularly larvae or adults from the Anisakidae family, which are widespread in marine fish and sharks.
The parasite cycle generally involves intermediate hosts such as crustaceans, then fish or cephalopods, which are subsequently consumed by the shark, serving as the definitive or paratenic host depending on the worm species.
The frilled shark feeds on deep-sea fish, cephalopods, and crustaceans, prey that may carry nematode larvae. An animal that is weakened, injured, or stressed—such as after accidental capture—may be more susceptible to the effects of a heavy parasite load, as documented in other sharks.
Transmission
Transmission occurs through ingestion of prey (crustaceans, fish, cephalopods) carrying nematode larvae, following the typical parasite cycle described in marine fish.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
Diagnosis is based on finding worms or their eggs, usually during necropsy, scientific dissection, or fecal examination if an animal were held in captivity. No standardized diagnostic protocol exists specifically for live frilled sharks, given how rarely they are observed.
Treatment
In sharks generally, antiparasitic treatment (benzimidazole class or other anthelmintics suitable for fish) can be considered by a veterinarian specializing in aquatic animals, if the animal is accessible and manageable. For the frilled shark, no data allow confirmation of a specific protocol; any intervention would remain experimental and decided case-by-case by a specialized team.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
No prevention measures are applicable in the natural environment for this deep-sea species. In the exceptionally rare event of specialized aquarium maintenance, quarantine and parasite screening of prey could reduce risk, by analogy with management protocols for other sharks in public aquariums.
Possible complications
A heavy parasite load could theoretically lead to digestive inflammation, nutrient malabsorption, and general weakness, as seen in other heavily parasitized cartilaginous fish.
When to see a veterinarian
Observation of a thin or lethargic animal during capture or stranding
Presence of visible worms in faeces or during handling
Prolonged refusal to feed in a specimen kept in captivity
Incidental discovery of parasites during scientific necropsy
Prognosis
Prognosis is very difficult to establish due to the lack of documented cases in living goblin sharks. In sharks generally, a light to moderate parasitic infestation is usually well tolerated, whereas a heavy parasite burden combined with stress may worsen the animal's overall condition.
Frequently asked questions
Is the goblin shark often parasitized by roundworms?
We assume so, like the majority of marine sharks, but very few specimens have been examined in detail because the species lives at great depth and is rarely captured.
Can a parasitic goblin shark be treated?
In theory, an antiparasitic treatment exists for fish, but no known experiment specifically addresses this species, which almost never survives long in captivity.
Is this parasite dangerous to humans?
Nematodes of the Anisakidae family can be transmitted to humans through consumption of improperly prepared raw fish, but the goblin shark is not a fish consumed commercially, so this risk remains theoretical for this species.
How is this parasitism detected?
Most often, it is discovered during an autopsy or scientific examination of a stranded or accidentally caught specimen, since examination of a living animal is extremely rare.
References
WOAH — Organisation mondiale de la santé animale (ex-OIE)
Content reviewed by the TunisieVet editorial team · Updated 07 September 2026
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