Gastrointestinal parasitism in frilled sharks (roundworms)
Gastrointestinal parasitism from roundworms refers to the presence of nematodes in the stomach or intestines of a frilled shark, a primitive and rare shark that typically lives between 500 and 1500 meters deep. This condition is very poorly...
What is it?
Gastrointestinal parasitism from roundworms refers to the presence of nematodes in the stomach or intestines of a frilled shark, a primitive and rare shark that typically lives between 500 and 1500 meters deep. This condition is very poorly documented in the scientific literature because the species is observed almost exclusively in the wild or through accidental capture, and rarely survives in captivity. Current knowledge relies largely on what has been described in other deep-sea sharks that share a similar lifestyle.
Key point
The species itself is classified as near threatened and extremely difficult to observe or treat; any veterinary intervention on a frilled shark remains exceptional and delicate.
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:
In frilled sharks, the specific clinical signs of this parasitic infection have not been formally described in the scientific literature. By comparison with other sharks, progressive weight loss despite apparent normal feeding, reduced activity, and sometimes abnormalities in feces if the animal can be observed may be expected. These signs remain theoretical for this particular species.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
Gastrointestinal parasitism in frilled sharks is caused by roundworms (nematodes) that live in the stomach or intestines of the animal. As with many sharks, these parasites probably belong to families known in deep-sea sharks and are transmitted through the food chain: the frilled shark becomes infected by eating prey (cephalopods, small fish, other sharks) already carrying parasitic larvae. The exact cycle in this particular species remains poorly documented due to lack of research, as the biology of this abyssal shark is very poorly understood.
Stress from accidental capture or attempted maintenance in captivity, general weakening of the animal, and consumption of heavily infested prey are considered risk factors, by analogy with other shark species.
Transmission
Transmission occurs through feeding: the frilled shark becomes infected by consuming prey (fish, cephalopods) carrying nematode larvae, following an indirect parasitic cycle that probably involves several intermediate hosts in the deep-sea food chain.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
Diagnosis is challenging because the frilled shark is a deep-sea species very rarely kept in captivity and poorly studied. In the few individuals observed (public aquariums, accidental catches), the veterinarian specializing in exotic or aquatic animals relies on faecal examination to look for eggs or worms, on endoscopy if the animal can be handled, or on necropsy if death occurs. Faecal parasitology analysis remains the primary tool when follow-up is possible.
Treatment
If management is attempted, it would rely on the use of anthelmintic drugs adapted with extreme caution to the particular physiology of this deep-sea species, under strict specialized veterinary supervision. No standardized protocol currently exists for this species.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
For this deep-sea wild species, there are no prevention measures applied in practice. In the rare event of maintenance in a specialized facility, careful sourcing and quality control of prey items, as well as regular faecal parasitology screening, could help limit the risk of initial infestation or reinfection.
Possible complications
Heavy infestation can lead to progressive weight loss, irritation or inflammation of the intestinal wall, or even partial obstruction if parasitic burden is very high. In an animal already weakened by captivity stress or the strain of transport from the deep sea, these complications can rapidly worsen the animal's general condition.
When to see a veterinarian
A lizardfish in captivity appears to be losing weight for no apparent reason.
Abnormalities are visible in the animal's feces or the animal shows an unusual drop in activity.
An accidentally captured lizardfish displays signs of marked weakness.
Any abnormality in an animal this rare should be reported immediately to a veterinarian specializing in exotic aquatic species.
Prognosis
The prognosis depends on the parasite burden and the animal's overall condition, but remains generally uncertain due to limited clinical experience with this species. Light infestation may cause no visible signs, whereas heavy infestation in an animal already stressed by captivity can worsen the prognosis.
Frequently asked questions
Can the frilled shark transmit its parasitic worms to humans?
No, the gastrointestinal nematodes known in deep-sea sharks are generally specific to fish and are not transmitted to humans through simple contact. The zoonotic risk has not been demonstrated for this species.
Can a frilled shark be kept like a typical aquarium fish?
No. This is a deep-sea species that is extremely fragile and almost never maintained in captivity for any length of time. Any treatment must be decided by a veterinarian specializing in exotic aquatic animals, taking into account its particular physiology.
How do you know if a frilled shark is parasitized?
Most often, the discovery is made during an autopsy after the animal's death, because clinical signs in deep-sea fish are difficult to observe and the species is rarely monitored during its lifetime.
Is this disease common in frilled sharks?
Its actual frequency is unknown. Intestinal parasitism is common in sharks generally, but no reliable quantitative data exist specifically for the frilled shark due to its rarity.
References
WOAH — Organisation mondiale de la santé animale (ex-OIE)
Content reviewed by the TunisieVet editorial team · Updated 07 September 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