Gastrointestinal Parasitism in Mudskippers (Roundworms)
Mudskippers (Periophthalmus spp.), also called mudskippers or walking fish, are small amphibious fish living in mangroves and mudflats. Like many aquatic and amphibious animals, they can harbour roundworms (nematodes) in their digestive tra...
What is it?
Mudskippers (Periophthalmus spp.), also called mudskippers or walking fish, are small amphibious fish living in mangroves and mudflats. Like many aquatic and amphibious animals, they can harbour roundworms (nematodes) in their digestive tract.
This parasitic infection is common in animals caught in the wild or kept in poorly maintained paludariums (aquatic-terrestrial tanks). It affects the animal's overall condition and may not be visible externally at first.
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 occur despite sometimes retained appetite, loss of appetite, abnormal abdominal swelling (bloating), loose or abnormally formed faeces, sometimes with worms visible to the naked eye.
The animal may become less active and less lively in its characteristic movements (jumping, crawling over mud), and its colour may fade. In advanced cases, abnormal swimming or locomotion may appear.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
Various species of roundworms (nematodes) can colonise the mudskipper's digestive tract. These parasites often have a life cycle involving intermediate hosts (small crustaceans, insects or other invertebrates present in mud or water).
Infestation usually occurs through ingestion of contaminated prey (nematode larvae) in the wild or when uncontrolled live prey is introduced in captivity.
At higher risk are recently wild-caught animals, paludariums where mud or water are not regularly changed, the presence of unquarantined live prey (bloodworms, brine shrimp, wild insects), high stocking density in the same tank, and chronic stress from inappropriate rearing conditions (temperature, salinity, humidity).
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 a fecal examination (coprology) to look for worm eggs or larvae under a microscope. The exotic animal veterinarian can also directly examine worms expelled in the stool if observed.
In some cases, a more thorough examination (such as direct observation or necropsy on a deceased animal) may be necessary to identify the specific type of parasite.
Treatment
Treatment relies on antiparasitic drugs belonging to the anthelmintic family (dewormers), prescribed and dosed only by a veterinarian competent in exotic animals, as the safety margin in these small aquatic species is very narrow.
Nutritional support and improved husbandry conditions generally accompany the medical treatment.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Prevention relies on good paludarium hygiene: regular cleaning of substrate and water, avoiding overcrowding, and systematic quarantine of any new animal before introduction into a shared tank.
Mudskippers should be fed only with live prey from controlled breeding rather than wild-caught, and periodic parasitological checks by a veterinarian specializing in exotic animals should be performed, especially for newly acquired wild animals.
Possible complications
A significant untreated infestation can lead to severe malnutrition, general weakness, and favor other opportunistic diseases due to immune system suppression. In extreme cases, intestinal blockage from worm accumulation is possible.
When to see a veterinarian
The animal is losing weight while appearing to eat normally.
The belly seems abnormally swollen or hard.
Worms are visible in the stool or near the animal.
The animal becomes unusually lethargic or remains immobile.
Stools have been soft or of unusual consistency for several days.
Prognosis
The prognosis is generally good if the infestation is detected early and treated by a veterinarian competent in exotic species. Without treatment, the animal's general condition can gradually deteriorate and become life-threatening, especially in young individuals or those already weakened.
Frequently asked questions
Is the parasitism of the mudskipper transmissible to humans?
Fish-specific nematodes such as those affecting the mudskipper are generally not transmissible to humans. However, it is still recommended to wash your hands after handling the animal or its tank, as a general precaution.
How can I know if my ball python has worms without seeing a veterinarian?
It is not possible to confirm a parasitic infestation without veterinary examination. A microscopic analysis of feces is necessary to identify parasites with certainty.
Can I deworm my mudskipper myself using over-the-counter products?
No, this is strongly discouraged. Mudskippers are sensitive animals with a narrow therapeutic margin; incorrect dosing can be toxic or even fatal. Only a veterinarian specializing in exotic animals should prescribe treatment.
How can I prevent my eyelids from becoming reinfested after treatment?
The vivarium must be carefully cleaned, the water and substrate renewed, and care must be taken to avoid reintroducing uncontrolled live prey that could carry parasite larvae.
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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