Intestinal parasitism in shrimp (roundworms)
Intestinal parasitism by roundworms (nematodes) is a parasitic disease affecting the digestive tract of spotted shrimp. Microscopic or visible worms become established in the shrimp's intestines and disrupt its digestion. This condition is...
What is it?
Intestinal parasitism by roundworms (nematodes) is a parasitic disease affecting the digestive tract of spotted shrimp. Microscopic or visible worms become established in the shrimp's intestines and disrupt its digestion. This condition is mainly encountered in farming operations, in ponds where animal density is high. It progressively weakens shrimp without necessarily causing rapid death, making it more of an economic problem for producers than an immediate health emergency.
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:
Infested shrimp eat less and grow more slowly than others.
They appear generally less active, with slowed behavior.
The intestine may appear abnormal (dilated, discolored) on direct observation during examination, but this is not visible to the naked eye without opening the animal.
In advanced cases, marked growth retardation of the group is observed along with mortality that generally remains limited unless other stress factors are present (poor water quality, overcrowding).
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 nematodes (roundworms) that parasitize the shrimp's intestine. These worms belong to families known to infest aquatic crustaceans, particularly in farming environments. Infestation most often occurs through ingestion of eggs or larvae present in the water, pond sediments, or via intermediate hosts such as small aquatic organisms that the shrimp consumes.
Overcrowding in rearing ponds promotes transmission among individuals.
Poor water quality and contaminated sediments increase the parasite burden in the environment.
Insufficient water exchange or irregular cleaning of ponds allows accumulation of parasite eggs.
Stress from transport, handling, or sudden changes in temperature or salinity can weaken shrimp and worsen disease signs.
Transmission
Transmission occurs through the digestive route, via ingestion of nematode eggs or larvae present in the water, sediments, or intermediate prey.
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 direct examination of the shrimp intestine, performed by a specialist (dissection and microscopic observation). Monitoring the group's performance (growth, mortality, feeding behavior) can also help guide suspicion before laboratory confirmation.
Treatment
There is no practical individual treatment at the scale of a single animal in aquaculture. Management involves pond measures (water quality improvement, density reduction) and, in some cases, antiparasitic agents incorporated into feed, under supervision of an aquaculture pathology specialist.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Water quality management is the primary preventive measure: regular water exchange and monitoring of physical and chemical parameters.
Periodic cleaning and drying of ponds between production cycles reduces sediment contamination.
Reasonable stocking density limits transmission among individuals.
Quarantine and health monitoring of post-larvae before introduction into ponds are also recommended to avoid introducing already infected animals.
Possible complications
Significant untreated infestation can cause marked growth retardation in the group, reduced yield at harvest, and increased susceptibility of animals to other diseases or environmental stress.
When to see a veterinarian
Growth slowdown observed in a large portion of the group.
General decline in appetite or activity in the pond.
Unusual mortality associated with growth slowdown.
Suspected poor water quality combined with signs of weakness in the shrimp.
Prognosis
The outlook for the batch is usually favourable if pond management measures are put in place quickly. Without intervention, slowed growth may impact the profitability of the farm, although mortality directly linked to this parasitism typically remains limited.
Frequently asked questions
Is intestinal parasitism caused by roundworms dangerous for humans?
No, this disease is specific to shrimp and is not known to be transmissible to humans through normal consumption and proper cooking.
Can roundworms be seen with the naked eye?
Generally no, observation requires dissection and microscopic examination performed by a specialist.
How can I prevent this disease in a fish farm?
Prevention mainly relies on good water management, regular cleaning of ponds, and appropriate stocking density.
Does this disease affect only the spotted shrimp?
No, other farmed shrimp species can be affected by similar intestinal nematodes.
References
FAO — Organisation des Nations unies pour l'alimentation et l'agriculture
WOAH — Organisation mondiale de la santé animale (ex-OIE)
Content reviewed by the TunisieVet editorial team · Updated 26 October 2026
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